Furthermore, I acknowledge the support of my undergraduate friends Amit, Gorachand, Partha, Subrata, Arpan, Sandipan and Kamalesh. Furthermore, I acknowledge the cooperation of my colleagues, Gaurab, Harish, Priyotosh, Pratik, Dilip, Raunak, Sainiwetha in my research.
Synopsis
The gel fraction follows the opposite trend of the swelling ratio, with MCC gel having the highest gel fraction of 96.98%. The in vitro release study with AIF and PBS shows that Cephalexin initially bursts due to swelling of the gels, followed by a steady release.
Reaction scheme of βCD-xylan hydrogel formation 91 Figure 4.3. Reaction scheme of βCD-CMC hydrogel formation 92. Reaction scheme of βCD-MCC hydrogel formation 93 Figure 4.5. Reaction scheme of βCD gel hydrogel formation 94 Figure 4.6. a) Wide-scan XPS spectra of βCD–xylan, (b) deconvolution.
List of Tables
List of Symbols
Kf Freundlich constants relate to the adsorption capacity nf Freundlich constants relate to the adsorption intensity R Ideal gas constant (8.314 J mol-1 K-1). The ratio between the amount of metal ion released by the metal ion-loaded hydrogel and the amount of metal ion charged during the desorption phase.
List of Abbreviations
Introduction ________________________
Highlights
- Hydrogel
- Hydrogel forming materials
- Classification of Hydrogel
- Applications of hydrogel
- Cellulose, hemicellulose and cyclodextrin
- Microcrystalline cellulose
- Carboxymethyl cellulose
- Xylan
- β-Cyclodextrin
- Crosslinker
- Hydrogels based on cellulose, hemicellulose and cyclodextrin
- Applications in the field of delivery of biomolecules and removal of metal ions
- Delivery of Cephalexin
- Delivery of Vitamin B 12
- Adsorption of Ni (II) and Cd (II)
- Objectives of the thesis
- Overview of the chapters
- Chapter 2: Synthesis, characterization of microcrystalline cellulose based hydrogels and in vitro release of Cephalexin
- Chapter 3: Synthesis, characterization of carboxymethyl cellulose- xylan based hydrogels and in vitro release of Vitamin B 12
- Chapter 4: Synthesis, characterization of β-cyclodextrin-cellulose/
- Chapter 5: Concluding remarks & future scope
The CMC-based hydrogels have long been used as a carrier for drugs and biological macromolecules [43]. CDs form inclusion complex with the guest molecules (drug, biomolecule, metal ions, etc.) The cross-linked network of hydrogel prevents leaching of CD upon entering the physiological fluids.
Synthesis, characterization of microcrystalline cellulose based hydrogels and in vitro release of Cephalexin
Keywords
Chapter summary
FT-IR spectroscopy is adopted for chemical characterization, while swelling ratio and gel fraction are used for physical characterization of hydrogels. Rheological characterization of the synthesized hydrogels elucidates the flow behavior of the gels at a wide shear rate.
Materials and methods
- Materials
- Preparation of hydrogels
- Characterization 1.FT-IR spectroscopy
- Morphology
- Rheology
- Equilibrium swelling ratio
- Gel fraction
- Loading of Cephalexin
- Preparation of artificial gastric fluid and artificial intestinal fluid
- In vitro release of Cephalexin
- UV-vis spectroscopy
Freeze-dried hydrogels were ground and mixed with excess dried potassium bromide (KBr). Briefly, a certain amount of freeze-dried hydrogel is immersed in pH buffer or DI water at 298 K for 48 hours.
Results and discussions
- FT-IR spectra
- Morphology of hydrogels
- Rheological analysis
- Swelling ratio and gel fraction measurement
- Loading and in vitro release of Cephalexin
- Comparison of Cephalexin release with literature
The in vitro release of Cephalexin at three physiological buffers namely; AGF, AIF and PBS are performed for 8 hours and are shown in Figure 2.12a-c. The lower amount of Cephalexin release in AGF followed by the accelerated release in AIF and PBS can also be attributed to the existence of the drug in different forms. For this to occur, the initial burst release of Cephalexin is higher in PBS compared to the in vitro release in AIF.
Comparison with literature on in vitro release of Cephalexin using hydrogel Article Monomers Drug loading. The in vitro release of Cephalexin in physiological buffers is compared with the two previous reports given in the literature (Table 2.2). In this work, we have shown the in vitro release of Cephalexin in three physiological buffers independently as well as its sequential release in AGF, AIF and PBS.
Furthermore, the release of Cephalexin in PBS is higher than reported by Tomić et al.
Conclusions
For the oral route of administration, the carrier will not remain in the gastrointestinal tract for a long time as reported by Tomić et al., but a larger amount of drug release is required within a certain period. Therefore, a cumulative release of 87–98% in PBS within 8 h clarifies the effectiveness of MCC-based hydrogels as an effective carrier of Cephalexin.
