Influence of pH and ionic strength on the antibacterial effect of hyaluronic acid/chitosan films assembled layer-by-layer

Antibacterial Films of Silver Nanoparticles Embedded into Carboxymethylcellulose/Chitosan Multilayers on Nanoporous Silicon: A Layer-by-Layer Assembly Approach Comparing Dip and Spin Coating

The design and engineering of antibacterial materials are key for preventing bacterial adherence and proliferation in biomedical and household instruments. Silver nanoparticles (AgNPs) and chitosan (CHI) are broad-spectrum antibacterial materials with different properties whose combined application is currently under optimization. This study proposes the formation of antibacterial films with AgNPs embedded in carboxymethylcellulose/chitosan multilayers by the layer-by-layer (LbL) method. The films were deposited onto nanoporous silicon (nPSi), an ideal platform for bioengineering applications due to its biocompatibility, biodegradability, and bioresorbability. We focused on two alternative multilayer deposition processes: cyclic dip coating (CDC) and cyclic spin coating (CSC). The physicochemical properties of the films were the subject of microscopic, microstructural, and surface-interface analyses. The antibacterial activity of each film was investigated against Escherichia coli (Gram-negative) and Staphylococcus aureus (Gram-positive) bacteria strains as model microorganisms. According to the findings, the CDC technique produced multilayer films with higher antibacterial activity for both bacteria compared to the CSC method. Bacteria adhesion inhibition was observed from only three cycles. The developed AgNPs-multilayer composite film offers advantageous antibacterial properties for biomedical applications.

Synthetic versus Natural Precursor Layer: A Study on the Properties of Biocompatible Chitosan/Carboxymethyl Cellulose Nanofilms

Polyelectrolyte multilayers are nanofilms with vast applications in numerous areas such as medicine and food industry. Recently, they have been getting a lot of attention as potential food coatings for the prevention of fruit decay during transportation and storage, and therefore the coatings need to be biocompatible. In this study, we fabricated thin films made of biocompatible polyelectrolytes, positively charged polysaccharide chitosan, and negatively charged carboxymethyl cellulose on a model silica surface. Typically, to enhance the properties of the prepared nanofilms, the first layer (precursor layer) of poly(ethyleneimine) is used. However, for the construction of completely biocompatible coatings, this could be problematic due to potential toxicity. This study offers an option for a viable candidate as a replacement precursor layer: chitosan itself was adsorbed from a more concentrated solution. In the case of chitosan/carboxymethyl cellulose films, using chitosan over poly(ethyleneimine) as a precursor layer has shown a twofold increase in film thickness, as well as an increase in film roughness. In addition, these properties can be tuned by the presence of a biocompatible background salt (e.g., sodium chloride) in the deposition solution that has proven to change the film thickness and surface roughness depending on the salt concentration. Such a straightforward way of tuning the properties of these films combined with their biocompatibility makes this precursor material a prime candidate for use as a potential food coating.

Application of BCXZM Composite for Arsenic Removal: EPS Production, Biotransformation and Immobilization of Bacillus XZM on Corn Cobs Biochar

This study determined the effect of Bacillus XZM extracellular polymeric substances (EPS) production on the arsenic adsorption capacity of the Biochar-Bacillus XZM (BCXZM) composite. The Bacillus XZM was immobilized on corn cobs multifunction biochar to generate the BCXZM composite. The arsenic adsorption capacity of BCXZM composite was optimized at different pHs and As(V) concentrations using a central composite design (CCD)2² and maximum adsorption capacity (42.3 mg/g) was attained at pH 6.9 and 48.9 mg/L As(V) dose. The BCXZM composite showed a higher arsenic adsorption than biochar alone, which was further confirmed through scanning electron microscopy (SEM) micrographs, EXD graph and elemental overlay as well. The bacterial EPS production was sensitive to the pH, which caused a major shift in the -NH, -OH, -CH, -C=O, -C-N, -SH, -COO and aromatic/-NO₂ peaks of FTIR spectra. Regarding the techno economic analysis, it was revealed that USD 6.24 are required to prepare the BCXZM composite to treat 1000 gallons of drinking water (with 50 µg/L of arsenic). Our findings provide insights (such as adsorbent dose, optimum operating temperature and reaction time, and pollution load) for the potential application of the BCXZM composite as bedding material in fixed-bed bioreactors for the bioremediation of arsenic-contaminated water in future.

