Controlled release of tinidazole and theophylline from chitosan based composite hydrogels

Preparation and Characterization of Theophylline Controlled Release Matrix System Incorporating Poloxamer 407, Stearyl Alcohol, and Hydroxypropyl Methylcellulose: A Novel Formulation and Development Study

BACKGROUND

Theophylline (THN), a bronchodilator with potential applications in emerging conditions like COVID-19, requires a controlled-release delivery system due to its narrow therapeutic range and short half-life. This need is particularly crucial as some existing formulations demonstrate impaired functionality. This study aims to develop a new 12-h controlled-release matrix system (CRMS) in the form of a capsule to optimize dosing intervals.

METHODS

CRMSs were developed using varying proportions of poloxamer 407 (P-407), stearyl alcohol (STA), and hydroxypropyl methylcellulose (HPMC) through the fusion technique. Their in vitro dissolution profiles were then compared with an FDA-approved THN drug across different pH media. The candidate formulation underwent characterization using X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, differential scanning calorimetry, and thermogravimetric analysis. Additionally, a comprehensive stability study was conducted.

RESULTS

In vitro studies showed that adjusting the concentrations of excipients effectively controlled drug release. Notably, the CRMS formulation 15 (CRMS-F15), which was composed of 30% P-407, 30% STA, and 10% HPMC, closely matched the 12 h controlled-release profile of an FDA-approved drug across various pH media. Characterization techniques verified the successful dispersion of the drug within the matrix. Furthermore, CRMS-F15 maintained a consistent controlled drug release and demonstrated stability under a range of storage conditions.

CONCLUSIONS

The newly developed CRMS-F15 achieved a 12 h controlled release, comparable to its FDA-approved counterpart.

Chitosan-based intelligent polymeric networks for site-specific colon medication delivery: A comprehensive study on controlled release of diloxanide furoate and network formation dynamics

Oral medications are prone to gastric degradation and enzymatic inactivation, diminishing their efficacy. This study investigates a solution by developing intelligent polymeric networks, incorporating chitosan, methacrylic acid, N, N, methylene bisacrylamide, and montmorillonite clay, to enable the controlled release of Diloxanide Furoate (DF), an anti-protozoal drug. Employing a swelling-assisted diffusion technique, drug loading percentages varied from 63.96 % to 76.82 % among different formulations. Increased chitosan and methacrylic acid content enhanced drug loading, while N, N, methylene bisacrylamide and montmorillonite clay demonstrated an inverse relationship affecting diffusion and swelling. Equilibrium swelling studies unveiled formulation-dependent behaviors, with chitosan reducing swelling and methacrylic acid promoting it. Higher N, N, methylene bisacrylamide concentrations decreased swelling, indicating a denser cross-linked structure, while montmorillonite clay reduced hydrophilicity and swelling capacity. Further analyses confirmed successful gel formation, particularly in formulations with higher chitosan, methacrylic acid, and N, N, methylene bisacrylamide content, while montmorillonite clay limited gel fraction due to restricted polymer chain mobility. Techniques such as Fourier transform infrared spectroscopy, Differential scanning calorimetry, and thermal gravimetric analyses supported network development, enhancing thermal stability and cross-linking density. This research underscores the flexibility of polymeric networks for precise drug delivery, offering potential advancements in targeted therapies for various medical conditions.

Fabrication of Stimuli-Responsive Quince/Mucin Co-Poly (Methacrylate) Hydrogel Matrices for the Controlled Delivery of Acyclovir Sodium: Design, Characterization and Toxicity Evaluation

Free-radical polymerization technique was adopted to fabricate a stimuli-responsive intelligent quince/mucin co-poly (methacrylate) hydrogel for the controlled delivery of acyclovir sodium. The developed hydrogel matrices were appraised using different parameters, such as drug loading (%), swelling kinetics, pH- and electrolyte-responsive swelling, and sol-gel fraction. Drug-excipient compatibility study, scanning electron microscopy, thermal analysis, powder X-ray diffraction (PXRD) analysis, in vitro drug release studies, drug release kinetics and acute oral toxicity studies were conducted. The results of drug loading revealed an acyclovir sodium loading of 63-75% in different formulations. The hydrogel discs exhibited pH-responsive swelling behavior, showing maximum swelling in a phosphate buffer with a pH of 7.4, but negligible swelling was obvious in an acidic buffer with a pH of 1.2. The swelling kinetics of the developed hydrogel discs exhibited second-order kinetics. Moreover, the hydrogel discs responded to the concentration of electrolytes (CaCl2 and NaCl). The results of the FTIR confirm the formation of the hydrogel via free-radical polymerization. However, the major peaks of acyclovir remain intact, proving drug-excipient compatibility. The results of the SEM analysis reveal the porous, rough surface of the hydrogel discs with multiple cracks and pores over the surface. The results of the PXRD disclose the amorphous nature of the fabricated hydrogel. The dissolution studies showed a minor amount of acyclovir sodium released in an acidic environment, while an extended release up to 36 h in the phosphate buffer was observed. The drug release followed Hixen-Crowell's kinetics with Fickian diffusion mechanism. The toxicity studies demonstrated the non-toxic nature of the polymeric carrier system. Therefore, these results signify the quince/mucin co-poly (methacrylate) hydrogel as a smart material with the potential to deliver acyclovir into the intestine for an extended period of time.

