Cus omized hyb id and NIR-ligh igge ed
he mo esponsi e d ug deli e y mic opa icles syn he ized
by pho opolyme iza ion in a one-s ep low ocusing
con inuous mic o eac o
Isabel O iz de Solo zano†‡§*, G acia Mendoza†‡,, Manuel A uebo†‡§*, Vic o
Sebas ian†‡§
†Depa men o Chemical Enginee ing. A agon Ins i u e o Nanoscience (INA) and
Ins i u o de Ciencia de Ma e iales de A agón (ICMA), Uni e sidad de Za agoza-CSIC,
Uni e si y o Za agoza, Campus Río Eb o-Edi icio I+D, C/ Poe a Ma iano Esquillo
S/N, 50018-Za agoza, Spain
‡A agon Heal h Resea ch Ins i u e (IIS A agón), 50009 Za agoza, Spain
§Ne wo king Resea ch Cen e on Bioenginee ing, Bioma e ials and Nanomedicine,
CIBER-BBN, 28029-Mad id, Spain
*Co esponding au ho : [email p o ec ed]; a uebom@uniza .es.
KEYWORDS: The mo esponsi e; pho opolyme iza ion; bupi acaine; mic opa icles;
LED; mic o luidics; coaxial; PNIPAm, Hollow gold nanopa icles, NIR-ligh igge ed,
d ug deli e y.
ABSTRACT
Pho opolyme iza ion is a selec i e echnique ha akes ad an age o ligh -sensi i e
molecules o ini ia e and p opaga e monome ic s uc u es o ende co alen ly bonded
mac omolecula ma e ials known as polyme s. He ein, we p esen a no el one-s ep
mic o luidic syn hesis o cus omized hyb id- he mo esponsi e Poly(N-
isop opylac ylamide) (PNIPAm) based mic opa icles (MPs) con aining plasmonic
hollow gold nanopa icles (HGNPs) and bupi acaine (BVP) used as a model d ug.
Those hyb id mic opa icles we e p epa ed using a low- ocusing mic o eac o coupled
o a UV LED de ice buil wi h a simple ou e PTFE ubing and an inne lexible
capilla y. Di e en ubing cha ac e is ics and low a e a ios we e al e ed in o de o
con ol he size o he esul ing mic opa icles. In addi ion, componen s such as
monome , c osslinke and pho oini ia o concen a ions, as well as LED in ensi y and
i adia ion ime we e uned o ob ain di e en MPs and hei cha ac e is ics and
polyme iza ion a es we e compa ed by Gel pe mea ion Ch oma og aphy (GPC).
The mo esponsi e p ope ies we e analyzed and he p esence o HGNPs was con i med
in ligh -ac i a ed igge ed d ug elease applica ions. Bupi acaine loading and elease
s udies we e demons a ed wi h he esul ing hollow and solid mic opa icles (which
we e ob ained depending on he polyme iza ion a e used) and hei empe a u e
esponsi eness was assessed using a NIR lase when HGNPs we e p esen in he
cons uc s. Finally, cy o oxici y s udies, cell-cycle a es and apop o ic induc ion we e
ca ied ou o ce i y hei sui abili y o u he biomedical applica ions o be used as
igge able d ug depo s.
1 In oduc ion
Enginee ed polyme ic mic opa icles (MPs) ha e become e y in e es ing
mul i unc ional pla o ms in biomedicine.1 Biosensing2, d ug deli e y3 o issue
enginee ing4 a e some o he a eas in which MPs s andou as ad anced ma e ials a he
cu ing edge o unc ional polyme s. Howe e , hei biological sui abili y depends on
hei p ope ies, which ha e a di ec ela ionship wi h hei size, composi ion, s uc u e
and con igu a ion. Thus, con olling hem has u ned in o he key challenge o
esea che s o he ield.5,6
Con en ional discon inuous polyme iza ion me hods, such as emulsion6,7, dispe sion8 o
sp aying9, do no allow a good con ol o e he inal MPs p ope ies. This usually leads
o polydispe si y and low ep oducibili y10,11,12 e en a educed p oduc ion scales due o
he he e ogeneous dis ibu ion o eac an s and empe a u es and an insu icien mixing.
In he las yea s, he p oduc ion o monodispe se pa icles o biomedical use has
s imula ed g ea in e es in a my iad o scien i ic and enginee ing ields o ake
ad an age o hei bene i s in con olling d ug elease a es and ob aining eliable
esul s. Con inuous mic o luidic de ices ha e in oduced di e en app oaches o
o e come hese p e ious limi a ions.13,14 Mic o-sized channels pe mi o handle luid
lows a he mic oscale e y p ecisely leading o highly ep oducible syn hesis and
na ow size dis ibu ions in he esul ing MPs due o an e icien mixing d i en by
molecula di usion.15,16 Mic o luidic sys ems o e also some ad an ages agains
classical sys ems17: homogenous eac ion condi ions, po abili y, high sensi i i y, low
ene gy consump ion, highly in eg a ed mul i unc ion and easy scalabili y.
D ople mic o luidics has been demons a ed o be one o he mos e icien
mic o luidic app oaches hanks o he acile con ol o he eac ion condi ions and as
MP o ma ion18. Two ypes o low ocusing de ices ha e been conside ed in he
d ople based mic o luidics app oach o p oduce sphe ical MP19: 1) a chip-based low
ocusing de ice wi h a T o Ψ shaped mic ochannel in eg a ed on a chip, and 2) a
capilla y-based low ocusing de ice (coaxially aligned mic ocapilla ies). Glass-made
mic ochips and capilla ies a e e y expensi e, as well as agile ma e ials.20,21 Glass
manu ac u ing has he limi a ions o a complica ed welding and gas igh sealing, a
di icul in eg a ion in a mac o-sys em (connec ing o he mac o scale) and also any
pos e io modi ica ion is no economically iable. On he o he hand, he design and
ab ica ion o mic o luidic silicon-based chips could be expensi e, labou -in ensi e and
equi es clean oom acili ies. Fu he mo e, polyme iza ion eac ions can easily p omo e
chip blockage, p ecluding a s able low. Consequen ly, while some p oblems can be
o e come by ca e ul choice o he eac ion condi ions, he e is a need o low-cos ,
modula componen s ha can be easily assembled in o low- ocusing de ices by use s
lacking p o iciency o access o mic o ab ica ion acili ies22. In his sense, polyme ic
PTFE coaxially aligned capilla ies p o ide a eal al e na i e hanks o hei ease o
ab ica ion and modi ica ion, lexibili y, e-usabili y and excellen chemical and
mechanical p ope ies and op ical anspa ency.23,24
Mic opa icle p ecipi a ion can be p o oked by ionic c osslinking25, empe a u e
induced gela ion26 o by polyme iza ion27. Polyme iza ion can be ca ied ou upon hea
assis ed adical gene a ion o by UV i adia ed pho opolyme iza ion among o he
echniques.28 In his sense, pho opolyme iza ion ep esen s a as p ocess ha ing a
p ecise con ol o e he cha ac e is ics o he inal polyme a e he induc ion by UV-
ligh lamp exposu e20 a oiding he po en ial p oblems ha high empe a u e may
p o oke on biomolecules used du ing he syn hesis. The use o ligh emi ing diodes
(LEDs) holds g ea p omise in he ield o pho opolyme iza ion due he ollowing
ad an ages29: 1) low ene gy consump ion, 2) no ozone elease, 3) low hea gene a ion,
4) low ope a ing cos s and main enance, 5) high li e imes, 6) easy and sa e handling, 7)
100% ou pu immedia ely ob ained a e u n-on, and 8) easily con olled in ensi y.