Polysaccharide Layer-by-Layer Coating for Polyimide-Based Neural Interfaces

Implantable flexible neural interfaces (IfNIs) are capable of directly modulating signals of the central and peripheral nervous system by stimulating or recording the action potential. Despite outstanding results in acute experiments on animals and humans, their long-term biocompatibility is hampered by the effects of foreign body reactions that worsen electrical performance and cause tissue damage. We report on the fabrication of a polysaccharide nanostructured thin film as a coating of polyimide (PI)-based IfNIs. The layer-by-layer technique was used to coat the PI surface due to its versatility and ease of manufacturing. Two different LbL deposition techniques were tested and compared: dip coating and spin coating. Morphological and physiochemical characterization showed the presence of a very smooth and nanostructured thin film coating on the PI surface that remarkably enhanced surface hydrophilicity with respect to the bare PI surface for both the deposition techniques. However, spin coating offered more control over the fabrication properties, with the possibility to tune the coating’s physiochemical and morphological properties. Overall, the proposed coating strategies allowed the deposition of a biocompatible nanostructured film onto the PI surface and could represent a valid tool to enhance long-term IfNI biocompatibility by improving tissue/electrode integration.

Physicochemical aspects of design of ultrathin films based on chitosan, pectin, and their silver nanocomposites with antiadhesive and bactericidal potential

Implant-related infection is one of the serious problems in regenerative medicine. Promising approach to overcome the problems caused by bacterial growth on the medical implants is their modification by bioactive coatings. A versatile technique for designing multilayer films with tailored characteristics at the nanometer scale is layer-by-layer assembly. In this study, multilayer films based on biopolymers (pectin and chitosan) and their nanocomposites with silver nanoparticles have been prepared and evaluated. The buildup of multilayers was monitored using the quartz crystal microbalance with dissipation technique. The morphology of the obtained films was investigated by atomic force microscopy. We have demonstrated that pectin-Ag-containing films were characterized by the linear growth and smooth defect-free surface. When pectin-Ag was substituted for the pectin in the multilayer systems, the properties of the formed coatings were significantly changed: the film rigidity and surface roughness increased, as well as the film growth acquired the parabolic character. All prepared multilayer films have shown antibacterial activity against gram-positive (Staphylococcus aureus) and gram-negative (Escherichia coli) bacteria. The significant decrease in the number of the adhered E. coli on the multilayer surface has been determined; moreover, many of the cells were misshapen with cytoplasm leaking. The prepared multilayer films showed a mild activity against S. aureus predominantly due to the antiadhesive effect. Our results indicate that antibacterial activity of biopolymer multilayers is determined by the film composition and physicochemical characteristics and can be associated with their antiadhesive and bactericidal behaviors.

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.

Antibacterial catechol-based hyaluronic acid, chitosan and poly (N-vinyl pyrrolidone) coatings onto Ti6Al4V surfaces for application as biomedical implant

Bacterial contamination in implanted biomedical devices is a critical daily concern. The most used material for permanent implant in biomedical field is Ti6Al4V alloy due to its beneficial mechanical properties and high biocompatibility. Accordingly, in this work different polymeric antibacterial coatings poly(N-vinyl pyrrolidone) (PVP), hyaluronic acid (HA) and chitosan (CHI) were developed and comparatively analysed for Ti6Al4V surface covering. The adhesion of these coatings to Ti6Al4V substrates were carried out after the conjugation of these polymers with the so well-known bioadhesive properties of catechol (CA) anchor group. These surface modifications were characterized by X-ray photoelectronic spectroscopy, contact angle measurements and atomic force microscopy. In addition, the stability of CA-conjugated polymeric coatings was compared with the coatings formed with unconjugated polymers. Finally, the cytocompatibility and antibacterial properties against gram-positive and gram-negative strains on coated Ti6Al4V substrates were assessed confirming the effectiveness of these polymeric coatings against bacterial infections for future applications in protecting biomedical implants.

