Controlling antimicrobial activity and drug loading capacity of chitosan-based layer-by-layer films

High-flexible chitosan-based composite membrane with multi-layer biopolymer coatings for anti-bacterial drug delivery and wound healing

Flexible chitosan-based membranes were prepared by casting/solvent evaporation method using chitosan flocks as raw material. To improve mechanical and biological properties, chitosan microspheres (CMs) were prepared and integrated to form the composite membranes. Two different anti-bacterial drugs, e.g., tetracycline hydrochloride (TH) and silver sulfadiazine (AgSD), were loaded into the CMs and composite membranes to enhance their anti-bacterial properties. Furthermore, composite membranes were alternately coated by multi-layers of oxidized alginate (OAlg) and carboxymethyl chitosan (CMCS) via the layer-by-layer self-assembly and Schiff-base cross-linking. Our results demonstrated that the microspheres and multi-layer coatings could improve the swelling, water vapor transmission and hydrophilicity of the composite membranes. The chitosan microspheres and multi-layer coatings increased the tensile strength and decreased the elongation at the break of the membranes. Our composite membrane had better mechanical properties, slow drug release, anti-bacterial properties, which could promote cell proliferation. This composite membrane has great application potential in inhibiting bacterial infection and promoting wound regeneration.

Chitosan coatings with different degrees of deacetylation regulate the postharvest quality of sweet cherry through internal metabolism

In this study, chitosan coatings with different degrees of deacetylation (DD, 88.1 % and 95.2 %) were electrostatically sprayed on sweet cherries to evaluate their impacts on postharvest characteristics and internal metabolism. The results showed that chitosan coating could effectively delay the change of weight, color, firmness, and maintain the content of total phenols, flavonoids and titratable acids, and inhibit the activities of β-galactosidase and polyphenol oxidase during cold storage. The storage qualities and physiological activities of sweet cherry were significantly correlated with the contents of sorbitol, 4-hydroxycinnamic acid, hydrogenated hydroxycinnamic acid, tyrosine, proline, glutamine, phenylalanine, and other metabolites. Chitosan coating may modulate fruit quality by inhibiting the energy metabolism, accelerating the accumulation of carbohydrates, and promoting the metabolism of phenylalanine and flavonoid. Especially, chitosan coating with 88.1 % DD had better wettability on sweet cherry's peel and displayed more obvious preservation effect through stronger metabolic regulation ability.

Optimization of kappa-carrageenan cationization using experimental design for model-drug release and investigation of biological properties

Cationization is a promising chemical modification technique that improves properties by attaching permanent positive charges to the backbone of biopolymers. Carrageenan is a widely available and non-toxic polysaccharide, commonly used in food industry but with low solubility in cold water. We performed a central composite design experiment to check the parameters that most influence the degree of cationic substitution and the film solubility. Hydrophilic quaternary ammonium groups on the carrageenan backbone enhance interaction in drug delivery systems and create active surfaces. Statistical analysis indicated that within the studied range, only the molar ratio between the cationizing reagent and the repeating disaccharide unit of carrageenan had a significant effect. Optimized parameters using 0.086 g of sodium hydroxide and glycidyltrimethylammonium/disaccharide repeating unit of 6.83 achieved 65.47 % degree of substitution and 4.03 % solubility. Characterizations confirmed the effective incorporation of cationic groups into the commercial structure of carrageenan and thermal stability improvement of the derivatives.