pH Responsive Hydrogels for the Delivery of Capecitabine: Development, Optimization and Pharmacokinetic Studies

The objective of the current study was to achieve a sustained release profile of capecitabine (CAP), an anticancer agent frequently administered in conventional dosage form due to its short plasma half-life. A drug-loaded smart pH responsive chitosan/fenugreek-g-poly (MAA) hydrogel was synthesized by an aqueous free radical polymerization technique. The developed network was evaluated for capecitabine loading %, swelling response, morphology, structural and compositional characteristics, and drug release behavior. Significantly higher swelling and in vitro drug release rate were exhibited by formulations at pH 7.4 than at pH 1.2, demonstrating the pH responsive character of hydrogels. Swelling percentage and CAP loading ranged within 74.45-83.54% and 50.13-72.43%, respectively. Maximum release, up to 93%, was demonstrated over 30 h, evidencing the controlled release pattern of CAP from hydrogels. The optimized formulation was further screened for acute oral toxicity studies. No signs of oral, dermal, or ocular toxicities were noticed, confirming safety evidence of the network. Furthermore, pharmacokinetic analysis demonstrated the sustained release response of CAP from hydrogels as confirmed by a significant increase in plasma half-life (t_1/2) (13 h) and AUC (42.88 µg h/mL) of CAP. Based on these findings, fabricated hydrogels are strongly recommended as a biocompatible carrier for colorectal delivery of active agents.

Effect of pectin and attapulgite filler on swelling, network parameters and controlled release of diltiazem hydrochloride from polyacrylic copolymer gel

Pectin grafted polyacrylic copolymer hydrogels were made by free radical crosslink copolymerization of acrylic acid (AA) and acrylamide (AM) in an aqueous solution of pectin. N'N-methylene bis acrylamide (MBA) was used as a crosslinker. During the polymerization reaction the attapulgite (APG) filler was also incorporated in situ into the network of the copolymer gel. Several filled hydrogels were prepared by varying the amount of pectin and APG filler. These hydrogels were characterized by FTIR, ¹³C NMR, XRD, TGA, SEM, mechanical properties, DMA, swelling, diffusion characteristics and network parameters. The release kinetics of a model drug diltiazem hydrochloride (DT) was studied with these hydrogels. The wt% of pectin, APG and MBA was optimized with a central composite design (CCD) model of response surface methodology (RSM) with equilibrium swelling ratio (ESR), drug adsorption (mg/100 mg gel) and drug release% in 16 h as response. Accordingly, the hydrogel prepared with 5:1 AA:AM molar ratio, 25 wt% monomer concentration, 1% each of initiator and MBA concentration, 18 wt% pectin and 2 wt% APG showed an optimized ESR of 17.75, drug loading of 27.58 and a drug release % of 92.5 in 16 h at a solution pH of 7.4.

pH responsive release of paclitaxel by self-assembling Chitosan-ethyl vanillin@GNRs nanocomposites

Carboxylation chitosan achieved by alkalization linked with ethyl vanillin to obtain Chitosan-ethyl vanillin (EV-CMCS) compound through Schiff base reaction and confirmed by FT-IR, UV, XRD, TG and NMR. EV-CMCS refluxed with GNRs for acquisition of EV-CMCS@GNRs nanocomposites for PTX Loading and release. Results demonstrated that both EV-CMCS and EV-CMCS@GNRs are nanoscale composites with excellent solubilization due to their micelle structure taking CMC values of 0.06683 mg/mL and 0.06537 mg/mL. It was found that the loading and encapsulation rate of EV-CMCS and EV-CMCS@GNRs for PTX are 19.59~37.64% and 60.36~80.79% as well as 20.99~37.02% and 58.78~79.77%. Compared with only the delayed release of EV-CMCS that it have 11.5% and 18.7% accumulative release amount for 24 h and 14.9% and 23.7% for 48 h under both pH 6.8 and 7.4, the EV-CMCS@GNRs represent sudden release that it have an accumulative release amount of 90.2% for 24 h and 96.0% for 48 h at pH 6.8. It deduced that the broken Schiff base under acidic condition can increase CMC of EV-CMCS@GNRs, which offered an alternative way for paclitaxel delivery for tumor therapy.

Advancements in release-active antimicrobial biomaterials: A journey from release to relief

Escalating medical expenses due to infectious diseases are causing huge socioeconomic pressure on mankind globally. The emergence of antibiotic resistance has further aggravated this problem. Drug-resistant pathogens are also capable of forming thick biofilms on biotic and abiotic surfaces to thrive in a harsh environment. To address these clinical problems, various strategies including antibacterial agent delivering matrices and bactericidal coatings strategies have been developed. In this review, we have discussed various types of polymeric vehicles such as hydrogels, sponges/cryogels, microgels, nanogels, and meshes, which are commonly used to deliver antibiotics, metal nanoparticles, and biocides. Compositions of these polymeric matrices have been elaborately depicted by elucidating their chemical interactions and potential activity have been discussed. On the other hand, various implant/device-surface coating strategies which exploit the release-active mechanism of bacterial killing are discussed in elaboration. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Cardiovascular Disease Implantable Materials and Surgical Technologies > Nanomaterials and Implants Therapeutic Approaches and Drug Discovery > Nanomedicine for Infectious Disease.

