Thiolated pectin: Synthesis, characterization and evaluation as a mucoadhesive polymer

Thiol-Ene Click Reaction in Constructing Liquid Separation Membranes for Water Treatment

In the evolving landscape of water treatment, membrane technology has ascended to an instrumental role, underscored by its unmatched efficacy and ubiquity. Diverse synthesis and modification techniques are employed to fabricate state-of-the-art liquid separation membranes. Click reactions, distinguished by their rapid kinetics, minimal byproduct generation, and simple reaction condition, emerge as a potent paradigm for devising eco-functional materials. While the metal-free thiol-ene click reaction is acknowledged as a viable approach for membrane material innovation, a systematic elucidation of its applicability in liquid separation membrane development remains conspicuously absent. This review elucidates the pre-functionalization strategies of substrate materials tailored for thiol-ene reactions, notably highlighting thiolation and introducing unsaturated moieties. The consequential implications of thiol-ene reactions on membrane properties-including trade-off effect, surface wettability, and antifouling property-are discussed. The application of thiol-ene reaction in fabricating various liquid separation membranes for different water treatment processes, including wastewater treatment, oil/water separation, and ion separation, are reviewed. Finally, the prospects of thiol-ene reaction in designing novel liquid separation membrane, including pre-functionalization, products prediction, and solute-solute separation membrane, are proposed. This review endeavors to furnish invaluable insights, paving the way for expanding the horizons of thiol-ene reaction application in liquid separation membrane fabrication.

Design of quetiapine fumarate loaded polyethylene glycol decorated graphene oxide nanosheets: Invitro-exvivo characterization

Quetiapine Fumarate (QF) is an atypical antipsychotic with poor oral bioavailability (9%) due to its low permeability and pH-dependent solubility. Therefore, this study aims to design QF-loaded polyethylene glycol (PEG) functionalized graphene oxide nanosheets (GON) for nasal delivery of QF. In brief, GO was synthesized using a modified Hummers process, followed by ultra-sonication to produce GON. Subsequently, PEG-functionalized GON was prepared using carbodiimide chemistry (PEG-GON). QF was then decorated onto the cage of PEG-GON using the π-π stacking phenomenon (QF@PEG-GON). The QF@PEG-GON nanocomposite underwent several spectral characterizations, in vitro drug release, mucoadhesion study, ex vivo diffusion study, etc. The surface morphology of QF@PEG-GON nanocomposite validates the cracked nature of the nanocomposite, whereas the diffractograms and thermogram of nanocomposite confirm the conversion of QF into an amorphous form with uniform distribution in PEG-GON. Moreover, an ex vivo study of PEG-GON demonstrates superior mucoadhesion capacity due to its surface functional groups and hydrophilicity. The percent drug loading content and percent entrapment efficiency of the nanocomposite were found to be 9.2±0.62% and 92.3±1.02%, respectively. The developed nanocomposite exhibited 43.82±1.65% drug release within 24h, with the Korsemeyer-Peppas model providing the best-fit release kinetics (R2: 0.8614). Here, the interlayer spacing of PEG-GON prevented prompt diffusion of the buffer, leading to a delayed release pattern. In conclusion, the anticipated QF@PEG-GON nanocomposite shows promise as a nanocarrier platform for nasal delivery of QF.

Nitric oxide-releasing thiolated starch nanoparticles embedded in gelatin sponges for wound dressing applications

This study introduces a novel wound dressing by combining nitric oxide-releasing thiolated starch nanoparticles (NO-TS NPs) with gelatin. First, starch was thiolated (TS), and then its nanoparticles were prepared (TS NPs). Subsequently, NPs were covalently bonded to sodium nitrite to obtain NO-releasing TS NPs (NO-TS-NPs) that were incorporated into gelatin sponges at various concentrations. The resulting spherical TS NPs had a mean size of 85.42 ± 5.23 nm, which rose to 100.73 ± 7.41 nm after bonding with sodium nitrite. FTIR spectroscopy confirmed S-nitrosation on the NO-TS NPs' surface, and morphology analysis showed well-interconnected pores in all sponges. With higher NO-TS NPs content, pore size, porosity, and water uptake increased, while compressive modulus and strength decreased. Composites exhibited antibacterial activity, particularly against E. coli, with enhanced efficacy at higher NPs' concentrations. In vitro release studies demonstrated Fickian diffusion, with faster NO release in sponges containing more NPs. The released NO amounts were non-toxic to fibroblasts, but samples with fewer NO-TS NPs exhibited superior cellular density, cell attachment, and collagen secretion. Considering the results, including favorable mechanical strength, release behavior, antibacterial and cellular properties, gelatin sponges loaded with 2 mg/mL of NO-TS NPs can be suitable for wound dressing applications.