Then, he assembly o LED de ices and mic o luidics o con ol he polyme iza ion
p ocess is an in e es ing al e na i e o deal wi h he con olled p oduc ion o polyme
MPs. Polyme iza ion o d ople s can be accomplished upon inco po a ing a cu ing agen
di ec ly in o he d ople , o in he con inuous phase. The pho oini ia o solubili y in he
dispe se o con inuous phase will be he key alue o selec he polyme iza ion
app oach. D ople polyme iza ion can be accomplished du ing d ople o ma ion, inside
he mic o eac o chip30,31, o in a o ally sepa a ed s ep o -chip32,33,34. Time, in ensi y o
ligh , and eac ion componen s de e mine he composi ion, size and p ope ies o he
syn he ized MPs.35,36
MPs p e ail as d ug deli e y ehicles, conside ing ha a la ge numbe o p oduc s
based on polyme MPs ha e al eady been comme cialized. To name a ew: 1) T els a ®
injec able mic osphe es loaded wi h ip o elin pamoa e and Enan one LP® loaded wi h
Leup o elin and Lup on® depo loaded wi h leup olide ace a e o p os a e cance
ea men . 2) Sandos a in LAR® depo loaded wi h oc eo ide ace a e and Soma ulin L
loaded wi h lan eo ide o ac omegaly ea men . 3) Rispe dal Cons a® depo loaded
wi h ispe idone o he ea men o schizoph enia as well as o he longe - e m
ea men o Bipola I diso de . 4) Nu opin® depo loaded wi h ecombinan human
g ow h ho mone as g ow h ho mone egula o ; and 5) Vi i ol® depo loaded wi h
nal exone o ea ing alcohol dependence and p e en ing elapse o opioid
dependence. One o he mos p omising MPs so a o biomedical applica ions a e gel
s uc u es.37 Thei capabili y o espond o se e al ex e nal s imuli such as empe a u e38
o pH39 make hem ex emely in e es ing in biomedicine. Among hem, mic ogels based
on he mo esponsi e polyme s a e widely s udied. One o hem, poly(N-

isop opylac ylamide) (PNIPAm) p esen s a b oad a ie y o oppo uni ies in o de o
cus omize he inal p oduc acco ding o he desi ed applica ion40,41,42. C osslinking,
monome and ini ia o concen a ion as well as low a e a io, i adia ion ime and
in ensi y o he UV-ligh sou ce, lead o MPs wi h comple ely di e en p ope ies43.
Mechanical and he mo esponsi e p ope ies o esul ed MPs a e de e mined by he
ine- uning o he syn hesis a iables. Syn hesis o hyb id PNIPAm MPs has been
conduc ed in con en ional ba ch ype eac o s, showing he possibili y o combine he
unc ion o bo h he mo esponsi e polyme s and s imuli sensi i e ino ganic NPs. Fo
example, Ekici e al.44 inco po a ed magne ic i on NPs in hyalu onic acid-PNIPAm
nanogels ob aining a double magne ism- empe a u e esponsi e sys em. Mo eo e ,
mic o luidics allows he p ecise and con olled encapsula ion in MPs o di e en
componen s om luo escen dyes45 o li e cells46,47 ha can be use ul in d ug deli e y
s udies o biosensing48. In gene al, he loading o ca gos capable o espond o ex e nal
s imuli such as ligh , ul asound o magne ic ields a e e y in e es ing o explo e he
e sa ili y o hyb id MPs. Supe pa amagne ic Fe3O4 NPs (SPIONs) ha e also been used
as igge s o achie ing a bu s elease o lipophilic subs ances encapsula ed in oil
co es om co e-shell PNIPAm mic opa icles a e induc ion by al e na ing magne ic
ields49. Also, gold nanos uc u es ha e been widely used o ligh - igge ed d ug
elease om PNIPAm mic ocapsules42. Wang e al.50 ecen ly showed he possibili y o
ac i a e shape ansi ion o Au nano ods-PNIPAm hyb id MPs using high powe NIR
lase i adia ion. Those hyb id MPs we e p oduced in se e al s ages, esul ing in a semi-
con inuous p ocess: 1) D op o ma ion in con inuous low, 2) D op sedimen a ion in
s agnan condi ions o 5 minu es a e collec ion in o de o ine une he shape and 3)
D op pho opolyme iza ion in s agnan condi ions unde 365 nm UV ligh du ing 5 min.
Kim e al.51 also used he same mic o luidic app oach o gene a e hollow PNIPAm
mic ocapsules con aining gold nano ods. Bu in his las case he double-emulsion
d ople s we e incuba ed in a glass ial o 12 hou s a oom empe a u e o comple e he
polyme iza ion, u ning i also as a semi-con inuous p ocess, which ep esen s a
d awback o inc ease he p oduc i i y. Al hough a high con ol o e he size and
he mo esponsi e p ope ies o he MPs we e achie ed by he epo ed me hods50,51, he
p oduc ion o PNIPAm hyb id MPs co-loading in he same MP d ugs and me al
nanopa icles (HGNPs) using a single low de ice in con inuous ashion by
pho opolyme iza ion is s ill lacking. The de elopmen o a new low syn hesis app oach
ha enables o add ess p e ious d awbacks would accele a e he ansla ion o hyb id
MPs applica ions o hei u u e biomedical use.
He ein, we p esen a acile, low-cos , and e icien me hod o p oducing d ug loaded
HGNPs-PNIPAm hyb id MPs, capable o une he s uc u e o he d ug ca ie MPs in
o de o achie e di e en pha macokine ics in d ug deli e y applica ions. A capilla y-
based low ocusing de ice wi h coaxially aligned mic o capilla ies was coupled o a
UV-LED o acili a e he con olled d ople o ma ion and as polyme iza ion a
di e en syn hesis condi ions ob aining cus omized MPs o pu pose-speci ic d ug
deli e y applica ions. Flow dynamics, eagen s a io and UV exposu e ime we e
s udied o achie e wo ypes o MPs ha beha e in a di e en way, acco dingly o he
ype o d ug deli e y a ge ed. The e icien simul aneous loading o a d ug and HGNPs
is also desc ibed. HGNPs we e selec ed as igge NPs o on-demand ligh - esponsi e
d ug deli e y. On i s pa , bupi acaine was used as a model d ug in o de o es he
pha macokine ic esponse o MPs wi h di e en shell hicknesses oge he wi h he
e e sible empe a u e-dependence o hyb id MPs sizes. HGNPs immobilized in he
hyd ogel ne wo k enable he localized hea ing o he MPs a e NIR ligh illumina ion,
p o iding he emo e con ol in he pe meabili y o he shell and he igge ed elease o
bupi acaine. Cy o oxici y analyses we e ca ied ou wi h he ma e ials de eloped in wo
di e en cell lines s udying hei subcy o oxic concen a ion and hei e ec in cell
memb ane and cell cycle.
