Nanofilms of hyaluronan/chitosan assembled layer-by-layer: An antibacterial surface for Xylella fastidiosa

Functionalization of breast implants by cyclodextrin in-situ polymerization: a local drug delivery system for augmentation mammaplasty

Mammaplasty is a widely performed surgical procedure worldwide, utilized for breast reconstruction, in the context of breast cancer treatment, and aesthetic purposes. To enhance post-operative outcomes and reduce risks (hematoma with required evacuation, capsular contracture, implant-associated infection and others), the controlled release of medicaments can be achieved using drug delivery systems based on cyclodextrins (CDs). In this study, our objective was to functionalize commercially available silicone breast implants with smooth and textured surfaces through in-situ polymerization of two CDs: β-CD/citric acid and 2-hydroxypropyl-β-CD/citric acid. This functionalization serves as a local drug delivery system for the controlled release of therapeutic molecules that potentially can be a preventive treatment for post-operative complications in mammaplasty interventions. Initially, we evaluated the pre-treatment of sample surfaces with O2 plasma, followed by chitosan grafting. Subsequently, in-situ polymerization using both types of CDs was performed on implants. The results demonstrated that the proposed pre-treatment significantly increased the polymerization yield. The functionalized samples were characterized using microscopic and physicochemical techniques. To evaluate the efficacy of the proposed system for controlled drug delivery in augmentation mammaplasty, three different molecules were utilized: pirfenidone (PFD) for capsular contracture prevention, Rose Bengal (RB) as anticancer agent, and KR-12 peptide (KR-12) to prevent bacterial infection. The release kinetics of PFD, RB, and KR-12 were analyzed using the Korsmeyer-Peppas and monolithic solution mathematical models to identify the respective delivery mechanisms. The antibacterial effect of KR-12 was assessed against Staphylococcus epidermidis and Pseudomonas aeruginosa, revealing that the antibacterial rate of functionalized samples loaded with KR-12 was dependent on the diffusion coefficients. Finally, due to the immunomodulatory properties of KR-12 peptide on epithelial cells, this type of cells was employed to investigate the cytotoxicity of the functionalized samples. These assays confirmed the superior properties of functionalized samples compared to unprotected implants.

Polymers showing intrinsic antimicrobial activity

Pathogenic microorganisms are considered to a major threat to human health, impinging on multiple sectors including hospitals, dentistry, food storage and packaging, and water contamination. Due to the increasing levels of antimicrobial resistance shown by pathogens, often caused by long-term abuse or overuse of traditional antimicrobial drugs, new approaches and solutions are necessary. In this area, antimicrobial polymers are a viable solution to combat a variety of pathogens in a number of contexts. Indeed, polymers with intrinsic antimicrobial activities have long been an intriguing research area, in part, due to their widespread natural abundance in materials such as chitin, chitosan, carrageen, pectin, and the fact that they can be tethered to surfaces without losing their antimicrobial activities. In addition, since the discovery of the strong antimicrobial activity of some synthetic polymers, much work has focused on revealing the most effective structural elements that give rise to optimal antimicrobial properties. This has often been synthesis targeted, with the generation of either new polymers or the modification of natural antimicrobial polymers with the addition of antimicrobial enhancing modalities such as quaternary ammonium or guanidinium groups. In this review, the growing number of polymers showing intrinsic antimicrobial properties from the past decade are highlighted in terms of synthesis; often based on post-synthesis modification and their utilization. This includes as surface coatings, for example on medical devices, such as intravascular catheters, orthopaedic implants and contact lenses, or directly as antibacterial agents (specifically as eye drops). Surface functionalisation with inherently antimicrobial polymers is highlighted and has been achieved via various techniques, including surface-bound initiators allowing RAFT or ATRP surface-based polymerization, or via physical immobilization such as by layer-by-layer techniques. This article also covers the mechanistic modes of action of intrinsic antimicrobial polymers against bacteria, viruses, or fungi.

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.

