Microencapsulation of norfloxacin in chitosan/chitosan oligosaccharides and its application in shrimp culture

ROS-responsive modified chitosan oligosaccharide nanocapsules for improving pesticide efficiency and intelligent release

BACKGROUND

Some traditional pesticide formulations are inefficient, leading to excessive use and abuse of pesticides, which in turn effects environment. Intelligent release pesticide formulations are ideal for improving pesticide utilization and persistence while reducing environmental pollution.

RESULTS

We designed a benzil-modified chitosan oligosaccharide (CO-BZ) to encapsulate avermectin (Ave). Ave@CO-BZ nanocapsules are prepared based on a simple interfacial method via cross-linking of CO-BZ with diphenylmethane diisocyanate (MDI). The Ave@CO-BZ nanocapsules have an average particle size of 100 nm and exhibited a responsive release performance for ROS. The cumulative release rate of nanocapsules at 24 h with ROS increased by about 11.4% compared to that without ROS. The Ave@CO-BZ nanocapsules displayed good photostability. Ave@CO-BZ nanocapsules can penetrate root-knot nematodes more easily and exhibited better nematicidal activity against root-knot nematodes. The pot experiment showed that the control effect of Ave CS at low concentration was 53.31% at the initial stage of application (15 d), while Ave@CO-BZ nanocapsules was 63.54%. Under the same conditions, the control effect of Ave@CO-BZ nanocapsules on root-knot nematodes was 60.00% after 45 days of application, while Ave EC was only 13.33%. The acute toxicity experiments of earthworms showed that the toxicity of nanocapsules was significantly lower than that of EC.

CONCLUSION

The ROS-responsive nanocapsules can improve the utilization of pesticides and non-target biosafety. This modified chitosan oligosaccharide has great potential as a bio stimuli-responsive material, and this simple and convenient method for preparing Ave@CO-BZ nanocapsules provides a direction for the effective utilization of pesticides. © 2023 Society of Chemical Industry.

Scalable Manufacture of Curcumin-Loaded Chitosan Nanocomplex for pH-Responsive Delivery by Coordination-Driven Flash Nanocomplexation

Metal coordination-driven nanocomplexes are known to be responsive to physiologically relevant stimuli such as pH, redox, temperature or light, making them well-suited for antitumor drug delivery. The ever-growing demand for such nanocomplexes necessitates the design of a scalable approach for their production. In this study, we demonstrate a novel coordination self-assembly strategy, termed flash nanocomplexation (FNC), which is rapid and efficient for the fabrication of drug-loaded nanoparticles (NPs) in a continuous manner. Based on this strategy, biocompatible chitosan (CS) and Cu2+ can be regarded anchors to moor the antitumor drug (curcumin, Cur) through coordination, resulting in curcumin-loaded chitosan nanocomplex (Cur-loaded CS nanocomplex) with a narrow size distribution (PDI < 0.124) and high drug loading (up to 41.75%). Owing to the excellent stability of Cur-loaded CS nanocomplex at neutral conditions (>50 days), premature Cur leakage was limited to lower than 1.5%, and pH-responsive drug release behavior was realized in acidic tumor microenvironments. An upscaled manufacture of Cur-loaded CS nanocomplex is demonstrated with continuous FNC, which shows an unprecedented method toward practical applications of nanomedicine for tumor therapy. Furthermore, intracellular uptake study and cytotoxicity experiments toward H1299 cells demonstrates the satisfied anticancer efficacy of the Cur-loaded CS nanocomplex. These results confirm that coordination-driven FNC is an effective method that enables the rapid and scalable fabrication of antitumor drugs.

Release of florfenicol in seawater using chitosan-based molecularly imprinted microspheres as drug carriers

Novel molecularly imprinted polymer (MIP) microspheres using functionalized chitosan as eco-friendly substrates were prepared by surface imprinting method and applied as drug delivery carriers to provide extended-release of florfenicol (FF) in seawater. The chitosan-based composites were characterized by scanning electron microscopy and Fourier transforms infrared spectroscopy analyses. The swelling behavior, adsorption capability, and selectivity for FF were investigated. The results show that the MIPs possessed high drug loading saturation capacity and specific recognition affinity for FF. The release studies of MIPs as drug delivery carriers were evaluated in natural seawater. The microspheres exhibited slow sustained release profiles of FF and the release behavior conformed to the first-order kinetic equation. The imprinted microspheres as drug delivery devices would be a promising application for improving the efficacy of the antibiotic without exposing the ecological system to excess FF in aquaculture.

Microencapsulation of immunoglobulin Y: optimization with response surface morphology and controlled release during simulated gastrointestinal digestion

Immunoglobulin Y (IgY) is an effective orally administered antibody used to protect against various intestinal pathogens, but which cannot tolerate the acidic gastric environment. In this study, IgY was microencapsulated by alginate (ALG) and coated with chitooligosaccharide (COS). A response surface methodology was used to optimize the formulation, and a simulated gastrointestinal (GI) digestion (SGID) system to evaluate the controlled release of microencapsulated IgY. The microcapsule formulation was optimized as an ALG concentration of 1.56% (15.6 g/L), COS level of 0.61% (6.1 g/L), and IgY/ALG ratio of 62.44% (mass ratio). The microcapsules prepared following this formulation had an encapsulation efficiency of 65.19%, a loading capacity of 33.75%, and an average particle size of 588.75 μm. Under this optimum formulation, the coating of COS provided a less porous and more continuous microstructure by filling the cracks on the surface, and thus the GI release rate of encapsulated IgY was significantly reduced. The release of encapsulated IgY during simulated gastric and intestinal digestion well fitted the zero-order and first-order kinetics functions, respectively. The microcapsule also allowed the IgY to retain 84.37% immune-activity after 4 h simulated GI digestion, significantly higher than that for unprotected IgY (5.33%). This approach could provide an efficient way to preserve IgY and improve its performance in the GI tract.

