In . J. Mol. Sci. 2015, 16, 24656-24672; doi:10.3390/ijms161024656
In e na ional Jou nal o
Molecula Sciences
ISSN 1422-0067
www.mdpi.com/jou nal/ijms
A icle
S aphylococcus au eus and MRSA G ow h and Bio ilm
Fo ma ion a e T ea men wi h An ibio ics and SeNPs
K is yna Cihalo a 1,2, Dagma Chudobo a 1,2, Pe Michalek 1,2, Ami a a Moulick 1,2,
Roman Gu an 1,2, Pa el Kopel 1,2, Voj ech Adam 1,2,3 and Rene Kizek 1,2,*
1 Depa men o Chemis y and Biochemis y, Mendel Uni e si y in B no, Zemedelska 1,
CZ-613 00 B no, Czech Republic; E-Mails: k iki.cihalo [email p o ec ed] (K.C.);
dagma .chudobo a@cen um.cz (D.C.); pe [email protected] (P.M.);
ami a [email protected] (A.M.); .gu [email protected] (R.G.);
[email p o ec ed] (P.K.); oj [email protected] (V.A.)
2 Cen al Eu opean Ins i u e o Technology, B no Uni e si y o Technology, Technicka 3058/10,
CZ-616 00 B no, Czech Republic
3 Depa men o Mic oelec onics, Facul y o Elec ical Enginee ing and Communica ion,
B no Uni e si y o Technology, Technicka 3058/10, CZ-616 00 B no, Czech Republic
* Au ho o whom co espondence should be add essed; E-Mail: [email p o ec ed];
Tel.: +420-5-4513-3350; Fax: +420-5-4521-2044.
Academic Edi o : Bing Yan
Recei ed: 30 July 2015 / Accep ed: 14 Sep embe 2015 / Published: 16 Oc obe 2015
Abs ac : Me hicillin- esis an S aphylococcus au eus (MRSA) is a dange ous pa hogen
esis an o β-lac am an ibio ics. Due o i s esis ance, i is di icul o manage he in ec ions
caused by his s ain. We examined his issue in e ms o obse a ion o he g ow h
p ope ies and abili y o o m bio ilms in sensi i e S. au eus and MRSA a e he
applica ion o an ibio ics (ATBs)—ampicillin, oxacillin and penicillin—and complexes o
selenium nanopa icles (SeNPs) wi h hese ATBs. The esul s sugges he s ong inhibi ion
e ec o SeNPs in complexes wi h con en ional ATBs. Using he impedance me hod, a
highe dis up ion o bio ilms was obse ed a e he applica ion o ATB complexes wi h
SeNPs compa ed o he g oup exposed o ATBs wi hou SeNPs. The bio ilm o ma ion was
in ensely inhibi ed (up o 99% ± 7% o S. au eus and up o 94% ± 4% o MRSA) a e
applica ion o SeNPs in compa ison wi h bac e ia wi hou an ibac e ial compounds whe eas
ATBs wi hou SeNPs inhibi ed S. au eus up o 79% ± 5% and MRSA up o 16% ± 2%
only. The ob ained esul s p o ide a basis o he use o SeNPs as a ool o he ea men
OPEN ACCESS
In . J. Mol. Sci. 2015, 16 24657
o bac e ial in ec ions, which can be complica ed because o inc easing esis ance o
bac e ia o con en ional ATB d ugs.
Keywo ds: S aphylococcus au eus; me hicillin- esis an S aphylococcus au eus;
an ibio ics; selenium nanopa icles
1. In oduc ion
The o ma ion o bio ilms is a na u al p ope y o a wide ange o bac e ial species [1,2]. These species
can cause many se ious bac e ial in ec ions ini ia ing se ious complica ions [3–5]. S aphylococci a e
ecognized as he mos equen causes o bio ilm-associa ed in ec ions [6], den al plaque [7] and his
excep ional s a us among bio ilm-associa ed pa hogens is due o he ac ha hey a e equen commensal
bac e ia on he human skin and mucous su aces (and hose o many o he mammals).