Engineered nanomaterials in plant diseases: can we combat phytopathogens?

Engineered nanomaterials (ENM) have a high potential for use in several areas of agriculture including plant pathology. Nanoparticles (NPs) alone can be applied for disease management due to their antimicrobial properties. Moreover, nanobiosensors allow a rapid and sensitive diagnosis of pathogens because NPs can be conjugated with nucleic acids, proteins and other biomolecules. The use of ENM in diagnosis, delivery of fungicides and therapy is an eco-friendly and economically viable alternative. This review focuses on different promising studies concerning ENM used for plant disease management including viruses, fungi, oomycetes and bacteria; diagnosis and delivery of antimicrobials and factors affecting the efficacy of nanomaterials, entry, translocation and toxicity. Although much research is required on metallic NPs due to the possible risks to the final consumer, ENMs are undoubtedly very useful tools to achieve food security in the world. KEY POINTS: • Increasing global population and fungicides have necessitated alternative technologies. • Nanomaterials can be used for detection, delivery and therapy of plant diseases. • The toxicity issues and safety should be considered before the use of nanomaterials.

Anti-phytopathogen terpenoid glycosides from the root bark of Chytranthus macrobotrys and Radlkofera calodendron

Chytranthus macrobotrys and Radlkofera calodendron are two Sapindaceae characterized by a lack of phytochemical data. Both root barks from the two Sapindaceae species were processed by ethanol extraction followed by the isolation of their primary constituents by liquid chromatography. This process yielded four previously undescribed terpenoid glycosides together with eight known analogues. Extracts and isolated compounds from C. macrobotrys and R. calodendron were then screened for antimicrobial activity against fifteen phytopathogens. The biological screening also involved extracts and pure compounds from Blighia unijugata and Blighia welwitschii, two Sapindaceae previously studied by our group. Phytopathogens were chosen based on their economic impact on agriculture worldwide. The selection was composed primarily of fungal species including; Pyricularia oryzae, Gaeumannomyces graminis var. tritici, Zymoseptoria tritici, Fusarium oxysporum, Botrytis cinerea, Pythium spp., Trichoderma spp. and Rhizoctonia solani. Furthermore, pure terpenoid glycosides were tested for the first time against wood-inhabiting phytopathogens such as; Phaeomoniella chlamydospora, Phaeoacremonium minimum, Fomitiporia mediterranea, Eutype lata and Xylella fastidiosa. Raw extracts exhibited different levels of activity dependent on the organism. Some pure compounds, including 3-O-α-L-arabinopyranosyl-(1 → 4)-β-D-xylopyranosyl-(1 → 3)-α-L-rhamnopyranosyl-(1 → 2)-α-L-arabinopyranosylhederagenin, 3-O-α-L-rhamnopyranosyl-(1 → 2)-α-L-arabinopyranosylhederagenin (α-hederin), 3-O-β-D-glucopyranosyl-(1 → 3)-α-L-rhamnopyranosyl-(1 → 2)-α-L-arabinopyranosylhederagenin (macranthoside A) and 3-O-α-L-arabinopyranosyl-(1 → 3)-α-L-rhamnopyranosyl-(1 → 2)-α-L-arabinopyranosylhederagenin (clemontanoside C), exhibited significant growth inhibitions on Pyricularia oryzae, Gaeumannomyces graminis var. tritici, Fomitiporia mediterranea and Zymoseptoria tritici. Monodesmoside triterpene saponins, in particular, exhibited MIC (IC₁₀₀) values as low as 25 μg/ml and IC₅₀ values as low as 10 μg/ml against these phytopathogens. Structure-activity relationships, as well as plant-microbe interactions, were discussed.

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.