2 Ma e ials and me hods
2.1 Ma e ials
N-isop opylac ylamide ≥99% (NIPAM), N,N’-me hylenebis(ac ylamide) 99% (BIS),
Span® 80, hexadecane, Reagen Plus®, 99%, cobal chlo ide hexahyd a e (ACS eagen
g ade), sodium ci a e ibasic dihyd a e (98%), poly( inylpy olidone) (PVP, Mw =
55000 Da), sodium bo ohyd ide (99%), gold(III) chlo ide hyd a e (50% Au basis) and
bupi acaine hyd ochlo ide monohyd a e (99%) we e pu chased om Sigma-Ald ich.
2,2 Die hoxyace ophenone (DEAP) was pu chased om Ac os O ganics.
2.2 Syn hesis o hollow gold nanopa icles (HGNPs)
Hollow gold nanopa icles (HGNPs) we e syn he ized ollowing p e ious wo ks
de eloped in ou g oup.52,53 In b ie , 400 mL o deionized (DI) wa e (0.1 % o 0.35 M
cobal chlo ide hexahyd a e) and 1.6 mL o 0.1 M sodium ci a e ihyd a e we e
deoxygena ed in a wo-necked ound-bo om lask by bubbling he solu ion wi h a gon
gas o 45 min. Bo h, 2 mL o 1 w .% o PVP and 400 µL o 1.0 M sodium bo ohyd ide,
we e added o he p e ious solu ion unde magne ic s i ing o ming cobal NPs. A gon
lux and s i ing we e kep o 15 min. A e ha , 380 mL o he esul ing NPs
dispe sion was ans e ed o a beake con aining 120 mL o DI wa e and 180 µL o 0.1
M gold (III) chlo ide hyd a e unde s i ing. Magne ic s i ing unde oom empe a u e
condi ions was sus ained o 30 min un il a comple e oxida ion o he esidual cobal
was p oduced. A g een colo ed dispe sion indica es he p esence o HGNPs, which we e
subsequen ly washed by se e al cen i uga ion s eps.
2.3 Mic o eac o cha ac e is ics
To p oduce HGNPs-PNIPAm hyb id mic opa icles, a coaxial capilla y mic o luidic
de ice was assembled (Figu e 1). The dimensions o he inne and ou e capilla ies we e
modi ied o une he esul ing mic opa icle sizes. The inne and ou e capilla ies we e
made o PEEK (hyd ophilic) and PTFE (hyd ophobic), espec i ely. The inne capilla y
diame e was a ied om 150 µm o 25 µm, whe eas ou e capilla y diame e was
al e ed om 560 µm o 790 µm. The dispe sed phase (aqueous) was injec ed a low
a es o low (2.5-30 µL/min) in o de o a oid co-lamina lows and uns eady
mic opa icle o ma ion. The inne capilla y was coaxially localized unde an op ical
mic oscope in o de ge an axisymme ic low- ocusing de ice whe e he dispe sed
phase is su ounded symme ically by he con inuous phase. The coaxial capilla y
eac o was suppo ed in a polyme housing ab ica ed by 3D-p in ing o a oid
capilla ies misalignmen and o a o luid dynamic ep oducibili y. In he downs eam
low a e d ople o ma ion, a UV i adia ion p o ided by a 4.6 W LED (365 nm
wa eleng h) was used o ac i a e he pho oini ia o and p omo e he o ma ion o
adicals o polyme ize he monome s inside he esul ed d ople s. LED in ensi y was
modula ed in o de o ob ain he op imum polyme iza ion a e.
Two di e en sy inge pumps (Ha a d Appa a us PHD ULTRA™) a selec ed low
a es we e used o con ol he d op esidence ime o he injec ed eagen s eams.
Finally, mic opa icles we e collec ed in a wa e ecipien in o de o a oid he blockage
o he ou e ubing.
p omo e a as polyme iza ion du ing he d op low in he mic o luidic sys em. The
esidence ime o o med d ople s is usually la ge in d ipping mode because low low
a es (inne and ou e phases) a e equi ed. In addi ion, d ople s p oduced unde
d ipping mode a e pinched o nea he inne capilla y ip, whe eas in je ing egime,
d ople s a e pinched o om an ex ended h ead gene a ed downs eam o he inne
capilla y ip. D ople o ma ion in co- lowing mic o luidic sys ems is sensi i e o he
iscous shea s ess o he ex e nal low and he capilla y p essu e esis ing he
de o ma ion o he in e nal phase.20 The dimensionless capilla y numbe (Ca) compa es
he ela i e impo ance be ween he ic ion o ce and he su ace ension. Then, we
conside ed p e ious s udies o d ople o ma ion in d ipping mode using simila
luids54, o selec he luid dynamic condi ions o ge s able d ople o ma ion. Se e al
ac o s such as s eam composi ion o capilla y dimensions we e uned in o de o
con ol he mo phology and he polyme iza ion e iciency o he sys em. The e ec o
hose pa ame e s will be discussed in he ollowing sec ions.
3.2 Mic opa icles Mo phology and dimensions
I is well accep ed ha he size o d ople o ma ion in a co- lowing mic o luidic de ice
depends on he capilla ies dimensions, and inne and ou e low a es. These pa ame e s
a e highly impo an because hey can modula e he compe i ion be ween iscous shea
s ess o he ex e nal s eam and capilla y p essu e esis ing de o ma ion o he in e nal
s eam. In his wo k, we ha e selec ed wo di e en inne and ou e capilla ies o une
he size o MPs unde a s able d ople o ma ion in d ipping egime.
Figu e 2 shows he a e aged MPs diame e ob ained unde di e en capilla y
dimensions and low a es. In gene al he mos impo an e ec is obse ed when he
ex e nal PTFE capilla y was modi ied.

Figu e 2: A e age MPs size depending on low a io and inne diame e o he mic o ea o
channels. a) and b) show he esul s o he smalles ex e nal PTFE ubing (560 µm) and la ge
(150 µm) and small (25 µm) in e nal capilla y, espec i ely. c) and d) p esen he esul s o he
la ge PTFE ubing (790 µm) and la ge (150 µm) and small (25 µm) in e nal capilla y,
espec i ely. Same colo s ep esen he same inne low. Fo each o hem, om le o igh
con inuous low inc eases. In e ed mic oscope images o MPs syn hesized wi h low a io o 5-
100 L/min a e shown in: e) ID: 150 µm and OD 560 µm; ) ID: 25 µm and OD 560 µm; g) ID:
150 µm and OD 790 µm; h) ID: 25 µm and OD 790 µm. i) Summa y and compa ison o MPs
diame e syn hesized wi h wo di e en low a ios and all combina ions o in e nal and ex e nal
ubing diame e s.
