DHA and l -carnitine loaded chitosan hydrogels as delivery systems for topical applications

A Review on the Design and Hydration Properties of Natural Polymer-Based Hydrogels

Hydrogels are hydrophilic 3D networks that are able to ingest large amounts of water or biological fluids, and are potential candidates for biosensors, drug delivery vectors, energy harvester devices, and carriers or matrices for cells in tissue engineering. Natural polymers, e.g., cellulose, chitosan and starch, have excellent properties that afford fabrication of advanced hydrogel materials for biomedical applications: biodegradability, biocompatibility, non-toxicity, hydrophilicity, thermal and chemical stability, and the high capacity for swelling induced by facile synthetic modification, among other physicochemical properties. Hydrogels require variable time to reach an equilibrium swelling due to the variable diffusion rates of water sorption, capillary action, and other modalities. In this study, the nature, transport kinetics, and the role of water in the formation and structural stability of various types of hydrogels comprised of natural polymers are reviewed. Since water is an integral part of hydrogels that constitute a substantive portion of its composition, there is a need to obtain an improved understanding of the role of hydration in the structure, degree of swelling and the mechanical stability of such biomaterial hydrogels. The capacity of the polymer chains to swell in an aqueous solvent can be expressed by the rubber elasticity theory and other thermodynamic contributions; whereas the rate of water diffusion can be driven either by concentration gradient or chemical potential. An overview of fabrication strategies for various types of hydrogels is presented as well as their responsiveness to external stimuli, along with their potential utility in diverse and novel applications. This review aims to shed light on the role of hydration to the structure and function of hydrogels. In turn, this review will further contribute to the development of advanced materials, such as "injectable hydrogels" and super-adsorbents for applications in the field of environmental science and biomedicine.

Modification of hygroscopicity and tabletability of l-carnitine by a cocrystallization technique

LC-MYR cocrystal with significant enhanced dissolution,tabletability and decreased hygroscopicity is more suitable for manufacturing solid dosage forms.

Celery cellulose hydrogel as carriers for controlled release of short-chain fatty acid by ultrasound

The feasibility of using celery cellulose hydrogels as carriers was explored for controlled release of short-chain fatty acids (SCFAs) triggered by ultrasound. The hydrogels were prepared with the phase inversion method and further characterized using FT-IR, SEM and XRD techniques. At the optimal cellulose concentration (8.33 and 6.25 mg/mL), the hydrogels (F₄ and F₅) exhibited the swelling ratio of 185%, and Young's modulus of the F₄ and F₅ was lower than that of others. The hydrogels were loaded with SCFAs owing to its hydrophilicity and swelling properties, and the maximum loading capacity of SCFAs achieved nearly 80%. Interestingly, the loaded SCFAs within hydrogel carrier could be readily released if an ultrasound trigger is exerted. Our results indicate that the ultrasound-triggered strategy for the SCFAs delivery system could provide a promising basis to achieve on-demand, reproducible, repeated, and tunable dosing of bioactive molecules.

Xylan-Based Hydrogels as a Potential Carrier for Drug Delivery: Effect of Pore-Forming Agents

Pore-forming agents have a significant influence on the pore structure of hydrogels. In this study, a porogenic technique was employed to investigate the preparation of macroporous hydrogels which were synthesized by radical copolymerization of carboxymethyl xylan with acrylamide and N-isopropylacrylamide under the function of a cross-linking agent. Six kinds of pore-forming agents were used: polyvinylpyrrolidone K30, polyethylene glycol 2000, carbamide, NaCl, CaCO₃, and NaHCO₃. The application of these hydrogels is also discussed. The results show that pore-forming agents had an important impact on the pore structure of the hydrogels and consequently affected properties of the hydrogels such as swelling ratio and mechanical strength, while little effect was noted on the thermal property of the hydrogels. 5-Fluorouracil was used as a model drug to study the drug release of the as-prepared hydrogels, and it was found that the drug release was substantially improved after using the NaHCO₃ pore-forming agent: a cumulative release rate of up to 71.05% was achieved.

