pH responsive cross-linked polymeric matrices based on natural polymers: effect of process variables on swelling characterization and drug delivery properties

Type A gelatin-amidated low methoxyl pectin complex coacervates for probiotics protection: Formation, characterization, and viability

This work developed and characterized the physicochemical properties of a type A gelatin and amidated low-methoxyl pectin complex coacervate (GA-LMAP-CC) hydrogel and evaluated its suitability for preserving the viability of probiotics under in vitro gastrointestinal conditions. The formation of GA-LMAP-CC was achieved via height electrostatic attraction at pH 3 and a mixing ratio of 1, exhibiting thermoreversible gel behavior. The hydrogel had a porosity of 44% and a water absorption capacity of up to 12 times. Water absorption profiles were obtained at different pH values (2, 5, and 7). The influence of GA-LMAP-CC depended on the medium, which controlled the hydration and water absorption rate. GA-LMAP-CC promoted the viability of B. longum BB536 and L. acidophilus strains under simulated gastrointestinal conditions, thereby enhancing their potential for intestinal colonization. The hydrogel has suitable properties for potential application in food and pharmaceutical areas to encapsulate and preserve probiotics.

An emerging terpolymeric nanoparticle pore former as an internal recrystallization inhibitor of celecoxib in controlled release amorphous solid dispersion beads: Experimental studies and molecular dynamics analysis

Solid oral controlled release formulations feature numerous clinical advantages for drug candidates with adequate solubility and dissolution rate. However, most new chemical entities exhibit poor water solubility, and hence are exempt from such benefits. Although combining drug amorphization with controlled release formulation is promising to elevate drug solubility, like other supersaturating systems, the problem of drug recrystallization has yet to be resolved, particularly within the dosage form. Here, we explored the potential of an emerging, non-leachable terpolymer nanoparticle (TPN) pore former as an internal recrystallization inhibitor within controlled release amorphous solid dispersion (CRASD) beads comprising a poorly soluble drug (celecoxib) reservoir and insoluble polymer (ethylcellulose) membrane. Compared to conventional pore former, polyvinylpyrrolidone (PVP), TPN-containing membranes exhibited superior structural integrity, less crystal formation at the CRASD bead surface, and greater extent of celecoxib release. All-atom molecular dynamics analyses revealed that in the presence of TPN, intra-molecular bonding, crystal formation tendency, diffusion coefficient, and molecular flexibility of celecoxib were reduced, while intermolecular H-bonding was increased as compared to PVP. This work suggests that selection of a pore former that promotes prolonged molecular separation within a nanoporous controlled release membrane structure may serve as an effective strategy to enhance amorphicity preservation inside CRASD.

Preparation, physicochemical characterization and swelling properties of composite hydrogel microparticles based on gelatin and pectins with different structure

Composite hydrogel microparticles based on pectins with different structures (callus culture pectin (SVC) and apple pectin (AU)) and gelatin were developed. Hydrogel microparticles were formed by the ionotropic gelation and electrostatic interaction of COO- groups of pectin and NH3+ groups of gelatin, which was confirmed by FTIR spectroscopy. The addition of gelatin to pectin-based gel formulations resulted in a decrease in gel strength, whereas increasing gelatin concentration enhanced this effect. The microparticle gel strength increased in proportion to the increase in the pectin concentration. The DSC and TGA analyzes showed that pectin-gelatin gels had the higher thermal stability than individual pectins. The gel strength, Ca2+ content and thermal stability of the microparticles based on gelatin and SVC pectin with a lower degree of methylesterification (DM) (14.8 %) were higher compared to that of microparticles based on gelatin and AU pectin with a higher DM (40 %). An increase in the SVC concentration, Ca2+ content and gel strength of SVC-gelatin microparticles led to a decrease in the swelling degree in simulated gastrointestinal fluids. The addition of 0.5 % gelatin to gels based on AU pectin resulted in increased stability of the microparticles in gastrointestinal fluids, while the microparticles from AU without gelatin were destroyed.