Smalle ou e capilla y yielded o mic opa icles be ween 400 and 500 µm (Figu e 2 b)
and a)); while a la ge ou e capilla y diame e gene a ed MPs o e 700 µm in diame e
(Figu e 2 c) and d)). These esul s can be a ionalized by he d ople o ma ion
mechanism. The junc ion close o he inne capilla y ip is obs uc ed by he inne luid
p o usion. The con inuous low close o he p o usion is es ic ed as he p o usion is
enla ged, es ablishing a p essu e g adien ac oss he p o usion. The d ople is pinched
o once he p essu e g adien in he con inuous low is su icien ly high o o e come
he capilla y p essu e inside he dispe sed d op. Viscous shea o ces a e usually
su icien ly la ge o pinch o he d ople be o e i g ows o block he ou e capilla y55.
Then, he d ople diame e is usually smalle han he ou e channel diame e . In
addi ion, he d ople diame e is in e sely p opo ional o he a e age eloci y o he
ca ie low because he d ag o ce inc eases as he con inuous phase eloci y does56.
This ac con i ms ha he MPs diame e inc eases as he low a e o he ou e s eam is
dec eased when he inne low a e is kep cons an ( he d ug o ce is educed). On he
o he hand, he inne capilla y size mainly a ec s MPs polydispe si y. A mo e con ined
d ople o ma ion bene i ed om a smalle capilla y, gene a ing na owe diame e
de ia ion. This is e lec ed in he di e en coe icien o a iance (CV) o MPs sizes
ob ained wi h he ou sys ems s udied. While MPs CVs ob ained wi h la ge inne
capilla y (790 µm) ha e alues be ween 15 nm (when inne low a e is 10 µL/min) o
100 nm (when con inuous phase ge s o 30 µL/min), a maximum a iance o 30 nm is
achie ed in expe imen s when using 25 µm inne capilla y. Simila esul s we e
p e iously obse ed wi h analogous pla o ms.57 D ipping equency p oduc ion ( ) o
all samples anges be ween 7.5 Hz o 0.2 Hz depending on he inne low a e and inal
size o MPs. Slow low a e (2.5 µL/min) and la ge inal MPs (~700 µm) lead o slow
d ople o ma ion and equencies a ound 0.2 Hz. Howe e , inc easing he inne low
a e up o 30 µL/min and con ining he size o he ou e capilla y, and hus he inal
MPs size (~400 µm), p o oked a as e d ople o ma ion and equencies o e 7.5 Hz.
I is o pa amoun impo ance o highligh ha his low d ipping equency was equi ed
in o de o ge a comple e polyme iza ion eac ion in con inuous ashion, a ac ha is
no el in his wo k.
Acco ding o he a o emen ioned polyme iza ion equi emen s, i is essen ial o achie e
ce ain le el o polyme iza ion a e in o de o ob ain s able MPs wi h a compe en
unc ionali y o a po en ial biomedical use. This ac , oge he wi h he luid dynamic
es ic ions equi ed o achie e a s able d ople gene a ion limi he a ailable phase low
a es. In his wo k a single LED sou ce has been conside ed, howe e using se e al
LEDs in se ies would po en ially inc ease he i adia ion ime allowing he use o la ge
low a es.
I has been demons a ed ha d ople size in coaxial low pla o ms wi h low a ios
wi hin ou wo king limi s do no change signi ican ly21. Howe e , i can s ill ha e small
e ec s on he inal MPs sizes. S a is ical analysis o ou esul s (Figu e S1) showed
some signi ican di e ences in almos all low a io combina ions sugges ing ha as
men ioned be o e, keeping he same inne low, he inc ease in he con inuous low a e
o all samples led o a sligh dec ease in he inal MPs size. In all cases, monodispe se
MPs we e ob ained wi h a ia ions less han 15 % o hei size in he wo s -case
scena io (150 µm inne capilla y) bu wi h a e age CV o 2.5 % in he mos s able cases
(25 µm inne capilla y).
3.3 Polyme iza ion e iciency and he mo esponsi e p ope ies
Pho opolyme iza ion eac ions depend on a se o di e en a iables (monome ,
pho oini ia o and c osslinke concen a ions and LED i adiance and ime o
i adia ion) and some o hem we e s udied using his co- lowing mic o luidic de ice.
Conside ing ha he main goal o his esea ch was o p oduce MPs wi h on-demand
ligh - esponsi e d ug deli e y abili y and allow a emo e con ol o he polyme ic shell
pe meabili y, we a emp ed he analysis o olume a io sh inkage in he esul ed MPs.
This pa ame e was also selec ed as a key ac o o analyze he polyme iza ion
e iciency and he mo- esponsi e p ope ies. I mus be highligh ed ha ei he an
unsuccess ul o limi ed polyme iza ion yield can induce MP collapse, agg ega ion o a
sca ce olume sh inkage upon a empe a u e a ia ion in he lowe c i ical solu ion
empe a u e (LCST) ange.
On he o he hand, c osslinking agen en ails a key ole in he sh inkage beha io o any
hyd ogel. Highe concen a ion o c osslinking molecules among o med polyme
chains leads o s e ic di icul ies o achie e a comple e sh inkage o he hyd ogel om
i s swollen hyd a ed s a e o i s sh unken dehyd a ed o m.
Figu e 3: Volume change wi h empe a u e o a) MPs syn he ized wi h 250 mg/mL monome
concen a ion and 40 µL DEAP and di e en c osslinke concen a ions; b) o g) Time-lapse
mic oscopy images o MPs syn he ized wi h he same condi ions a di e en empe a u es. All
samples we e syn he ized unde low a io o 5/100 µL/min, inne capilla y diame e : 25 µm
and ou e capilla y: 560 µm.
Figu e 3 a) ep esen s he olume a io wi h empe a u e ob ained o h ee di e en
samples con aining 25, 50 and 75 monome -c osslinke NIPAM-BIS a io, espec i ely.
The esul s con i m ha all MPs p oduced show a as esponse o en i onmen al
empe a u e. I is ele an ha d ama ic changes occu be ween 32-39ºC (LCST o
PNIPAm is 32ºC). This may be a ibu ed o polydispe si y in he polyme chain leng hs
and c osslinking deg ee58,59. I was also con i med ha he highes he NIPAM-BIS
a io, he la ges he a e o olume change o he pho o-polyme ized MPs is. The
olume change in PNIPAm MPs is a ionalized because MPs a e in a swollen and
hyd ophilic s a e below he LCST ha is swi ched o a sh unken and hyd ophobic s a e
abo e he LCST. The s a e ansi ion was s udied in a ime-lapse in e ed mic oscope a
di e en empe a u es. Figu es 3 b) o g) depic ep esen a i e op ical images a
di e en en i onmen al empe a u es, whe e he d ama ic educ ion o MPs size abo e
he LCST is clea ly obse ed as well as he e e sibili y o his p ocess once he
empe a u e dec eases. Simila beha io was also obse ed when monome
concen a ion and monome /c osslinke a ios (NIPAM/BIS) we e modi ied (Figu e S2)
con i ming he he mo esponsi e beha io o he inal polyme con o ming MPs.