Radiopaque Chitosan Ducts Fabricated by Extrusion-Based 3D Printing to Promote Healing After Pancreaticoenterostomy

Long-term placement of non-degradable silicone rubber pancreatic duct stents in the body is likely to cause inflammation and injury. Therefore, it is necessary to develop degradable and biocompatible stents to replace silicone rubber tubes as pancreatic duct stents. The purpose of our research was to verify the feasibility and biological safety of extrusion-based 3D printed radiopaque chitosan (CS) ducts for pancreaticojejunostomy. Chitosan-barium sulfate (CS-Ba) ducts with different molecular weights (low-, medium-, and high-molecular weight CS-Ba: LCS-Ba, MCS-Ba, and HCS-Ba, respectively) were soaked in vitro in simulated pancreatic juice (SPJ) (pH 8.0) with or without pancreatin for 16 weeks. Changes in their weight, water absorption rate and mechanical properties were tested regularly. The biocompatibility, degradation and radiopaque performance were verified by in vivo and in vitro experiments. The results showed that CS-Ba ducts prepared by this method had regular compact structures and good molding effects. In addition, the lower the molecular weight of the CS-Ba ducts was, the faster the degradation rate was. Extrusion-based 3D-printed CS-Ba ducts have mechanical properties that match those of soft tissue, good biocompatibility and radioopacity. In vitro studies have also shown that CS-Ba ducts can promote the growth of fibroblasts. These stents have great potential for use in pancreatic duct stent applications in the future.

Oral delivery of self-assembling bioactive peptides to target gastrointestinal tract disease

Peptides are known for their diverse bioactivities including antioxidant, antimicrobial, and anticancer activity, all three of which are potentially useful in treating colon-associated diseases. Beside their capability to stimulate positive health effects once released in the body, peptides are able to form useful nanostructures such as hydrogels. Combining peptide bioactivity and peptide gel-forming potentials can create interesting systems that can be used for oral delivery. This combination, acting as a two-in-one system, has the potential to avoid the need for delicate entrapment of a drug or natural bioactive compound. We here review the context and research progress, to date, in this area.

Preparation, Characterization, Swelling Potential, and In-Vitro Evaluation of Sodium Poly(Styrene Sulfonate)-Based Hydrogels for Controlled Delivery of Ketorolac Tromethamine

The objective of the current study work was to fabricate sodium poly(styrene sulfonate-co-poly acrylic acid) (SPSPAA) hydrogels by using a free radical co-polymerization method for controlled delivery of ketorolac tromethamine (KT). Polymer (sodium poly(styrene sulfonate) (SPS) polymerized with monomer acrylic acid (AA) in the presence of initiator ammonium peroxodisulfate (APS) and cross-linker N',N'-Methylene bisacrylamide (MBA). Different combinations of polymer, cross-linker and monomer, were employed for development of polymeric hydrogels. Various studies such as sol-gel, drug loading, dynamic swelling, and drug release studies were carried out to know the sol and gel portion of SPSPAA, swelling behavior of hydrogels at different pH media (1.2 and 7.4), quantification of drug loaded by fabricated hydrogels, and amount release of KT at pH 1.2 and 7.4. Higher dynamic swelling was found at pH 7.4 compared to pH 1.2, and as a result, greater percent release of drug was perceived at pH 7.4. Thermal stability, crystallinity, confirmation of functional groups and development of a new polymeric system, and surface morphology were evaluated via Thermogravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC), Powder X-ray Diffraction (PXRD), Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM) respectively. The results showed that the present work could be used as a potential candidate for controlled delivery of KT.

Wound Dressing Hydrogel of Enteromorpha prolifera Polysaccharide-Polyacrylamide Composite: A Facile Transformation of Marine Blooming into Biomedical Material

Great endeavors have been dedicated to the development of wound dressing materials. However, there is still a demand for developing a wound dressing hydrogel that integrates natural macromolecules without requiring extra chemical modifications, so as to enable a facile transformation and practical application in wound healing. Herein, a composite hydrogel was prepared with water-soluble polysaccharides from Enteromorpha prolifera (PEP) cross-linked with boric acid and polyacrylamide cross-linked via polymerization (PAM) using a one-pot method. The dual-network of this hydrogel enabled it to have an ultratough mechanical strength. Moreover, interfacial characterizations reflected that the hydrogen bonds and dynamic hydroxyl-borate bonds contributed to the self-healing ability of the PEP-PAM hydrogel, and the surface groups on the hydrogel allowed for tissue adhesiveness and natural antioxidant properties. Additionally, human epidermal growth factor-loaded PEP-PAM hydrogel promoted cell proliferation and migration in vitro and significantly accelerated wound healing in vivo on model rats. These progresses suggested a prospect for the PEP-PAM hydrogel as an effective and easily available wound dressing material. Remarkably, this work showcases that a wound dressing hydrogel can be facially developed by using natural polysaccharides as a one component and offers a new route for the high-value utilization of disastrous marine blooming biomass by transforming it into a biomedical material.

pH-Sensitive Biomaterials for Drug Delivery

The development of precise and personalized medicine requires novel formulation strategies to deliver the therapeutic payloads to the pathological tissues, producing enhanced therapeutic outcome and reduced side effects. As many diseased tissues are feathered with acidic characteristics microenvironment, pH-sensitive biomaterials for drug delivery present great promise for the purpose, which could protect the therapeutic payloads from metabolism and degradation during in vivo circulation and exhibit responsive release of the therapeutics triggered by the acidic pathological tissues, especially for cancer treatment. In the past decades, many methodologies, such as acidic cleavage linkage, have been applied for fabrication of pH-responsive materials for both in vitro and in vivo applications. In this review, we will summarize some pH-sensitive drug delivery system for medical application, mainly focusing on the pH-sensitive linkage bonds and pH-sensitive biomaterials.

