Cellulose nanocrystals-based materials as hemostatic agents for wound dressings: a review.

Wound dressings are devices used to stop bleeding and provide appropriate environmental conditions to accelerate wound healing. The effectiveness of wound dressing materials can be crucial to prevent deaths from excessive bleeding in surgeries and promote complete restoration of the injury. Some requirements for an ideal wound dressing are rapid hemostatic effect, high swelling capacity, antibacterial properties, biocompatibility, biodegradability, and mechanical strength. However, finding all these properties in a single material remains a challenge. In this context, nanocomposites have demonstrated an excellent capacity for this application because of their multifunctionality. One of the emerging materials used in nanocomposite manufacture is cellulose nanocrystals (CNCs), which are rod-like crystalline nanometric structures present on cellulose chains. These nanoparticles are attractive for wound healing applications because of their high aspect ratio, high mechanical properties, functionality and low density. Hence, this work aimed to present an overview of nanocomposites constituted by CNCs for wound healing applications. The review focuses on the most common materials used as matrices, the types of dressing, and their fabrication techniques. Novel wound dressings composites have improved hemostatic, swelling, and mechanical properties compared to other pure biopolymers while preserving their other biological properties. Films, nanofibers mats, sponges, and hydrogels have been prepared with CNCs nanocomposites, and in vitro and in vivo tests have proved their suitability for wound healing.

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.

Water-based synthesis of photocrosslinked hyaluronic acid/polyvinyl alcohol membranes via electrospinning.

Electrospinning is a versatile and low-cost technique widely used in the manufacture of nanofibrous polymeric membranes applied in different areas, especially in bioengineering. Hyaluronic acid (HA) is a biocompatible natural polymer, but it has rheological characteristics that make the electrospinning process difficult. Thus, its association with another polymer such as poly(vinyl alcohol) (PVA) is an alternative, as PVA has good rheological properties for electrospinning. Based on this, the aim of this work was to produce, by the conventional electrospinning method, cross-linked HA/PVA membranes free from organic solvent with a low degradation rate in PBS 7.4 solution after the photocrosslinking process and without using any organic solvent. The results showed that the electrospinning occurred effectively for all conditions tested, but the best result for complete cross-linking only occurred with 15 and 30% crosslinker, which was evidenced by infrared spectroscopy. The addition of crosslinker favored the stability of the electrospinning jet, especially for 30% crosslinker concentration. The membranes did not show cytotoxicity even after the cross-linking process, which indicates that the material has potential as a drug delivery device.

Silver nanoparticles incorporated into nanostructured biopolymer membranes produced by electrospinning: a study of antimicrobial activity

abstract This study examines the antimicrobial activity of silver nanoparticles incorporated into nanostructured membranes made of cellulose acetate (CA) and blends of chitosan/poly-(ethylene oxide, CTS/PEO) and prepared by electrospinning. The formation of chemically synthesized Ag nanoparticles (AgNPs) was monitored by UV-visible spectroscopy (UV-Vis) and characterized by transmission electron microscopy (TEM). The size distribution of the AgNPs was measured by dynamic light scattering (DLS), with an average size of approximately 20 nm. The presence of AgNPs on the surface of electrospun nanofibers was observed by field emission electron microscopy (FEG) and confirmed by TEM. The antimicrobial activity of AgNPs incorporated into nanostructured membranes made of CA and CTS/PEO electrospun nanofibers was evaluated in the presence of both Gram-positive bacteria, such as Staphylococcus aureus ATCC 29213 and Propionibacterium acnes ATCC 6919, and Gram-negative bacteria, such as Escherichia coli ATCC 25992 and Pseudomonas aeruginosa ATCC 17933. Microbiological results showed that the presence of AgNPs in CA and CTS/PEO nanostructured membranes has significant antimicrobial activity for the Gram-positive bacteria Escherichia coli and Propionibacterium acnes.

resumo Neste trabalho avaliou-se a atividade antimicrobiana das nanopartículas de prata (AgNPs) incorporadas em membranas de acetato celulose (AC) e blendas de quitosana/poli-óxido de etileno (CTS/PEO) preparadas pelo método de eletrofiação. A formação das AgNPs previamente sintetizadas foi monitorada por UV-Vis e caracterizada por microscopia eletrônica de transmissão (MET). A distribuição de tamanho das AgNPs foi mensurada por espalhamento de luz dinâmico, com tamanho médio em torno de 20 nm. A presença das NPs na superfície das nanofibras eletrofiadas foi observada por microscopia eletrônica com emissão de campo (FEG) e confirmada por MET. A atividade antimicrobiana das membranas nanoestruturadas de AC e CTS/PEO foi avaliada pelo uso de bactérias Gram-positivas, tais como Staphylococcus aureus ATCC 29213 e Propionibacterium acnes ATCC 6919, e Gram-negativas, como Escherichia coli ATCC 25992 e Pseudomonas aeruginosa ATCC 17933. Os resultados microbiológicos mostraram a presença das AgNPs nas membranas de AC e CTS/PEO com significativa atividade antimicrobiana para Escherichia coli e Propionibacterium acnes, respectivamente.

Coaxial nanofibers of chitosan-alginate-PEO polycomplex obtained by electrospinning.

Electrospinning of mucoadhesive membranes is a new and promising field of investigation in the pharmaceutical and biomedical area. The present study explored the electrospinning of two mucoadhesive polymers, chitosan and alginate, to form a core-shell type nanofibers for future applications as controlled drug delivery. Due to the charged functional groups present in these natural polysaccharides, they can complex to yield various nanodevices to be used in controlled release of several active ingredients. In this work, the core-shell type coaxial nanofibers formation was evidenced by the aid of transmission electron microscopy (TEM). Other characterization techniques as scanning electron microscopy (SEM), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), Infrared spectroscopy (FTIR) and X-ray diffraction (XRD), strongly suggest the formation of different molecular structures of the membranes obtained by the complexation of chitosan and alginate. Swelling rate and weight loss tests followed by SEM analyses confirmed that the nanofiber structure of these membranes were kept even after incubating them for 24h in water. The results of this work confirmed that core-shell nanofibers made of chitosan and alginate polycomplex is possible to be obtained with success.

Supports for enzyme immobilization

Macroporous silica gel, prepared from sodium silicate and hydrochloric acid, one grade of diatomaceous earth (celite 545) and nonporous glass were analyzed in terms of pore size by the mercury intrusion pressure method. The alkylamine derivatives of the above materials were examined for their suitability as supports for enzyme immobilization, using the enzyme glucose oxidase. The effectiveness of the immobilized enzyme was compared in relation to the free enzyme and particle size of the carier. The immobilized enzyme exhibited a broader range of optimum pH and greater thermal stability, among some properties considered