Electronic Supplementary Material (ESI) for Journal of Materials Chemistry B.
This journal is © The Royal Society of Chemistry 2014
Novel Carbon dot coated Alginate beads with superior stability, swelling
and pH responsive drug delivery
Neelam Gogoi and Devasish Chowdhury*
Electronic Supplementary Information (ESI)
Preparation of Carbon dots (CD)
Chitosan based carbon dots were synthesized using chitosan hydrogel. To prepare chitosan
(CH) hydrogels 1% glacial acetic acid solution and glycerol were mixed in the ratio of 1 part
acetic acid solution to 3 parts glycerol and used as the solvent. 0.1 g chitosan was dissolved
in 10 ml of the aforementioned solvent by stirring with a magnetic stirrer at room temperature
for 1– 2 h to form a clear pale yellow solution. The solution was neutralized by adding 5 N
NaOH. Immediately a clear, slightly tacky gel was formed. The gel, which apparently results
from the interaction of chitosan, glycerol and water, has a three dimensional structure, and no
free water or glycerol is apparent.
The prepared CH hydrogel was then dissolved in 30 ml of 0.1 M acetic acid and
heated in a microwave for 5-10 mins until a transparent thick liquid is observed. When
viewed under UV lamp this transparent thick liquid showed excellent blue coloured
fluorescence confirming the formation of carbon dots from chitosan hydrogel.
Photoluminescence properties of Carbon dot coated alginate beads(CA-CD) and carbon dot
coated alginate bead after drug loading
We studied the fluorescence properties of Carbon dot coated alginate beads(CA-CD)
and carbon dot coated alginate bead after drug loading (CA-CD/TC). In this regard solid
fluorescence was taken for Ca beads, CA-CD and CA-CD/TC as shown in figure S1 (A). As
evident from the figure PL emission is very weak. The weak PL emission is due to quenching
of carbon dot emission on coating on alginate bead.
B
CA
CA-CD
CA-CD / TC
200 At 320 nm
160
120
80
40
350
400
450 500 550
Wavelength (nm)
600
CD
CD + 0.01 mM TC
CD + 0.05 mM TC
CD + 0.04 mM TC
CD + 0.22 mM TC
60
PL Intensity (a.u)
PL Intensity (%) x 104
A
45
30
15
0
350
420
490
560
630
700
Wavelength (nm)
Figure S1. (A) Comparative solid photoluminescence emission spectrum of CA bead, CA-CD
(alginate bead coated with carbon dots) and CA-CD/TC (alginate bead coated with carbon dots after
drug loading).(B) Photoluminescence of carbon dots and its PL properties upon addition of TC and βTC.
PL properties of carbon dot in presence of TC and ß-TC was studied and shown in figure S1
(B). PL emission shows that there is quenching of PL intensity on addition of TC drug. Same
trend is also observed with ß-TC. It is observed that quenching of PL intensity is more
pronounced with ß-TC than TC.
A
B
Figure S2. Photograph of (A) CA bead, and (B) Chitosan coated calcium alginate bead.
B
A
C
Figure S3. Scanning Electron Microscope (SEM) image of outer surface of (A) CA-CD bead (B) CA-
% Cumulative drug release
CD bead at higher magnification and (C) CA bead.
80
A
B
C
70
60
50
40
30
20
0
20
40
60
Time (hrs)
80
100
Figure S4. % Cumulative Tetracycline drug release study at pH 1 of three sets of CA-CD (A, B and
C). [Preparation of these three sets of CA-CD → A: 10 CA beads coated in 10 ml CD solution, B: 20
CA beads coated in 10 ml CD solution, and C: 30 CA beads coated in 10 ml CD solution]
ase
% Cumulative rele
35
30
25
20
15
10
51
23
45
4
pH 6 7
2
e
8 90
Tim
6
8
10
rs)
u
(ho
Figure S5. 3-Dimensional plot of release of TC at different time interval at different pH condition
from acidic as in stomach to basic as in intestine
Surface Area = 1.477 m2/g
2000.0000
2.24E+04
A
1.90E+04
Surface Area = 10.58 m2/g
B
1.57E+04
1600.0000
1/[W(P0/P)-1]
1/[W(P0/P)-1]
1.24E+04
1200.0000
800.0000
9.00E+03
5.66E+03
2.31E+03
-1.04E+03
400.0000
-4.39E+03
-7.74E+03
0.0000
0.000E+00
8.000E-02
1.600E-01
-1.11E+04
0.0000
3.200E-01
2.400E-01
Relative Pressure, (P/P0)
0.0700
0.1400
0.2100
0.2800
0.3500
Relative Pressure, (P/P0)
Figure S6. BET plot (Surface area analysis) of (A) CA, and (B) CA-CD beads.
Y region
OH O
OH O
OH
H
HO
CH3
H
H
CONH2
OH
N(CH3)2
X region
Figure S7. Molecular structure of Tetracycline hydrochloride (TC) showing X and Y reactivity
regions.
1030
2089 1650
577
% T (a.u)
ß-TC
1476
3634
2843
ß-cd
1026
2457
2153
1674
2106
1635
1202 1030
TC
673
587
3500 3000 2500 2000 1500 1000
Wavenumber (cm-1)
3000
2000
1000 500
Figure S8. FTIR spectra of tetracycline (TC), ß-cyclodextrin (ß-cd) and ß-cyclodextrin-tetracyline
inclusion complex (ß-TC).