Chitosan-based smart hybrid materials: a physico-chemical perspective

Chitosan is one of the most studied cationic polysaccharides. Due to its unique characteristics of being water soluble, biocompatible, biodegradable, and non-toxic, this macromolecule is highly attractive for a broad range of applications. In addition, its complex behavior and the number of ways it interacts with different components in a system result in an astonishing variety of chitosan-based materials. Herein, we present recent advances in the field of chitosan-based materials from a physico-chemical perspective, with focus on aqueous mixtures with oppositely charged colloids, chitosan-based thin films, and nanocomposite systems. In this review, we focus our attention on the physico-chemical properties of chitosan-based materials, including solubility, mechanical resistance, barrier properties, and thermal behaviour, and provide a link to the chemical peculiarities of chitosan, such as its intrinsic low solubility, high rigidity, large charge separation, and strong tendency to form intra- and inter-molecular hydrogen bonds.

Advances in the application of chitosan as a sustainable bioactive material in food preservation

Chitosan is obtained from chitin and considered to be one of the most abundant natural polysaccharides. Due to its functional activity, chitosan has received intense and growing interest in terms of applications for food preservation over the last half-century. Compared with earlier studies, recent research has increasingly focused on the exploration of preservation mechanism as well as the targeted inhibition with higher efficiency, which is fueled by availability of more active composite ingredients and integration of more technologies, and gradually perceived as "chitosan-based biofilm preservation." In this Review, we comprehensively summarize the potential antimicrobial mechanisms or hypotheses of chitosan and its widely compounded ingredients, as well as their impacts on endogenous enzymes, oxidation and/or gas barriers. The strategies used for enhancing active function of the film-forming system and subsequent film fabrication processes including direct coating, bioactive packaging film and layer-by-layer assembly are introduced. Finally, future development of chitosan-based bioactive film is also proposed to broaden its application boundaries. Generally, our goal is that this Review is easily accessible and instructive for whose new to the field, as well as hope to advance to the filed forward.

Methods for the Assembly and Characterization of Polyelectrolyte Multilayers as Microenvironments to Modulate Human Mesenchymal Stromal Cell Response

Thin films are of interest in materials design because they allow for the modification of surface properties of materials while the bulk properties of the material are largely unaffected. In this work, we outline methods for the assembly of thin films using a technique known as layer-by-layer (LbL). Furthermore, their interactions with human mesenchymal stromal cells (hMSCs) are discussed. hMSCs are a subject of growing interest because of their potential to treat or cure diseases, given their immunosuppressive properties, multipotent differentiation capabilities, and tissue regeneration capabilities. Numerous improvements and modifications have been suggested for the harvesting, treatment, and culture of hMSCs prior to their administration in human subjects. Here, we discuss methods to assess the interactions of hMSCs with thin LbL-assembled films of heparin and collagen. Three different methods are discussed. The first details the preparation of heparin/collagen multilayers on different surfaces and the seeding of cells on these multilayers. The second method details the characterization of multilayers, including techniques to assess the thickness, roughness, and surface charge of the multilayers, as well as in situ deposition of multilayers. The third method details the analysis of cell interactions with the multilayers, including techniques to assess proliferation, viability, real-time monitoring of hMSC behavior, analysis of hMSC-adhesive proteins on the multilayers, immunomodulatory factor expression of hMSCs, and cytokine expression on heparin/collagen multilayers. We propose that the methods described in this work will assist in the design and characterization of LbL-assembled thin films and the analysis of hMSCs cultured on these thin films.

Probing axial metal distribution on biopolymer-based layer-by-layer films for antimicrobial use

This study presents the axial molar composition of polysaccharide-based polyelectrolyte multilayer (PEM) films loaded with silver ions for antimicrobial applications. Individual polymers (chitosan, hyaluronan or alginate) and silver composition were determined using X-Ray Photoelectron Spectroscopy coupled with C₆₀⁺ cluster ion sputtering technique, while the influence of silver loading on film topography was assessed using Atomic Force Microscopy. Despite the use of the layer-by-layer approach for film assembly, these PEM films present a non-stratified, nanoblend-like, polymer composition, with a nearly uniform metal distribution over the axial direction. Results also show surface antimicrobial activity towards Staphylococcus aureus bacteria and Candida albicans fungi over 20 h for hyaluronan/chitosan PEM, which is associated with its higher silver loading capacity. The interplay of bulk film composition and surface properties may provide valuable insights for engineering advanced materials with controlled spatio-temporal behavior.