Exploring film forming ability and improving its bioadhesiveness by thiolation of mucilaginous polysaccharides from Cassia uniflora seeds for drug delivery application

The objectives of the present work were to explore film forming ability of mucilaginous polysaccharides obtained from Cassia uniflora seeds and improving its bioadhesive potential by thiolation for drug delivery and other applications. Thiolation was achieved by esterification reaction with thioglycolic acid. The modification was confirmed by performing and comparing its zeta potential, DSC, and spectrophotometric characterization by FTIR and NMR with unmodified mucilaginous polysaccharide. The modified mucilaginous polysaccharides FTIR spectra showed an additional absorption band at 2565 cm-1 and new shifts appeared in the 1H (δ 3.24 and at δ 3.44 ppm) and 13C NMR spectra's (21.56 ppm) confirming the esterification of mucilaginous polysaccharides. The prepared films of thiolated and unmodified mucilaginous polysaccharides were evaluated for various parameters like thickness, pH, and weight measurement, The film formulation had a thickness of 0.16 to 0.18 mm, pH in the range of 6.79 to 7.09 and weight uniformity 0.89 to 0.94 mg. The results reveal that the films based on thiolated material improved bioadhesive properties after thiolation. The SEM photographs revealed a smooth surface of film formulations. The diclofenac-loaded film of thiolated mucilaginous polysaccharide also showed >1.5-fold an increase in in-vitro drug release and exhibited non Fickian transport mechanism. These findings could increase the possible applications of chemically modified-thiolated mucilaginous polysaccharides of Cassia uniflora seeds in drug delivery.

Bakuchiol nanoemulsion loaded electrospun nanofibers for the treatment of burn wounds

The present work aims to develop and evaluate the wound healing potential of bakuchiol nanoemulsion loaded electrospun scaffolds. Since oxidative stress and microbial burden leads the burn wounds to become chronic and fatal to patients, a phytoconstituent, bakuchiol (BAK), was screened on the basis of antioxidant and antimicrobial potential which also defined its dose. Furthermore, BAK was incorporated into a nanoemulsion to enhance its therapeutic efficacy, reduce its dosage frequency, and maximize its stability. The present study is inclined towards the collaborative interaction of natural products and novel drug delivery systems to develop safe and therapeutically efficient systems for burn wound healing. The optimized nanoemulsion showed excellent antioxidant and antimicrobial potential against wound susceptible pathogens, i.e., Candida albicans and Methicillin-resistant Staphylococcus aureus which was further loaded into gelatin based hydrogel and nanofibrous scaffold system. The mesh structure of scaffolds was chosen as a suitable carrier system for wound healing process not only because it offers resemblance to skin's anatomy but is also capable of providing uniform distribution of wound biomarkers across the skin. The prepared nanofibers were assessed for their analgesic, anti-inflammatory, and wound healing potential which was observed to be significantly better than its gel formulation.

Recent progress and treatment strategy of pectin polysaccharide based tissue engineering scaffolds in cancer therapy, wound healing and cartilage regeneration

Natural polymers and its mixtures in the form of films, sponges and hydrogels are playing a major role in tissue engineering and regenerative medicine. Hydrogels have been extensively investigated as standalone materials for drug delivery purposes as they enable effective encapsulation and sustained release of drugs. Biopolymers are widely utilised in the fabrication of hydrogels due to their safety, biocompatibility, low toxicity, and regulated breakdown by human enzymes. Among all the biopolymers, polysaccharide-based polymer is well suited to overcome the limitations of traditional wound dressing materials. Pectin is a polysaccharide which can be extracted from different plant sources and is used in various pharmaceutical and biomedical applications including cartilage regeneration. Pectin itself cannot be employed as scaffolds for tissue engineering since it decomposes quickly. This article discusses recent research and developments on pectin polysaccharide, including its types, origins, applications, and potential demands for use in AI-mediated scaffolds. It also covers the materials-design process, strategy for implementation to material selection and fabrication methods for evaluation. Finally, we discuss unmet requirements and current obstacles in the development of optimal materials for wound healing and bone-tissue regeneration, as well as emerging strategies in the field.

Development of thiolated xanthan gum-stearylamine conjugate based mucoadhesive system for the delivery of biochanin-A to melanoma cells

Recently, instead of creating new active compounds, scientists have been working to increase the bioavailability and residence time of existing drugs by modifying the characteristics of the delivery systems. In the present study, a novel mucoadhesive bioconjugate (SN-XG-SH) was synthesized by functionalizing a polysaccharide xanthan gum (XG) with cysteamine hydrochloride (CYS) and a lipid stearylamine (SN). FTIR, CHNS and 1H NMR studies confirmed the successful synthesis of SN-XG-SH. Mucoadhesion of the thiolated XG was enhanced and evaluated by different methods. Disulfide bond formation between thiolated XG and skin mucus enhances mucoadhesive behavior. The mucoadhesive bioconjugate was used to prepare nanoparticles for the delivery of hydrophobic biochanin-A (Bio-A) for the treatment of melanoma. The thiolated xanthan gum nanoparticles also demonstrated high drug entrapment efficiency, sustained drug release, and high storage stability. The drug loaded nanoparticles (Bio-A@TXNPs) significantly improved the cytotoxicity of Bio-A against human epidermoid cancer cells (A431 cells) by inducing apoptosis and changing mitochondrial membrane potential. In conclusion, thiolation of XG improves its mucoadhesive properties and prolongs the release of Bio-A. Thus, thiolated XG conjugate has a high potential for use as a bioadhesive agent in controlled and localised delivery of drugs in different skin diseases including melanoma.