Polyme iza ion e iciency is ela ed o he polyme iza ion a e and i has di ec in luence
in he leng h o he polyme ic chains o med and he possibili y o collapse and educe
hei olume and size unde high empe a u es. Figu e 4 shows he e ec o monome
(NIPAM) and pho oini ia o (DEAP) concen a ion on inal molecula weigh o
esul ed MPs and hei abili y o educe hei olume unde empe a u e a ia ions.

Figu e 4: a) Volume a io obse ed in samples syn hesized wi h di e en monome and
pho oini ia o concen a ions; b) GPC esul s o h ee di e en samples wi h di e en
DEAP/monome a io; c) Volume a io shown o wo samples polyme ized wi h wo di e en
LED ligh i adia ion in ensi ies.
Figu e 4 a) demons a es ha he pho oini ia o (DEAP) concen a ion is c ucial o
achie e a desi ed g ade o polyme iza ion ha is high enough o endow MPs o ma ion
wi h he app op ia e a e o olume change and he mosensi i e beha io . A high DEAP
concen a ion leads o a high concen a ion o adical species ha ini ia e
polyme iza ion. Howe e , he as es he polyme iza ion is, he sho e he polyme
chains o med and hen, he less he olume change when he en i onmen al
empe a u e inc eases. This obse a ion was also con i med by Gel Pe mea ion
Ch oma og aphy (GPC) (Figu e 4 b). The GPC ch oma og am p o ides he molecula
weigh dis ibu ion o he esul ing species, labeling he main molecula weigh peaks
(Figu e 4-b). Acco ding o GPC analysis, he molecula weigh o he esul ed polyme
is lowe as he pho oini ia o concen a ion is inc eased because a high densi y o
monome building blocks is ac i a ed by he adical species. This ac was also
e idenced by in e ed mic oscopy, whe e op ical images aken a di e en
en i onmen al empe a u es depic ed a signi ican sh inkage as he pho oini ia o
con en was dec eased (Figu e S3). On he o he hand, he ac i i y o he pho oini ia o
molecules is de e mined by hei s imula ion sou ce, he UV-LED ligh in ou sys em.
The i adiance o LED sou ce de e mines he eloci y o he polyme iza ion p ocess
leading o di e en polyme chain leng hs and hus o di e en pho o he mal p ope ies.
The e is an in ensi y h eshold ha de e mines he minimum in ensi y necessa y in o de
o ob ain igid and mechanically s able MPs below he one whe e no enough polyme
chains we e o med, and MPs did no keep hei shape a e exi ing he mic o luidic
pla o m. In ensi ies om 0.2 o 0.9 A we e used in ou s udy inding he h eshold
desc ibed be o e se a 0.7 A. A in ensi ies o 0.2 and 0.4 A no MPs o ma ion ook
place and easily b eakable MPs we e ob ained, espec i ely. Howe e , abo e 0.7 A no
signi ican changes we e obse ed when UV-LED ligh in ensi y was inc eased o 0.9 A
(Figu e 4 c) in ou sys em.
As he polyme iza ion is ini ia ed a he in e ace o he aqueous/o ganic phase o
de ached d ople s, he di usion o adical species ha conduc he polyme iza ion
eac ion migh ha e a ele an ole in he MPs s uc u e. In hese e ms, hollow o solid
MPs could be p oduced depending on he adical species d ople in e naliza ion. Kim e
al.31 co obo a ed he ela ionship o a high polyme iza ion a io wi h he imp o ed
mechanical s eng h o he esul ed MPs. Long i adia ion imes, high DEAP
concen a ion and high i adia ion in ensi y a o ed o ob ain a solid s uc u e and
mechanically esis an MPs. Howe e , he highly solid MPs ob ained unde hese
condi ions esul ed in low sh inkage a ios (~24 / %).
The polye hylene glycol diac yla e (PEGDA) pho opolyme iza ion eac ion om a
d ople mic o luidic de ice emulsi ica ion p ocess was also s udied by Fila o e al.36
showing he impo ance o he pho oini ia o concen a ion and he eac ion ime in he
inal co e-shell s uc u e and MPs esis ance. Howe e , a pla eau o ime eac ion exis s
a e y high pho oini ia o concen a ion whe e inc easing pho oini ia o concen a ion
does no lead o as e polyme iza ion eac ion. On he o he hand, when he monome
concen a ion inc eases, mo e monome molecules a e a ailable a he d ople su ace
leading o hicke MP shells and hus mo e mechanically esis an MPs. This is
explained due o a as e polyme iza ion p ocess wi h he same eac ion ime.
Conside ing ou p e ious ema ks, i was de ised he o ma ion o wo ypes o MPs
wi h a di e en in e nal s uc u e and good mechanical p ope ies, whe e he densi y o
polyme ic chains was uned in o de o modula e he oid ac ion and he a e o
olume sh inkage. Figu e 5 shows some o he mos ep esen a i e MPs p oduced by
uning he polyme iza ion a e, ei he by modi ying he low a e o he con inuous ou e
phase o he pho oini ia o concen a ion. MPs p oduced a he opposi e condi ions we e
disca ded because hey un easible applicabili y. Tha is, MPs p oduced wi h he smalles
low a e and pho oini ia o concen a ion (Figu e 5-a), because hey we e no
mechanically s able. On he o he hand, MPs p oduced a he highes low a e and
pho oini ia o concen a ion (Figu e 5-d), because o he high densi y o polyme ic
chains and igidi y would se iously a ec he a e o olume sh inkage. As a esul ,
in e media e condi ions we e selec ed as he p ope ones in o de o load he ca go and
s udy he empe a u e assis ed d ug elease (Figu e 5 b-c).
Figu e 5: F om le o igh MPs syn hesized wi h monome concen a ion o 150 mg/mL (a)
and b)) and 250 mg/mL (c) and d)). Images a) and c) we e syn he ized wi h 40 µL o
pho oini ia o (DEAP); while 500 µL o pho oini ia o (DEAP) we e used in images b) and d).
T ansi ion empe a u e in d ug deli e y applica ions may lead o di e en d ug elease
p o iles which could be app op ia e o a b oad a ie y o disease ea men s. This
uning o LCST can be achie ed by combining di e en monome s in he polyme ic
s uc u e. I has been p e iously demons a ed ha he p esence o di e se unc ional
g oups a he side chains o he polyme chain esul s in a ia ions o hyd ophobici y
and hus polyme -wa e in e ac ions60. Ac ylamide monome has been widely used in
o de o inc ease he ansi ion empe a u e in PNIPAm-based polyme s. The lack o
isop opyl g oups in i s side chain inc eases wa e -polyme in e ac ions making mo e
ene gy necessa y o old he polyme chains.
