Hyb id and biocompa ible cellulose/polyu e hane nanocomposi es wi h
wa e -ac i a ed shape memo y p ope ies
Lei e U binaa, Ana Alonso-Va onab, Aina a Sa alegia, Teodo o Paloma esb, A an xa
Eceizaa, Ma ía Ángeles Co cue aa,⁎, Aloña Re egia,⁎
a‘Ma e ials + Technology’ G oup, Enginee ing School o Gipuzkoa. Depa men o Chemical and
En i onmen al Enginee ing, Uni e si y o he Basque Coun y (UPV/EHU), Pza. Eu opa 1., 20018
Donos ia - San Sebas ián, Spain
bDepa men o Cellula Biology and His ology, Facul y o Medicine and Odon ology, Uni e si y o he
Basque Coun y (UPV/EHU), B. Sa iena, s/n 48940, Leioa-Bizkaia, Spain
Abs ac
Wa e -ac i a ed shape memo y bac e ial cellulose/polyu e hane nanocomposi es we e p epa ed
by he imme sion o bac e ial cellulose (BC) we memb anes in o wa e bo ne polyu e hane
(WBPU) dispe sions o di e en imes. The high a ini y be ween he hyd ophilic BC and wa e
s able polyu e hane led o he coa ing and embedding o he BC memb ane in o he WBPU, ac s
ha we e con i med by FTIR, SEM and mechanical es ing o he nanocomposi es. The
mechanical pe o mance o he nanocomposi es esul ed enhanced wi h espec o he nea
WBPU, con i ming he ein o cing e ec o he BC memb ane. An imp o emen o he shape
ixi y abili y and as e eco e y p ocess wi h he p esence o BC was obse ed. In 3 min, he
nanocomposi e wi h highes BC con en eco e ed he 92.8 ± 6.3% o he o iginal shape, while
he nea WBPU only eco e ed he 33.4 ± 9.6%. The ob ained esul s indica ed ha 5 min o
imp egna ion ime was enough o ob ain nanocomposi es wi h imp o ed mechanical pe o mance
and as shape eco e y o po en ial biomedical applica ions. The p esen wo k p o ides an
app oach o de eloping en i onmen ally iendly and biocompa ible BC/polyu e hane based
ma e ials wi h enhanced mechanical and shape memo y p ope ies.
Keywo ds: Bac e ial cellulose; Wa e bo ne polyu e hane; Nancomposi e; Biocompa ible; Wa e -
ac i a ed; Shape memo y
1. INTRODUCTION
The echnological de elopmen s ha imp o e ou heal h and li e quali y a e based on he esea ch
and design o new ma e ials wi h unique and imp o ed p ope ies. In ecen yea s, sma
ma e ials wi h he abili y o eco e hei o iginal shape a e being de o med in a empo a y
shape unde he applica ion o ex e nal s imulus, such as empe a u e, wa e , pH, ligh , e c,
known as shape memo y polyme s (SMPs), ha e gained special a en ion (Hage , Bode, Webe ,
This is he accep ed manusc ip o he a icle ha appea ed in inal o m in Ca bohyd a e Polyme s 216 : 86-96 (2019), which
has been published in inal o m a h ps://doi.o g/10.1016/j.ca bpol.2019.04.010. © 2019 Else ie unde CC BY-NC-ND
license (h p://c ea i ecommons.o g/licenses/by-nc-nd/4.0/)
& Schube , 2015). Polyu e hane (PU)-based he moplas ic polyme s posses shape memo y
p ope ies based on ansi ion empe a u es (glass ansi ion o mel ing empe a u e) and also can
be he mo-mois u e esponsi e, since he mois u e abso bed upon imme sing in o wa e has a
s ong in luence on hei p ope ies (Sun & Huang, 2010). This means ha hese ma e ials can
be ac i a ed upon imme sing in o wa e . This in e es ing ea u e opens new possibili ies o he
applica ion o PU and hei nanocomposi es in he biomedical ield o he de elopmen o
implan s, d ug deli e y ca ie s, ascula s en s, e c. allowing o minimizing in asi e su ge ies
(Small, Singhal, Wilson, & Mai land, 2010). Fo example, SMP-PUs ha e been de eloped able
o sel - igh in a wi eless manne (kno and su u e) by imme sing in o wa e a oom empe a u e.
In addi ion, SMP-PU-based sel e ac able s en s could be de eloped wi h he abili y o expand
in o de o deli e a ca he e and hen, sh ink back in o o iginal shape by wa e a oom
empe a u e o be emo ed easie (Huang, Yang, Zhao, & Ding, 2010).
Among PUs, he de elopmen o wa e bo ne polyu e hanes (WBPU) has expe ienced an inc ease
because hei use does no imply he use o o ganic sol en s, hus educing he amoun o ola ile
o ganic compounds eleased o he a mosphe e (Zhou e al., 2015). Mo eo e , WBPU dispe sions
p esen low iscosi ies and good ilm o ming abili y wi h s ong adhesion and la ge lexibili y
which make hem in e es ing o he de elopmen o di e en nanocomposi es (Wan & Chen,
2018; Zhang, Xu, Fan, Sun, & Wen, 2019). In addi ion, hese ma ixes in aqueous dispe sion
p esen good a ini y wi h hyd ophilic nanoen i ies and nano ein o cemen s, such as
polysaccha ides de i a i es, which leads o an imp o emen o he he mo-physical and
mechanical p ope ies o he esul ing polyu e hanes (San ama ia-Echa e al., 2016; Wang e
al., 2019). Among polysaccha ides, nanocellulosic ma e ials ha e gained much a en ion due o
hei nume ous po en ial applica ions in nano echnology (Jiang e al., 2018; Thomas e al., 2018).
Nanocellulose is widely used as a nanoen i y o p epa a ion o ad anced nanos uc u ed
ma e ials, since he use o nanocelluloses as ein o cemen s leads o an enhancemen o some
p ope ies, especially, mechanical p ope ies. Howe e , in o de o ob ain ad anced
nanocomposi es, a p ope dispe sion o he nanoen i y in he ma ix mus be achie ed.
Nanocelluloses possess ac i e hyd oxyl g oups which can in e ac by hyd ogen bonding wi h he
mac omolecula chains o WBPU ma ixes leading o an inc eased dispe sion, ein o cemen and
in e acial adhesion (Solanki, Das, & Thako e, 2018). Fu he mo e, nanocellulose can be
conside ed a good subs a e ma e ial o wa e -ac i a ed shape memo y ma e ials due o i s
su ace´s hyd oxyl g oups and in e molecula hyd ogen bonds. Song e al., 2018 de eloped a
cellulose based wa e -ac i a ed shape memo y composi e wi h sisal cellulose nano ibe s and
g aphene oxide which eached a shape eco e y a io nea ly o 100%.
In his way, bac e ial cellulose which is p oduced by some bac e ial s ains in he o m o a
gela inous and anslucen memb ane, has an in e es ing 3D nano ibe ne wo k con o ma ion.