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

We report on layer-by-layer (LbL) films of chitosans (CHI) and hyaluronic acid (HA) whose properties could be controlled by employing chitosans with different degrees of deacetylation (DD¯ ≈ 85%; 65%; 40%) and high average molecular weight (ca. 10⁶ g/mol). In spite of their high molecular weight, these chitosans are soluble within a wide pH range, including physiological pH. HA/CHI LbL films produced from polymer solutions at pH 4.5 were thinner, smoother, more hydrophilic than those prepared at pH 7.2. This is attributed to the more extended conformation adopted by chitosan due to its very high charge density at low pH, favoring a compact chain packing during the film formation and resulting in lower film thickness and roughness. The smoother HA/CHI LbL films obtained at pH 4.5 were effective against Escherichia coli, while the thicker, rougher LbL films fabricated at pH 7.2 could be used in the controlled released of Rose Bengal dye. In summary, the tuning of only two parameters, i.e. solution pH and DD¯ of chitosans, provides access to a library of HA/CHI LbL films for tailored, diversified applications.

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.

Sonication-Assisted Production of Fosetyl-Al Nanocrystals: Investigation of Human Toxicity and In Vitro Antibacterial Efficacy against Xylella Fastidiosa

Recently, there is a growing demand in sustainable phytopathogens control research. Nanotechnology provides several tools such as new pesticides formulations, antibacterial nanomaterials and smart delivery systems. Metal nano-oxides and different biopolymers have been exploited in order to develop nanopesticides which can offer a targeted solution minimizing side effects on environment and human health. This work proposed a nanotechnological approach to obtain a new formulation of systemic fungicide fosetyl-Al employing ultrasonication assisted production of water dispersible nanocrystals. Moreover, chitosan was applicated as a coating agent aiming a synergistic antimicrobial effect between biopolymer and fungicide. Fosetyl-Al nanocrystals have been characterized by morphological and physical-chemical analysis. Nanotoxicological investigation was carried out on human keratinocytes cells through cells viability test and ultrastructural analysis. In vitro planktonic growth, biofilm production and agar dilution assays have been conducted on two Xylella fastidiosa subspecies. Fosetyl-Al nanocrystals resulted very stable over time and less toxic respect to conventional formulation. Finally, chitosan-based fosetyl-Al nanocrystals showed an interesting antibacterial activity against Xylella fastidiosa subsp. pauca and Xylella fastidiosa subsp. fastidiosa.

Studies on the Mechanisms of Anti-Inflammatory Activity of Heparin- and Hyaluronan-Containing Multilayer Coatings-Targeting NF-κB Signalling Pathway

The use of implants can be hampered by chronic inflammatory reactions, which may result in failure of the implanted device. To prevent such an outcome, the present study examines the anti-inflammatory properties of surface coatings made of either hyaluronic acid (HA) or heparin (Hep) in combination with chitosan (Chi) prepared as multilayers through the layer-by-layer (LbL) technique. The properties of glycosaminoglycan (GAG)-modified surfaces were characterized in terms of surface topography, thickness and wettability. Results showed a higher thickness and hydrophilicity after multilayer formation compared to poly (ethylene imine) control samples. Moreover, multilayers containing either HA or Hep dampened the inflammatory response visible by reduced adhesion, formation of multinucleated giant cells (MNGCs) and IL-1β release, which was studied using THP-1 derived macrophages. Furthermore, investigations regarding the mechanism of anti-inflammatory activity of GAG were focused on nuclear transcription factor-кB (NF-κB)-related signal transduction. Immunofluorescence staining of the p65 subunit of NF-κB and immunoblotting were performed that showed a significant decrease in NF-κB level in macrophages on GAG-based multilayers. Additionally, the association of FITC-labelled GAG was evaluated by confocal laser scanning microscopy and flow cytometry showing that macrophages were able to associate with and take up HA and Hep. Overall, the Hep-based multilayers demonstrated the most suppressive effect making this system most promising to control macrophage activation after implantation of medical devices. The results provide an insight on the anti-inflammatory effects of GAG not only based on their physicochemical properties, but also related to their mechanism of action toward NF-κB signal transduction.