Polysaccharide-based layer-by-layer nanoarchitectonics with sulfated chitosan for tuning anti-thrombogenic properties

The development of blood-interacting surfaces is critical to fabricate biomaterials for medical use, such as prostheses, implants, biosensors, and membranes. For instance, thrombosis is one of the leading clinical problems when polymer-based materials interact with blood. To overcome this limitation is necessary to develop strategies that limit platelets adhesion and activation. In this work, hyaluronan (HA)/chitosan (Chi) based-films, recently reported in the literature as platforms for tumor cell capture, were developed and, subsequently, functionalized with sulfated chitosan (ChiS) using a layer-by-layer technique. ChiS, when compared to native Chi, presents the unique abilities to confer anti-thrombogenic properties, to reduce protein adsorption, and also to limit calcification. Film physicochemical characterization was carried out using FTIR and XPS for chemical composition assessment, AFM for the surface morphology, and contact angle for hydrophilicity evaluation. The deposition of ChiS monolayer promoted a decrease in both roughness and hydrophilicity of the HA/Chi films. In addition, the appearance of sulfur in the chemical composition of ChiS-functionalized films confirmed the film modification. Biological assay indicated that the incorporation of sulfated groups limited platelet adhesion, mainly because a significant reduction of platelets adhesion to ChiS-functionalized films was observed compared to HA/Chi films. On balance, this work provides a new insight for the development of novel antithrombogenic biomaterials, opening up new possibilities for devising blood-interaction surfaces.

Antibacterial and Antifungal Efficacy of Medium and Low Weight Chitosan-Shelled Nanodroplets for the Treatment of Infected Chronic Wounds

Purpose

Medium versus low weight (MW vs LW) chitosan-shelled oxygen-loaded nanodroplets (cOLNDs) and oxygen-free nanodroplets (cOFNDs) were comparatively challenged for biocompatibility on human keratinocytes, for antimicrobial activity against four common infectious agents of chronic wounds (CWs) – methicillin-resistant Staphylococcus aureus (MRSA), Streptococcus pyogenes, Candida albicans and C. glabrata – and for their physical interaction with cell walls/membranes.

Methods

cNDs were characterized for morphology and physico-chemical properties by microscopy and dynamic light scattering. In vitro oxygen release from cOLNDs was measured through an oximeter. ND biocompatibility and ability to promote wound healing in human normoxic/hypoxic skin cells were challenged by LDH and MTT assays using keratinocytes. ND antimicrobial activity was investigated by monitoring upon incubation with/without MW or LW cOLNDs/cOFNDs either bacteria or yeast growth over time. The mechanical interaction between NDs and microorganisms was also assessed by confocal microscopy.

Results

LW cNDs appeared less toxic to keratinocytes than MW cNDs. Based on cell counts, either MW or LW cOLNDs and cOFNDs displayed long-term antimicrobial efficacy against S. pyogenes, C. albicans, and C. glabrata (up to 24 h), whereas a short-term cytostatic effects against MRSA (up to 6 h) was revealed. The internalization of all ND formulations by all four microorganisms, already after 3 h of incubation, was showed, with the only exception to MW cOLNDs/cOFNDs that adhered to MRSA walls without being internalized even after 24 h.

Conclusion

cNDs exerted bacteriostatic and fungistatic effects, due to the presence of chitosan in the outer shell and independently of oxygen addition in the inner core. The duration of such effects strictly depends on the characteristics of each microbial species, and not on the molecular weight of chitosan in ND shells. However, LW chitosan was better tolerated by human keratinocytes than MW. For these reasons, the use of LW NDs should be recommended in future research to assess cOLND efficacy for the treatment of infected CWs.

Layer-by-layer assembly methods and their biomedical applications

Various biomedical applications arising due to the development of different LbL assembly methods with unique process properties.

Recent advances in chitosan-based layer-by-layer biomaterials and their biomedical applications

In recent years, chitosan-based biomaterials have been continually and extensively researched by using layer-by-layer (LBL) assembly, due to their potentials in biomedicine. Various chitosan-based LBL materials have been newly developed and applied in different areas along with the development of technologies. This work reviews the recent advances of chitosan-based biomaterials produced by LBL assembly. Driving forces of LBL, for example electrostatic interactions, hydrogen bond as well as Schiff base linkage have been discussed. Various forms of chitosan-based LBL materials such as films/coatings, capsules and fibers have been reviewed. The applications of these biomaterials in the field of antimicrobial applications, drug delivery, wound dressings and tissue engineering have been comprehensively reviewed.