Elucidation of techno-functional, structural and rheological characteristics of pectin extracted from the peel of different banana (Musa. spp) varieties

Pectin is a polysaccharide mainly used in food processing industries as an emulsifier, thickener, stabilizer and in pharmaceuticals as an excipient, wall material and bio adhesive for improving delivery and efficiency. Raising demand for pectin, pushes to explore unconventional plant-based sources for the extraction of pectin. This work is aimed to explore the possibility of extracting pectin from the peel of banana varieties and to decipher the chemical and techno-functional properties. Among the varieties, Nendran, a plantain banana recorded higher pectin recovery (23.42 %), swelling power (23.10 gg-1), anhydrouronic acid (AUA) content (72.86 %) and emulsifying activity (46.19 %). Pectin from the banana peels exhibited the equivalent weight (g/mol) ranging from 943.40 (var. Bhimkol) to 1282.05 (var. Nendran). Morphological observations revealed that the extracted pectin has fragments with uneven sizes and inter-particle voids in the structure. Banana pectin behaved similar to commercial pectin in terms of rheological, textural and structural profiles. HPLC analysis and NMR spectra confirmed the dominance of galacturonic acid in the banana peel pectins. The study unveiled and opened up the avenues of utilizing banana peel as a complementary biomass for the extraction of pectin which could be used in different industrial applications.

Characterization of a low-methoxyl pectin extracted from red radish (Raphanus sativus L.) pomace and its gelation induced by NaCl

There is an increasing demand for obtaining pectin from new sources. Red radish (Raphanus sativus L.) pomace pectin extracted by alkali was low-methoxyl pectin with esterification degree of 10.17 %, galacturonic acid content of 69.71 % (wt), and average molar weight of 78.59 kDa. The pectin primarily consisted of rhamnogalacturonan I and homogalacturonan domains. The predominant monosaccharides of the pectin were galacturonic acid (46.32 mol%), arabinose (16.03 mol%), galactose (10.46 mol%), and rhamnose (10.28 mol%), respectively. The red radish pomace pectin solution exhibited a shear-thinning behavior. NaCl could induce gelation of red radish pomace pectin, and the gel properties of red radish pomace pectin were considerably affected by the NaCl concentration. As the NaCl concentration (0.25-0.50 mol/L) increased, the rate of gelation accelerated, and the time to gelation point appeared earlier. There was an optimal NaCl concentration (0.50 mol/L) for the pectin to form a gel with the greatest solid-like properties, gel hardness (33.84 g) and water-holding capacity (62.41 %). Gelation force analysis indicated gel formation mainly caused by electrostatic shielding effect of Na+ and hydrogen bonding. This research could facilitate the applications of the red radish pomace pectin in the realm of edible hydrocolloids.

Tannic acid-coated cellulose nanocrystals with enhanced mucoadhesive properties for aquaculture

Mucoadhesion can be exploited as a strategy to target drug and nutrient delivery to the outer mucosal layers of fish in aquaculture farms. Cellulose nanocrystals (CNC) derived from cellulose pulp fibers can interact with the mucosal membranes via hydrogen bonding, however, their mucoadhesive properties are weak and should be enhanced. In this study, CNC were coated with tannic acid (TA), a plant polyphenol with excellent wet-resistant bioadhesive properties, to strengthen their mucoadhesive capability. The optimal CNC:TA mass ratio was determined to be 20:1. The modified CNCs were 190 ± 40 nm in length and 21 ± 4 nm wide and displayed excellent colloidal stability, with a zeta potential of -35 mV. Turbidity titrations and rheological measurements revealed that the modified CNC possessed superior mucoadhesive properties compared to pristine CNC. Modification with tannic acid introduced additional functional groups for stronger hydrogen bond formation and hydrophobic interactions with mucin, which was confirmed by a large reduction in viscosity enhancement values in the presence of chemical blockers (urea and Tween80). The enhanced mucoadhesion of the modified CNC could be utilized for the fabrication of a mucoadhesive drug delivery system to promote sustainable aquaculture practices.

Physicochemical and functional properties of RG-I enriched pectin extracted from thinned-young apples

The demand for obtaining pectin from new sources has been continuously increasing. The abundant but underutilized thinned-young apple is a potential source of pectin. In this study, an organic acid (i.e., citric acid) and two inorganic acids (i.e., hydrochloric acid and nitric acid) commonly used in commercial pectin production were applied to extract pectin from three varieties of thinned-young apples. The physicochemical and functional properties of the thinned-young apple pectin were comprehensively characterized. The highest pectin yield (8.88 %) was obtained from Fuji apple using citric acid extraction. All pectin was high methoxy pectin (HMP) and rich in RG-I regions (>56 %). The citric acid extracted pectin had the highest molecular weight (Mw) and lowest degree of esterification (DE) values, and exhibited great thermal stability and shear-thinning property. Furthermore, Fuji-apple pectin possessed significantly better emulsifying properties compared to pectin obtained from the other two varieties of apples. Thus, pectin extracted with citric acid from Fuji thinned-young apples has great potential to be applied in the food industry as a natural thickener and emulsifier.

