Carrageenan/Chitin Nanowhiskers Cryogels for Vaginal Delivery of Metronidazole.

The development of polymeric carriers based on partially deacetylated chitin nanowhiskers (CNWs) and anionic sulfated polysaccharides is an attractive strategy for improved vaginal delivery with modified drug release profiles. This study focuses on the development of metronidazole (MET)-containing cryogels based on carrageenan (CRG) and CNWs. The desired cryogels were obtained by electrostatic interactions between the amino groups of CNWs and the sulfate groups of CRG and by the formation of additional hydrogen bonds, as well as by entanglement of carrageenan macrochains. It was shown that the introduction of 5% CNWs significantly increased the strength of the initial hydrogel and ensured the formation of a homogeneous cryogel structure, resulting in sustained MET release within 24 h. At the same time, when the CNW content was increased to 10%, the system collapsed with the formation of discrete cryogels, demonstrating MET release within 12 h. The mechanism of prolonged drug release was mediated by polymer swelling and chain relaxation in the polymer matrix and correlated well with the Korsmeyer-Peppas and Peppas-Sahlin models. In vitro tests showed that the developed cryogels had a prolonged (24 h) antiprotozoal effect against Trichomonas, including MET-resistant strains. Thus, the new cryogels with MET may be promising dosage forms for the treatment of vaginal infections.

Alginate Gel Reinforcement with Chitin Nanowhiskers Modulates Rheological Properties and Drug Release Profile.

Hydrogels are promising materials for various applications, including drug delivery, tissue engineering, and wastewater treatment. In this work, we designed an alginate (ALG) hydrogel containing partially deacetylated chitin nanowhiskers (CNW) as a filler. Gelation in the system occurred by both the protonation of alginic acid and the formation of a polyelectrolyte complex with deacetylated CNW surface chains. Morphological changes in the gel manifested as a honeycomb structure in the freeze-dried gel, unlike the layered structure of an ALG gel. Disturbance of the structural orientation of the gels by the introduction of CNW was also expressed as a decrease in the intensity of X-ray diffraction reflexes. All studied systems were non-Newtonian liquids that violated the Cox-Merz rule. An increase in the content of CNW in the ALG-CNW hydrogel resulted in increases in the yield stress, maximum Newtonian viscosity, and relaxation time. Inclusion of CNW prolonged the release of tetracycline due to changes in diffusion. The first phases (0-5 h) of the release profiles were well described by the Higuchi model. ALG-CNW hydrogels may be of interest as soft gels for controlled topical or intestinal drug delivery.