In ou p oposed mic o luidic pla o m, his a ied monome combina ions d i en o
ob ain cus omized he mo esponsi e MPs wi h desi ed LCST is easy o ca y ou . We
demons a ed ha adding Ac ylamide (AAm) as co-monome he LCST o he esul ing
MPs can be easily modi ied (See Figu e S4). LCSTs o MPs wi h di e en ac ylamide
pe cen ages a e summa ized in Table 1.
co esponding bupi acaine concen a ion. High cell iabili y (> 70%) was obse ed o
all MPs concen a ion es ed o bo h solid and hollow MPs exuda es showing mo e
compa ibili y han ee BVP in human ib oblas . Following s udies we e de eloped a a
MPs concen a ion o 0.5 mg/mL as i was conside ed as subcy o oxic dose ollowing
he ISO 10993-5 s anda d, which s a es a iabili y o 70% as he h eshold o
conside ing non-cy o oxic concen a ions.62
Cell apop osis s udies by low cy ome y we e selec ed o show he po en ial cell
memb ane e ec caused by he MPs exudes (Table 2). The incuba ion o he wo cell
lines (TPH1 mac ophages and human de mal ib oblas s) a he subcy o oxic
concen a ion (0.5 mg/mL) wi h MPs exuda es loaded wi h HGNPs and BVP did no
show ema kable changes compa ed o non- ea ed samples. Only mac ophages showed
a sligh inc ease in nec osis and la e apop osis o hollow and solid loaded MPs,
espec i ely (<3%) and a consequen dec ease in cellula iabili y (<4%).

Figu e 8: Cy o oxici y esul s o wo cell lines: a) Human ib oblas s and b) mac ophages o
wo di e en shell hickness MPs denomina ed solid and hollow MPs loaded wi h HGNPs and
Bupi acaine; and ee bupi acaine. Mean alues and SD ob ained om i es samples.
Table 2: Apop osis esul s ob ained by low cy ome y
Con ol
Exude solid MPs
Exude hollow MPs
Mac ophages (%)
Nec osis
4.43
2.09
7.41
La e apop osis
1.72
5.74
2.58
Ea ly apop osis
0.59
1.44
1.14
Viabili y
93.26
90.74
88.87
Fib oblas s (%)
Nec osis
0.51
0.33
0.38
La e apop osis
1.99
2.47
2.01
Ea ly apop osis
3.05
3.18
2.76
Viabili y
94.44
94.02
94.85
Cell cycle s udies a e depic ed in Table 3. Cell ea men o 24 h wi h HGNPs-BVP
loaded PNIPAm MPs exuda es a subcy o oxic doses (0.5 mg/mL) did no display
accen ua ed e ec s on cell cycle. A sligh inc ease in G2 phase in mac ophages (<2%)
and in S phase in ib oblas s (<4%) a e he only changes obse ed a e ea men
compa ed o con ol samples. The e o e, a he doses es ed he exuda es eleased by he
MPs he e p epa ed did no show cy o oxici y, cell-cycle a es o apop o ic induc ion.
Table 3: Cell cycle esul s ob ained by low cy ome y
Con ol
Exude solid MPs
Exuda e hollow MPs
Mac ophages (%)
G1
55.72
53.44
54.11
S
13.32
13.49
13.41
G2
30.96
33.08
32.48
Fib oblas s (%)
G1
45.72
43.83
44.19
S
31.34
35.99
35.17
G2
22.94
20.18
20.64
4 Conclusions
Summing up, in his wo k we ob ained he mosensi i e ligh - esponsi e hyb id MPs
loaded wi h an anes he ic d ug using an inno a i e one-s ep con inuous syn hesis
me hod. A simple, e sa ile and highly p oduc i e mic o luidic syn hesis was de eloped
o his pu pose. The in luence o he eac ion condi ions in he inal MPs cha ac e is ics
was analyzed. The p esence o plasmonic HGNPs in he MPs was demons a ed as
po en ial igge o d ug deli e y applica ions in biomedicine. In o de o es d ug
loading and elease beha io , bupi acaine was selec ed as a d ug o in e es and he
in e ac ion, loading capaci y and elease s udies con i med he sui abili y o he MPs
ob ained o eaching unable d ug deli e y p o iles. Finally, cy o oxici y assays showed
a subcy o oxic dose o 0.5 mg/mL u he used o s udy he cell me abolism and cell
cycle showing no ema kable in luence in any o he cell lines s udied. Al oge he , make
his mic o luidic de ice sui able o MPs syn hesis o u he local ea men
applica ions such as he ea men o ch onic pain whe e an anes he ic depo could be
ex e nally ac i a ed o elease i s ca go on demand. Fu he imp o emen s such as
di e en capilla y sizes, LED i adia ion a angemen s o in oduc ion o o he d ug
molecules o ino ganic nanopa icles would be he nex s eps o expand he possibili ies
o his no el mic o luidic de ice.
5 Acknowledgmen s
Financial suppo om he ERC Consolida o G an p og am (ERC-2013-CoG-614715,
NANOHEDONISM) is g a e ully acknowledged. CIBER-BBN is an ini ia i e unded
by he VI Na ional R&D&i Plan 2008-2011 inanced by he Ins i u o de Salud Ca los III
wi h he assis ance o he Eu opean Regional De elopmen Fund.
6 Associa ed con en
Suppo ing igu es a e a ailable in Suppo ing In o ma ion File.
Addi ional in o ma ion o he e e sible MPs swelling unde lase i adia ion is
p esen ed in Suppo ing Mo ie_S1.
7 Re e ences
(1) Choi, A.; Seo, K. D.; Kim, D. W.; Kim, B. C.; Kim, D. S. Recen Ad ances in
Enginee ing Mic opa icles and Thei Nascen U iliza ion in Biomedical Deli e y
and Diagnos ic Applica ions. Lab Chip 2017, 17 (4), 591–613.
(2) Jung, S.; Choi, C. H.; Lee, C. S.; Yi, H. In eg a ed Fab ica ion-Conjuga ion
Me hods o Polyme ic and Hyb id Mic opa icles o P og ammable D ug
Deli e y and Biosensing Applica ions. Bio echnol. J. 2016, 11 (12), 1561–1571.
(3) Xu, Q.; Hashimo o, M.; Dang, T. T.; Hoa e, T.; Kohane, D. S.; Whi esides, G.
M.; Lange , R.; Ande son, D. G. P epa a ion o Monodispe se Biodeg adable
Polyme Mic opa icles Using a Mic o luidic Flow-Focusing De ice o
Con olled D ug Deli e y. Na l. Ins . Heal. Public Access 2010, 5 (13), 1575–
1581.
(4) Jiang, W.; Li, M.; Chen, Z.; Leong, K. W. Cell-Laden Mic o luidic Mic ogels o
Tissue Regene a ion. Lab Chip 2016, 16 (23), 4482–4506.
(5) Be kland, C.; King, M.; Cox, A.; Kim, K.; Pack, D. W. P ecise Con ol o PLG
Mic osphe e Size P o ides Enhanced Con ol o D ug Release Ra e. J. Con ol.
Release 2002, 82 (1), 137–147.
(6) Ag awal, G.; Ag awal, R. S imuli-Responsi e Mic ogels and Mic ogel-Based
Sys ems: Ad ances in he Exploi a ion o Mic ogel Colloidal P ope ies and
Thei In e acial Ac i i y. Polyme s (Basel). 2018, 10 (4).