Potential of Wood Hemicelluloses and Their Derivates as Food Ingredients

A holistic utilization of all lignocellulosic wood biomass, instead of the current approach of using only the cellulose fraction, is crucial for the efficient, ecological, and economical use of the forest resources. Use of wood constituents in the food and feed sector is a potential way of promoting the global economy. However, industrially established food products utilizing such components are still scarce, with the exception of cellulose derivatives. Hemicelluloses that include xylans and mannans are major constituents of wood. The wood hemicelluloses are structurally similar to hemicelluloses from crops, which are included in our diet, for example, as a part of dietary fibers. Hence, structurally similar wood hemicelluloses have the potential for similar uses. We review the current status and future potential of wood hemicelluloses as food ingredients. We include an inventory of the extraction routes of wood hemicelluloses, their physicochemical properties, and some of their gastrointestinal characteristics, and we also consider the regulatory route that research findings need to follow to be approved for food solutions, as well as the current status of the wood hemicellulose applications on that route.

Recent Advances and Prospects for Plant Gum-Based Drug Delivery Systems: A Comprehensive Review

This work is an effort to first introduce plant-based gums and discussing their drug delivery applications. The composition of these plant gums and their major characteristics, which make them suitable as pharmaceutical excipients are also described in detail. The various modifications methods such as physical and chemical modifications of gums and polysaccharides have been discussed along with their applications in different fields. Consequently, plant-based gums modification such as etherification and grafting is attracting much scientific attention to satisfy industrial demand. The evaluation tests to characterize gum-based drug delivery systems have been summarized. The release behavior of drug from plant-gum-based drug delivery is being discussed. Thus, this review is an attempt to critically summarize different aspect of plant-gum-based polysaccharides to be utilized in drug delivery systems having potential industrial applications.

Injectable methacrylated gelatin/thiolated pectin hydrogels carrying melatonin/tideglusib-loaded core/shell PMMA/silk fibroin electrospun fibers for vital pulp regeneration

Use of injectable hydrogels attract attention in the regeneration of dental pulp due to their ability to fill non-uniform voids such as pulp cavities. Here, gelatin methacrylate/thiolated pectin hydrogels (GelMA/PecTH) carrying electrospun core/shell fibers of melatonin (Mel)-polymethylmethacrylate (PMMA)/Tideglusib (Td)-silk fibroin (SF) were designed as an injectable hydrogel for vital pulp regeneration, through prolonged release of Td and Mel to induce proliferation and odontoblastic differentiation of dental pulp stem cells (DPSC). H NMR and FTIR confirmed methacrylation of Gel and thiolation of Pec. Addition of PMMA/SF increased degradation and water retention capacities of GelMA/PecTH. Rheological analyses and syringe tests proved the injectability of the hydrogel systems. Release studies indicated that Td and Mel were released from the fibers inside the hydrogels sequentially due to their specific locations. This release pattern from the hydrogels resulted in DPSC proliferation and odontogenic differentiation in vitro. Gene expression studies showed that the upregulation of DMP1, DSPP, and Axin-2 genes was promoted by GelMA/PecTH carrying PMMA/SF loaded with Mel (50 µg/mL) and Td (200 nM), respectively. Our results suggest that this hydrogel system holds promise for use in the regeneration of pulp tissue.

Thiolated pectin-chitosan composites: Potential mucoadhesive drug delivery system with selective cytotoxicity towards colorectal cancer

Mucoadhesive drug delivery systems (DDS) may promote safer chemotherapy for colorectal cancer (CRC) by maximizing local drug distribution and residence time. Carbohydrate polymers, e.g. pectin (P) and chitosan (CS), are potential biomaterials for CRC-targeted DDS due to their gelling ability, mucoadhesive property, colonic digestibility, and anticancer activity. Polymer mucoadhesion is augmentable by thiolation, e.g. pectin to thiolated pectin (TP). Meanwhile, P-CS polyelectrolyte complex has been shown to improve structural stability. Herein, we fabricated, characterized, and evaluated 5-fluorouracil-loaded primary DDS combining TP and CS as a composite (TPCF) through triple crosslinking actions (calcium pectinate, polyelectrolyte complex, disulfide). Combination of these crosslinking yields superior mucoadhesion property relative to single- or dual-crosslinked counterparts, with comparable drug release profile and drug compatibility. PCF and TPCF exhibited targeted cytotoxicity towards HT29 CRC cells with milder cytotoxicity towards HEK293 normal cells. In conclusion, TP-CS composites are promising next-generation mucoadhesive and selectively cytotoxic biomaterials for CRC-targeted DDS.