Excessi e use o me hicillin an ibio ics (ATBs) led o he o ma ion o me hicillin- esis an
S. au eus (MRSA) wi h adhesion p ope ies. The occu ence o esis an s ains o bac e ia is a
complica ion o all medical p ac ices ha a e commonly encoun e ed in ecen ime wi h CA-MRSA
(communi y-associa ed me hicillin- esis an S. au eus) [8] and HA-MRSA (hospi al-acqui ed
me hicillin- esis an S. au eus) [9]. These s ains a e unlike non- esis an S. au eus esis an o β-lac am
ATBs [10]. All MRSA s ains ca y an acqui ed gene ic de e minan -mecA o mecC- which encodes
low a ini y penicillin binding p o eins-PBP2a [11]. The mecA gene is p esen on a S aphylococcal
casse e ch omosome mec (SCCmec), which is a genomic island ha concen a es β-lac am ATBs
esis ance genes and o he esis ance genes [12]. The majo i y o MRSA ound in clinical es ing a e
mul id ug esis an (MDR) [13]. MRSA may be esis an o o he g oups o an ibio ics such as
aminoglycosids, ce alospo ins, penicillins o glycopep ides. Included in he glycopep ides g oup is
ancomycin, which has long been conside ed he an ibio ic o las eso agains se ious and
mul i-d ug- esis an in ec ions caused by G am-posi i e bac e ia. Howe e , ancomycin esis ance has
eme ged, i s in en e ococci [14,15] and, mo e ecen ly, in S aphylococcus au eus [16].
Because o an inc easing esis ance o bac e ial species o ATBs, i is necessa y o de elop new
me hods o bac e ial inhibi ion. Recen ly, scien is s we e inc easingly ocused on he ac i i y o sil e
nanopa icles ha exhibi an ibac e ial, an i i al and an i ungal e ec s [17], as in he case o gold
nanopa icles [18], TiO2 nanopa icles [19], o a mix u e o Ag/ZnO nanopa icles [20]. A s udy [21]
compa ed he an ibac e ial e ec be ween sil e and selenium nanopa icles; an ibac e ial e ec s o
selenium nanopa icles inhibi ed he bac e ia S. au eus su p isingly be e han nanopa icles o sil e
phospha e. In ano he s udy, selenium nanopa icles (SeNPs) showed good p ope ies as an ibac e ial
d ugs. The e ec o selenium nanopa icles was con i med in a s udy by T an e al. [22] ha showed
ha he g ow h o S. au eus is inhibi ed a e h ee hou s o incuba ion wi h SeNPs. The combina ion
o ATBs d ugs, which a e aimed a g oups o mul i-d ug esis an bac e ia [23], wi h he me al
nanopa icles can also ep esen a new al e na i e as pha maceu ical ools wi h a high an ibac e ial
e ec on a b oad spec um o bo h esis an and non- esis an bac e ia [24]. Me al nanopa icles
in e ac ing wi h cellula componen s (DNA, RNA and ibosomes) deac i a e and e ec i ely al e
cellula p ocesses [25]. Me al nanopa icles pene a e he cell memb ane o each he cy osol due o
In . J. Mol. Sci. 2015, 16 24658
hei abili y o dissol e slowly while eleasing ions, bu he exac mechanism o he me al
nanopa icles an imic obial ac ion emains unclea [21].
Fo de e mining an ibac e ial e ec o esis an bac e ia we compa ed non- esis an S. au eus and
me hicillin- esis an S. au eus. This s udy examined he changes on he cellula le el in cul u es o
S. au eus and MRSA a e incuba ion wi h ATBs and complexes o SeNPs wi h ATBs. A he same
ime, a en ion was ocused on he changes o bio ilm o ma ion a e ATBs and complexes o SeNPs
wi h ATBs ea men . Real- ime cell analysis (RTCA) on xCELLigence de ice was used o his
de e mina ion [26,27]. The me hod wo ks on he p inciple o cell adhesion on he su ace o elec odes,
which modula es he esul ing impedance [28]. In he case o bac e ia adhe ence o bio ilm on he
su ace o he elec odes occu s [29] and he eby he change o he ela i e impedance is obse ed [30].
The s udy was suppo ed h ough moni o ing o he ac i i y o he exp ession p ocess o ATB
esis ance genes.