pH-responsive and porous vancomycin-loaded PLGA microspheres: evidence of controlled and sustained release for localized inflammation inhibition in vitro

Adequate delivery of antibiotics to infected sites is crucial for the effective treatment of bacterial infections. A controlled and sustained release system based on porous and pH-responsive poly(lactic-co-glycolic acid) (PLGA)-vancomycin (Van) microspheres was developed. In this system, drug release is triggered by the weakly acidic environment, like local inflamed tissues. The microspheres, developed through the W1/O/W2 double-emulsion evaporation method, comprised a PLGA-based shell and a core containing Van and the bubble-generating agent of NaHCO3. The optimized preparation conditions for PLGA-NaHCO3-Van microspheres were investigated and characterized. The PLGA-NaHCO3-Van microspheres exhibited porous microstructures with regular shape and uniform size and the characteristic of controlled drug release, which could be attributed to the incorporation of NaHCO3. The results of the Kirby-Bauer assay confirmed that released Van retained effective antibacterial activity towards standard Staphylococcus aureus and methicillin-resistant S. aureus (MRSA) infected clinical samples, suggesting their further promising application in local anti-infection.

Properties and in vitro drug release of pH- and temperature-sensitive double cross-linked interpenetrating polymer network hydrogels based on hyaluronic acid/poly (N-isopropylacrylamide) for transdermal delivery of luteolin

In this study, we prepared double cross-linked interpenetrating polymer network (IPN) hydrogels composed of temperature sensitive poly (N-isopropylacrylamide) (PNIPAM) and pH sensitive hyaluronic acid (HA) by radical polymerization and Michael addition. Their physicochemical properties for transdermal delivery of luteolin inhibiting the hyperproliferation of keratinocytes in psoriasis were investigated and drug release studies were performed. Double networks of HA/PNIPAM IPN hydrogel were identified through FT-IR and ¹³CNMR. By measuring the swelling ratios pH and temperature sensitivity were confirmed, and it was influenced by the content of a cross-linking agent. As a result of texture analysis and rheometry, a IPN hydrogel with 3% crosslinker content had the most adhesive and stable cross-linked network. Therefore, luteolin was loaded on this hydrogel. Its drug release behavior was determined at various temperatures and pH using several drug release kinetic models. As a result of skin permeation study, HA/PNIPAM IPN hydrogel effectively delivers luteolin to the epidermis and dermis. No toxicity was observed as a result of observing cytotoxicity of the hydrogel for application to the skin. In conclusion, IPN hydrogels can be developed as carriers of transdermal delivery system of luteolin for psoriasis skin relief.

Carnitine, A New Precursor in the Formation of the Plant Growth Regulator Mepiquat

Carnitine is demonstrated as an effective methyl donor in the formation of the plant growth regulator N, N-dimethylpiperidinium (mepiquat), encompassing either N-methylation/decarboxylation of pipecolic acid, or Maillard pathways followed by transmethylation reactions. The formation of mepiquat and the intermediate compounds was monitored (180-300 °C, up to 180 min) using HPLC-MS/MS in different binary or ternary model systems composed of (i) lysine/fructose/carnitine, (ii) lysine/glucose/carnitine, or (iii) pipecolic acid (PipAc)/carnitine. The highest yield of mepiquat was 2.4% after 120 min incubation at 290 °C (PipAc/carnitine model system). The highest yield was recorded in fructose and glucose (Maillard) systems after 180 min at 230 °C. The full-scan mode was used to monitor the formation of the corresponding intermediates (piperidine and N-methylpiperidine, the demethylated intermediates of carnitine). The new pathways of mepiquat formation indicate that the occurrence of low levels of this thermally induced compound is potentially more widespread in some selected cooked foodstuffs. For the first time, mepiquat was detected in oven-cooked beef, reaching up to 82.5 μg/kg. These amounts are not expected to significantly contribute to the overall exposure via different foodstuffs, as reported in previous studies.