Antioxidant and antimicrobial applications of biopolymers: A review

Biopolymers have generated mounting interest among researchers and industrialists over the recent past. Rising consciousness on the use of eco-friendly materials as green alternatives for fossil-based biopolymers has shifted the research focus towards biopolymers. Advances in technologies have opened up new windows of opportunities to explore the potential of biopolymers. In this context, this review presents a critique on applications of biopolymers in relation to antioxidant and antimicrobial activities. Some biopolymers are reported to contain inherent antioxidant and antimicrobial properties, whereas, some biopolymers, which do not possess such inherent properties, are used as carriers for other biopolymers or additives having these properties. Modifications are often performed in order to improve the properties of biopolymers to suit them for different applications. This review aims at presenting an overview on recent advances in the use of biopolymers with special reference to their antioxidant and antimicrobial applications in various fields.

Engineering the surface of prostate tumor cells and hyaluronan/chitosan multilayer films to modulate cell-substrate adhesion properties

This paper explores different film assembly conditions of the polyelectrolyte solutions of hyaluronan (HA) and chitosan (CHI), as well as both substrate and cell surface modifications, to investigate PC3 cells adhesion properties. UV-Visible, AFM-IR and Zeta potential techniques indicate that the solution ionic strength is a relevant parameter to modulate the free carboxylic groups of HA on the film surface. In addition, capacitive coupling measurements suggest that assembly conditions that favor surface charge mobility inhibit cell adhesion due to polymer rearrangements that support non-specific electrostatic interactions of positively charged CHI residues and the negatively charged cell moieties, rather than specific CD44-hyaluronan interactions. Moreover, the PC3 cells treatment with hyaluronidase and anti-CD44 antibody also highlighted the importance of CD44 binding site availability on the tumor cell adhesion properties. Finally, the conjugation of wheat germ agglutinin on the film surface proved to be a suitable strategy to boost the PC3 cell adhesion properties. Our results reveal the remarkable capacity of HA/CHI films to modulate cell-substrate properties, which pave the road for the development of surfaces suitable for several applications based on biosensing.

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.

Potential of Natural Biomaterials in Nano-scale Drug Delivery

BACKGROUND

The usage of natural biomaterials or naturally derived materials intended for interface with biological systems has steadily increased in response to the high demand of amenable materials, which are suitable for purpose, biocompatible and biodegradable. There are many naturally derived polymers which overlap in terms of purpose as biomaterials but are equally diverse in their applications.

METHODS

This review examines the applications of the following naturally derived polymers; hyaluronic acid, silk fibroin, chitosan, collagen and tamarind polysaccharide (TSP); further focusing on the biomedical applications of each as well as emphasising on individual novel applications.

RESULTS

Each of the polymers was found to demonstrate a wide variety of successful biomedical applications fabricated as wound dressings, scaffolds, matrices, films, sponges, implants or hydrogels to suit the therapeutic need. Interestingly, blending and amelioration of polymer structures were the two selection strategies to modify the functionality of the polymers to suit the purpose. Further, these polymers have shown promise to deliver small molecule drugs, proteins and genes as nano-scale delivery systems.

CONCLUSION

The review highlights the range of applications of the aforementioned polymers as biomaterials. Hyaluronic acid, silk fibroin, chitosan, collagen and TSP have been successfully utilised as biomaterials in the subfields of implant enhancement, wound management, drug delivery, tissue engineering and nanotechnology. Whilst there are a number of associated advantages (i.e. biodegradability, biocompatibility, non-toxic, nonantigenic as well as amenability) the selected disadvantages of each individual polymer provide significant scope for their further exploration and overcoming challenges like feasibility of mass production at a relatively low cost.