Gelation behavior and mechanism of Nicandra physalodes (Linn.) Gaertn. seeds pectin induced by Glucono-delta-lactone

In this study, the physicochemical properties of pectin from Nicandra physalodes (Linn.) Gaertn. seeds (NPGSP) were analysed firstly, and the rheological behavior, microstructure and gelation mechanism of NPGSP gels induced by Glucono-delta-lactone (GDL) were investigated. The hardness of NPGSP gels was increased from 26.27 g to 226.77 g when increasing GDL concentration from 0 % (pH = 4.0) to 1.35 % (pH = 3.0), and the thermal stability was improved. The peak around 1617 cm^-1 was decreased as the adsorption peak of the free carboxyl groups was attenuated with addition of GDL. GDL increased the crystalline degree of NPGSP gels, and its microstructure exhibited more smaller spores. Molecular dynamics was performed on systems of pectin and gluconic acid (GDL hydrolysis product), indicating that inter-molecular hydrogen bonds and van der Waals forces were the main interactions to promote gels formation. Overall, NPGSP has the potential commercial value for developing as a thickener in food processing.

pH-responsive in situ gelling properties of thiolated citrus high-methoxyl pectin and its potential gel mechanism

pH-responsive in situ gelling properties of thiolated citrus high-methoxyl pectin (TCHMP) were investigated in this study. The gelation capacity results revealed that the in situ gelation behavior of TCHMP only occurred when the pH value was higher than 6.25. The gel strength increased from 26.63 g to 42.77 g as the pH value increased from 7.4 to 8.9. Rheological measurements confirmed that the apparent viscosity and viscoelasticity of TCHMP were highly dependent on pH value and dialysis time. Compared with the control group, the apparent viscosity of TCHMP dialyzed in phosphate-buffered saline (PBS) of pH 8.9 for 180 min increased 695-fold. During the dialysis process of TCHMP at different pH values (7.4-8.9), the final thiol groups content decreased and the final disulfide bonds content increased with the increase in pH value. This illustrates that the mechanism of in situ gelation is mainly the oxidation of thiol-thiol groups to form disulfide bonds. These results can put forward new insights into the pH-responsive in situ gelling properties of TCHMP and provide a theoretical basis for the application of TCHMP in neutral and alkaline gel systems.

Surface Modification with Particles Coated or Made of Polymer Multilayers

The coating of particles or decomposable cores with polyelectrolytes via Layer-by-Layer (LbL) assembly creates free-standing LbL-coated functional particles. Due to the numerous functions that their polymers can bestow, the particles are preferentially selected for a plethora of applications, including, but not limited to coatings, cargo-carriers, drug delivery vehicles and fabric enhancements. The number of publications discussing the fabrication and usage of LbL-assembled particles has consistently increased over the last vicennial. However, past literature fails to either mention or expand upon how these LbL-assembled particles immobilize on to a solid surface. This review evaluates examples of LbL-assembled particles that have been immobilized on to solid surfaces. To aid in the formulation of a mechanism for immobilization, this review examines which forces and factors influence immobilization, and how the latter can be confirmed. The predominant forces in the immobilization of the particles studied here are the Coulombic, capillary, and adhesive forces; hydrogen bonding as well as van der Waal's and hydrophobic interactions are also considered. These are heavily dependent on the factors that influenced immobilization, such as the particle morphology and surface charge. The shape of the LbL particle is related to the particle core, whereas the charge was dependant on the outermost polyelectrolyte in the multilayer coating. The polyelectrolytes also determine the type of bonding that a particle can form with a solid surface. These can be via either physical (non-covalent) or chemical (covalent) bonds; the latter enforcing a stronger immobilization. This review proposes a fundamental theory for immobilization pathways and can be used to support future research in the field of surface patterning and for the general modification of solid surfaces with polymer-based nano- and micro-sized polymer structures.

Potential of pectin for biomedical applications: a comprehensive review

Pectin is a polysaccharide extracted from various plants, such as apples, oranges, lemons, and it possesses some beneficial effects on human health, including being hypoglycemic and hypocholesterolemic. Therefore, pectin is used in various pharmaceutical and biomedical applications. Meanwhile, its low mechanical strength and fast degradation rate limit its usage as drug delivery devices and tissue engineering scaffolds. To enhance these properties, it can be modified or combined with other organic molecules or polymers and/or inorganic compounds. These materials can be prepared as nano sized drug carriers in the form of spheres, capsules, hydrogels, self assamled micelles, etc., for treatment purposes (mostly cancer). Different composites or blends of pectin can also be produced as membranes, sponges, hydrogels, or 3D printed matrices for tissue regeneration applications. This review is concentrated on the properties of pectin based materials and focus especially on the utilization of these materials as drug carriers and tissue engineering scaffolds, including 3D printed and 3D bioprinted systems covering the studies in the last decade and especially in the last 5 years.

The gelation behavior of thiolated citrus high-methoxyl pectin induced by sodium phosphate dibasic dodecahydrate

The present study found that sodium phosphate dibasic dodecahydrate (Na₂HPO₄) was capable of inducing the gelation of thiolated citrus high-methoxyl pectin (TCHMP). TCHMP was synthesized by amidation of citrus high-methoxyl pectin. The gel formation exhibited an obvious concentration-dependence, including TCHMP and Na₂HPO₄ concentration. For Na₂HPO₄-induced TCHMP gels (TCHMPGs), gel strength and water holding capacity (WHC) increased, while the microcellular network structure was more compact with the increase of TCHMP and Na₂HPO₄ concentration. Dynamic viscoelastic experiment showed when Na₂HPO₄ concentration was more than or equal to 0.5 mol/L, TCHMP sols could be transferred into gels within 30 min. Crystal property was not changed while thermal stability was improved after phase transition. Gelling forces analysis indicated that disulfide bonds were the main interaction forces in TCHMPGs. Consequently, TCHMPGs were covalently crosslinked and exhibited satisfactory gel performance. The results provide a theoretical basis for the formation of gels by Na₂HPO₄ induced TCHMP.