This spa ial con igu a ion a ou s he in e -chain hyd ogen bonds gene a ing a igh and s ong
cellulose nano ibe ne wo k wi h high mechanical p ope ies and s abili y e en in mois
en i onmen s. This ea u e makes BC an in e es ing empla e o he de elopmen o a wide
ange o nanocomposi es (Hu, Chen, Yang, Li, & Wang, 2014). In addi ion he use o BC
memb ane as a nano ein o cemen could be an in e es ing possibili y o coun e ac he di icul y
o ob ain a good dispe sion o he nanoen i ies in polyme ma ixes. In ac , BC has been used in
he p epa a ion o nanocomposi es wi h PUs and PU p epolyme s based on cas o oil showing
good adhesion, anspa ency and lexibili y wi h po en ial applica ions in elec onic de ices
(Pin o, Ba ud, Poli o, Ribei o, & Messaddeq, 2013, 2015). Mo eo e , due o i s biocompa ibili y,
BC exhibi s in e es ing p ope ies o in i o and in i o applica ions in biomedicine (Piche h e
al., 2017). Wu e al. (2014) de eloped sil e nanopa icle/BC hyb id gel-memb anes wi h
imp o ed an imic obial ac i i y o use hem as an an imic obial wound d essing. Kim, Cai, and
Chem, (2010) de eloped BC/chi osan, BC/polye hylene glycol and BC/gela ine composi es o
issue-enginee ing sca olds and wound d essing ma e ials by he imme sion o BC pellicles in
he polyme ic solu ions.
In he p esen wo k, wa e -ac i a ed nanocomposi es based on WBPU and BC ha e been
de eloped. The use o wa e -dispe sed polyu e hanes acili a es he p epa a ion o
nanocomposi es wi hou he use o o ganic sol en s and sol en exchanges o he BC
memb anes which ha e s ong a ini y wi h wa e . The e a e o he wo ks in which nanocelluloses
(El-Fa ah, Hasan, Keshawy, El Saeed, & Aboelenien, 2018), cellulose nanoc ys als
(San ama ia-Echa e al., 2016) o bac e ial cellulose (Pin o e al., 2013, 2015) ha e been used
o p epa e composi es wi h polyu e hanes. Howe e , o he bes o ou knowledge, no wo k has
been ound which exploi s he po en ial o he whole BC memb ane as a empla e o wa e bo ne
polyu e hanes o p epa e nanocomposi es wi h p o en enhanced wa e -ac i a ed shape memo y
p ope ies and biocompa ibili y. Fo his, BC memb anes ha e been embedded in o WBPU
dispe sion o p oduce nanocomposi es wi h imp o ed s i ness and enhanced shape memo y
p ope ies. The mo phology, in e ac ions be ween polyme s and he mal, he momechanical and
mechanical p ope ies o he nanocomposi es ha e been in es iga ed by scanning elec on
mic oscopy (SEM), Fou ie ans o m in a ed spec oscopy (FTIR), he mog a ime ic analysis
(TGA), di e en ial scanning calo ime y (DSC), dynamic-mechanical analysis (DMA) and
ensile es s. In o de o e alua e he po en ial applica ions o hese nanocomposi es in he
biomedical ield, he in i o biocompa ibili y was s udied by cy o oxici y and cell adhesion
assays. Addi ionally, wa e -ac i a ed shape memo y p ope ies we e analysed by old-deploy
shape memo y es me hod. The esul s ob ained p o e ha high pe o mance wa e -ac i a ed
shape memo y nanocomposi es can be de eloped o biomedical applica ions using wo
biocompa ible and eco- iendly ma e ials, WBPU dispe sion and BC memb anes, ollowing an
easy imp egna ion me hod.
2. MATERIALS AND METHODS
2.1. Chemicals
Bac e ial cellulose cul u e medium was p epa ed wi h apple esidues collec ed om a cide
p oduce o Gipuzkoa (No hen Spain) and comme cial suga cane. Po assium hyd oxide (KOH)
and ace ic acid glacial ( echnical g ade) we e ob ained by Pan eac Applychem. Imp ape m DL
3746 WBPU wi h 37 w % o solids con en and 87.1 ± 0.3 nm pa icle size and 0.083 ± 0.016
polydispe si y (de e mined by ligh sca e ing) was kindly supplied by Co es o (Ge many). N,N-
dime hyl o mamide (DMF) was pu chased om Ald ich. Phospha e bu e ed solu ion (PBS) and
calcein-AM we e supplied by Sigma-Ald ich (S Louis, MO, EEUU). Sodium py u a e and non-
essen ial amino acids we e ob ained by Gibco (Li e Technologies, UK). Penicillin-s ep omycin
was supplied by Lonza (Sweden) and e al bo ine se um by Bioch om AG (UK). E hidium
homodime -1 was supplied by Molecula P obes (Eugene, O egon, USA).
2.2. P epa a ion o BC/WBPU nanocomposi es
Fi s ly, BC memb anes we e g own in a cul u e medium p epa ed wi h a mix u e o apple esidues
om he cide p oduc ion and suga cane acco ding o a published p o ocol (U bina e al., 2017).
Then, BC memb anes we e pu i ied by ea ing wi h KOH solu ion (2 w %) o 24 h a oom
empe a u e, in o de o emo e non-cellulosic compounds, and ho oughly washed wi h unning
wa e un il a comple e neu aliza ion. BC/polyu e hane nanocomposi es we e p epa ed by
imme sing BC we memb anes in 50 mL o he comme cial WBPU dispe sion unde s i ing
condi ions a oom empe a u e o di e en imes, 5, 30, 60 and 120 min. Subsequen ly, he
memb anes we e emo ed om he dispe sion and d ained. Finally, hese we e d ied a oom
empe a u e o 4 days in o de o ob ain anspa en nanocomposi e ilms. The as p epa ed
nanocomposi es we e designa ed as BC/WBPU5, BC/WBPU30, BC/WBPU60 and
BC/WBPU120, whe e he numbe indica es he imme sion ime. As a e e ence, a nea WBPU
ilm was p epa ed by cas ing and d ied in he same condi ions as he nanocomposi es.
Addi ionally, nea BC ilms we e p epa ed by d ying he BC memb anes be ween Te lon pla es
o a oid he sh inkage in he o en a 55 °C o wo days. In he case o he BC/WBPU
nanocomposi es, he d ying me hod ollowed o he nea BC memb anes was no be sui able
because his PU p esen ed a ansi ion empe a u e a ound 50 °C, so a slow d ying p ocess a oom
empe a u e was p e e able. The hickness o he nanocomposi es, nea WBPU ilm and nea BC
memb ane in d y s a e was measu ed wi h a gauge.
2.3. Cha ac e iza ion o BC/WBPU nanocomposi es
In o de o es ima e he composi ion o he nanocomposi es, he amoun o BC was de e mined in
he BC/WBPU5 and BC/WBPU120 nanocomposi es, which we e he memb anes p epa ed wi h
he sho es and he la ges imme sion imes. Fo his, consecu i e ex ac ions wi h DMF, which
esul ed o be an e ec i e sol en o PU emo al, we e ca ied ou o a week o ensu e he
comple e emo al o he PU om he BC memb ane. This ac was con i med by FTIR analysis
o he esul an d ied BC samples, as no cha ac e is ic bands co esponding o he PU we e
obse ed in he FTIR spec a o he d ied samples. Finally, DMF was elimina ed om he ex ac
in a o a y e apo a o (100 mba , 97 °C). The amoun o BC in he nanocomposi es was es ima ed
using wo a iables: h ough he weigh di e ence be ween he ini ial nanocomposi e and he BC
a e he elimina ion o PU, and hough he weigh di e ence be ween he WBPU/DMF and he
collec ed WBPU a e DMF emo al om he lask. Each sys em was measu ed in duplica e. All
he samples we e kep in a desicca o in o de o a oid humidi y e ec s be o e each
cha ac e iza ion p ocedu e.