Using Carbomer-Based Hydrogels for Control the Release Rate of Diclofenac Sodium: Preparation and In Vitro Evaluation

The aim of the current research work was to prepare Car934-g-poly(acrylic acid) hydrogels by the free-radical polymerization technique. Various concentrations of carbopol, acrylic acid and ethylene glycol dimethacrylate were employed for the fabrication of Car934-g-poly(acrylic acid) hydrogels. Fourier-transform infrared spectroscopy (FTIR), Thermogravimetric analysis (TGA), Differential scanning calorimetry (DSC), Scanning electron microscope (SEM) and Powder X-ray diffractometry (PXRD) studies were performed to know the structural arrangement, thermal stability, physical appearance and amorphous network of developed hydrogels. FTIR analysis revealed that carbopol reacted with acrylic acid during the process of polymerization and confirmed the grafting of acrylic acid over the backbone of carbopol. TGA and DSC studies showed that developed hydrogels were thermally stable. Surface morphology was analyzed by SEM, which confirmed a porous network of hydrogels. PXRD analysis indicated that crystallinity of the drug was reduced by the amorphous network of hydrogels. Furthermore, swelling studies for all developed hydrogels were performed at both media, i.e., pH 1.2 and 7.4, and higher swelling was exhibited at pH 7.4. Sol–gel analysis was performed to evaluate the soluble unreacted part of the fabricated hydrogels. Similarly, an in-vitro study was conducted for all hydrogel formulations at both acidic (pH 1.2) and basic (pH 7.4) mediums, and a greater drug release was observed at pH 7.4. Different kinetics such as zero-order, first-order, the Higuchi model and the Korsmeyer–Peppas model were applied to know the mechanism of release order of drugs from the hydrogels.

Specific Anti-biofilm Activity of Carbon Quantum Dots by Destroying P. gingivalis Biofilm Related Genes

Introduction

Biofilms protect bacteria from antibiotics and this can produce drug-resistant strains, especially the main pathogen of periodontitis, Porphyromonas gingivalis. Carbon quantum dots with various biomedical properties are considered to have great application potential in antibacterial and anti-biofilm treatment.

Methods

Tinidazole carbon quantum dots (TCDs) and metronidazole carbon quantum dots (MCDs) were prepared by a hydrothermal method with the clinical antibacterial drugs tinidazole and metronidazole, respectively. Then, TCDs and MCDs were characterized by transmission electron microscopy, UV–visible spectroscopy, infrared spectroscopy and energy-dispersive spectrometry. The antibacterial effects were also investigated under different conditions.

Results

The TCDs and MCDs had uniform sizes. The results of UV–visible and energy-dispersive spectrometry confirmed their important carbon polymerization structures and the activity of the nitro group, which had an evident inhibitory effect on P. gingivalis, but almost no effect on other bacteria, including Escherichia coli, Staphylococcus aureus and Prevotella nigrescens. Importantly, the TCDs could penetrate the biofilms to further effectively inhibit the growth of P. gingivalis under the biofilms. Furthermore, it was found that the antibacterial effect of TCDs lies in its ability to impair toxicity by inhibiting the major virulence factors and related genes involved in the biofilm formation of P. gingivalis, thus affecting the self-assembly of biofilm-related proteins.

Conclusion

The findings demonstrate a promising new method for improving the efficiency of periodontitis treatment by penetrating the P. gingivalis biofilm with preparations of nano-level antibacterial drugs.

Synthesis and Characterization of Lyophilized Chitosan-Based Hydrogels Cross-Linked with Benzaldehyde for Controlled Drug Release

In this study, chitosan-based hydrogels were produced by incorporating three drugs with a different solubility into a polymer matrix. The lyophilized chitosan salt was prepared using an innovative and less-expensive synthetic process by the freeze-drying technique. Firstly, the three drugs (caffeine, ascorbic acid, and 5-fluorouracil (5-FU)) were selected as model drugs to test the in vitro release behavior of the hydrogel. The drugs were solubilized in chitosan salt, lyophilized, and cross-linked with benzaldehyde involving the formation of a Schiff base with (–C=N-) linkage to produce a physical hydrogel. Subsequently, the physicochemical properties of N-benzyl chitosan and lyophilized chitosan salt were evaluated by Fourier-transform infrared (FTIR) spectra, scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). The intrinsic viscosity of the conventional chitosan was determined by the Mark–Houwink–Sakurada equation. Moreover, the kinetics of hydrogel swelling and drug release were studied by the UV-visible method at physiological conditions (pH = 7.4 at 37°C). The results show that lyophilized N-benzyl chitosan had a maximum swelling ratio of 720 ± 2% by immersion in phosphate-buffered saline solutions (PBS) (pH = 7.4 at 37°C). In vitro drug releases were evaluated in PBS, and the obtained results show that the maximum drug release after 24 h was 42% for caffeine, 99% for 5-FU, and 94% for ascorbic acid. Then, to optimize the cumulative release of caffeine, Tween 20 was added and 98% as a release percentage was obtained. The drug-loading results were investigated with the Korsmeyer–Peppas kinetic model and applied to determine the drug release mechanism.