Site-specific delivery of cisplatin and paclitaxel mediated by liposomes: A promising approach in cancer chemotherapy

The site-specific delivery of drugs, especially anti-cancer drugs has been an interesting field for researchers and the reason is low accumulation of cytotoxic drugs in cancer cells. Although combination cancer therapy has been beneficial in providing cancer drug sensitivity, targeted delivery of drugs appears to be more efficient. One of the safe, biocompatible and efficient nano-scale delivery systems in anti-cancer drug delivery is liposomes. Their particle size is small and they have other properties such as adjustable physico-chemical properties, ease of functionalization and high entrapment efficiency. Cisplatin is a chemotherapy drug with clinical approval in patients, but its accumulation in cancer cells is low due to lack of targeted delivery and repeated administration results in resistance development. Gene and drug co-administration along with cisplatin/paclitaxel have resulted in increased sensitivity in tumor cells, but there is still space for more progress in cancer therapy. The delivery of cisplatin/paclitaxel by liposomes increases accumulation of drug in tumor cells and impairs activity of efflux pumps in promoting cytotoxicity. Moreover, phototherapy along with cisplatin/paclitaxel delivery can increase potential in tumor suppression. Smart nanoparticles including pH-sensitive nanoparticles provide site-specific delivery of cisplatin/paclitaxel. The functionalization of liposomes can be performed by ligands to increase targetability towards tumor cells in mediating site-specific delivery of cisplatin/paclitaxel. Finally, liposomes can mediate co-delivery of cisplatin/paclitaxel with drugs or genes in potentiating tumor suppression. Since drug resistance has caused therapy failure in cancer patients, and cisplatin/paclitaxel are among popular chemotherapy drugs, delivery of these drugs mediates targeted suppression of cancers and prevents development of drug resistance. Because of biocompatibility and safety of liposomes, they are currently used in clinical trials for treatment of cancer patients. In future, the optimal dose of using liposomes and optimal concentration of loading cisplatin/paclitaxel on liposomal nanocarriers in clinical trials should be determined.

Novel Hydrogel Membranes Based on the Bacterial Polysaccharide FucoPol: Design, Characterization and Biological Properties

FucoPol, a fucose-rich polyanionic polysaccharide, was used for the first time for the preparation of hydrogel membranes (HMs) using Fe³⁺ as a crosslinking agent. This study evaluated the impact of Fe³⁺ and FucoPol concentrations on the HMs' strength. The results show that, above 1.5 g/L, Fe³⁺ concentration had a limited influence on the HMs' strength, and varying the FucoPol concentration had a more significant effect. Three different FucoPol concentrations (1.0, 1.75 and 2.5 wt.%) were combined with Fe³⁺ (1.5 g/L), resulting in HMs with a water content above 97 wt.% and an Fe³⁺ content up to 0.16 wt.%. HMs with lower FucoPol content exhibited a denser porous microstructure as the polymer concentration increased. Moreover, the low polymer content HM presented the highest swelling ratio (22.3 ± 1.8 g/g) and a lower hardness value (32.4 ± 5.8 kPa). However, improved mechanical properties (221.9 ± 10.2 kPa) along with a decrease in the swelling ratio (11.9 ± 1.6 g/g) were obtained for HMs with a higher polymer content. Furthermore, all HMs were non-cytotoxic and revealed anti-inflammatory activity. The incorporation of FucoPol as a structuring agent and bioactive ingredient in the development of HMs opens up new possibilities for its use in tissue engineering, drug delivery and wound care management.

Enzymatic Crosslinked Hydrogels of Gelatin and Poly (Vinyl Alcohol) Loaded with Probiotic Bacteria as Oral Delivery System

Probiotic bacteria are widely used to prepare pharmaceutical products and functional foods because they promote and sustain health. Nonetheless, probiotic viability is prone to decrease under gastrointestinal conditions. In this investigation, Lactiplantibacillus plantarum spp. CM-CNRG TB98 was entrapped in a gelatin−poly (vinyl alcohol) (Gel−PVA) hydrogel which was prepared by a “green” route using microbial transglutaminase (mTGase), which acts as a crosslinking agent. The hydrogel was fully characterized and its ability to entrap and protect L. plantarum from the lyophilization process and under simulated gastric and intestine conditions was explored. The Gel−PVA hydrogel showed a high probiotic loading efficiency (>90%) and survivability from the lyophilization process (91%) of the total bacteria entrapped. Under gastric conditions, no disintegration of the hydrogel was observed, keeping L. plantarum protected with a survival rate of >94%. While in the intestinal fluid the hydrogel is completely dissolved, helping to release probiotics. A Gel−PVA hydrogel is suitable for a probiotic oral administration system due to its physicochemical properties, lack of cytotoxicity, and the protection it offers L. plantarum under gastric conditions.