SEM was used o analyze he c oss sec ions o he nea BC and BC/WBPU5 nanocomposi e. P io
o SEM assay, ilms we e eeze- ac u ed wi h liquid ni ogen in o de o expose he c oss sec ion
o he ilm. Scanning elec on mic oscope JEOL JSM-6400 was used wi h a wol amium ilamen
ope a ing a an accele a ed ol age o 20 kV and a a wo king dis ance o 5–10 mm. Samples we e
coa ed wi h app oxima ely 20 nm o ch omium using a Quo um Q150 TES me allize .
FTIR spec oscopy was used o analyze he possible in e ac ions be ween BC and WBPU in he
nanocomposi es. A Nicole Nexus spec opho ome e p o ided wi h MKII Golden Ga e accesso y
(Specac) wi h diamond c ys al a a nominal incidence angle o 45° and ZnSe lens was used.
Spec a we e eco ded in a enua ed o al e lec ance (ATR) mode be ween 4000 and 650 cm−1
a e aging 32 scans wi h a esolu ion o 4 cm−1.
Mechanical es ing was ca ied ou a oom empe a u e using an Uni e sal Tes ing Machine
(MTS Insigh 10) wi h a load cell o 10 kN and pneuma ic g ips. Samples we e cu in 30×5 mm2
ec angula specimens. Fo he de e mina ion o he elas ic modulus (E), a c osshead a e o
0.5mm min−1 was se using a ideo ex ensome e . Maximum s eng h (σmax) and elonga ion a
b eak (εb) we e measu ed a a c osshead a e o 50mm min−1 using also a ideo ex ensome e . A
leas se en samples we e es ed o each se o samples, being he a e age alues epo ed.
The mal p ope ies we e s udied by DSC using a Me le Toledo 822e equipmen , p o ided wi h
a obo ic a m and an elec ic in acoole as he e ige a o uni . Aluminium pan con aining sample
(5–10 mg) was hea ed om -75 o 200 °C a a scanning a e o 2 °C min−1 in ni ogen a mosphe e.
Glass ansi ion empe a u e was de e mined as he in lec ion poin o he hea capaci y change,
whe eas mel ing empe a u e and en halpy we e es ablished as he maximum and he a ea unde
he endo he m peak, espec i ely.
The mal deg ada ion was s udied by TGA. Measu emen s we e pe o med by using a TGA/SDTA
851 Me le Toledo ins umen . Samples (2 mg) we e scanned om 25 o 800 °C a a hea ing a e
o 10 °C min−1. These es s we e ca ied ou unde ni ogen a mosphe e in o de o p e en he
he moxida i e deg ada ion.
The momechanical beha io was analyzed by DMA using an Eplexo 100 N analyse , Gabo
equipmen . Tensile mode measu emen s we e ca ied ou om -100 o 100 °C a a scanning a e
o 2 °C min−1. The s a ic s ain was es ablished as 0.05% and he ope a ing equency was ixed
a 1 Hz.
Fo he swelling s udy o he nea WBPU and BC/WBPU nanocomposi es, h ee samples o each
one we e imme sed in deionized wa e du ing 24 h a oom empe a u e. A di e en ime
in e als, samples we e emo ed om wa e , wiped wi h il e pape o ee wa e emo al and
hen weighed. The wa e holding capaci y (WHC) was calcula ed om Eq. 1:
𝑊𝐻𝐶 (%)= (𝑊𝑤𝑒𝑡−𝑊𝑑𝑟𝑦
𝑊𝑑𝑟𝑦 )∙100 (1)
whe e Wwe is he weigh o swollen samples a di e en imes and Wd y is he weigh o he
p e iously d ied samples.
2.4. Biocompa ibili y es s
The in i o biocompa ibili y o he nea BC memb ane and he nanocomposi e p epa ed wi h he
sho es imme sion ime (BC/WBPU5 nanocomposi e) was con i med by cy o oxici y assay as
well as adhesion es s (cell iabili y (Li e/Dead)).
Sho - e m cy o oxici y es s wi h nea BC and BC/WBPU nanocomposi e we e pe o med in
o de o e alua e he p esence and/o elease o oxic deg ada ion p oduc s. The ex ac i e me hod
ISO 10993−11:2009 was used. Cy o oxici y was assessed by P es oBlue® (In i ogen, USA), a
esazu in-based solu ion ha unc ions as a colo ime ic cell iabili y indica o . Fo his assay,
mu ine ib oblas s (L929 cells) we e seeded in o 96-well pla es a a densi y o 4×103 cells/well in
100 μL o comple e cul u e medium. A e 24 h, he medium was eplaced wi h 100 μL o nega i e
con ol (comple e medium), posi i e con ol (DMSO, 10% in comple e medium) o bioma e ial´s
ex ac i e media and a 10% o P es oBlue® was added. The op ical densi y was measu ed a 570
and 600 nm in a spec opho ome e (Syne gy HT spec opho ome e , Bio ek, USA) a di e en
ime poin s (0, 24 and 48 h). The iabili y o he cells was calcula ed ollowing he Eq.2.
𝑉𝑖𝑎𝑏𝑖𝑙𝑖𝑡𝑦 (%)= [𝐴𝑏𝑠]𝑠𝑎𝑚𝑝𝑙𝑒
[𝐴𝑏𝑠]𝑛𝑒𝑔𝑎𝑡𝑖𝑣𝑒 𝑐𝑜𝑛𝑡𝑟𝑜𝑙 ∙100 (2)
whe e [Abs]sample is he abso bance o he sample cells and [Abs]nega i e con ol is he abso bance o
he nega i e con ol cells (in his case highdensi y polye hylene). All assays we e conduc ed in
iplica e and a e age alues and s anda d de ia ions we e es ima ed.
The analysis o cell long e m adhesion was ca ied ou by pe o ming Li e/Dead assays. Samples
o 0.5 cm2 we e p epa ed (3 eplica es o each sample) and p io o analysis he ma e ials we e
s e ilized. Nea BC was s e ilized wi h e hanol 70% ( / ) o 2 h, while BC/WBPU
nanocomposi e was s e ilized unde ul a iole ligh o 30 min ( o p e en he dissolu ion o he
WBPU). Then, ma e ials we e washed 3 imes wi h phospha e bu e ed saline (PBS om Sigma-
Ald ich) and incuba ed in 500 μL o a comple e medium (Dulbecco's modi ied Eagle's medium
(DMEM) supplemen ed wi h sodium py u a e 1 mM, 1% o non-essen ial amino acids, 1%
penicillin-s ep omycin and e al bo ine se um 10%) a 37 °C o 24 h. A e p e-we ing, he
medium was emo ed and 50,000 cells (Mu ine ib oblas s L929) we e seeded on he ma e ials
acco ding o ISO 10,993-11: 2009. A e incuba ing o 90 min o ensu e adhesion, PBS was
added o he su ounding wells o p e en d ying. Finally, 500 μL o comple e medium was added
o he wells wi h ma e ials. Images o he samples we e aken a e 3, 7 and 14 days. The medium
was emo ed and samples we e washed wi h PBS h ee imes. Subsequen ly, calcein-AM 4mM
and e hidium homodime -1 in PBS we e added. Calcein-AM (λex/λem: 495/515 nm) epo s he
es e ase ac i i y o li ing cells emi ing in g een and homodime -1 emi s in ed (λex/λem: 493/630
nm), indica ing he loss o in eg i y o he plasma memb ane (Al house & Hopkins, 1995). A e
incuba ing he samples in he da k a 37 °C o 20 min, he analysis was ca ied ou in an Olympus
LV500 con ocal mic oscope (Olympus, Japan).