Synthesis, characterization of carboxymethyl cellulose- xylan based hydrogels and in vitro release of Vitamin B 12
Chapter summary
This chapter attempts the synthesis of CMC and xylan based homopolymerized and copolymerized hydrogels using EGDE crosslinker in alkaline medium. The hydrogels are physically characterized by swelling ratio and gel fraction, while FT-IR spectroscopy reveals the functional moieties associated with the gels. Flow behavior, gel point, gelation temperature and gelation time are determined from the rheological behavior of the gels.
VB12 is loaded into the hydrogels and subsequent studies involve in vitro release in AGF, AIF and PBS.
Materials and methods
- Materials
- Preparation of hydrogels
- Characterization
- Rheology
- Loading of VB 12
- Release of VB 12
The FT-IR spectroscopy characterization procedure, morphology, swelling ratio, and gel fraction are similar to the characterization procedure described in Chapter 2 for the corresponding techniques. Next, a temperature scan of the precursor solution is performed at a temperature range of 298-353 K with 1% strain obtained from LVR and at a frequency of 1 Hz obtained from the frequency sweep test. The precursor solution is timed for 60 minutes at the appropriate gelation temperature with 1% strain obtained from the LVR and at a frequency of 1 Hz obtained from the frequency sweep test.
A preweighed amount of freeze-dried hydrogels was immersed in 20 mL of VB12 solution (0.5 mg mL-1). The appropriate volume of supernatant was collected and appropriately diluted to measure the concentration of residual VB12 by UV–vis spectroscopy. The VB12-loaded dried hydrogels were placed in buffers and 20 mL of buffer solution was added.
After each hour, 5 ml of buffer solution was collected and replaced with 5 ml of fresh buffer solution.
Results and discussions
- FT-IR spectra
- Morphology of hydrogels
- Rheological analysis
- Swelling ratio measurement and gel fraction
- Loading of VB 12
- In vitro release of VB 12
- Comparison of VB 12 release with literature
From the FESEM images (Figure 3.4), the microstructure of the xylan gel appears to be coarse in nature with random elongations. In vitro release of VB12 from the hydrogel network in AGF, AIF and PBS buffers is given in Figure 3.13a-c. Thus, the in vitro release of VB12 in these buffers will clarify the release behavior of the vitamin in simulated physiological fluids.
PBS would be a realistic attempt to simulate the in vitro release of VB12 in the gastrointestinal tract [117]. From Figure 3.13a-c it is observed that the in vitro release of VB12 depends on the pH of the medium. The in vitro release study in different physiological buffers also determines the efficiency of the hydrogels as an effective carrier of VB12.
Comparison with literature of in vitro release of VB12 using hydrogel Article Monomers VB12 loading.
Conclusions
Synthesis, characterization of β-cyclodextrin- cellulose/hemicellulose based hydrogels for the removal of
Chapter summary
Therefore, in this chapter, the polysaccharide-based hydrogels are used to adsorb Ni (II) and Cd (II) from aqueous solutions. CMC, MCC, xylan is cross-linked with EGDE to produce hydrogels; namely βCD-CMC, βCD-MCC and βCD-xylan, in alkaline medium at 1:1 molar ratio. The synthesized hydrogels are characterized with FT-IR spectroscopy, X-ray photoelectron spectroscopy, swelling ratio, gel fraction and the morphologies are observed in optical microscope and FESEM.
The equilibrium adsorption data are fitted in Langmuir and Freundlich isotherm model to reveal the nature of adsorption. The time-resolved adsorption capacities are fitted to pseudo-first-order and pseudo-second-order models to determine the kinetics of adsorption.
Materials and methods 1. Materials
- Preparation of hydrogels
- Characterization
- X-ray photoelectron spectroscopy
- Adsorption experiments
- Atomic absorption spectroscopy
Furthermore, the morphology of Cd(II) and Ni(II) charged hydrogels in the fluorescent mode within the same microscope under 475 nm wavelength light. PZC of the hydrogel was identified by the intersection of the curve at the zero value of ApH. The adsorption of metals using hydrogels was carried out in aqueous solutions of Cd(II) and Ni(II).
Adsorption experiments were performed at different dosages of adsorbents, concentrations, pH of metal solutions and temperature. Where C0 and Ce (in mg L-1) are the initial and equilibrium concentrations of metal ions in the solution, respectively. Where C0, Ct, Ce are the initial, time-resolved and equilibrium concentration of metal ions in the solution (mg L-1), V is the volume of the metal ion solution taken up for adsorption (in L) and m is the dry weight of the hydrogel (gm).