Preparation and application of pH-responsive drug delivery systems

Microenvironment-responsive drug delivery systems (DDSs) can achieve targeted drug delivery, reduce drug side effects and improve drug efficacies. Among them, pH-responsive DDSs have gained popularity since the pH in the diseased tissues such as cancer, bacterial infection and inflammation differs from a physiological pH of 7.4 and this difference could be harnessed for DDSs to release encapsulated drugs specifically to these diseased tissues. A variety of synthetic approaches have been developed to prepare pH-sensitive DDSs, including introduction of a variety of pH-sensitive chemical bonds or protonated/deprotonated chemical groups. A myriad of nano DDSs have been explored to be pH-responsive, including liposomes, micelles, hydrogels, dendritic macromolecules and organic-inorganic hybrid nanoparticles, and micron level microspheres. The prodrugs from drug-loaded pH-sensitive nano DDSs have been applied in research on anticancer therapy and diagnosis of cancer, inflammation, antibacterial infection, and neurological diseases. We have systematically summarized synthesis strategies of pH-stimulating DDSs, illustrated commonly used and recently developed nanocarriers for these DDSs and covered their potential in different biomedical applications, which may spark new ideas for the development and application of pH-sensitive nano DDSs.

Iron delivery systems for controlled release of iron and enhancement of iron absorption and bioavailability

Iron deficiency is a global nutritional problem, and adding iron salts directly to food will have certain side effects on the human body. Therefore, there is growing interest in food-grade iron delivery systems. This review provides an overview of iron delivery systems, with emphasis on the controlled release of iron during gastrointestinal digestion, as well as the enhancement of iron absorption and bioavailability. Iron-bearing proteins are easily degraded by digestive enzymes and absorbed through receptor-mediated endocytosis. Instead, protein aggregates are slowly degraded in the stomach, which delays iron release and serves as a potential iron supplement. Amino acids, peptides and polysaccharides can bind iron through iron binding sites, but the formed compounds are prone to dissociation in the stomach. Moreover, peptides and polysaccharides can deliver iron by mediating the formation of ferric oxyhydroxide which is absorbed through endocytosis or bivalent transporter 1. In addition, liposomes are unstable during gastric digestion and iron is released in large quantities. Complexes formed by polysaccharides and proteins, and microcapsules formed by polysaccharides can delay the release of iron in the gastric environment and prolong iron release in the intestinal environment. This review is conducive to the development of iron functional ingredients and dietary supplements.

Smart vaginal bilayer films of Tenofovir based on Eudragit® L100/natural polymer for the prevention of the sexual transmission of HIV

In the absence of an effective vaccine, vaginal microbicides are essential for preventing the sexual transmission of HIV to women. Antiretroviral vaginal films have emerged as promising choices, especially those offering mucoadhesivity and controlled drug release. Tenofovir-loaded bilayer films based on Eudragit® L100 (EL100) and a biopolymer - gum arabic, karaya gum, pectin or tragacanth gum - were developed in a single-stage process. Cytotoxicity studies in three human cell lines indicated no toxicity of the excipients at the concentrations tested. Raman spectroscopy and SEM confirmed the formation of the two layers and their anchoring. Texture analysis showed no major differences between the batches. The swelling of the film is conditioned by its biopolymer nature and by the amount of EL100, which acts as structuring agent thus enhancing swelling. Tragacanth gum-based batches showed high mucoadhesion regardless the amount of EL100. The controlled release of Tenofovir in simulated vaginal fluid was faster in the presence of simulated seminal fluid due to the dissolution of EL100. Films containing 400 mg of EL100 and tragacanth gum are promising candidates for future studies, as they could sexually safeguard women from HIV for at least one week and ensure greater protection during intercourse.

