Cellular Internalization and Toxicity of Chitosan Nanoparticles Loaded with Nobiletin in Eukaryotic Cell Models (Saccharomyces cerevisiae and Candida albicans)

This study involved the synthesis and characterization of chitosan nanoparticles loaded with nobiletin (CNpN) and assessed their toxicity and cellular internalization in eukaryotic cell models (Saccharomyces cerevisiae and Candida albicans). Nanoparticles were prepared via the nanoprecipitation method and physicochemically characterized to determine their hydrodynamic diameter using dynamic light scattering (DLS), their surface charge through ζ-potential measurements, and their chemical structure via Fourier-transform infrared spectroscopy (FTIR). The hydrodynamic diameter and ζ-potential of chitosan nanoparticles (CNp) and CNpN were found to be 288.74 ± 2.37 nm and 596.60 ± 35.49 nm, and 34.51 ± 0.66 mV and 37.73 ± 0.19 mV, respectively. The scanning electron microscopy (SEM) images displayed a particle size of approximately 346 ± 69 nm, with notable sphericity for CNpN. FTIR analysis provided evidence of potential imine bonding between chitosan and nobiletin. Membrane integrity damage could be observed in both S. cerevisiae and C. albicans yeast stained with propidium iodide, demonstrating membrane integrity damage caused by CNp and CNpN, where higher concentration treatments inhibited the development of yeast cells. These findings suggest a selective therapeutic potential of CNpN, which could be promising for the development of antifungal and anticancer therapies. This study contributes to understanding the interaction between nanoparticles and eukaryotic cells, offering insights for future biomedical applications.

Antimicrobial Actions and Applications of Chitosan

Chitosan is a naturally originating product that can be applied in many areas due to its biocompatibility, biodegradability, and nontoxic properties. The broad-spectrum antimicrobial activity of chitosan offers great commercial potential for this product. Nevertheless, the antimicrobial activity of chitosan varies, because this activity is associated with its physicochemical characteristics and depends on the type of microorganism. In this review article, the fundamental properties, modes of antimicrobial action, and antimicrobial effects-related factors of chitosan are discussed. We further summarize how microorganisms genetically respond to chitosan. Finally, applications of chitosan-based biomaterials, such as nanoparticles and films, in combination with current clinical antibiotics or antifungal drugs, are also addressed.

Preparation and characterization of thermoresponsive poly(N-isopropylacrylamide) copolymers with enhanced hydrophilicity

The poly(N-isopropylacrylamide) copolymers with the enhanced hydrophilicity were synthesized by free radical polymerization from a mixture of the monomers N-isopropylacrylamide (NIPAAm), N-vinyl pyrrolidone (NVP), hydroxypropyl methacrylate (HPM) and 3-trimethoxysilypropyl methacrylate (TMSPM) at different feeding ratios. The attenuated total reflectance-Fourier transform infrared spectrometry (ATR-FTIR), nuclear magnetic resonance (1H-NMR) and gel permeation chromatography (GPC) were applied to characterize the resultant copolymers. The lower critical solution temperature (LCST) of the copolymers was determined via dynamic light scattering (DLS). By alternating the molar ratios of NIPAAm and NVP, the copolymers were synthesized to have their own distinctive LCST from 25°C to 40°C. Regardless of the starting feed ratio used, the final copolymers had the similar monomeric ratio as planned. The copolymer films were then formed on platinum wafers by drop coating and thermal annealing owing to 3-trimethoxysilyl crosslinking and reacting with hydroxyl groups. The surface wettability and morphology of the specimens were observed using contact angle measurements and scanning electron microscopy (SEM), respectively. The results demonstrated that with the increase of the NVP content, the film surface became more hydrophilic. The surface microstructure of the thermoresponsive films varied depending on the copolymer composition and ambient temperature. The experimental results indicated that the addition of NVP not only increased the LCST of copolymers but also improved the hydrophilicity of the products derived from the copolymers. This ability to elevate the LCST of the polymers provides excellent flexibility in tailoring transitions for specific uses, like controlled drug release and nondestructive cell harvest.

Enzyme-free electrochemical detection of nanomolar levels of the organophosphorus pesticide paraoxon-ethyl by using a poly(N-isopropyl acrylamide)-chitosan microgel decorated with palladium nanoparticles

A rapid voltammetric method is described for the determination of the organophosphorus pesticide paraoxon-ethyl (PEL). A glassy carbon electrode (GCE) was modified with a composite consisting of a poly(N-isopropylacrylamide)-chitosan microgel with incorporated palladium nanoparticles. The microgel was characterized by FE-SEM, EDX, XPS, FTIR, XRD, and EIS. The modified GCE is shown to enable direct electro-reductive determination of PEL by using differential pulse voltammetry. The method works in pH 7 solution and in the 0.01 μM to 1.3 mM PEL concentration range. At a typical working potential of -0.66 V (vs. Ag/AgCl) (at 50 mV/s), the detection limit is as low as 0.7 nM, and the electrochemical sensitivity is 1.60 μA μM^-1 cm^-2. Intriguingly, the modified GCE displays good recovery when applied to bok choy and water samples. Graphical abstract Schematic of an electrochemical method for determination of paraoxon ethyl (PEL) in bok choy extract and water by using poly(N-isopropyl acrylamide)-chitosan microgel decorated with palladium nanoparticle-modified glassy carbon electrodes (PdNPs/PNIPAM-CT microgel/GCE).

Let There be Light: Polymeric Micelles with Upper Critical Solution Temperature as Light-Triggered Heat Nanogenerators for Combating Drug-Resistant Cancer

Complete drug release and efficient drug retention are two critical factors in reversing drug resistance in cancer therapy. In this regard, polymeric micelles with an upper critical solution temperature (UCST) are designed as a new exploration to reverse drug resistance. The amphiphilic UCST-type block copolymers are used to encapsulate photothermal agent IR780 and doxorubicin (DOX) simultaneously. The integrated UCST-type drug nanocarriers show light-triggered multiple synergistic effects to reverse drug resistance and are expected to kill three birds with one stone: First, owing to the photothermal effect of IR780, the nanocarriers will be dissociated upon exposure to laser irradiation, leading to complete drug release. Second, the photothermal effect-induced hyperthermia is expected to avoid the efflux of DOX and realize efficient drug retention. Last but not least, photothermal ablation of cancer cells can be achieved after laser irradiation. Therefore, the UCST-type drug nanocarriers provide a new strategy in reversing drug resistance in cancer therapy.

Concepts for Developing Physical Gels of Chitosan and of Chitosan Derivatives

Chitosan macro- and micro/nano-gels have gained increasing attention in recent years, especially in the biomedical field, given the well-documented low toxicity, degradability, and non-immunogenicity of this unique biopolymer. In this review we aim at recapitulating the recent gelling concepts for developing chitosan-based physical gels. Specifically, we describe how nowadays it is relatively simple to prepare networks endowed with different sizes and shapes simply by exploiting physical interactions, namely (i) hydrophobic effects and hydrogen bonds-mostly governed by chitosan chemical composition-and (ii) electrostatic interactions, mainly ensured by physical/chemical chitosan features, such as the degree of acetylation and molecular weight, and external parameters, such as pH and ionic strength. Particular emphasis is dedicated to potential applications of this set of materials, especially in tissue engineering and drug delivery sectors. Lastly, we report on chitosan derivatives and their ability to form gels. Additionally, we discuss the recent findings on a lactose-modified chitosan named Chitlac, which has proved to form attractive gels both at the macro- and at the nano-scale.