(7) Chan, K. M. C.; Li, R. H.; Chapman, J. W.; T ac, E. M.; Koble , J. B.; Zei els, S.
M.; Lange , R.; Ka ajanagi, S. S. Func ionalizable Hyd ogel Mic opa icles o
Tunable Size and S i ness o So -Tissue Fille Applica ions. Ac a Bioma e .
2014, 10 (6), 2563–2573.
(8) Ci illo, G.; Iemma, F.; Spizzi i, U. G.; Puoci, F.; Cu cio, M.; Pa isi, O. I.; Picci,
N. Syn hesis o S imuli-Responsi e Mic ogels o in Vi o Release o Diclo enac
Die hyl Ammonium. J. Bioma e . Sci. Polym. Ed. 2011, 22 (4–6), 823–844.
(9) Bazzano, M.; La o e, D.; Pisano, R.; Sange mano, M.; Woe ne , M. Nano-
S uc u ed Polyme ic Mic opa icles P oduced ia Ca ionic Ae osol
Pho opolyme iza ion. J. Pho ochem. Pho obiol. A Chem. 2017, 346, 364–371.
(10) Vladisa lje ić, G. T.; Williams, R. A. Recen De elopmen s in Manu ac u ing
Emulsions and Pa icula e P oduc s Using Memb anes. Ad . Colloid In e ace
Sci. 2005, 113 (1), 1–20.
(11) Cha cosse ;, C.; Fessi, H. MEMBRANE EMULSIFICATION AND
MICROCHANNEL EMULSIFICATION PROCESSES. Re . Chem. Eng. 2005,
21, 1–32.
(12) De Gees , B. G.; U banski, J. P.; Tho sen, T.; Demees e , J.; De Smed , S. C.
Syn hesis o Monodispe se Biodeg adable Mic ogels in Mic o luidic De ices.
Langmui 2005, 21 (23), 10275–10279.
(13) Choi, C. H.; Wei z, D. A.; Lee, C. S. One S ep Fo ma ion o Con ollable
Complex Emulsions: F om Func ional Pa icles o Simul aneous Encapsula ion
o Hyd ophilic and Hyd ophobic Agen s in o Desi ed Posi ion. Ad . Ma e . 2013,
25 (18), 2536–2541.
(14) Ma, S.; Thiele, J.; Liu, X.; Bai, Y.; Abell, C.; Huck, W. T. S. Fab ica ion o
Mic ogel Pa icles wi h Complex Shape ia Selec i e Polyme iza ion o Aqueous
Two-Phase Sys ems. Small 2012, 8 (15), 2356–2360.
(15) Nos a i, Z.; Li, N.; Michaud, F.; Ranamukhaa achchi, S.; Ka agiozo , S.; Soulez,
G.; Ma el, S.; Saa chi, K.; Hä eli, U. O. De elopmen o a Co lowing De ice o
he Size-Con olled P epa a ion o Magne ic-Polyme ic Mic osphe es as
Emboliza ion Agen s in Magne ic Resonance Na iga ion Technology. ACS
Bioma e . Sci. Eng. 2018, 4 (3), 1092–1102.
(16) Xu, J. H.; Zhao, H.; Lan, W. J.; Luo, G. S. A No el Mic o luidic App oach o
Monodispe sed Chi osan Mic osphe es wi h Con ollable S uc u es. Ad .
Heal hc. Ma e . 2012, 1 (1), 106–111.
(17) Sebas ian, V.; A uebo, M. Mic o luidic P oduc ion o Ino ganic Nanoma e ials
o Biomedical Applica ions; Else ie Inc., 2018.
(18) Dong, H.; Tang, G.; Ma, T.; Cao, X. One-S ep Fab ica ion o Ino ganic/O ganic
Hyb id Mic osphe es wi h Tunable Su ace Tex u e o Con olled D ug Release
Applica ion. J. Ma e . Sci. Ma e . Med. 2016, 27 (1), 7.

(19) Seo, K. D.; Kim, D. S.; Sánchez, S. Fab ica ion and Applica ions o Complex-
Shaped Mic opa icles ia Mic o luidics. Lab Chip 2015, 15 (18), 3622–3626.
(20) Choi, C.-H.; Jung, J.-H.; Kim, D.-W.; Chung, Y.-M.; Lee, C.-S. No el One-Po
Rou e o Monodispe se The mosensi i e Hollow Mic ocapsules in a Mic o luidic
Sys em. Lab Chip 2008, 8 (9), 1544–1551.
(21) Kanai, T.; Oh ani, K.; Fukuyama, M.; Ka aku a, T.; Hayakawa, M. P epa a ion o
Monodispe se PNIPAM Gel Pa icles in a Mic o luidic De ice Fab ica ed by
S e eoli hog aphy. Polym. J. 2011, 43 (12), 987–990.
(22) Xi, W.; Kong, F.; Yeo, J. C.; Yu, L.; Sonam, S.; Dao, M.; Gong, X.; Lim, C. T.
So Tubula Mic o luidics o 2D and 3D Applica ions. P oc. Na l. Acad. Sci.
2017, 114 (40), 10590–10595.
(23) Ren, K.; Dai, W.; Zhou, J.; Su, J.; Wu, H. Whole-Te lon Mic o luidic Chips.
P oc. Na l. Acad. Sci. 2011, 108 (20), 8162–8166.
(24) Nge, P. N.; Roge s, C. I.; Woolley, A. T. Ad ances in Mic o luidic Ma e ials,
Func ions, In eg a ion and Applica ions. Chem. Re . 2013, 113 (4), 2550–2583.
(25) Hu, Y.; Wang, S.; Abbaspou ad, A.; A dekani, A. M. Fab ica ion o Shape
Con ollable Janus Algina e/PNIPAAm Mic ogels ia Mic o luidics Technique
and O -Chip Ionic C oss-Linking. Langmui 2015, 31 (6), 1885–1891.
(26) Velasco, D.; Tuma kin, E.; Kumache a, E. Mic o luidic Encapsula ion o Cells
in Polyme Mic ogels. Small 2012, 8 (11), 1633–1642.
(27) Sei e , S.; Wei z, D. A. Con olled Fab ica ion o Polyme Mic ogels by
Polyme -Analogous Gela ion in D ople Mic o luidics. So Ma e 2010, 6 (14),
3184.
(28) Li, W.; Zhang, L.; Ge, X.; Xu, B.; Zhang, W.; Qu, L.; Choi, C. H.; Xu, J.; Zhang,
A.; Lee, H.; Wei z, D. A. Mic o luidic Fab ica ion o Mic opa icles o
Biomedical Applica ions. Chem. Soc. Re . 2018, 47 (15), 5646–5683.
(29) Die lin, C.; Schweize , S.; Xiao, P.; Zhang, J.; Mo le -Sa a y, F.; G a , B.;
Fouassie , J. P.; Lale ée, J. Pho opolyme iza ion upon LEDs: New
Pho oini ia ing Sys ems and S a egies. Polym. Chem. 2015, 6 (21), 3895–3912.