2.5. Shape memo y beha iou
The shape memo y e ec was in es iga ed by old-deploy shape memo y es (Cai, Jiang, Zheng,
& Xie, 2013; Liu, Han, Tan, & Du, 2010). Samples (30×10mm2) we e imme sed in a wa e ba h
a 60 °C inside closed con aine s and olded (θd) by applying ex e nal cons an o ce. Then, hey
we e cooled down in an ice wa e ba h unde he ex e nal o ce o ix he empo a y shape. This
o ce was hen emo ed a e holding o se e al minu es and a ma ginal eco e y occu ed (θ1)
and he bending angle became ixed (θ ). Finally, he specimens we e imme sed in wa e a 40 °C
and he change o he angle wi h ime (θ ) was eco ded using a ideo came a. The shape ixi y
a io (R ) and he shape eco e y a io (R ) we e calcula ed om Eqs. 3 and 4, espec i ely.
𝑅𝑓= 𝜃𝑓
180°∙100=180°−𝜃1
180°∙100 (3)
𝑅𝑟= 𝜃𝑡−𝜃1
180°−𝜃1∙100 (4)
The measu e o he bending es angles was ca ied ou h ough an open sou ce image-p ocessing
p og am, ImageJ. Each sys em was es ed in iplica e in o de o calcula e he s anda d de ia ion.
The shapememo y s udy p ocedu e is indica ed in Scheme 1, whe e he empe a u es o each
phase a e p esen ed: Ts (s o age empe a u e), Td (de o ma ion empe a u e), T ( ixa ion
empe a u e) and T ( eco e y empe a u e).
Scheme 1. Fold-deploy shape memo y es p ocedu e.
3. RESULTS AND DISCUSSION
3.1. Cha ac e iza ion o BC/WBPU nanocomposi es
Fi s ly, he e ec o he imp egna ion ime o he WBPU dispe sion in o BC memb anes in he
mo phology and hickness o he esul ing BC/WBPU nanocomposi es was analyzed. As i can
be obse ed in Table 1, he e is a di ec ela ionship be ween he imp egna ion ime and he
hickness o he nanocomposi es. As he imp egna ion ime inc eased, he hickness o he
nanocomposi e was g ea e , which sugges s ha he quan i y o WBPU in he BC/WBPU
nanocomposi e was highe .
I was es ima ed ha BC/WBPU5 con ained a 1.8 ± 0.1 w % o BC while BC/WBPU120
con ained 0.6 ± 0.1 w % o BC (da a ob ained by he weigh di e ence be ween he ini ial
nanocomposi e and he BC memb ane a e he elimina ion o PU, al hough he esul s ob ained
wi h bo h me hodologies we e e y simila ). These esul s con i med ha he nanocomposi es
con ained high amoun o polyu e hane, p obably due o he high a ini y be ween bo h polyme s
and he BC po ous s uc u e. In his way, he po ous s uc u e o he BC nano ibe ne wo k and
he nanome ic size o WBPU pa icles (87.1 ± 0.3 nm) in wa e p obably a ou ed he pene a ion
and coa ing o he BC s uc u e. Addi ionally, he polyu e hane used in his wo k was wa e based,
which p obably acili a ed he di usion and imp egna ion o he WBPU nanopa icles in o he
BC we memb ane as bo h componen s we e hyd ophilic. Some p elimina y expe imen s we e
pe o med wi h d y BC memb anes and he esul s con i med ha he imp egna ion was mo e
e ec i e in he case o using we memb anes. This was p obably due o he ac ha BC
memb anes we e al eady swollen, which led o a g ea e di usion o he WBPU nanopa icles
hough he BC memb anes a he s udied ime in e als.
Table 1. Thickness o nea BC memb ane, BC/WBPU nanocomposi es and nea WBPU.
Sample
Thickness (mm)
BC
0.04 ± 0.01
BC/WBPU5
0.22 ± 0.05
BC/WBPU30
0.33 ± 0.05
BC/WBPU60
0.35 ± 0.07
BC/WBPU120
0.42 ± 0.05
WBPU
0.43 ± 0.17
This ac was con i med by SEM analysis. Fig. 1 a), b) and c) shows he mic os uc u e o he
c oss sec ion o he BC memb ane (x10,000, x250 and x1,000, espec i ely). In Fig. 1 e) and )
he mic os uc u e o he c oss sec ion o BC/WBPU5 nanocomposi e can be obse ed (x250 and
x1,000). As i can be seen, BC p esen ed he ypical compac ed laye ed s uc u e wi h nano ib ous
con o ma ion (Bodin e al., 2006; Klemm, Schumann, Udha d , & Ma sch, 2001). In he case o
he nanocomposi e, he p esence o he BC was no app ecia ed due o he high amoun o WBPU
and he embedding o he BC memb ane in o he WBPU. This ac , esul ed in an inc ease o ilm
hickness and made i e y complica ed o obse e he BC in o he nanocomposi es by SEM.
As i can be obse ed in Fig. 1. d), BC/WBPU nanocomposi es exhibi ed excellen anspa ency.
I has been p e iously epo ed ha he nano ibe pape s a e anslucen due o he e ec o he
ligh di ac ion a he in e ace be ween he cellulose nano ibe s and he ai in e s ices be ween
hem (Nogi, Iwamo o, Nakagai o, & Yano, 2009). The 3D nano-sized ibe ne wo k o he BC
wi h ai in e s ices in be ween makes i e y anslucen , so he anspa ency o he
nanocomposi es implies ha hese gaps may had been comple ely illed by he polyu e hane and
he su ace had been coa ed. This was also obse ed in a p e ious wo k de eloped in ou esea ch
g oup in which BC memb anes we e imp egna ed wi h poly(lac ic acid) (PLA), al hough he
e ec was less p onounced as PLA and BC did no show such a good a ini y (U bina e al., 2016).
These esul s would con i m ha as he polyu e hane used in he p esen wo k was wa e based,
he L929 cells cul u ed in he ex ac ed media o bo h, nea BC and BC/WBPU5 was signi ican ly
highe han he es ablished accep ance limi o 70% o his alue. Consequen ly, he ob ained
esul s a e good indica ion when hinking on he u u e biomedical applica ion o he s udied
polyme s.
Fig. 4. a) Abso bance a 540 nm e sus incuba ion ime o a posi i e con ol, nega i e con ol, nea BC
and BC/WBPU5 and b) Viabili y o L-929 mu ine ib oblas cells as unc ion o incuba ion ime.