2. Resul s and Discussion
2.1. In luence o An ibac e ial Compounds o G ow h P ope ies
Mic obiological de e mina ion o he inhibi ion zone sizes showed e iden inhibi o y e ec
esul ing om he applica ion o SeNPs enhanced by o ming a complex wi h ampicillin, oxacillin and
penicillin. The ATBs alone demons a ed an ibac e ial p ope ies only o sensi i e S. au eus wi h sizes
o he g ow h inhibi ion zones wi hin he ange o 4–12 mm (Figu e 1A). Howe e , he complexes o
SeNPs wi h ATBs showed he signi ican an ibac e ial e ec wi h inhibi ion zone sizes wi hin he ange
o 6–13 mm o sensi i e S. au eus (Figu e 1(Aa)) and 3–5 mm o MRSA (Figu e 1(Ab)). A e he
applica ion o ampicillin, he obse ed sizes o g ow h inhibi ion zones we e 4 and 6 mm o non- esis an
S. au eus (Figu e 1(Aa)) and 0 and 4 mm o MRSA (Figu e 1(Ab)). Applica ion o oxacillin p o ided
he highes g ow h inhibi ion zones wi h sizes o 12 and 13 mm o non- esis an S. au eus (Figu e 1(Aa))
and 0 and 5 mm o MRSA (Figu e 1(Ab)). In he case o penicillin, he sizes o inhibi ion zones we e
7 and 8 mm o non- esis an S. au eus (Figu e 1(Aa)) and 0 and 3 mm o MRSA (Figu e 1(Ab)).
Applica ion o o he d ugs exhibi ed simila esul s. Al hough MRSA did no o m inhibi ion zones
a e applica ion o he discs con aining ATBs wi hou SeNPs, complexes o SeNPs wi h ATBs
mani es ed inhibi ion zones be ween 4–6 mm. Applica ion o complex o SeNPs wi h AMP, OXA,
PNC has abou 0%, 25%, 54% highe inhibi ion e ec han SeNPs alone o non- esis an S. au eus,
espec i ely, and abou 25%, 40%, 0% highe inhibi ion e ec han SeNPs alone o MRSA,
espec i ely. The inhibi ion e ec o SeNPs is abou 50% highe o non- esis an S. au eus han o
MRSA. In he case o non- esis an S. au eus, la ge inhibi ion zones we e obse ed a e he
applica ion o complexes o SeNPs wi h ATBs han ATBs alone. In he non- esis an S. au eus case,
ampicillin, oxacillin and penicillin caused highe inhibi o y e ec s (44%, 8% and 13% espec i ely)
when applied in combina ion wi h SeNPs han ATBs alone (Figu e 1(Aa)). Applica ion o ATBs in
combina ion wi h SeNPs caused 100% highe inhibi ion e ec because ATBs do no cause o ma ion o
he inhibi ion zones (Figu e 1(Ab)). Muhsin e al. [31] epo ed ha he applica ion o sil e
nanopa icles caused a 17 mm wide g ow h inhibi ion zone o S. au eus. On he o he hand, he use
o gen amycin alone could cause a g ow h inhibi ion zone o la ge size (31 mm). Howe e , he
In . J. Mol. Sci. 2015, 16 24659
modi ica ion o sil e nanopa icles wi h gen amycin showed a small inc ease o he inhibi ion zone
wid h up o 33 mm [31].
Figu e 1. (A) De e mina ion o inhibi ion zones a e applica ion o ci cula discs on he
S. au eus (a) and MRSA (b) s ains wi h 100 µM concen a ion o ampicillin, oxacillin,
penicillin o complexes (100 µM o nanopa icles and 100 µM o ATBs) o SeNPs wi h
ampicillin, SeNPs wi h oxacillin and SeNPs wi h penicillin. Cul i a ion was ca ied ou a
37 °C o 24 h; (B) Op imiza ion o SeNPs concen a ion o non- esis an S. au eus (a)
and MRSA (b) o o he measu emen s; (C) G ow h cu es a e applica ion o ATBs
(ampicillin— ed line, oxacillin-g een line, penicillin—pu ple line) on S. au eus (a) and
MRSA (c)—blue line and complexes o SeNPs (100 μM) wi h he same ATBs (100 μM)
S. au eus (b) and MRSA (d)—blue line. All da a ep esen mean ± S.D. NS, no
signi ican , * p < 0.05.