(30) Si akuma an, D.; Muelle , E.; Hoa e, T. Mic o luidic P oduc ion o Deg adable
The mo esponsi e Poly(: N -Isop opylac ylamide)-Based Mic ogels. So Ma e
2017, 13 (47), 9060–9070.
(31) Kim, Y. S.; Lee, H. M.; Kim, J. H.; Joo, J.; Cheong, I. W. Hyd ogel Adso ben s
o Poly(N-Isop opylac ylamide-Co-Me hac yloyloxyme hyl-12-C own-4) o
Li+ eco e y P epa ed by D ople Mic o luidics. RSC Ad . 2015, 5 (14), 10656–
10661.
(32) Cheng, C. J.; Chu, L. Y.; Ren, P. W.; Zhang, J.; Hu, L. P epa a ion o
Monodispe se The mo-Sensi i e Poly(N-Isop opylac ylamide) Hollow
Mic ocapsules. J. Colloid In e ace Sci. 2007, 313 (2), 383–388.
(33) Ge, X. H.; Huang, J. P.; Xu, J. H.; Luo, G. S. Con olled S imula ion-Bu s
Ta ge ed Release by Sma Decen e ed Co e-Shell Mic ocapsules in G a i y and
Magne ic Field. Lab Chip 2014, 14 (23), 4451–4454.
(34) Mou, C. L.; Ju, X. J.; Zhang, L.; Xie, R.; Wang, W.; Deng, N. N.; Wei, J.; Chen,
Q.; Chu, L. Y. Monodispe se and Fas -Responsi e Poly(N -Isop opylac ylamide)
Mic ogels wi h Open-Celled Po ous S uc u e. Langmui 2014, 30 (5), 1455–
1464.
(35) Pa k, S.; Kim, D.; Ko, S. Y.; Pa k, J. O.; Akella, S.; Xu, B.; Zhang, Y.; F aden, S.
Con olling Uni o mi y o Pho opolyme ized Mic oscopic Hyd ogels. Lab Chip
2014, 14 (9), 1551–1563.
(36) Fila o , N. A.; Nozd iukhin, D. V.; Buka in, A. S. The Kine ic S udy o
Solidi ica ion PEGDA Mic opa icles in Flow-Focusing Mic o luidic Chip. J.
Phys. Con . Se . 2017, 917 (4), 1–5.
(37) Chen, J.; Huang, K.; Chen, Q.; Deng, C.; Zhang, J.; Zhong, Z. Tailo -Making
Fluo escen Hyalu onic Acid Mic ogels ia Combining Mic o luidics and
Pho oclick Chemis y o Sus ained and Localized Deli e y o He cep in in
Tumo s. ACS Appl. Ma e . In e aces 2018, 10 (4), 3929–3937.
(38) Jeong, W. C.; Kim, S. H.; Yang, S. M. Pho o he mal Con ol o Memb ane
Pe meabili y o Mic ocapsules o On-Demand Release. ACS Appl. Ma e .
In e aces 2014, 6 (2), 826–832.
(39) Homayun, B.; Sun, C.; Kuma , A.; Mon emagno, C.; Choi, H. J. Facile
Fab ica ion o Mic opa icles wi h PH-Responsi e Mac opo es o Small
In es ine Ta ge ed D ug Fo mula ion. Eu . J. Pha m. Biopha m. 2018, 128
(Ma ch), 316–326.
(40) Huang, S.; Lin, B.; Qin, J. Mic o luidic Syn hesis o Tunable Poly-(N-
Isop opylac ylamide) Mic opa icles ia PEG Adjus men . Elec opho esis 2011,
32 (23), 3364–3370.
(41) Zhang, K.; Wu, W.; Guo, K.; Chen, J.; Zhang, P. Syn hesis o Tempe a u e-
Responsi e Poly(N-Isop opyl Ac ylamide)/ Poly(Me hyl Me hac la e)/Silica
Hyb id Capsules om In e se Picke ing Emulsion Polyme iza ion and Thei
Applica ion in Con olled D ug Release. Langmui 2010, 26 (11), 7971–7980.
(42) Budhlall, B. M.; Ma quez, M.; Vele , O. D. Mic owa e, Pho o- And The mally
Responsi e PNIPAm-Gold Nanopa icle Mic ogels. Langmui 2008, 24 (20),
11959–11966.
(43) Heida, T.; Neubaue , J. W.; Seuss, M.; Hauck, N.; Thiele, J.; Fe y, A.
Mechanically De ined Mic ogels by D ople Mic o luidics. Mac omol. Chem.
Phys. 2017, 218 (2), 1–19.
(44) Ekici, S.; Ilgin, P.; Yilmaz, S.; Ak as, N.; Sahine , N. Tempe a u e and Magne ic
Field Responsi e Hyalu onic Acid Pa icles wi h Tunable Physical and Chemical
P ope ies. Appl. Su . Sci. 2011, 257 (7), 2669–2676.
(45) Sei e , S.; Thiele, J.; Aba e, A. R.; Wei z, D. A. Sma Mic ogel Capsules om
Mac omolecula P ecu so s. 2010, 01238 (14), 1–9.
(46) Akba i, S.; Pi bodaghi, T.; Kamm, R. D.; Hammond, P. T. A Ve sa ile
Mic o luidic De ice o High Th oughpu P oduc ion o Mic opa icles and Cell
Mic oencapsula ion. Lab Chip 2017, 17 (12), 2067–2075.
(47) S einhilbe , D.; Rossow, T.; Wedepohl, S.; Paulus, F.; Sei e , S.; Haag, R. A
Mic ogel Cons uc ion Ki o Bioo hogonal Encapsula ion and PH-Con olled
Release o Li ing Cells. Angew. Chemie - In . Ed. 2013, 52 (51), 13538–13543.
(48) Cele i, G.; Na ale, C. Di; Causa, F.; Ba is a, E.; Ne i, P. A. Func ionalized
Poly(E hylene Glycol) Diac yla e Mic ogels by Mic o luidics: In Si u Pep ide
Encapsula ion o in Se um Selec i e P o ein De ec ion. Colloids Su aces B
Bioin e aces 2016, 145, 21–29.
(49) Wang, W.; Liu, L.; Ju, X. J.; Ze ouki, D.; Xie, R.; Yang, L.; Chu, L. Y. A No el
The mo-Induced Sel -Bu s ing Mic ocapsule wi h Magne ic a ge ing P ope y.
ChemPhysChem 2009, 10 (14), 2405–2409.
(50) Wang, J.; Zhu, X.; Wei, L.; Ye, Y.; Liu, Y.; Li, J.; Mei, T.; Wang, X.; Wang, L.
Con olled Shape T ans o ma ion and Loading Release o Sma Hemisphe ical
Hyb id Mic ogels T igge ed by ‘Inne Engines.’ Chemis ySelec 2018, 3 (15),
4067–4074.
(51) Kim, B.; Soo Lee, H.; Kim, J.; Kim, S. H. Mic o luidic Fab ica ion o Pho o-
Responsi e Hyd ogel Capsules. Chem. Commun. 2013, 49 (18), 1865–1867.