In addi ion, long- e m cell adhesion es we e ca ied ou by Li e/Dead assays. Fig. 5 shows he
luo escence con ocal mic oscopy images (x20) whe e calcein-AM shows cell iabili y (g een)
and e hidium homodime -1 non- iable cells ( ed). As i can be obse ed, signi ican cellula
adhesion and p oli e a ion we e ound o bo h, nea BC and BC/WBPU5 nanocomposi e. The e
is a la ge numbe o adhe en cells ha show iabili y (g een), and a sho age o dead cells ( ed).
The cul u e eached he monolaye in 3 days, showing adhesion and s able g ow h un il day 14.
In he las s age (C and F), he numbe o non iable cells inc eased, p obably due o he high
densi y o he cul u e. The cells esponded in a simila manne o bo h ma e ials, so since he
composi ion o he ma e ials di ec ly a ec s cell iabili y and adhesion, i is concluded ha bo h
BC and BC/WBPU nanocomposi es a e biocompa ible ma e ials.
3.3. Shape memo y p ope ies
The shape memo y p ope ies, namely shape ixi y a io (R ) and he shape eco e y a io (R ), o
he nea WBPU and wo nanocomposi es (5 and 120 min o imp egna ion) a e analyzed in his
sec ion. The shape eco e y p ocess in wa e as unc ion o ime o he nea WBPU and
BC/WBPU nanocomposi es can be obse ed in Figu e S1 and he esul s o shape eco e y a io
in wa e along ime a e shown in Fig. 6. a). All he esul s a e ga he ed in Table 4.
The shape ixi y a ios o he samples summa ized in Table 4, sugges ha he shape ixi y abili y
is enhanced wi h he p esence o BC. This beha io has been also obse ed in o he wo ks
in ol ing polyu e hane ma ixes ein o ced wi h nanocellulose and i can be asc ibed o he
p esence o he nume ous hyd oxyl g oups o he BC nano-ne wo k (Luo, Hu, & Zhu, 2011; Zhu
e al., 2012). These can con ibu e o he o ma ion o hyd ogen bonds be ween BC and WBPU,
esul ing in a highe igidi y, inc easing he modulus o he ma e ial and hus, a ou ing he ixi y
o he ma e ial´s shape espec o he nea WBPU (Wang, Cheng, Liu, Kang, & Liu, 2018).
Mo eo e , hese esul s a e in acco dance o he ones ob ained by DMA, whe e i can be seen ha
he s o age modulus o he nanocomposi es in he glassy s a e is highe wi h he p esence o BC
espec o he WBPU. Acco ding o Ra na and Ka ge -Kocsis (2008) a high glass s a e modulus
will p o ide he ma e ial wi h high ixi y du ing simul aneous cooling and unloading.
Fig. 5. Adhesion and iabili y o L929 cells on BC (A–C) and BC/WBPU5 (D–F). Calcein-AM shows cell
iabili y (g een) and e hidium homodime -1 non- iable cells ( ed/ ci cles). Images ob ained by con ocal
mic oscopy (20x) (Fo in e p e a ion o he e e ences o colou in his igu e legend, he eade is e e ed
o he web e sion o his a icle).
Conside ing he possible applica ion o hese nanocomposi es in medical de ices igge ed by
human body liquids, he shape eco e y was analyzed in wa e a 40 °C. This was se aking in o
accoun ha he sui able eco e y empe a u e mus be sligh ly highe han body empe a u e (>
37 °C) bu no oo high so as no o damage he no mal cells and issues (Cai e al., 2013). As i
can be obse ed in Fig. 6. a), he inco po a ion o he BC also induces o a as e eco e y p ocess
due o i s hyd ophilic na u e. The wa e molecules di use h ough he nanocomposi e and he
hyd ogen bonds be ween wa e and BC´s hyd oxyl g oups make he ilm become so e , so he
eco e y o he o iginal shape is as e (Zhu e al., 2012). In 3 min, he BC/WBPU5 eco e ed
92.8 ± 6.3% o he o iginal shape, while BC/WBPU120 eco e ed 72.0 ± 5.1% and nea WBPU
only 33.4 ± 9.6%. In he case o he nea WBPU needed 25–30 min o eco e 73.0 ± 3.5% o he
o iginal shape.
Fig. 6. a) Shape eco e y a io in wa e and b) WHC o BC/WBPU5 and BC/WBPU120 nanocomposi es
and nea WBPU (de ailed igu e co esponds o WHC in he ime in e al om 0 o 100 min).
Addi ionally o he p esence o BC, he chemical s uc u e and hickness o he nanocomposi es
as well as he mo emen o molecula a chi ec u e ha e in luence on he shape memo y eco e y.
Huang, Yang, Zhao, & Ding (2010) epo ed ha he eco e y a io in mois u e induced eco e y
is lowe han in he mally induced eco e y. In mois u e induced eco e y sys ems he e is a
s ong dependency on he sample size because he wa e abso p ion is easie on he sample´s
su ace, so he sa u a ion is as e han inside he ma e ial. This means ha hin ilms a e mo e
sui able o mois u e induced eco e y sys ems han bulky ma e ials. In his case, i has been
obse ed (in Table 1) ha as imp egna ion ime inc eased, he hickness o he nanocomposi e
inc eased (0.22 ± 0.05 and 0.42 ± 0.05mm o BC/WBPU5 and BC/WBPU120 nanocomposi es,
espec i ely) and his can ha e an in luence on he shape memo y p ope ies. BC/WBPU5
p esen ed he as es eco e y and was he hinnes nanocomposi e, so hese esul s co ela ed
wi h his ac . Song e al., 2018 also epo ed ha when he ma e ial p esen s a well a ayed laye ed
s uc u e he mo emen o wa e molecules in he ma ix a e imme sion in wa e is a ou ed. As
i has been obse ed in SEM images (Fig. 1. a), b) and c)), BC p esen s a laye ed s uc u e so his
ac can help o he eco e y p ocess in he nanocomposi es. In addi ion, he empe a u e a which
he es was pe o med may ha e helped o he eco e y o he shape. As i has been p e iously
epo ed, he inc ease o he empe a u e leads o a weakening o he hyd ogen bonding, so he
sys em will ha e g ea e eco e y capaci y (Yildi im, Yu se e , Yilgo , Yilgo , & Wilkes, 2018).
The e ec o he empe a u e can also be impo an i he eco e y empe a u e is highe han any
ansi ion. As i was obse ed in he DSC he mog ams (Fig. 3. a)), he second ansi ion o he
WBPU s a ed a ound 40 °C, so in his case as he es was pe o med below he ansi ion
empe a u e, e e y hing indica ed ha he phenomenon o shape eco e y was mainly caused by
wa e and he e ec o empe a u e would be minimal. These esul s sugges ha hese ma e ials
could be sui able o de elop apid esponsi e ma e ials o di e en ields such us senso s,
a i icial muscles, sel -expandable s en s o de ices in ol ing minimally in asi e su ge y in he
human body.
Table 4. Ma ginal eco e y angle (θ1), shape ixi y (R ) and eco e y (R ) a ios and maximun wa e
up ake o BC/WBPU5 and BC/WBPU120 nanocomposi es, and nea WBPU.