In . J. Mol. Sci. 2015, 16 24660
The an ibac e ial ac i i y o ATBs o hei complexes wi h SeNPs a e 24 h was con i med by he
me hod o he g ow h cu es [21]. The 50% inhibi o y concen a ion was de e mined in he p e ious
s udy [21] and o ou s udy, 100 µM concen a ions o SeNPs in combina ion wi h 100 µM o ATB
(Figu e 1(Ba,b)) was used. Concen a ion o SeNPs ha showed inhibi o y di e ences be ween
non- esis an S. au eus and MRSA we e selec ed o measu emen s in his pape . ATBs concen a ions
we e chosen on he basis o p e ious measu emen s. Fo he compa ison o ATBs wi h o wi hou
SeNPs, we used only one concen a ion (100 µM) o ATBs, and i was ound ha he ATBs applied in
combina ion wi h SeNPs (100 µM) showed a g ea e an ibac e ial e ec han ATBs alone. The
inhibi ion e ec o ATBs was signi ican on a non- esis an S. au eus (Figu e 1(Ca)). Bu in he case o
MRSA, ATBs, as expec ed, we e mos ly ine ec i e (Figu e 1(Cc)). Only oxacillin showed low
an ibac e ial ac i i y wi h MRSA wi hou an ibac e ial compounds. The applica ion o complexes o
SeNPs wi h ATBs caused almos comple e inhibi ion o bo h s ains (non- esis an S. au eus and
MRSA) in he case o all 3 ypes o applied ATBs-ampicillin, oxacillin, penicillin (Figu e 1(Cb,d)).
2.2. In luence o An ibac e ial Compounds o Bio ilm Fo ma ion
The assessmen o he an imic obial componen s was u he ca ied ou o es he iabili y o he
cells. The ela i e impedance depending on he adhe ence o cell cul u e o he gold elec odes in eal
ime was used o his pu pose. Real ime xCELLigence analysis sys em is an impedance-based cell
de ec ion pla o m ha p o ides a non-in asi e, label- ee way o con inuous cellula moni o ing [32–34].
This me hod has been used in many published esea ch s udies [27,35–37]. Junka e al. [28] showed
ha xCELLigence sys em can also be use ul o mic obiological es s, including (i) measu emen s o
mo phological changes in p oka yo ic cells; (ii) measu emen o bac e ial bio ilm o ma ion and
(iii) impac o an isep ics on he bio ilm s uc u e.
Figu e 2A depic s he applica ion o SeNPs on he non- esis an S. au eus and MRSA, showing ha
he bio ilm o ma ion was mo e hampe ed in p esence o SeNPs han in con ol (S. au eus o MRSA
wi hou applica ion o an ibac e ial componen s). The xCELLigence sui abili y o he mic obiological
es s was con i med in he same way as in he s udy p e iously conduc ed by Junka e al. [28]. The
es ed bac e ia mus always be able o adhe e on he su ace o elec ode a he bo om in he measu ing
well [7,38]. The abili y o des oy he bio ilm o ma ion is one o he i ulence ac o s in bac e ia wi h
low sensi i i y o ATBs [39].
A e applica ion o he an ibac e ial agen s, he bio ilm is dis up ed and bac e ial cells a e eleased
om he su ace o elec odes. This end is measu ed as an impedance alues and depic ed in he
g aph (Figu e 2A,B). The di e ences in he ela i e impedance o S. au eus showed dec eases in he
alues o all componen s applied in compa ison wi h he con ol, which is caused by balanced
iola ion o he bio ilm o med on he elec ode su ace. In he case o non- esis an S. au eus, ATBs
and complexes o SeNPs wi h ATBs dis up ed he bac e ial bio ilm, and a e ha a highe e ec on
hese bac e ia could be seen (Figu e 2A). The bio ilm o med by MRSA (Figu e 2(Bb,c)) was mo e
esis an o ATBs and complexes o SeNPs wi h ATBs han he bio ilm o med by he non- esis an
S. au eus (Figu e 2(Ab,c)). Figu e 2B shows he pe cen age dec ease o bio ilm o ma ion a e
applica ion o ATBs and complexes o SeNPs wi h ATBs in compa ison wi h con ol. The con ol
sample o non- esis an S. au eus eached he ela i e impedance alues o 0.29 and he con ol sample

In . J. Mol. Sci. 2015, 16 24661
o MRSA eached 0.52 a e 24-h measu emen and om hese alues he dec ease o he ela i e
impedance a e applica ion o ATBs and complexes o SeNPs wi h ATBs was calcula ed. The
measu emen s we e pe o med in iplica es. Low adhesion showed a dec easing end caused by he
bio ilm o ma ion on he elec odes, and om his we can conclude ha he applica ion o ATBs and
complexes o SeNPs wi h ATBs caused dis up ion o he bio ilm on he elec odes. The esul s a e
summa ized in Table 1.