The concentration of metal ions in solution during adsorption was measured by Atomic Absorption Spectroscopy (or AAS, for short) (Manufacturer: Varian Australia, Model: .AA240FS) using flame mode.
Results and discussions 1. FT-IR spectra
- XPS analysis
- Morphology
- Swelling ratio and gel fraction
- Point of zero charge
- Removal of Cd(II) and Ni(II)
- Effect of adsorbent dosage
- Effect of concentration
- Effect of pH
- Effect of temperature
- Adsorption of Cd (II) and Ni (II) from mixed feed
- Equilibrium adsorption isotherm
- Adsorption kinetics
- Thermodynamic parameters
- Proposed adsorption mechanism
- Comparison of metal removal study with literature
The removal efficiency of the hydrogels decreases with the increase in concentrations, which also increases the adsorption capacity. These imply at lower concentrations that all adsorption sites are not occupied by the metal ions. Due to the selective adsorption, smaller amounts of Cd (II) and Ni (II) are adsorbed than the adsorption of individual metal ions.
Equilibrium adsorption capacity (qe) and removal of Cd (II) and Ni (II) from mixed feed, (a) qe of metal ions, (b) removal of metal ions. In contrast to the adsorption kinetics of Cd (II), time-resolved adsorption capacities of Ni (II) are characteristically placed. The lower regression values indicate the ability of pseudo-first-order model in describing the adsorption of metal ions on the hydrogel surface.
For that, the pseudo-second order agrees well for the adsorption of Cd(II) and Ni(II) on the hydrogel surface than the pseudo-first-order model. Based on the thermodynamic calculations, it can be concluded that the adsorption of Cd (II) and Ni (II) in hydrogel is a physisorption process. Here, the comparison in the performance of the adsorption of Cd(II) and Ni(II) using βCD-cellulose/hemicellulose based hydrogels is reported with a few literature reports.
Conclusions
Concluding remarks and future scope
Overall conclusion
Cellulose variants such as microcrystalline cellulose (MCC), carboxymethyl cellulose (CMC) and hemicellulose variant such as xylan are being cross-linked with EGDE to produce cellulose-hemicellulose-based hydrogels. Homopolymerized hydrogels as well as copolymerized hydrogels are synthesized in different molar ratios consisting of precursor monomers. The swelling ratios of cellulose-hemicellulose-based hydrogels are measured in DI water and physiological buffers, namely, AGF, AIF and PBS.
The smallest swelling ratio for all hydrogels is observed in AGF and this increases steadily with pH and a higher swelling ratio is obtained for DI water. For the βCD-cellulose/hemicellulose-based hydrogels, the swelling ratio is measured in DI water as well as pH=2 to 8 and it is found to follow a similar swelling ratio trend. In the rheological study, shear thinning behavior for cellulose-hemicellulose-based hydrogels is observed within a shear range of 0.01-1000 s-1.
All cellulose-hemicellulose-based hydrogels can withstand a frequency of more than 10 Hz before their cross-linking structure is broken.
Future direction
T., “Delivery of hydroxyapatite to dentinal tubules using a carboxymethyl cellulose dental hydrogel for the treatment of dentin hypersensitivity,” J. B., “Characterization of novel photocrosslinked carboxymethyl cellulose hydrogels for encapsulation of Nucleus Pulposus cells,” Acta Biomater. Bigand, V., Pinel, C., Da Silva Perez, D., Rataboul, F., Huber, P. and Petit-Conil, M., "Cationization of galactomannan and xylan hemicellulose", Carbohydr.
A., "Carboxymethyl Cellulose (CMC)-Based Pol-IPNs as Carriers for Controlled Release of Ciprofloxacin: An In Vitro Dynamic Study," J. K., "Synthesis of Carboxymethyl Cellulose-g-Poly(acrylic Acid)/LDH Hydrogel for Controlled In Vitro Release of Vitamin B12," Appl. A., "Radiation Synthesis of Superabsorbent Hydrogels Based on Carboxymethyl Cellulose/Sodium Alginate for Heavy Metal Ion Absorbent from Wastewater," J.
Ahemen, I., Meludu, O., Odoh, E., "Effect of sodium carboxymethyl cellulose concentration on the photophysical properties of zinc sulfide nanoparticles."
Appendix A: List of publications &
List of publications
Debashis Kundu and Tamal Banerjee. Carboxymethyl cellulose-xylan hydrogel
List of conference presentations
![Figure 2.5. FESEM morphology of hydrogels at 1 μm [a-c] and 200 nm [d - f]. (a) and (d) MCC gel, (b) and (e) MCC-xylan, (c) – (f) MCC-CMC](https://thumb-ap.123doks.com/thumbv2/azpdfnet/10553948.0/67.918.148.820.105.866/figure-fesem-morphology-hydrogels-mcc-mcc-xylan-mcc.webp)