Kinetics and controlled release of lidocaine from novel carrageenan and alginate-based blend hydrogels

The controlled release of drug from drug carrier has been a point of concern for the researchers to ensure the bioavailability of drug with reduced side effects. The formulation in this study is based upon biopolymers; carrageenan (CG), sodium alginate (SA) and various molecular weights of polyethylene glycol (PEG), cross-linked with (3-Aminopropyl)triethoxysilane, APTES for the sustained release of model drug (lidocaine). The physicochemical properties of the formulated hydrogel blends include bonding pattern (using Fourier Transform Infra-Red Spectroscopy (FTIR), Thermogravimetric analysis (TGA), X-ray diffraction (XRD), swelling study, antimicrobial activity and morphology of hydrogel films was analyzed by scanning electron microscopy (SEM). The as-prepared hydrogels show an improved cell compatibility against 3T3 cell line as well as cell proliferation and kinetics of drug release showed that these hydrogels are potential for controlled release of lidocaine, a numbing agent. GAP 60 exhibited maximum swelling percent (910%) and was employed to load the drug. By using in vitro model, the drug release was studied in PBS solution. Non-Fickian and other kinetic models (Zero order, Higuchi, Hixson, Korsmeyer Peppas and Baker-Lonsdale) for diffusion were followed in results. The improved properties showed that the formulated hydrogels can easily be used for the sustain drug release studies.

Loading of Cefixime to pH sensitive chitosan based hydrogel and investigation of controlled release kinetics

Chitosan (biopolymer) and polyvinyl pyrolidone (PVP) with aminopropyletriethoxy silane (cross linker) based hydrogels were prepared and tested for controlled drug release. The drug release and kinetics were studied as a function of pH. Formulations were characterized by Fourier Transform Infrared (FTIR) and Thermogravimetric (TGA) analysis and TAP 32 hydrogel formulation was the most stable and hydrogel samples showed promising antibacterial activity against E. coli strain. The maximum swelling (4386%) was observed for TAP 32 formulation in distilled water, which was decreased with the concentration of ions. The diffusion exponent (n) values of all hydrogel formulations were recorded to be <0.5, which is an indication of Quasi-Fickian diffusion. The maximum swelling was observed at pH 2 and decreased at higher pH. The pH sensitivity of hydrogels found to be promising for their use in drug delivery, which was tested for cefixime drug. Drug release of 81.6% was observed for the period of 12 h in a simulated gastric fluid (SGF). The values of R² for zero order, first order, Higuchi, Hixson, Korsmeyer-Peppas and Baker-Lonsdale were 0.97, 0.9818, 0.99, 0.99, 0.88 and 0.80, respectively. The hydrogels based on chitosan and PVP revealed potential for controlled cefixime drug release in gastric pH medium.

Controlling Fluid Diffusion and Release through Mixed-Molecular-Weight Poly(ethylene) Glycol Diacrylate (PEGDA) Hydrogels

Due to their inherent ability to swell in the presence of aqueous solutions, hydrogels offer a means for the delivery of therapeutic agents in a range of applications. In the context of designing functional tissue-engineering scaffolds, their role in providing for the diffusion of nutrients to cells is of specific interest. In particular, the facility to provide such nutrients over a prolonged period within the core of a 3D scaffold is a critical consideration for the prevention of cell death and associated tissue-scaffold failure. The work reported here seeks to address this issue via fabrication of hybrid 3D scaffolds with a component fabricated from mixed-molecular-weight hydrogel formulations capable of storing and releasing nutrient solutions over a predetermined time period. To this end, poly(ethylene) glycol diacrylate hydrogel blends comprising mixtures of PEGDA-575 Mw and PEGDA-2000 Mw were prepared via UV polymerization. The effects of addition of the higher-molecular-weight component and the associated photoinitiator concentration on mesh size and corresponding fluid permeability have been investigated by diffusion and release measurements using a Theophylline as an aqueous nutrient model solution. Fluid permeability across the hydrogel films has also been determined using a Rhodamine B solution and associated fluorescence measurements. The results indicate that addition of PEGDA-2000 Mw to PEGDA-575 Mw coupled with the use of a specific photoinitiator concentration provides a means to change mesh size in a hydrogel network while still retaining an overall microporous material structure. The range of mesh sizes created and their distribution in a 3D construct provides for the conditions required for a more prolonged nutrient release profile for tissue-engineering applications.