Figu e 2. (A) Moni o ing o bio ilm dis up ion a e applica ion o 100 μM SeNPs on
S. au eus—blue line (a) and ATBs (100 μM): ampicillin— ed line, oxacillin—g een line,
penicillin—pu ple line on S. au eus—blue line (b) and complexes o SeNPs (100 μM) wi h
he same ATBs (100 μM) on S. au eus—blue line (c); (B) Moni o ing o bio ilm dis up ion
a e applica ion o 100 μM SeNPs on MRSA—blue line (a) and ATBs (100 μM)
ampicillin— ed line, oxacillin—g een line, penicillin—pu ple line on MRSA—blue line
(b) and complexes o SeNPs (100 μM) wi h he same ATBs (100 μM) on MRSA—blue
line (c); (C) Compa ison o di e ences in ela i e impedance a e applica ion o 100 μM
concen a ion o ATBs o complexes o ATBs wi h SeNPs (100 μM) and SeNPs alone
(100 μM) on S. au eus (a) and MRSA (b) a e 24 h o measu emen . All da a ep esen
mean ± S.D. om h ee measu emen s, NS, no signi ican , * p < 0.05.
In . J. Mol. Sci. 2015, 16 24662
Table 1. Pe cen age dis up ion o bio ilm a e ea men o an ibac e ial componen
(ATBs, SeNPs + ATBs) a e 24 h (Figu e 2(Ca,b)).
Compounds
Bio ilm Dis up ion (%)
S. au eus MRSA
ATB SeNPs + ATBs ATB SeNPs + ATBs
AMP 74 ± 2 93 ± 3 6 ± 5 94 ± 4
OXA 79 ± 5 96 ± 2 16 ± 2 93 ± 4
PNC 71 ± 2 99 ± 7 0 86 ± 2
SeNPs 81 ± 4 55 ± 3
The applica ion o complex o SeNPs wi h ATBs (SeNPs wi h ampicillin, SeNPs wi h oxacillin,
SeNPs wi h penicillin) caused a wo old dec ease in he ela i e impedance compa ed o ATBs only.
Fo non- esis an S. au eus he signi ican ly highe e ec o SeNPs wi h ATBs was no obse ed,
howe e inc eased inhibi ion o bio ilm o ma ion in case o complexes o SeNPs wi h ATBs
was con i med.
2.3. De e mina ion o Exp ession In ensi y o mecA Gene
The mecA gene is esponsible o bac e ial esis ance o β-lac am ATBs and occu s a
s aphylococcal ch omosome casse e mec (SCCmec), which besides mecA gene con ains a numbe o
o he genes causing he esis ance [10]. I s exp ession was moni o ed a e applica ion and also a e
24-h cul i a ion in he p esence o ATBs alone (50 µM) o a same concen a ion o ATBs in
complexes wi h SeNPs (100 µM). Bac e ial s ain MRSA e en wi hou d ugs applica ion always
exhibi ed he exp ession o his gene in compa ison wi h he s ain o S. au eus, whe e his exp essed
gene was absen .
Exp ession o he mecA gene in MRSA wi hou an ibac e ial compounds was highe (by 84%) han
he s anda d exp ession o he 16S gene. Fluo escence alues o 16S ( he housekeeping gene wi h a
luminescence le el 13,098 a.u. (abso bance uni s) o non- esis an S. au eus and 12,544 a.u. o
MRSA) wa e sub ac ed om he mecA (Figu e 3A).
Fo non- esis an S. au eus he exp ession o mecA gene eached he in ensi y o luo escence o
13,059 a.u. while o MRSA was he luo escence in ensi y much highe (36 imes). S. au eus g ew
only in he p esence o 50 µM ampicillin and penicillin, bu no in he p esence o 50 µM
concen a ion o oxacillin. Fo ampicillin and penicillin, non- esis an S. au eus eached a e y low
exp ession o mecA gene (17,315 and 15,543 a.u., espec i ely). MRSA showed highe exp ession by
14% in he case o using 50 µM concen a ions o ampicillin o oxacillin, and low exp ession o mecA
gene a e 24 h cul i a ion wi h 50 µM penicillin, when compa ing wi h MRSA wi hou applica ion o
an ibac e ial compounds (Figu e 3A).
In MRSA, he exp ession o he mecA gene was dec eased a e applica ion o ATBs wi h selenium
nanopa icles when compa ed wi h exp ession o he mecA gene in MRSA wi hou an ibac e ial
compounds. Highe luo escence in ensi y o mecA gene exp ession was obse ed in MRSA a e
incuba ion wi h 50 μM o ATBs (ampicillin, oxacillin and penicillin) alone (Figu e 3), as compa ed o
complexes o SeNPs wi h ATBs, o which he luo escence in ensi ies o exp ession we e 48%, 70%
and 90% lowe , espec i ely (Figu e 3B).