Application of calcium carbonate nanocarriers for controlled release of phytodrugs against Xylella fastidiosa pathogen

Calcium carbonate-based hollow or porous particles are one of the preferred carriers for fabrication of drug delivery systems. We have developed an eco-friendly method to produce calcium carbonate nanocrystals, which have shown biocompatibility and optimal capacity to across cell membrane in human cell lines providing new tools in cancer therapy. The success of drug delivery systems has paved the way for the development of systems for controlled release of agrochemicals. In this work, we exploited calcium carbonate nanocrystals as carriers for targeted release of phytodrugs investigating a potential control strategy for the pathogen Xylella fastidiosa. This pathogen is the causal agent of the Olive Quick Decline Syndrome that is an unprecedented emergency in Italy and potentially in the rest of Europe. We studied nanocrystals interactions with bacteria cells and the application in planta to verify olive plants uptake. Ultrastructural analysis by electron microscopy shown an alteration of bacteria wall following nanocrystals interaction. Nanocrystals were adsorbed from roots and they translocated in plants tissues. Calcium carbonate carriers were able to encapsulate efficiently two types of antimicrobial substances and the potential efficacy was tested in experiment under greenhouse conditions.

Effect of Different Crosslinking Strategies on Physical Properties and Biocompatibility of Freestanding Multilayer Films Made of Alginate and Chitosan

Freestanding multilayer films prepared by layer-by-layer technique have attracted interest as promising materials for wound dressings. The goal is to fabricate freestanding films using chitosan (CHI) and alginate (ALG) including subsequent crosslinking to improve the mechanical properties of films while maintaining their biocompatibility. Three crosslinking strategies are investigated, namely use of calcium ions for crosslinking ALG, 1-ethyl-3-(-3-dimethylaminopropyl) carbodiimide combined with N-hydroxysuccinimide for crosslinking ALG with CHI, and Genipin for crosslinking chitosan inside the films. Different characteristics, such as surface morphology, wettability, swelling, roughness, and mechanical properties are investigated showing that films became thinner, exhibited rougher surfaces, had lower water uptake, and increased mechanical strength after crosslinking. Changes of wettability are moderate and dependent on the crosslinking method. In vitro cytotoxicity and cell attachment studies with human dermal fibroblasts show that freestanding CHI-ALG films represent a poorly adhesive substratum for fibroblasts, while studies using incubation of plastic-adherent fibroblast beneath floating films show no signs of cytotoxicity in a time frame of 7 days. Results from cell experiments combined with film characteristics after crosslinking, indicate that crosslinked freestanding films made of ALG and CHI may be interesting candidates for wound dressings.

Antimicrobial biopolymer formation from sodium alginate and algae extract using aminoglycosides

Antimicrobial biopolymers provide a biodegradable, sustainable, safe, and cheap approach to drug delivery and wound dressing to control bacterial infection and improve wound healing respectively. Here, we report a one-step method of making antimicrobial alginate polymer from sodium alginate and aqueous extract of Wakame using antibiotic aminoglycosides. Thin layer chromatography of commercially available sodium alginate and Wakame extract showed similar oligosaccharide profiles. Screening of six aminoglycosides showed that kanamycin disulfate and neomycin sulfate produces the highest amount of biopolymer; however, kanamycin disulfate produces the most malleable and form fitting biopolymer. Image texture analysis of biopolymers showed similar quantification parameters for all the six aminoglycosides. Weight of alginate polymer as a function of aminoglycoside concentration follows a growth model of prion protein, consistent with the aggregating nature of both processes. Slow release of antibiotics and the resulting zone of inhibition against E. coli DH5α were observed by agar well diffusion assay. Inexpensive method of production and slow release of antibiotics will enable diverse applications of antimicrobial alginate biopolymer reported in this paper.