Preparation and characterization of thermally crosslinked films based on chitosan and poly(2-ethyl-2-oxasoline)

Сrosslinked films based on chitosan (СHI) and poly(2-ethyl-2-oxazoline) (POZ) were prepared by thermal crosslinking. The optimal synthesis conditions and the composition of the film compositions were determined. The highest yield of the gel fraction was observed for CHI:POZ (80:20) films with a crosslinking time of 4 h at a temperature of 100°С. The main physicochemical properties of films based on pure CHI and CHI:POZ have been studied. The film swelling ability was reduced with the increase of poly(2-ethyl-2-oxazolin) content. The formation of crosslinks between N,N’-methylene-bis-acrylamide and functional amine groups of chitosan was proposed based on IR-spectroscopy data.

A facile method to fabricate thermo- and pH-sensitive hydrogels with good mechanical performance based on poly(ethylene glycol) methyl ether methacrylate and acrylic acid as a potential drug carriers

A thermo- and pH-sensitive hydrogel was prepared by a facile free aqueous radical copolymerization of PEGMA and AAc without any crosslinkers for controlled drug delivery. The successful fabrication of hydrogels was confirmed by Fourier transform infrared spectroscopy (FT-IR) and thermo gravimetric analysis (TGA) measurements. The morphological, mechanical and swelling properties of the obtained hydrogels were studied systematically. The results showed that the morphological and mechanical behaviors of the resultant hydrogels were strongly affected by the content of AAc. Moreover, the obtained hydrogels showed an excellent thermo-, pH- and salinity sensitivities. Release profiles of 5-Fu were studied at different pH (gastric pH 1.2 and intestinal pH 7.4) and temperatures (25 °C and 37 °C). The results showed that the release is very low at pH 1.2/37 °C and high at pH 7.4/25 °C. The cytotoxicity of hydrogels to cells was determined by an MTT assay. The result demonstrated that the blank hydrogels had negligible toxicity to cells, whereas the 5-Fu-loaded hydrogels remained high in cytotoxicity for LO2 and HepG-2 cells. Results of the present investigation exemplify the potential of this novel thermo- and pH-sensitive hydrogel for the controlled and targeted delivery of the anti cancer drug 5-Fu.

Fabrication and evaluation of dental fillers using customized molds via 3D printing technology

In view of the high incidence and long-term treatment of dental caries, personalized dental fillers with long therapeutic action have broad application prospects in the dental clinic. The objective of this study was to fabricate and evaluate novel dental fillers using state-of-the-art 3D printing technology. Tinidazole (TNZ), a commonly used antibacterial drug in the dental clinic, was chosen as the model compound. Models of molars with carious cavities were obtained via 3D scanning. TNZ dental fillers were indirectly produced by thermal pressing using customized 3D printed molds. In addition, bio-relevant in vitro dissolution and mechanical testing methods were developed using customized 3D printed release and compression molds, respectively. It was observed that the formability, mechanical properties, and release behavior of the TNZ dental fillers were affected by mold materials, plasticizers, and release modifiers. The developed dental fillers were capable of sustained releasing TNZ over one week. The TNZ release characteristics can be tailored based on clinical requirements by varying hydroxypropyl methylcellulose E5 (HPMC-E5) concentrations and filler dimensions. Moreover, computational simulation based on the finite element method showed that the biomechanical behavior of the TNZ dental fillers met the daily use requirement. The present study demonstrated that the state-of-the-art 3D printing technology can be used to design and fabricate personalized dental fillers with high mechanical strength and "on-demand" drug release characteristics.

Synthesis and characterizations of o-nitrochitosan based biopolymer electrolyte for electrochemical devices

For the past decade, much attention was focused on polysaccharide natural resources for various purposes. Throughout the works, several efforts were reported to prepare new function of chitosan by chemical modifications for renewable energy, such as fuel cell application. This paper focuses on synthesis of the chitosan derivative, namely, O-nitrochitosan which was synthesized at various compositions of sodium hydroxide and reacted with nitric acid fume. Its potential as biopolymer electrolytes was studied. The substitution of nitro group was analyzed by using Attenuated Total Reflectance Fourier Transform Infra-Red (ATR-FTIR) analysis, Nuclear Magnetic Resonance (NMR) and Elemental Analysis (CHNS). The structure was characterized by X-ray Diffraction (XRD) and its thermal properties were examined by using differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). Whereas, the ionic conductivity of the samples was analyzed by electrochemical impedance spectroscopy (EIS). From the IR spectrum results, the nitro group peaks of O-nitrochitosan, positioned at 1646 and 1355 cm^-1, were clearly seen for all pH media. At pH 6, O-nitrochitosan exhibited the highest degree of substitution at 0.74 when analyzed by CHNS analysis and NMR further proved that C-6 of glucosamine ring was shifted to the higher field. However, the thermal stability and glass transition temperatures were decreased with acidic condition. The highest ionic conductivity of O-nitrochitosan was obtained at ~10⁻⁶ cm^-1. Overall, the electrochemical property of new O-nitrochitosan showed a good improvement as compared to chitosan and other chitosan derivatives. Hence, O-nitrochitosan is a promising biopolymer electrolyte and has the potential to be applied in electrochemical devices.

Facile Synthesis of Chitosan Based-(AMPS-co-AA) Semi-IPNs as a Potential Drug Carrier: Enzymatic Degradation, Cytotoxicity, and Preliminary Safety Evaluation

OBJECTIVE

The study describes the development of chitosan-based (AMPS-co-AA) semi-IPN hydrogels using free radical polymerization technique.