Injectable hydrogel loaded with paclitaxel and epirubicin to prevent postoperative recurrence and metastasis of breast cancer

Post-operative recurrence and metastasis is a major challenge for breast cancer treatment. Local chemotherapy is a promising strategy that can overcome this problem. In this study, we synthesized an injectable hyaluronic acid (HA)-based hydrogel loaded with paclitaxel (PTX) nanoparticles and epirubicin (EPB) (PPNPs/EPB@HA-Gel). PPNPs/EPB@HA-Gel steadily released the encapsulated drugs to achieve long-term inhibition of tumor recurrence and metastasis in a murine post-operative breast tumor model, which prolonged their survival without any systemic toxicity. The drug-loaded hydrogel inhibited the proliferation and migration of tumor cells in vitro, and significantly increased tumor cell apoptosis in vivo. Therefore, PPNPs/EPB@HA-Gel can be used as a local chemotherapeutic agent to prevent postoperative recurrence and metastasis of breast cancer.

Control of Surface Properties of Hyaluronan/Chitosan Multilayered Coatings for Tumor Cell Capture

Prostate cancer (PCa) is a slow-growing neoplasm that has, when diagnosed in its early stages, great chances of cure. During initial tumor development, current diagnostic methods fail to have the desired accuracy, thus, it is necessary to develop or improve current detection methods and prognostic markers for PCa. In this scenario, films composed of hyaluronic acid (HA) and chitosan (CHI) have demonstrated significant capture potential of prostate tumor cells (PC3 line), exploring HA as a CD44 receptor ligand and direct mediator in cell-film adhesion. Here, we present a strategy to control structural and cell adhesion properties of HA/CHI films based on film assembly conditions. Films were built via Layer-by-layer (LbL) deposition, where the pH conditions (3.0 and 5.0) and number of bilayers (3.5, 10.5, and 20.5) were controlled. The characterization of these films was carried out using profilometry, ultraviolet-visible (UV-VIS), atomic force microscopy (AFM) and contact angle measurements. Multilayer HA/CHI films produced at pH 3.0 gave optimum surface wettability and availability of free carboxyl groups. In turn, at pH 5.0, the coverings were thinner and presented a smoother surface. Films prepared with 3.5 bilayers showed greater tumor cell capture regardless of the pH condition, while films containing 10.5 and 20.5 bilayers presented a significant swelling process, which compromised their cell adhesion potential. This study shows that surface chemistry and morphology are critical factors for the development of biomaterials designed for several cell adhesion applications, such as rapid diagnostic, cell signaling, and biosensing mechanisms.

Nanopharmaceutical-based regenerative medicine: a promising therapeutic strategy for spinal cord injury

Spinal cord injury (SCI) is a neurological disorder that can lead to loss of perceptive and athletic function due to the severe nerve damage. To date, pieces of evidence detailing the precise pathological mechanisms in SCI are still unclear. Therefore, drug therapy cannot effectively alleviate the SCI symptoms and faces the limitations of systemic administration with large side effects. Thus, the development of SCI treatment strategies is urgent and valuable. Due to the application of nanotechnology in pharmaceutical research, nanopharmaceutical-based regenerative medicine will bring colossal development space for clinical medicine. These nanopharmaceuticals (i.e. nanocrystalline drugs and nanocarrier drugs) are designed using different types of materials or bioactive molecules, so as to improve the therapeutic effects, reduce side effects, and subtly deliver drugs, etc. Currently, an increasing number of nanopharmaceutical products have been approved by drug regulatory agencies, which has also prompted more researchers to focus on the potential treatment strategies of SCI. Therefore, the purpose of this review is to summarize and elaborate the research progress as well as the challenges and future of nanopharmaceuticals in the treatment of SCI, aiming to promote further research of nanopharmaceuticals in SCI.