Sample
θ1 (°)
R (%)
R (%)3 min
R (%) inal
Maximum wa e up ake (%)
BC/WBPU5
26.6 ± 4.6
86.0 ± 5.5
92.8 ± 6.3
94.5 ± 7.2
30.1 ± 6.8
BC/WBPU120
32.7 ± 4.7
81.8 ± 2.7
72.0 ± 5.1
78.2 ± 8.4
33.5 ± 6.4
WBPU
43.7 ± 4.8
75.7 ± 2.7
33.4 ± 9.6
73.0 ± 3.5
49.2 ± 0.8
In iew o he esul s o he shape memo y es , i was in e es ing o analyze he wa e holding
capaci y (WHC) o nea WBPU and BC/WBPU nanocomposi es, since he shape eco e y was
p edic ably ela ed o he abso p ion o wa e . In o de o analyze he in luence o he p esence o
BC in he nanocomposi es in he wa e in ake, nea WBPU and BC/WBPU5 and BC/WBPU120
nanocomposi es we e imme sed in wa e a oom empe a u e o a ce ain ime and he WHC
was calcula ed. I is commonly known ha BC p esen s a high WHC (Aze edo, Ba ud, Fa inas,
Vasconcellos, & Cla o, 2019; Ul-Islam, Khan, & Pa k, 2012; U bina e al., 2017), so he in ake
o wa e in he samples was de e mined and he esul s a e compiled in Fig. 6. b). These esul s
con i med ha wa e up ake inc eased apidly in he p esence o BC up o 1 h o imme sion. A e
ha momen , BC/WBPU nanocomposi es s a ed o app oach equilib ium, and a e 2 h o
imme sion he equilib ium was eached. The wa e up ake o he nea WBPU was slowe and he
equilib ium was eached be ween 24 and 48 h o imme sion. As i can be obse ed in Table 4, i
can be concluded ha he p esence o BC induces o a as e wa e up ake, bu limi s he wa e
con en allowed in he nanocomposi e. This could be due o he ac ha hyd ogen bonding
in e ac ions be ween BC and WBPU (seen in he FTIR s udy) led o less −OH a ailable in he BC
s uc u e o in e ac wi h wa e molecules. This has been also obse ed by o he au ho s (Popescu,
Doga u, & Popescu, 2017). This can be a posi i e ea u e, since abso bed wa e can accumula e
in he in e ace be ween componen s in blends leading o a delamina ion (Lyu & Un e eke , 2009).
These esul s co obo a ed he ones ob ained in he shape memo y es since he nanocomposi es
abso bed mo e wa e a sho e imes (which would induce a dec ease o Tg (Zhang e al., 2018))
and hus, hey p esen ed g ea e eco e y and a lowe imes.
4. CONCLUSIONS
In his wo k, lexible, anspa en and biocompa ible nanocomposi es wi h enhanced mechanical
pe o mance and wa e -ac i a ed shape memo y p ope ies we e de eloped by he combina ion
o BC memb anes and WBPU dispe sions wi h po en ial applica ions in he biomedical ield.
BC we memb anes we e imme sed in WBPU dispe sions o di e en imes and he BC
memb anes esul ed embedded and coa ed by he WBPU, sugges ing he good a ini y o bo h
polyme s due o hei hyd ophilic na u e. Addi ionally, he FTIR s udy e ealed hyd ogen bond
in e ac ions be ween BC and WBPU. This ea u e was ela ed o he wa e holding capaci y o
he nanocomposi es, since he p esence o BC limi ed he wa e con en allowed in he
nanocomposi e. Mechanical es showed ha he elas ome ic p ope ies o he WBPU we e
main ained in he nanocomposi es, bu an imp o emen o he modulus and s eng h o he
nanocomposi es wi h espec o he nea WBPU was obse ed. This sugges ed he e ec i e BC-
ein o cemen and i was con i med by DMA analysis, whe e i was obse ed ha he s o age
modulus o he nanocomposi es was highe on all empe a u e ange compa ed o he nea
WBPU. The in i o biocompa ibili y and cell adhesion es s o he nanocomposi es showed non-
oxic beha iou making hem sui able o biomedical applica ions. Fu he mo e, wa e ac i a ed
shape memo y p ope ies we e analyzed by old-deploy es me hod. The esul s e ealed an
imp o emen o he shape ixi y abili y and as e eco e y p ocess wi h he p esence o BC. The
BC/WBPU5 eco e ed 92.8 ± 6.3% o he o iginal shape in 3 min, while o he same ime pe iod
he nea WBPU only 33.4 ± 9.6%. This could be due o he as e di usion o he wa e molecules
h ough he nanocomposi e and he hyd ogen bonding be ween wa e and BC hyd oxyl g oups.
The ob ained esul s indica ed ha 5 min o imp egna ion ime was enough o ob ain
nanocomposi es wi h imp o ed mechanical pe o mance and as shape eco e y o po en ial
biomedical applica ions.
Aknowledgemen s
The au ho s hank o he inancial suppo om he Spanish Minis y o Economy and
Compe i i eness (MINECO) (MAT2016-76294-R) and he Basque Go e nmen in he ame o
G upos Consolidados (IT-776-13). The au ho s would also like o acknowledge he echnical
suppo p o ided by SGIke o UPV/EHU. The Basque Go e nmen is g ea ly acknowledged o
he PhD g an PIF PRE_2014_1_371 o he esea che Lei e U bina.
Re e ences
Alemi, B., & Shodja, H. M. (2018). E ec i e shea modulus o solids ein o ced by andomly
o ien ed- / aligned-ellip ic mul i-coa ed nano ibe s in mic opola elas ici y. Composi es Pa B
Enginee ing, 143, 197–206. h ps://doi.o g/10.1016/j.composi esb.2018.02.011.
Al house, G. C., & Hopkins, S. M. (1995). Assesmen s o boa spe m iabili y using a
combina ion o wo luo opho es. The iogenology, 43, 595–603. h ps://doi.o g/10.1016/0093-
691X(94)00065-3.
Auad, M. L., Con os, V. S., Nu , S., A angu en, M. I., & Ma co ich, N. E. (2008).
Cha ac e iza ion o nanocellulose- ein o ced shape memo y polyu e hanes. Polyme
In e na ional, 57, 651–659. h ps://doi.o g/10.1002/pi.2394.
Aze edo, H. M. C., Ba ud, H., Fa inas, C. S., Vasconcellos, V. M., & Cla o, A. M. (2019).
Bac e ial cellulose as a aw ma e ial o ood and ood packaging applica ions. F on ie s in
Sus ainable Food Sys ems, 3, 1–14. h ps://doi.o g/10.3389/ su s.2019.00007.
Bodin, A., Bäckdahl, H., Fink, H., Gus a sson, L., Risbe g, B., & Ga enholm, P. (2006). In luence
o cul i a ion condi ions on mechanical and mo phological p ope ies o bac e ial cellulose ubes.
Bio echnology and Bioenginee ing, 97, 425–434. h ps://doi.o g/10.1002/bi .21314.
Cai, Y., Jiang, J.-S., Zheng, B., & Xie, M.-R. (2013). Syn hesis and p ope ies o magne ic
sensi i e shape memo y Fe3O4/poly(ε -cap olac one)-Polyu e hane Nanocomposi es. Jou nal o
Applied Polyme Science, 127, 49–56. h ps://doi.o g/10.1002/app.36849.