METHODS

The resulting hydrogels were characterized using Fourier Transform Infrared Spectroscopy (FTIR), Thermogravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC), X-Ray diffraction (XRD), and Scanning Electron Microscopy (SEM). The successful crosslinking of chitosan, 2- Acrylamido-2-Methylpropane Sulfonic Acid (AMPS), and Acrylic Acid (AA) was confirmed by FT IR. Unloaded and drug-loaded hydrogels exhibited higher thermal stability after crosslinking compared to the individual components. XRD confirmed the decrease in crystallinity after hydrogel formation and molecular dispersion of Oxaliplatin (OXP) in the polymeric network. SEM showed rough, vague and nebulous surface resulting from crosslinking and loading of OXP.

RESULTS

The experimental results revealed that swelling and drug release were influenced by the pH of the medium being low at acidic pH and higher at basic pH. Increasing the concentration of chitosan and AA enhanced the swelling, drug loading and drug release while AMPS was found to act inversely.

CONCLUSION

It was confirmed that the hydrogels were degraded more by specific enzyme lysozyme as compared to the non-specific enzyme collagenase. In-vitro cytotoxicity suggested that the unloaded hydrogels were non-cytotoxic while crude drug and drug-loaded hydrogel exhibited dose-dependent cytotoxicity against HCT-116 and MCF-7. Results of acute oral toxicity on rabbits demonstrated that the hydrogels are non-toxic up to 3900 mg/kg after oral administration, as no toxicity or histopathological changes were observed in comparison to control rabbits. These pH-sensitive hydrogels appear to provide an ideal basis as a safe carrier for oral drug delivery.

Antibacterial Hydrogels

Antibacterial materials are recognized as important biomaterials due to their effective inhibition of bacterial infections. Hydrogels are 3D polymer networks crosslinked by either physical interactions or covalent bonds. Currently, hydrogels with an antibacterial function are a main focus in biomedical research. Many advanced antibacterial hydrogels are developed, each possessing unique qualities, namely high water swellability, high oxygen permeability, improved biocompatibility, ease of loading and releasing drugs, and structural diversity. Here, an overview of the structures, performances, mechanisms of action, loading and release behaviors, and applications of various antibacterial hydrogel formulations is provided. Furthermore, the prospects in biomedical research and clinical applications are predicted.

Antimicrobial hydrogels: promising materials for medical application

The rapid emergence of antibiotic resistance in pathogenic microbes is becoming an imminent global public health problem. Local application of antibiotics might be a solution. In local application, materials need to act as the drug delivery system. The drug delivery system should be biodegradable and prolonged antibacterial effect should be provided to satisfy clinical demand. Hydrogel is a promising material for local antibacterial application. Hydrogel refers to a kind of biomaterial synthesized by a water-soluble natural polymer or a synthesized polymer, which turns into gel according to the change in different signals such as temperature, ionic strength, pH, ultraviolet exposure etc. Because of its high hydrophilicity, unique three-dimensional network, fine biocompatibility and cell adhesion, hydrogel is one of the suitable biomaterials for drug delivery in antimicrobial areas. In this review, studies from the past 5 years were reviewed, and several types of antimicrobial hydrogels according to different ingredients, different preparations, different antimicrobial mechanisms, different antimicrobial agents they contained and different applications, were summarized. The hydrogels loaded with metal nanoparticles as a potential method to solve antibiotic resistance were highlighted. Finally, future prospects of development and application of antimicrobial hydrogels are suggested.

Mechanical Properties of Herbal Patches from Chitosan-Based Polymer Blends for Medical Applications

Recently, Thai herbs are widely used as medicine to treat some illnesses. Zingiber cassumunar Roxb., known by the Thai name “Plai”, is a popular anti-inflammatory, antispasmodic herbal body and muscle treatment. This research aimed to prepare herbal patches that incorporated the 3 g of crude Z. cassumunar oil. The herbal patches made from different polymer blends were 2 g of 3.5%w/v chitosan and 5 g of 20%w/v hydroxypropyl methylcellulose (HPMC), or 2 g of 3.5%w/v chitosan and 5 g of 20%w/v polyvinyl alcohol (PVA) using 2 g of glycerin as a plasticizer. They were prepared by mixing all ingredients in a beaker and produced by solvent casting method in hot air oven at 70±2oC. The completed herbal patches were evaluated for their mechanical properties including Young’s modulus, ultimate tensile strength, elongation at break, T-peel strength, and tack adhesion. The thickness of blank and herbal patches was 0.263-0.282 mm and 0.269-0.275 mm, respectively. Young’s modulus, ultimate tensile strength, elongation at break, T-peel strength, and tack adhesion were 104.73-142.71 MPa, 87.92-93.28 MPa, 154.39-174.98 %, 3.43-4.88 MPa, and 5.29-7.02 MPa, respectively, for blank patches, and 116.83-147.28 MPa, 89.49-100.47 MPa, 133.78-159.27 %, 2.01-3.98 MPa, and 4.03-5.19 MPa, respectively, for herbal patches. We prepared herbal blended patches made from chitosan/PVA or chitosan/HPMC polymer matrix blends incorporating the crude Z. cassumunar oil. They had good mechanical properties that might be developed for herbal medicinal application.

