Hyaluronic acid electrospinning: Challenges, applications in wound dressings and new perspectives.

Hyaluronic acid (HA) has already been consolidated in the literature as an extremely efficient biopolymer for biomedical applications. In addition to its biodegradability, HA also has excellent biological properties. In the nanofiber form, this polymer can mimic biological tissues, mainly the layers of the skin, and therefore has great potential as structures for the construction of wound dressings. Despite the numerous efforts from the scientific community proposing new dressings, this is an area in constant evolution. A dressing that brings together all the properties of an ideal dressing has not been developed yet. Electrospinning is a simple and versatile technique that correctly aligned with the functional properties of HA can produce multifunctional nanofiber structures capable of promoting skin recover quickly. This review discusses (i) key strategies for successful electrospinning of HA, (ii) main challenges and advances found in the electrospinning process, (iii) the bioactive properties of this polymer in the treatment of wounds, as well as (iv) the results obtained in the last decade by the in vitro and in vivo evaluation of the healing properties of these nanosystems.

Morphological and mechanical characterization of chitosan-calcium phosphate composites for potential application as bone-graft substitutes

Introduction: Bone diseases, aging and traumas can cause bone loss and lead to bone defects. Treatment of bone defects is challenging, requiring chirurgical procedures. Bone grafts are widely used for bone replacement, but they are limited and expensive. Due to bone graft limitations, natural, semi-synthetic, synthetic and composite materials have been studied as potential bone-graft substitutes. Desirable characteristics of bone-graft substitutes are high osteoinductive and angiogenic potentials, biological safety, biodegradability, bone-like mechanical properties, and reasonable cost. Herein, we prepared and characterized potential bone-graft substitutes composed of calcium phosphate (CP) - a component of natural bone, and chitosan (CS) - a biocompatible biopolymer. Methods CP-CS composites were synthetized, molded, dried and characterized. The effect of drying temperatures (38 and 60 °C) on the morphology, porosity and chemical composition of the composites was evaluated. As well, the effects of drying temperature and period of drying (3, 24, 48 and 72 hours) on the mechanical properties - compressive strength, modulus of elasticity and relative deformation-of the demolded samples were investigated. Results Scanning electron microscopy and gas adsorption-desorption analyses of the CS-CP composites showed interconnected pores, indicating that the drying temperature played an important role on pores size and distribution. In addition, drying temperature have altered the color (brownish at 60 °C due to Maillard reaction) and the chemical composition of the samples, confirmed by FTIR. Conclusion Particularly, prolonged period of drying have improved mechanical properties of the CS-CP composites dried at 38 °C, which can be designed according to the mechanical needs of the replaceable bone.

Non-Cytotoxic Quantum Dot-Chitosan Nanogel Biosensing Probe for Potential Cancer Targeting Agent.

Quantum dot (Qdot) biosensors have consistently provided valuable information to researchers about cellular activity due to their unique fluorescent properties. Many of the most popularly used Qdots contain cadmium, posing the risk of toxicity that could negate their attractive optical properties. The design of a non-cytotoxic probe usually involves multiple components and a complex synthesis process. In this paper, the design and synthesis of a non-cytotoxic Qdot-chitosan nanogel composite using straight-forward cyanogen bromide (CNBr) coupling is reported. The probe was characterized by spectroscopy (UV-Vis, fluorescence), microscopy (Fluorescence, Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and Dynamic Light Scattering. This activatable ("OFF"/"ON") probe contains a core-shell Qdot (CdS:Mn/ZnS) capped with dopamine, which acts as a fluorescence quencher and a model drug. Dopamine capped "OFF" Qdots can undergo ligand exchange with intercellular glutathione, which turns the Qdots "ON" to restore fluorescence. These Qdots were then coated with chitosan (natural biocompatible polymer) functionalized with folic acid (targeting motif) and Fluorescein Isothiocyanate (FITC; fluorescent dye). To demonstrate cancer cell targetability, the interaction of the probe with cells that express different folate receptor levels was analyzed, and the cytotoxicity of the probe was evaluated on these cells and was shown to be nontoxic even at concentrations as high as 100 mg/L.

Emprego de membrana de quitosana em feridas cutâneas induzidas experimentalmente em equinos / Chitosan film in horses with experimentally induced skin wound

O objetivo deste estudo foi avaliar os efeitos da membrana (filme) de quitosana no processo de reparação de feridas cutâneas distais em equinos. Foram induzidas feridas cutâneas nas regiões metacarpianas e metatarsianas de quatro equinos adultos. No grupo tratado, oito feridas foram recobertas com membrana de quitosana e, no grupo controle, apenas higienização com solução de cloreto de sódio 0,9%. No período experimental, foram avaliados o diâmetro da ferida, formação de tecido de granulação exuberante, tipo de exsudato que a recobria, análise histológica, bem como as características da membrana de quitosana (plasticidade durante manipulação e presença ou ausência da membrana a cada troca). A membrana de quitosana não interferiu no tempo de cicatrização, podendo servir como material de recobrimento de feridas cutâneas, potencialmente com vantagens, se for empregada como meio condutor de substâncias que interfiram positivamente no processo cicatricial, abrindo campo para novos estudos.

The aim of this study was to evaluate the effects of chitosan film on wound repair in horse distal limb. Skin wounds were induced on metacarpus and metatarsus region of four adults horses. On treat group, eight wounds were covered with chitosan film and on control group sodium chlorid 0.9% was used. During the experimental period, it was evaluated the wound diameter, exuberant granulation tissue formation, kind of exudat, histological analyzes, and some characteristics of the chitosan film (plasticity during handling and presence or absence of film on each change). The chitosan film had not interfered on healing time, might serving to cover skin wounds, with potential advantages, if it is used as a conductive of substances that interfere positively in the healing process, opening a field to news studies.