Influence of gelatin and collagen incorporation on peroxidase-mediated injectable pectin-based hydrogel and bioactivity of fibroblasts

Pectin has recently attracted increasing attention for biomedical and pharmaceutical applications. Due to the lack of adhesion molecules in polysaccharides, phenolic hydroxyl conjugated gelatin was added to enzymatically-gellable peroxidase-modified pectin derivative and compared with phenolic hydroxyl -pectin/collagen. Both pectin and gelatin were modified by tyramine hydrochloride in the presence of EDC/NHS. The phenolic hydroxyl -pectin/phenolic hydroxyl -gelatin, phenolic hydroxyl-pectin/collagen, and phenolic hydroxyl -pectin hydrogels were prepared using horseradish peroxidase and hydrogen peroxide_. The hydrogels were characterized by gelation time analysis. Morphology, enzymatic biodegradation, mechanical and swelling properties as well as water vapor transmission rate were also evaluated. Fibroblasts were cultured for 7 days, and the survival rate was evaluated using conventional MTT assay. Hydrogels composed of Ph-pectin/Ph-gelatin showed decreased biodegradation rate, and WVTR and further improved mechanical performance in comparison with other groups. Both phenolic hydroxyl -pectin/collagen and phenolic hydroxyl -pectin/phenolic hydroxyl -gelatin hydrogels exhibited porous structures. The hydrogels composed of collagen promoted cell survival rate 1.4 and 3.5 times compared to phenolic hydroxyl -gelatin and phenolic hydroxyl -pectin based hydrogels at the end of 7 days, respectively (p < 0.001). The study demonstrated the potential of enzymatically-gellable pectin-based hydrogels as cost-effective frameworks for use in tissue engineering applications.

Thiolated PVP-Amphotericin B Complexes: An Innovative Approach toward Highly Mucoadhesive Gels for Mucosal Leishmaniasis Treatment

The aim of this study was to synthesize polymeric excipients that can form mucoadhesive hydrogels containing amphotericin B (AmB) for the treatment of mucosal leishmaniasis. 2-(2-Acryloylaminoethyldisulfanyl)-nicotinic acid (ACENA) was copolymerized with N-vinyl pyrrolidone to obtain thiolated polyvinylpyrrolidone (PVP) that was then complexed with AmB to improve its solubility. The resulting structure of thiolated PVP was evaluated by ¹H nuclear magnetic resonance to confirm S-protected thiol groups, and the average molecular mass was determined by size exclusion chromatography. Moreover, variants of thiolated PVP-AmB were studied for the thiol content, amount of complexed AmB, cytotoxicity, mucoadhesive properties, and antileishmaniasis activity. The highest achieved degree of thiolation was 772 ± 24.64 μmol/g, and the amount of complexed AmB was 27.05 ± 0.31 μmol per g of polymer. Thiolated PVP and thiolated PVP-AmB variants (0.5% m/v) showed no cytotoxicity, whereas the equivalent concentration of free AmB reduced Caco-2 cell viability to 70% within 24 h. Thiol-functionalized PVP and PVP-AmB complexes displayed 7.66- and 7.20-fold higher adhesion to the mucosal surface in comparison to unmodified PVP and PVP-AmB, respectively. In addition, variants of thiolated PVP-AmB complexes displayed 100% antileishmaniasis activity in comparison to the 80% killing efficiency of Fungizone, which has been applied in the equivalent AmB concentration of 0.2 μg/mL. Thiol-functionalized PVP proved to be a promising novel excipient for the delivery of AmB providing enhanced solubility and improved mucoadhesive properties which are beneficial for the treatment of mucosal leishmaniasis.

Gelatin carrageenan sericin hydrogel composites improves cell viability of cryopreserved SaOS-2 cells

Cryopreservation and the low revival rate of cryopreserved cells remains a major challenge in cell based bone regeneration therapies. In our current study we aimed to develop a sericin based hydrogel composite incorporating various drugs and growth factors to enhance cell attachment, cryopreservation to increase the cellular viability upon revival. Sericin, gelatin and carrageenan blended hydrogel composites were prepared and explored for their physicochemical properties. The hydrogels prepared were porous and showed higher biocompatibility. Further, silver nanoparticles, alendronate and insulin like growth factor (IGF-1) were incorporated into the hybrid hydrogels individually and checked for sustained drug release profile. IGF-1 incorporated hydrogels composites showed better osteogenic cell attachment, proliferation and cell revival upon cryopreservation. The clonogenic potential of seeded cells upon 30 days of cryopreservation was also evaluated which was 55% in IGF-1 incorporated scaffold cells. A flow cytometry based staining protocol using Annexin V was developed which showed a live cell population up to 80% even after 30 days of crypreservation. These results validate the potential of our formulated hydrogels as cell based systems aimed for increasing cell survival upon cryopreservation and thus has a great potential for bone repair and regeneration.