Ciolacu, D., Ciolacu, F., & Popa, V. I. (2010). Amo phous cellulose-s uc u e and
cha ac e iza ion. Cellulose Chemis y and Technology, 45, 13–21.
El-Fa ah, M. A., Hasan, A. M. A., Keshawy, M., El Saeed, A. M., & Aboelenien, O. M. (2018).
Nanoc ys alline cellulose as an eco- iendly ein o cing addi i e o polyu e hane coa ing o
augmen ed an ico osi e beha iou . Ca bohyd a e Polyme s, 183, 311–318.
h ps://doi.o g/10.1016/j.ca bpol.2017.12.084.
Feng, X., Ullah, N., Wang, X., Sun, X., Li, C., Bai, Y., e al. (2015). Cha ac e iza ion o bac e ial
cellulose by Gluconace obac e hansenii CGMCC 3917. Jou nal o Food Science, 80, E2217.
h ps://doi.o g/10.1111/1750-3841.13010.
Figuei edo, A. G. P. R., Figuei edo, A. R. P., Alonso-Va ona, A., Fe nandes, S. C. M., Paloma es,
T., Rubio-Azpei ia, E., e al. (2013). Biocompa ible bac e ial cellulosepoly(2-hyd oxye hyl
me hac yla e) nanocomposi e ilms. BioMed Resea ch In e na ional, 2013, 1–14.
h ps://doi.o g/10.1155/2013/698141.
Guo, L., Sa o, H., Hashimo o, T., & Ozaki, Y. (2010). FTIR s udy on hyd ogen-bonding
in e ac ions in biodeg adable polyme blends o poly(3-hyd oxybu y a e) and poly(4-
inylphenol). Mac omolecules, 43, 3897–3902. h ps://doi.o g/10.1021/ma100307m.
Hage , M. D., Bode, S., Webe , C., & Schube , U. S. (2015). Shape memo y polyme s: Pas ,
p esen and u u e de elopmen s. P og ess in Polyme Science, 3, 49–50.
h ps://doi.o g/10.1016/j.p ogpolymsci.2015.04.002.
Hu, W., Chen, S., Yang, J., Li, Z., & Wang, H. (2014). Func ionalized bac e ial cellulose
de i a i es and nanocomposi es. Ca bohyd a e Polyme s, 101, 1043–1060.
h ps://doi.o g/10.1016/j.ca bpol.2013.09.102.
Huang, W. M., Yang, B., Zhao, Y., & Ding, Z. (2010). The mo-mois u e esponsi e polyu e hane
shape-memo y polyme and composi es: A e iew. Jou nal o Ma e ials Chemis y, 20, 3367–
3381. h ps://doi.o g/10.1039/B922943D.
Jiang, F., Li, T., Li, Y., Zhang, Y., Gong, A., Dai, J., e al. (2018). Wood-based nano echnologies
owa d sus ainabili y. Ad anced Ma e ials, 30(1703453), 1–39.
h ps://doi.o g/10.1002/adma.201703453.
Jiao, L., Xiao, H., Wang, Q., & Sun, J. (2013). The mal deg ada ion cha ac e is ics o igid
polyu e hane oam and he ola ile p oduc s analysis wi h TG-FTIR-MS. Polyme Deg ada ion
and S abili y, 98, 2687–2696. h ps://doi.o g/10.1016/j.polymdeg ads ab.2013.09.032.
Kim, J., Cai, Z., & Chem, Y. (2010). Biocompa ible bac e ial cellulose composi es o biomedical
applica ion. Jou nal o Nano echnology in Enginee ing and Medicine, 1, 1–7.
h ps://doi.o g/10.1115/1.4000062.
Kizil as, E. E., Kizil as, A., & Ga dne , D. J. (2015). Syn hesis o bac e ial cellulose using ho
wa e ex ac ed wood suga s. Ca bohyd a e Polyme s, 124, 131–138.
h ps://doi.o g/10.1016/j.ca bpol.2015.01.036.
Klemm, D., Schumann, D., Udha d , U., & Ma sch, S. (2001). Bac e ial syn hesized cellulose-
a i icial blood essels o Mic osu ge y. P og ess in Polyme Science, 26, 1561–1603.
h ps://doi.o g/10.1016/S0079-6700(01)00021-1.
Liu, Y., Han, C., Tan, H., & Du, X. (2010). The mal, mechanical and shape memo y p ope ies
o shape memo y epoxy esin. Ma e ials Science and Enginee ing A, 527, 2510–2514.
h ps://doi.o g/10.1016/j.msea.2009.12.014.
Luo, H., Hu, J., & Zhu, Y. (2011). Tunable shape eco e y o polyme ic nano-composi es.
Ma e ials Le e s, 65, 3583–3585. h ps://doi.o g/10.1016/j.ma le .2011.08.006.
Lyu, S. P., & Un e eke , D. (2009). Deg adabili y o polyme s o implan able biomedical
de ices. In e na ional Jou nal o Molecula Sciences, 10, 4033–4065.
h ps://doi.o g/10.3390/ijms10094033.
Nakagai o, A. N., Iwamo o, S., & Yano, H. (2005). Bac e ial cellulose: The ul ima e nanoscala
cellulose mo phology o he p oduc ion o high-s eng h composi es. Applied Physics A, 80, 93–
97. h ps://doi.o g/10.1007/s00339-004-2932-3.
Nogi, M., Iwamo o, S., Nakagai o, S. N., & Yano, H. (2009). Op ically anspa en nano ibe
pape . Ad anced Ma e ials, 21, 1595–1598. h ps://doi.o g/10.1002/adma.200803174.
Pei, A., Malho, J.-M., Ruokolainen, J., Zhou, Q., & Be glund, L. A. (2011). S ong nanocomposi e
ein o cemen e ec s in polyu e hane elas ome wi h low olume ac ion o cellulose
nanoc ys als. Mac omolecules, 44, 4422–4427. h ps://doi.o g/10.1021/ma200318k.
Piche h, G. F., Pi ich, C. L., Sie akowski, M. R., Woehl, M. A., Sakakiba a, C. N., Fe nandes de
Souza, C., e al. (2017). Bac e ial cellulose in biomedical applica ions: A e iew. In e na ional
Jou nal o Biological Mac omolecules, 104, 97–106.
h ps://doi.o g/10.1016/j.ijbiomac.2017.05.171.
Pin o, E. R. P., Ba ud, H. S., Sil a, R. R., Palmie i, M., Poli o, W. L., Calil, V. L., e al. (2015).
T anspa en composi es p epa ed om bac e ial cellulose and cas o oil based polyu e hane as
subs a es o lexible OLEDs. Jou nal o Ma e ials Chemis y C, 3, 11557–11774.
h ps://doi.o g/10.1039/c5 c02359a.
Pin o, E. R. P., Ba ud, H. S., Poli o, W. L., Ribei o, S. J. L., & Messaddeq, Y. (2013). P epa a ion
and cha ac e iza ion o he bac e ial cellulose/polyu e hane nanocomposi es. Jou nal o The mal
Analysis and Calo ime y, 114, 549–555. h ps://doi.o g/10.1007/s10973-013-3001-y.
Popescu, M.-C., Doga u, B.-I., & Popescu, C.-M. (2017). The in luence o cellulose nanoc ys als
con en on he wa e so p ion p ope ies o bio-based composi e ilms. Ma e ials & Design, 132,
170–177. h ps://doi.o g/10.1016/j.ma des.2017.06.067.