Layer-by-Layer Deposition of Hyaluronan and Quercetin-Loaded Chitosan Nanoparticles onto Titanium for Improving Blood Compatibility

Surface modification is an effective way to improve the hemocompatibility of biomaterials. Quercetin has significant anticoagulation and antithrombotic effects, and thus it is a promising candidate agent for the surface modification of blood-contacting materials. In this study, quercetin was successfully encapsulated in tripolyphosphate–chitosan nanoparticles (TCs) based on the ionic gelation of chitosan with tripolyphosphate (TPP) anions. Then, hyaluronan acid (HA)/quercetin-loaded TPP–chitosan nanoparticle (QTCs) films, in addition to HA/TCs films, were prepared separately using an electrostatic layer-by-layer self-assembly technique. The encapsulation of quercetin in the chitosan nanoparticles was confirmed by UV spectra. The quercetin-loaded multilayer coatings were also successfully self-assembled, as confirmed by the UV spectra and contact angle measurements. Platelet adhesion experiments were carried out with platelet-enriched plasma so as to evaluate the blood compatibility of the different samples. There were many platelets on the surfaces of the glass and HA/TC-coated titanium, which were partially activated but not aggregated. Meanwhile, many more platelets were observed on the uncoated titanium surfaces, most of which developed pseudopodia. By contrast, the platelet adhesion and activation were reduced remarkably on the surface of the HA/QTC-coated titanium. These results showed that the multilayer coatings containing quercetin could act as potential biomaterials to improve the anticoagulation performance of blood-contacting materials.

The application of hyaluronic acid in bone regeneration

Hyaluronic acid (HA) exists naturally as an important component of the extracellular matrix (ECM) in the human body. In recent decades, HA has been widely used in bone regeneration, and is currently a popular topic, particularly in the craniofacial and dental fields. From maxilla augmentation to craniofacial bone trauma, there is now a large demand for bone regenerative therapy. Serving as a cell-seeding scaffold or a carrier for bioactive components, hyaluronic acid-incorporated scaffolds and carriers in bone regeneration can be fabricated into either rigid or colloidal forms. Since the type of material used is a critical factor in the biological properties of a scaffold, HA derivatives or HA-incorporated composite scaffolds have shown excellent potential for improving osteogenesis and mineralization. Furthermore, in order to better enhance osteogenesis, local delivery carriers based on hyaluronic acid derivatives, rather than specifically serving as scaffolds, can be established by loading different osteoinductive or osteogenetic components and acquiring different release patterns. Such osteoinductive carriers immobilized on implant surfaces are also effective in improving osseointegration. Thus, as such a competent biomaterial, hyaluronic acid should be considered a promising tool in bone regeneration.

Effect of Cellulose Nanocrystals from Different Lignocellulosic Residues to Chitosan/Glycerol Films

Interest in nanocellulose obtained from natural resources has grown, mainly due to the characteristics that these materials provide when incorporated in biodegradable films as an alternative for the improvement of the properties of nanocomposites. The main purpose of this work was to investigate the effect of the incorporation of nanocellulose obtained from different fibers (corncob, corn husk, coconut shell, and wheat bran) into the chitosan/glycerol films. The nanocellulose were obtained through acid hydrolysis. The properties of the different nanobiocomposites were comparatively evaluated, including their barrier and mechanical properties. The nanocrystals obtained for coconut shell (CS), corn husk (CH), and corncob (CC) presented a length/diameter ratio of 40.18, 40.86, and 32.19, respectively. Wheat bran (WB) was not considered an interesting source of nanocrystals, which may be justified due to the low percentage of cellulose. Significant differences were observed in the properties of the films studied. The water activity varied from 0.601 (WB Film) to 0.658 (CH Film) and the moisture content from 15.13 (CS Film) to 20.86 (WB Film). The highest values for tensile strength were presented for CC (11.43 MPa) and CS (11.38 MPa) films, and this propriety was significantly increased by nanocellulose addition. The results showed that the source of the nanocrystal determined the properties of the chitosan/glycerol films.