The production of gel beads of soybean hull polysaccharides loaded with soy isoflavone and their pH-dependent release

Core-shell hydrogel beads were successfully produced from soybean hull polysaccharides (SHP). Using electron microscopy, the beads were found to be spherical with smooth surfaces and have tight gel network internal structures. Fourier transform infrared spectroscopy, differential scanning calorimetry, and X-ray diffraction were used to investigate the interaction between soy isoflavone and SHP in the gel beads mesh-like structure. Furthermore, the encapsulation efficiency and loading capacity of gel beads for soy isoflavone are 66.90% and 4.67%, respectively, and have the ability of pH-responsive release in vitro. Through the mathematical model of kinetics, we found that the release of soy isoflavone from gel beads showed Fickian diffusion in release media (pH 2.0 and 7.4), but showed non-Fickian diffusion at pH 4.0 and 6.8. This polymer can be extended to prepare more versatile delivery and controlled release system, appealing for food, pharmaceutical, biomedicine and cosmetics applications.

Pectin polymers for colon-targeted antitumor drug delivery

The use of chemotherapeutic drugs in the treatment of malignant tumors is always associated with the severe side effects negatively affecting all organs and systems in human body. One of the approaches for reduction of the toxic influence and enhancement of the antitumor drug administration efficiency is supposed to be the use of the biopolymer delivery systems. Pectins are considered the most promising components for colon targeted drug dosage forms as they are stable in the changing gastrointestinal media and easily degraded by pectinases produced by colonic microflora. A various range of the pectin-containing delivery systems were developed contributing higher concentration of the active drug molecules in particular site inside intestine and their lower blood level resulting in lowered risk of the severe side effects. This review discusses the various forms of the pectin-based materials such as hydrogels, tablets and pellets, films, microspheres, microsponges, nanoparticles, etc. as drug delivery device and attempted to report the vast literature available on pectin biopolymers in drug delivery applications.

HEMA based pH-sensitive semi IPN microgels for oral delivery; a rationale approach for ketoprofen

Objectives: The study aimed to develop safe, effective, and targeted drug delivery system for administration of nonsteroidal anti-inflammatory drugs (NSAIDs) in the form of microgels. We developed pH responsive microgels to overcome the mucosal damage caused by traditional immediate release dosage forms. Colon targeting and controlled release formulations have the potential to improve efficacy and reduce undesirable effects associated with NSAIDs.Methods: The pH sensitive oral hydrogel demonstrates the potential to target the colon. Cellulose acetate phthalate (CAP) and hydroxyethyl methacrylate (HEMA) based microgel particles were produced using a free radical polymerization technique using ammonium persulfate (APS) initiator and methylenebisacrylamide (MBA) as the crosslinking agent. Swelling and in-vitro drug release studies were performed at a range of pH conditions. The produced formulations were characterized using Fourier transform infrared spectroscopy, thermogravimetric analysis, differential scanning calorimetry, scanning electron microscopy (SEM), and X-ray diffraction. Biocompatibility of the microgels was analyzed in cytotoxicity studies.Key findings: The swelling and release rate were negligible at pH 1.2, which confirmed the pH-responsiveness of CAP-co-poly(HEMA). The co-polymeric system prevents the release of ketoprofen sodium in the stomach owing to limited swelling at gastric pH, whilst promoting release at the basic pH observed in the colon. SEM images confirmed porous nature of the microgels that facilitate effective drug diffusion through the polymeric matrix. Cytotoxicity studies revealed biocompatibility of hydrogels.Conclusion: These investigations showed that that the controlled drug release and gastro-protective drug delivery of NSAIDS was achieved using CAP-co-poly(HEMA) microgel particles.