In . J. Mol. Sci. 2015, 16 24663
In non- esis an S. au eus, mecA gene exp ession was obse ed o be 37% highe a e incuba ion
wi h 50 µM concen a ion o ampicillin in compa ison wi h con ol (S. au eus wi hou an ibac e ial
compounds). Non- esis an S. au eus did no g ow a e applica ion o oxacillin (50 µM) hus, gene
exp ession could no be de e mined (Figu e 3B). In he case o ATBs wi h selenium nanopa icles,
he g ow h o non- esis an S. au eus was obse ed only a e applica ion o 50 µM concen a ion o
penicillin (Figu e 3B). The exp ession was measu able only in he case o penicillin. This exp ession
was by 7% highe compa ed o non- esis an S. au eus wi hou an ibac e ial compounds.
MecA gene exp ession in esis an s ains o bac e ia was discussed in he s udy o Rudkin e al. [40],
whe e he use o di e en concen a ions o oxacillin inc eased he le el o exp ession o mecA gene
and hey de ec ed a highe le el o oxici y in CA-MRSA han in HA-MRSA. I was obse ed, ha in
he HA-MRSA, high exp ession o PBP2a educed he oxici y by dis up ing he ag quo um sensing
sys em, which con ols he exp ession o i ulence.
Figu e 3. Moni o ing o mecA gene exp ession in bac e ial s ains S. au eus and MRSA
a e 24 h o g ow h wi h (A) 50 µM ATBs concen a ion and wi h (B) 100 µM
concen a ion o SeNPs wi h 50 µM ATBs concen a ion in complexes using PCR and
subsequen gel elec opho esis. Con ols a e bac e ial s ains (S. au eus and MRSA)
wi hou applica ion o an ibac e ial componen . All da a ep esen mean ± S.D. NS, no
signi ican , * p < 0.05.
2.4. De e mina ion o Changes in P o ein S uc u e
The signi ican changes in he p o ein composi ion o bac e ial s ains caused by he e ec o
selenium nanopa icles we e obse ed using mass spec ome y. In he mass spec a o non- esis an
S. au eus wi h di e en ATBs, h ee peaks wi h m/z 4306, 6355 and 6845 we e selec ed as signi ican
peaks showing he di e ences be ween mass spec a (Figu e 4A). Simila ly, in he mass spec a o
MRSA, peaks wi h m/z 5303, 6356 and 7567 we e selec ed (Figu e 4B). Peaks wi h he same o simila
m/z alue we e desc ibed in a ious publica ions [41,42]. I is ob ious ha he p esence o selenium
nanopa icles causes dis inc changes in p o ein p o iles—acco ding o he mass spec a, he mos
In . J. Mol. Sci. 2015, 16 24664
e icien we e SeNPs wi h oxacillin in he case o non- esis an S. au eus (Figu e 4A) and wi h
ampicillin and penicillin in he case o MRSA (Figu e 4B). These compounds caused he supp essed
exp ession o almos all p o eins compa ed o he con ol s ain o non- esis an S. au eus and MRSA
wi hou he addi ion o SeNPs (Figu e 4A,B). These esul s can be a sui able basis o compa ison o
he p o ein ep esen a ion and hei e ec on he pa hogenici y o bac e ia.
Figu e 4. The compa ison o MALDI-TOF mass spec a o (A) S. au eus and (B) MRSA
wi h ampicillin, SeNPs wi h ampicillin, oxacillin, SeNPs wi h oxacillin, penicillin and
SeNPs wi h penicillin. The analysis was pe o med in linea posi i e mode. A solu ion o
2,5-dihyd oxybenzoic acid (concen a ion 20 mg·mL
−1
) in 30% ace oni ile and 0%, 1%
i luo oace ic acid was used as a ma ix. The lase powe was se o 75%. The highligh ed
peaks show he bigges di e ences in compa ed spec a.
These p o ein changes may a ec he pa hogenici y o bac e ia. In e ac ion o me al ions wi h DNA
can a ec he p o ein-DNA in e ac ions [43]. In he case o sil e nanopa icles, he in e ac ion wi h
In . J. Mol. Sci. 2015, 16 24671
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