Multilayered mucoadhesive hydrogel films based on Ocimum basilicum seed mucilage/thiolated alginate/dopamine-modified hyaluronic acid and PDA coating for sublingual administration of nystatin

The present study establishes an experimental design for the preparation of new bi and tri-layer mucoadhesive sublingual films based on basil (Ocimum basilicum L.) seed mucilage (OBM) as novel plant-polysaccharide for oromucosal administration of nystatin (Nys). The films formulation consists of a drug reservoir-mucoadhesive layer cross-linked via CaCl₂, with protective mucoadhesive layers based on thiolated alginate (TA) and polydopamine (PDA). OBM served as a new mucoadhesive polysaccharide in second layers, where the dopamine-modified-hyaluronic acid (DHA) improved the mucoadhesive strength and swelling rate properties. The drug-loaded formulations of trilayer film with PDA coating, and bilayer film with DHA/OBM (1:1) in the second layer, showed the desired mucoadhesion properties (about 69 and 75.3% respectively). The obtained results revealed that the bilayer film containing DHA had a superior swelling degree in the range of 15-19 (g/g). While the PDA coating sample showed the highest resistance to water uptake and erosion. The bilayer film (DHA/OBM with 1:1 ratio) provided a maximum drug release of 86% after 4 h. The selected formulations indicated good mechanical properties with no cytotoxicity.

Development of mucoadhesive modified kappa-carrageenan/pectin patches for controlled delivery of drug in the buccal cavity

In this study, modified kappa-carrageenan/pectin hydrogel patches were fabricated for treatment of buccal fungal infections. For this purpose, kappa-carrageenan-g-acrylic acid was modified with different thiolated agents (L-cysteine and 3-mercaptopropionic acid), and the thiol content of the resulting modified kappa-carrageenan was confirmed by elemental analyzer. Then, the hydrogel patches were fabricated, and characterized by Fourier-transform infrared spectroscopy, thermogravimetric analysis, ex vivo mucoadhesion test, and swelling behavior. Triamcinolone acetonide was added either directly or by encapsulating within the poly(lactic-co-glycolic acid) nanoparticles. The release amount of the drug from the directly loaded patch was 7.81 mg/g polymer, while it was 3.28 mg/g polymer for the encapsulated patch with the same content at 7 hr. The hydrogel patches had no cytotoxicity by cell culture studies. Finally, the drug loaded hydrogel patches were demonstrated antifungal activity against Aspergillus fumigatus and Aspergillus flavus. These results provide that the novel modified kappa-carrageenan and pectin based buccal delivery system has promising antifungal property, and could have advantages compared to conventional buccal delivery systems.

Imaging application and radiosensitivity enhancement of pectin decorated multifunctional magnetic nanoparticles in cancer therapy

In this contribution, we report the fabrication of multifunctional nanoparticles with gold shell over an iron oxide nanoparticles (INPs) core. The fabricated system combines the magnetic property of INPs and the surface plasmon resonance of gold. The developed nanoparticles are coated with thiolated pectin (TPGINs), which provides stability to the nanoparticles dispersion and allows the loading of hydrophobic anticancer drugs. Curcumin (Cur) is used as the model drug and an encapsulation efficiency of approximately 80% in TPGINs is observed. Cytotoxicity study with HeLa cells shows that Cur-loaded TPGINs have better viability percent (~30%) than Cur alone (~40%) at a dose of 30 μg of TPGINs. Further, annexin V-PI assay demonstrated the enhanced anticancer activity of Cur-loaded TPGINs via induction of apoptosis. The use of TPGINs leads to a significant enhancement in generating reactive oxygen species (ROS) in HeLa cells through improved radiosensitization by gamma irradiation (0.5 Gy). TPGINs are further evaluated for imparting contrast in magnetic resonance imaging (MRI) with the r₂ relaxivity in the range of 11.06-13.94 s^-1 μg^-1 mL when measured at 7 Tesla. These experimental results indicate the potential of TPGINs for drug delivery and MR imaging.

Thiolated Thermoresponsive Polymer Scaffolds with Tunable Mucoadhesivity for Intestinal Applications

Treatments for inflammatory bowel disease largely involve lifelong drug prescriptions or surgical intervention that can lead to poor quality of life for patients. Regenerative therapies involving stem cells have been shown to induce tissue regeneration but are limited in their efficacy by inefficient delivery mechanisms. Scaffold-based delivery of cells has been a key research focus of tissue engineers seeking to translate advances in stem cell research into clinical solutions. Biomaterial scaffolds that are delivered noninvasively to form in situ solid structures around the cells are preferable over surgically delivered monolithic scaffolds. We synthesized a novel biomaterial for in situ-forming, thermoresponsive intestinal scaffolds by thiolation of poly (N-isopropylacrylamide-co-glycidyl methacrylate) by conjugation of cysteine. Thiolation of the polymer enables chemical crosslinking with the intestinal mucus, enhancing mucoadhesion and permitting control of scaffold retention time in the intestinal environment. This study reports the synthesis and characterization of the thiolated polymer and investigates its crosslinking behavior, mucoadhesive properties, and cytocompatibility for potential tissue engineering applications in the intestine.