Light modulates the effect of antibiotic norfloxacin on photosynthetic processes of Microcystis aeruginosa

Norfloxacin is one of the widely used antibiotics, often detected in aquatic ecosystems, and difficultly degraded in the environment. However, how norfloxacin affects the photosynthetic process of freshwater phytoplankton is still largely unknown, especially under varied light conditions. In this study, we investigated photosynthetic mechanisms of Microcystis aeruginosa in responses to antibiotic norfloxacin (0-50 μg/L) for 72 h under low (LL; 50 μmol photons m^-2 s^-1) and high (HL; 250 μmol photons m^-2 s^-1) growth light regimes. We found that environmentally related concentrations of norfloxacin inhibited the growth rate and operational quantum yield of photosynthesis system II (PSII) of M. aeruginosa more under HL than under LL, suggesting HL increased the toxicity of norfloxacin to M. aeruginosa. Further analyses showed that norfloxacin deactivated PSII reaction centers under both growth light regimes with increased minimal fluorescence yields only under HL, suggesting that norfloxacin not only damaged reaction centers of PSII, but also inhibited energy transfer among phycobilisomes in M. aeruginosa under HL. However, non-photosynthetic quenching decreased in the studied species by norfloxacin exposure under both growth light regimes, suggesting that excess energy might not be efficiently dissipated as heat. Also, we found that reactive oxygen species (ROS) content increased under norfloxacin treatments with a higher ROS content under HL compared to LL. In addition, HL increased the absorption of norfloxacin by M. aeruginosa, which could partly explain the high sensitivity to norfloxacin of M. aeruginosa under HL. This study firstly reports that light can strongly affect the toxicity of norfloxacin to M. aeruginosa, and has vitally important implications for assessing the toxicity of norfloxacin to aquatic microorganisms.

A review on the preparation of chitosan oligosaccharides and application to human health, animal husbandry and agricultural production

Chitosan oligosaccharides (COS) are the degraded products of chitin or chitosan prepared by chemical or enzymatic hydrolysis. As compared to chitosan, COS not only exhibit some specific physicochemical properties such as excellent water solubility, biodegradability and biocompatibility, but also have a variety of functionally biological activities including anti-inflammation, anti-bacteria, immunomodulation, neuroprotection and so on. This review aims to summarize the preparation and structural characterization methods of COS, and will discuss the application of COS or their derivatives to human health, animal husbandry and agricultural production. COS have been demonstrated to prevent the occurrence of human health-related diseases, enhance the resistance to diseases of livestock and poultry, and improve the growth and quality of crops in plant cultivation. Overall, COS have presented a broad developmental potential and application prospect in the healthy field that deserves further exploration.

Interactions of oligochitosan with blood components

Oligochitosan (OCHI) is known to have some specific biological activities. However, its interactions with blood components and related correlation with molecular structures remains to be clarified due to its growing use in biomedical areas. Herein, a series of OCHI were prepared by hydrogen peroxide induced degradation combined fractionation in ethanol solutions and their molecular structures were characterized by GPC, FTIR, ¹H and ¹³C NMR, and then the interactions of the prepared OCHI with blood components, including red blood cells (hemolysis, deformability, and aggregation), coagulation system, complement (C3a, and C5a activation), and platelet (activation, and aggregation), were investigated. For red blood cells, OCHI has a quite low risk of hemolysis in a dose- and MW-dependent manner and the deformability and aggregation were observed in its high MW fraction. The coagulation tests revealed that OCHI is capable of a mild anticoagulation through blocking the intrinsic pathway and the anticoagulation corresponding MW was identified. In terms of complement, OCHI could inhibit C3a in a dose-dependent manner and activate C5a with its high MW fraction. In addition, there is no significant effect of OCHI on platelet activation and aggregation. Based on above results, the interactions related mechanism was discussed and proposed.

Determination of the Deacetylation Degree of Chitooligosaccharides

The methods for determination of chitosan content recommended in the Chinese Pharmacopoeia and the European Pharmacopoeia are not applicable for evaluation of the extent of deacetylation (deacetylation degree, DD) in chitooligosaccharides (COS). This study explores two different methods for assessment of DD in COS having relatively high and low molecular weights: an acid-base titration with bromocresol green indicator and a first order derivative UV spectrophotometric method for assessment of DD in COS. The accuracy of both methods as a function of molecular weight was also investigated and compared to results obtained using ¹H NMR spectroscopy. Our study demonstrates two simple, fast, widely adaptable, highly precise, accurate, and inexpensive methods for the effective determination of DD in COS, which have the potential for widespread commercial applications in developing country.