pH-Switchable and self-healable hydrogels based on ketone type acylhydrazone dynamic covalent bonds

Stimuli-responsive hydrogels using dynamic covalent bonds (DCBs) as cross-links may exhibit simultaneously the stimuli-responsibility of the physical gels and stability of the chemical gels. We prepared well-defined, ketone-based polymers based on commercially available diacetone acrylamide (DAAM) by a reversible addition-fragmentation chain transfer (RAFT) polymerization technique. The polymers could react with hexanedihydrazide yielding hydrogels. The mechanics, flexible properties and gelator concentration of the hydrogels can be tuned by varying the ratio of DAAM. Gelation time and hydrogel stability were gravely affected by the pH of the surrounding medium. The hydrogels possess self-healing ability without any external stimuli and undergo switchable sol-gel transition by the alternation of pH. In addition, the hydrogels showed pH-responsive controlled release behavior for rhodamine B. These kinds of ketone-type acylhydrazone DCB hydrogels, avoiding the aldehyde component, may ameliorate their biocompatibility and find potential applications in biomedicines, tissue engineering, etc.

pH responsive N-succinyl chitosan/Poly (acrylamide-co-acrylic acid) hydrogels and in vitro release of 5-fluorouracil

There has been significant progress in the last few decades in addressing the biomedical applications of polymer hydrogels. Particularly, stimuli responsive hydrogels have been inspected as elegant drug delivery systems capable to deliver at the appropriate site of action within the specific time. The present work describes the synthesis of pH responsive semi-interpenetrating network (semi-IPN) hydrogels of N-succinyl-chitosan (NSC) via Schiff base mechanism using glutaraldehyde as a crosslinking agent and Poly (acrylamide-co-acrylic acid)(Poly (AAm-co-AA)) was embedded within the N-succinyl chitosan network. The physico-chemical interactions were characterized by Fourier transform infrared (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and field emission scanning electron microscope (FESEM). The synthesized hydrogels constitute porous structure. The swelling ability was analyzed in physiological mediums of pH 7.4 and pH 1.2 at 37°C. Swelling properties of formulations with various amounts of NSC/ Poly (AAm-co-AA) and crosslinking agent at pH 7.4 and pH 1.2 were investigated. Hydrogels showed higher swelling ratios at pH 7.4 while lower at pH 1.2. Swelling kinetics and diffusion parameters were also determined. Drug loading, encapsulation efficiency, and in vitro release of 5-fluorouracil (5-FU) from the synthesized hydrogels were observed. In vitro release profile revealed the significant influence of pH, amount of NSC, Poly (AAm-co-AA), and crosslinking agent on the release of 5-FU. Accordingly, rapid and large release of drug was observed at pH 7.4 than at pH 1.2. The maximum encapsulation efficiency and release of 5-FU from SP2 were found to be 72.45% and 85.99%, respectively. Kinetics of drug release suggested controlled release mechanism of 5-FU is according to trend of non-Fickian. From the above results, it can be concluded that the synthesized hydrogels have capability to adapt their potential exploitation as targeted oral drug delivery carriers.

Bioresponsive Materials for Drug Delivery Based on Carboxymethyl Chitosan/Poly(γ-Glutamic Acid) Composite Microparticles

Carboxymethyl chitosan (CMCS) microparticles are a potential candidate for hemostatic wound dressing. However, its low swelling property limits its hemostatic performance. Poly(γ-glutamic acid) (PGA) is a natural polymer with excellent hydrophilicity. In the current study, a novel CMCS/PGA composite microparticles with a dual-network structure was prepared by the emulsification/internal gelation method. The structure and thermal stability of the composite were determined by Fourier transform infrared spectroscopy (FTIR), X-ray powder diffraction (XRD), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), and thermogravimetric analysis (TGA). The effects of preparation conditions on the swelling behavior of the composite were investigated. The results indicate that the swelling property of CMCS/PGA composite microparticles is pH sensitive. Levofloxacin (LFX) was immobilized in the composite microparticles as a model drug to evaluate the drug delivery performance of the composite. The release kinetics of LFX from the composite microparticles with different structures was determined. The results suggest that the CMCS/PGA composite microparticles are an excellent candidate carrier for drug delivery.

pH Sensitive Hydrogels in Drug Delivery: Brief History, Properties, Swelling, and Release Mechanism, Material Selection and Applications

Improving the safety efficacy ratio of existing drugs is a current challenge to be addressed rather than the development of novel drugs which involve much expense and time. The efficacy of drugs is affected by a number of factors such as their low aqueous solubility, unequal absorption along the gastrointestinal (GI) tract, risk of degradation in the acidic milieu of the stomach, low permeation of the drugs in the upper GI tract, systematic side effects, etc. This review aims to enlighten readers on the role of pH sensitive hydrogels in drug delivery, their mechanism of action, swelling, and drug release as a function of pH change along the GI tract. The basis for the selection of materials, their structural features, physical and chemical properties, the presence of ionic pendant groups, and the influence of their pKa and pKb values on the ionization, consequent swelling, and targeted drug release are also highlighted.