Thiolated okra chitosan nanoparticles: preparation and optimisation as intranasal drug delivery agents

AIM

The preparation of thiolated okra gum by use of full factorial design to optimise the reaction conditions.

METHODS

Thiolated gum was obtained by esterification optimised by full factorial design. The effect of varying the thiolated Okra concentration, chitosan concentration, pH, and stirring speed on particle size, entrapment efficiency and zeta potential was observed using Box-Behnken design.

RESULTS

Maximum yield and degree of substitution were obtained at reaction time of 152 min, 6.73 ml of thioglycolic acid and 70 °C of temperature. The optimised calculated parameters were thiolated okra concentrations of (0.07% w/v), chitosan concentration (0.05% w/v), pH (3), stirring speed (4430 rpm), which yielded nanoparticles of size 294.3 ± 0.3 nm, 43.57 ± 1.21% entrapment and 23.29 ± 2.3 mV of Zeta potential.

CONCLUSION

NPs were observed to be promising for brain targeting.

Thiolated sodium alginate conjugates for mucoadhesive and controlled release behavior of metformin microspheres

The absorption of BCS III drugs can be improved by inhibiting the P-glycoprotein (P-gp) efflux and by increasing the mucoadhesion of natural polymers. In the present study, an esterification of sodium alginate (SA) with thioglycolic acid (TGA) was applied for the preparation of thiolated sodium alginate (TSA). The Ellman's test was applied to quantify the thiol group and a di-sulphide bond test was performed to confirm any SS linkages. The FTIR, DSC, XRD, ¹H NMR and charring point determinations were confirmed the thiol group of TSA. The gel like rheological properties with porcine mucous was confirmed by viscoelasticity properties and the mucoadhesion with the rabbit intestine was carried out after compression of 30 mg tablets of TSA. The content of thiol group was in the range of 320-730 μmoL/g of the polymer. The FTIR spectrum showed a characteristic peak of sulfhydryl group at 2557 cm^-1 in TSA and the reduction of the charring point from 220 °C to 178 °C was confirmed the thiolation of TSA. A direct relationship of mucoadhesion and swelling was observed with the concentration of TGA and SA, respectively. The prepared microspheres were 2-7 μm in size, excellent rheological properties and non-fickian drug release behavior was observed.

Thiolation of Biopolymers for Developing Drug Delivery Systems with Enhanced Mechanical and Mucoadhesive Properties: A Review

Biopolymers are extensively used for developing drug delivery systems as they are easily available, economical, readily modified, nontoxic, biodegradable and biocompatible. Thiolation is a well reported approach for enhancing mucoadhesive and mechanical properties of polymers. In the present review article, for the modification of biopolymers different thiolation methods and evaluation/characterization techniques have been discussed in detail. Reported literature on thiolated biopolymers with enhanced mechanical and mucoadhesive properties has been presented conspicuously in text as well as in tabular form. Patents filed by researchers on thiolated polymers have also been presented. In conclusion, thiolation is an easily reproducible and efficient method for customization of mucoadhesive and mechanical properties of biopolymers for drug delivery applications.

Silica Nanoparticles in Transmucosal Drug Delivery

Transmucosal drug delivery includes the administration of drugs via various mucous membranes, such as gastrointestinal, nasal, ocular, and vaginal mucosa. The use of nanoparticles in transmucosal drug delivery has several advantages, including the protection of drugs against the harsh environment of the mucosal lumens and surfaces, increased drug residence time, and enhanced drug absorption. Due to their relatively simple synthetic methods for preparation, safety profile, and possibilities of surface functionalisation, silica nanoparticles are highly promising for transmucosal drug delivery. This review provides a description of silica nanoparticles and outlines the preparation methods for various core and surface-functionalised silica nanoparticles. The relationship between the functionalities of silica nanoparticles and their interactions with various mucous membranes are critically analysed. Applications of silica nanoparticles in transmucosal drug delivery are also discussed.

Okra-Thioglycolic Acid Conjugate—Synthesis, Characterization, and Evaluation as a Mucoadhesive Polymer