Ra na, D., & Ka ge -Kocsis, J. (2008). Recen ad ances in shape memo y polyme s and
composi es: A e iew. Jou nal o Ma e ials Science, 43, 254–269.
h ps://doi.o g/10.1007/s10853-007-2176-7.
San ama ia-Echa , A., Uga e, L., Ga cía-As ain, C., A belaiz, A., Co cue a, M. A., & Eceiza,
A. (2016). Cellulose nanoc ys als ein o ced en i onmen ally- iendly wa e bo ne polyu e hane
nanocomposi es. Ca bohyd a e Polyme s, 151, 1203–1209.
Small, W., Singhal, P., Wilson, T. S., & Mai land, D. J. (2010). Biomedical applica ions o
he mally ac i a ed shape memo y polyme s. Jou nal o Ma e ials Chemis y, 20, 3356–3366.
h ps://doi.o g/10.1016/j.ca bpol.2016.06.069.
Solanki, A., Das, M., & Thako e, S. (2018). A e iew on ca bohyd a e embedded polyu e hanes:
An eme ging a ea in he scope o biomedical applica ions. Ca bohyd a e Polyme s, 181, 1003–
1016. h ps://doi.o g/10.1016/j.ca bpol.2017.11.049.
Song, L., Li, Y., Xiong, Z., Pan, L., Luo, Q., Xu, X., e al. (2018). Wa e -Induced shape memo y
e ec o nanocellulose pape s om sisal cellulose nano ibe s wi h g aphene oxide. Ca boyd a e
Polyme s, 179, 110–117. h ps://doi.o g/10.1016/j.ca bpol.2017.09.078.
Sun, W., & Huang, M. (2010). The mo/mois u e esponsi e shape-memo y polyme o possible
su ge y/ope a ion inside li ing cells in u u e. Ma e ials & Design, 31, 2684–2689.
h ps://doi.o g/10.1016/j.ma des.2009.11.036.
Thomas, B., Raj, M. C., A hi a, K. B., Rubiyah, M. H., Joy, J., Moo es, A., e al. (2018).
Nanocellulose, a e sa ile g een pla o m: F om biosou ces o ma e ials and hei applica ions.
Chemical Re iews, 118, 11575–11625. h ps://doi.o g/10.1021/acs.chem e .7b00627.
Ul-Islam, M., Khan, T., & Pa k, J. K. (2012). Wa e holding and elease p ope ies o bac e ial
cellulose ob ained by in si u and ex si u modi ica ion. Ca bohyd a e Polyme s, 88, 596–603.
h ps://doi.o g/10.1016/j.ca bpol.2012.01.006.
U bina, L., Alga , I., Ga cía-As ain, C., Gabilondo, N., González, A., Co cue a, M. A., e al.
(2016). Biodeg adable composi es wi h imp o ed ba ie p ope ies and anspa ency om he
imp egna ion o PLA o bac e ial cellulose memb anes. Jou nal o Applied Polyme Science,
24(5), 2071–52082. h ps://doi.o g/10.1002/app.43669.
U bina, L., He nández-A iaga, A. M., Eceiza, A., Gabilondo, N., Co cue a, M. A., P ie o, M. A.,
e al. (2017). By-p oduc s o he cide p oduc ion: An al e na i e sou ce o nu ien s o p oduce
bac e ial cellulose. Cellulose, 24, 2071–2082. h ps://doi.o g/10.1007/s10570-017-1263-4.
Wan, T., & Chen, D. (2018). Mechanical enhancemen o sel -healing wa e bo ne polyu e hane
by g aphene oxide. P og ess in O ganic Coa ings, 121, 73–79.
h ps://doi.o g/10.1016/j.po gcoa .2018.04.016.
Wang, Y., Cheng, Z., Liu, Z., Kang, H., & Liu, Y. (2018). Cellulose nano ibe s/polyu e hane
shape memo y composi es wi h as wa e - esponsi i y. Jou nal o Ma e ials Chemisi y B, 6,
1668–1677. h ps://doi.o g/10.1039/c7 b03069j.
Wang, X., Zhang, Y., Liang, H., Zhou, X., Fang, C., Zhang, C., e al. (2019). Syn hesis and
p ope ies o cas o oil-based wa e bo ne polyu e hane/sodium algina e composi es wi h unable
p ope ies. Ca bohyd a e Polyme s, 208, 391–397. h ps://doi.o g/10.1016/j.ca bpol.2018.12.090.
Wu, J., Zheng, Y., Song, W., Luan, J., Wen, X., Wu, Z., e al. (2014). In si u syn hesis o sil e -
nanopa icles/bac e ial cellulose composi es o slow- eleased an imic obial wound d essing.
Ca bohyd a e Polyme s, 102, 762–771. h ps://doi.o g/10.1016/j.ca bpol.2013.10.093.
Wu, G.-M., Liu, G- ., Chen, J., & Kong, Z-w. (2017). P epa a ion and p ope ies o he mose
composi e ilms om wo-componen wa e bo ne polyu e hane wi h low loading le el
nano ib illa ed cellulose. P og ess in O ganic Coa ings, 106, 170–176.
h ps://doi.o g/10.1016/j.po gcoa .2016.10.031.
Yildi im, E., Yu se e , M., Yilgo , E., Yilgo , I., & Wilkes, G. L. (2018). Tempe a u e dependen
changes in he hyd ogen bonded ha d segmen ne wo k and mic ophase mo phology in a model
polyu e hane: Expe imen al and simula ion s udies. Jou nal o polyme science, pa B: Polyme s
physics, 56, 182–192. h ps://doi.o g/10.1002/polb.24532.
Zhang, Z-x., Qi, X-d., Li, S- ., Yang, J-h., Zhang, N., Huang, T., e al. (2018). Wa e ac ua ed
shape-memo y and mechanically-adap i e poly(e hylene inyl ace a e) achie ed by adding
hyd ophilic poly ( inyl alcohol). Eu opean Polyme Jou nal, 98, 237–245.
h ps://doi.o g/10.1016/j.eu polymj.2017.11.031.
Zhang, P., Xu, P., Fan, H., Sun, Z., & Wen, J. (2019). Co alen ly unc ionalized g aphene owa ds
molecula -le el dispe sed wa e bo ne polyu e hane nanocomposi e wi h balanced comp ehensi e
pe o mance. Applied Su ace Science, 471, 595–606.
h ps://doi.o g/10.1016/j.apsusc.2018.11.235.
Zhou, X., Li, Y., Fang, C., Li, S., Cheng, Y., Lei, W., e al. (2015). Recen ad ances in syn hesis
o wa e bo ne polyu e hane and hei applica ion in wa e -based ink: A e iew. Jou nal o
Ma e ials Science & Technology, 31, 708–722. h ps://doi.o g/10.1016/j.jms .2015.03.002.
Zhu, Y., Hu, J., Luo, H., Young, R. J., Deng, L., Zhang, S., e al. (2012). Rapidly swi chable
wa e -sensi i e shape-memo y cellulose/elas ome nano-composi es. So Ma e , 8, 2509–2517.
h ps://doi.o g/10.1039/c2sm07035a.