Smart Freeze-Dried Bigels for the Prevention of the Sexual Transmission of HIV by Accelerating the Vaginal Release of Tenofovir during Intercourse

Sub-Saharan African women are still at risk from the human immunodeficiency virus (HIV), and sex with men is the main route of transmission. Vaginal formulations containing antiretroviral drugs are promising tools to give women the power to protect themselves. The aim of this work was to obtain freeze-dried bigels containing pectin, chitosan, or hypromellose for the vaginal controlled release of Tenofovir, which is accelerated in the presence of semen. Nine batches of bigels were formulated using different proportions of these polymers in the hydrogel (1, 2, and 3% w/w). The bigels obtained were freeze-dried and then underwent hardness and deformability, mucoadhesion, swelling, and drug release tests, the last two in simulated vaginal fluid (SVF) and SVF/simulated seminal fluid (SSF) mixture. The formulation containing 3% pectin (fd3P) has the highest values for hardness, resistance to deformation, and good mucoadhesivity. Its swelling is conditioned by the pH of the medium, which is responsive to the controlled release of Tenofovir in SVF, with the fastest release in the SVF/SSF mixture. fd3P would be an interesting smart microbicidal system to allow faster release of Tenofovir in the presence of semen, and thus increase women’s ability to protect themselves from the sexual transmission of HIV.

Scaffolding polymeric biomaterials: Are naturally occurring biological macromolecules more appropriate for tissue engineering?

Nowadays, tissue and organ failures resulted from injury, aging accounts, diseases or other type of damages is one of the most important health problems with an increasing incidence worldwide. Current treatments have limitations including, low graft efficiency, shortage of donor organs, as well as immunological problems. In this context, tissue engineering (TE) was introduced as a novel and versatile approach for restoring tissue/organ function using living cells, scaffold and bioactive (macro-)molecules. Among these, scaffold as a three-dimensional (3D) support material, provide physical and chemical cues for seeding cells and has an essential role in cell missions. Among the wide verity of scaffolding materials, natural or synthetic biopolymers are the most commonly biomaterials mainly due to their unique physicochemical and biological features. In this context, naturally occurring biological macromolecules are particular of interest owing to their low immunogenicity, excellent biocompatibility and cytocompatibility, as well as antigenicity that qualified them as popular choices for scaffolding applications. In this review, we highlighted the potentials of natural and synthetic polymers as scaffolding materials. The properties, advantages, and disadvantages of both polymer types as well as the current status, challenges, and recent progresses regarding the application of them as scaffolding biomaterials are also discussed.

The Structural, Crystallinity, and Thermal Properties of pH-responsive Interpenetrating Gelatin/Sodium Alginate-based Polymeric Composites for the Controlled Delivery of Cetirizine HCl

OBJECTIVES

The present work aimed to design and synthesize pH-sensitive cross-linked Ge/SA hydrogels using different ratios of each polymer, and to investigate the effect of each polymer on dynamic, equilibrium swelling, and in vitro release pattern of cetirizine hydrochloride, which was selected as a model drug.

MATERIALS AND METHODS

These gelatin and sodium alginate hydrogels were prepared at room temperature through free radical polymerization using glutaraldehyde as a crosslinker. These polymeric composites were used as model systems to envisage various important characterizations. The in vitro release pattern of drug was investigated in three different mediums (phosphate buffer solution of pH 1.2, 5.5, 7.5 whose ionic strength was kept constant). Various structure property relationships that affect its release behavior were determined such as swelling analysis, porosity, sol-gel analysis, average molecular weight between crosslinks (Mc), solvent interaction parameter (χ), volume fraction of polymer (V2,s) and diffusion coefficient. The structural, crystallinity, and thermal stability were confirmed using FTIR, XRD, and DSC analysis.

RESULTS

These hydrogels showed maximum swelling at pH 1.2. Zero-order, first-order, Higuchi, and Peppas models were applied to demonstrate the release pattern of drug. The release of drug occurred through non-Fickian diffusion or anomalous mechanism. Porosity was found increased with an increase in concentration of both polymers, and porosity decreased when the concentration of the crosslinker was increased. Gel fraction increased with an increase in concentration of SA, Ge, and glutaraldehyde.

CONCLUSION

The prepared pH sensitive hydrogels can be used as a potential carrier for the sustained delivery of cetirizine hydrochloride.