The success of mucoadhesive drug delivery systems relies on the type of polymer used, which becomes adhesive naturally upon hydration. Intended polymers should be able to maintain prolonged contact with biological membranes, and to protect or cater the drug to a prolonged period. Most of the hydro polymers form weak non-covalent bonds, that hinder localization of dosage forms at specific sites resulting in therapeutic inefficiency. This can be overcome by the thiol functionalization of natural polymers. In the present study, natural okra gum (OG) was extracted, followed by thiolation (TOG) and evaluated for mucoadhesion property and its role in enhancing the efficacy of repaglinide as a model drug (short-acting Type II antidiabetic drug). The thiol functionalization of OG (TOG) was confirmed by a Fourier-transform infrared spectroscopy (FTIR) study that showed a polyhedral to a spherical shape that had a rougher surface. Differential scanning calorimetry (DSC) and X-Ray Diffraction (XRD) studies of TOG indicated a decline in endothermic transition temperature and high crystallinity, respectively, in comparison to OG. CSFR (Crushing Strength: Friability Ratio), weight and thickness variations of repaglinidetablets formulated using TOG were >80% and <2.5% respectively. The highest swelling index (107.89 ± 1.99%) and strong mucoadhesion due to high disulfide bonds were observed for repaglinide TOG tablets in comparison to RG OG tablets. In-vitro release studies indicated a controlled drug release from thiolated formulations proportional to the concentration of thiomers that have a good correlation with in-vivo studies. Pharmacokinetic studies indicated higher AUC (area under the curve), longer t1/2 with thiomers. and Level A IVIV (in vitro in vivo) correlation was established from the bioavailability and dissolution data. Consequently, all the obtained results suggest that thiomers based formulations can be promising drug delivery systems, even in targeting onerous mucosal surfaces like nasal, ocular or vaginal.

Silica coating of carboxymethyl tamarind kernel polysaccharide beads to modify the release characteristics

In present study, the release characteristics of ibuprofen-loaded carboxymethyl tamarind kernel polysaccharide beads were modified by coating with silica. The influence of concentrations of carboxymethyl tamarind kernel polysaccharide, calcium chloride and tetraethoxysilane on the % entrapment and in vitro release of ibuprofen was optimized using response surface methodology. The coating of beads with silica restricted the drug release from the beads but at the same time the ethanol formed as by-product of the sol gel process leached out the drug. The optimized batch of beads were prepared using carboxymethyl tamarind kernel powder-12.5 (%, w/v), calcium chloride-10.12 (%, w/v) and coated with tetraethoxysilane-0.25 M, entrapped 89.2% and released 92% of drug over 24 h. Energy dispersive X-ray analysis confirmed the coating of silica on the beads. The coating with silica shielded the crevices on the surface of beads but it did not elicit any significant change in thermal stability of beads. Further, in vitro release was found to be in good agreement with the swelling study. Modeling analysis revealed that ibuprofen was released from the beads following zero-order kinetics with erosion of the matrix as the main mechanism of drug release. Thus, silica coating provides a facile strategy to formulate sustained release formulations.

Development of Microspheres Based on Thiol-Modified Sodium Alginate for Intestinal-Targeted Drug Delivery

Bioactive peptide drugs are mostly delivered by parenteral administration, which brings great pain and risks to patients. Oral administration is an acceptable alternative form. However, peptide drugs are extremely sensitive to the strong acidic environment in the stomach after oral administration. They would be degraded by pepsin and trypsin in the gastrointestinal tract. Herein, we present microspheres for intestinal-targeted peptides drug delivery through oral administration. Sodium alginate was reacted with l-cysteine to bring it into thiol groups. Then sodium alginate-l-cysteine conjugates were mixed with native sodium alginate and emulsified by an improved method. Ca²⁺ was used to fix the emulsion to get the microspheres. Bovine serum albumin was used as the simulating drug to assess the feasibility of microspheres as intestinal delivery carriers. The results showed that the microspheres exhibited spherical properties and narrow size distribution. The drug-loading capacity of microspheres was not compromised after thiol-modification. It is interesting that the microspheres can maintain structural integrity and hold drugs in the strong acidic environment in the stomach. Conversely, the microspheres presented sustained intestinal-targeted drugs release ability as expected. Moreover, thiol-modification further improved the adherence ability of microspheres on the inner walls of the small intestine, which is good for enhancing drug permeability. In sum, the microspheres based on thiol-modified sodium alginate have promising applications as intestinal-targeted macromolecular drug carriers.

New pectin-induced green fabrication of Ag@AgCl/ZnO nanocomposites for visible-light triggered antibacterial activity

The pectin (CEP) was used as matrix material to prepare Ag@AgCl/ZnO nanocomposites with a green method for photocatalytic antibacterial activity in visible-light. Briefly, Ag@AgCl plasmonic hybrids were prepared in the CEP macromolecule matrix with size control, which was attributed to the stability of carboxyl and hydroxyl groups on the CEP. Subsequently, an effective and green two-steps approach was explored for the fabrication of CEP-Ag@AgCl/ZnO nanocomposites with resource saving and environment friendly. Interestingly, more Ag⁺ was converted into metallic Ag in the CEP-Ag@AgCl/ZnO than that in the CEP-Ag@AgCl. This phenomenon was attributed that the reducibility of free hemiacetal hydroxyl groups on CEP was realized with the help of NaOH in the preparation of CEP-ZnO. In addition, the CEP chains were not obviously destroyed except for the change in the crystallinity after the preparation of the CEP-Ag@AgCl/ZnO nanocomposites, indicating that the method was non-destructive. Moreover, the pH triggered release of Zn²⁺ and low release of Ag⁺ in CEP-Ag@AgCl/ZnO nanocomposites with excellent photocatalytic antibacterial activity were confirmed in this work. The proposed green process provides a new idea for the large-scale production of antibacterial pectin-based nanocomposites in industry with a low-cost.