Microbicidal gentamicin-alginate hydrogels

Sodium alginate (Alg) reacted with antibiotic gentamicin sulfate (GS) in an aqueous-phase condition mediated by carbodiimide chemistry, in the molar ratios Alg: GS of (1:0.5), (1:1) and (1:2). The Alg-GS conjugated derivatives were characterized by elemental analysis for nitrogen content, Fourier transform infrared spectroscopy in the attenuated total reflection mode (FTIR-ATR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), thermogravimetric analyses (TGA) and water sorption measurements. XPS and FTIR-ATR analyses clearly indicated that GS molecules covalently attached to the backbone of the alginate chains by amide bond formation. The highest amount of GS bound to Alg (43.5 ± 0.4 wt%) and the highest swelling ratio (4962 ± 661%) were observed for the Alg-GS (1:2) sample. Bioluminescence assays with Pseudomonas aeruginosa PAO1/lecA:lux and colony forming counting of Staphylococcus aureus and Escherichia coli upon contact with all Alg-GS conjugates revealed microbicidal activity; however, Alg-GS (1:2) was the most efficient, due to the highest GS content.

Scalable production of core-shell nanoparticles by flash nanocomplexation to enhance mucosal transport for oral delivery of insulin

Scalable manufacturing continues to present a major barrier for clinical translation of nanotherapeutics. Methods available for fabricating protein-encapsulating nanoparticles in a scalable fashion are scarce. Protein delivery often requires multiple functionalities to be incorporated into the same vehicle. Specifically for nanoparticle-mediated oral delivery of protein therapeutics, protection in GI tract, site-specific release, facilitating transmucosal permeation, and enhancing epithelial transport are a few desirable features to be engineered into a nanoparticle system. Here we devised a sequential flash nanocomplexation (FNC) technique for the scalable production of a core-shell structured nanoparticle system by combining materials choice and particle size and structure to fulfill these functions, therefore enhancing the delivery efficiency of insulin. This method is highly effective in controlling the size, generating core-shell structure with high encapsulation efficiency (97%) and payload capacity (67%) using insulin/l-penetratin complex nanoparticles as a core coated with hyaluronic acid (HA). Both the in vitro and in vivo models confirmed that the HA coating on these core-shell nanoparticles enhanced the permeation of nanoparticles through the intestinal mucus layer and improved trans-epithelial absorption of insulin nanoparticles; and the enhancement effect was most prominent using HA with the highest average molecular weight. The insulin-loaded nanoparticles were then encapsulated into enteric microcapsules (MCs) in an FNC process to provide additional protection against the acidic environment in the stomach while allowing rapid release of insulin nanoparticles when they reach small intestine. The optimized multifunctional MCs delivered an effective glucose reduction in a Type I diabetes rat model following a single oral administration, yielding a relative bioavailability of 11% in comparison with subcutaneous injection of free-form insulin. This FNC technique is highly effective in controlling particle size and structure to improve delivery properties and function. It can be easily extended to oral delivery for other protein therapeutics.

Investigation of the Internal Chemical Composition of Chitosan-Based LbL Films by Depth-Profiling X-ray Photoelectron Spectroscopy (XPS) Analysis

Chitosan-based thin films were assembled using the layer-by-layer technique, and the axial composition was accessed using X-ray photoelectron spectroscopy with depth profiling. Chitosan (CHI) samples possessing different degrees of acetylation ([Formula: see text]) and molecular weight ([Formula: see text]) produced via the ultrasound-assisted deacetylation reaction were used in this study along with two different polyanions, namely, sodium polystyrenesulfonate (PSS) and carboxymethylcellulose (CMC). When chitosan, a positively charged polymer in aqueous acid medium, was combined with a strong polyanion (PSS), the total positive charge of chitosan, directly related to its [Formula: see text], was the key factor affecting the film formation. However, for CMC/CHI films, the pH of the medium and [Formula: see text] of chitosan strongly affected the film structure and composition. Consequently, the structure and the axial composition of chitosan-based films can be finely adjusted by choosing the polyanion and defining the chitosan to be used according to its DA and [Formula: see text] for the desired application, as demonstrated by the antibacterial tests.

Roughness dynamic in surface growth: Layer-by-layer thin films of carboxymethyl cellulose/chitosan for biomedical applications

Surfaces are responsible for important interactions of biomaterials since they create the interface with the biological environment and affect the response that the body will have to the material. Surface roughness and morphology have great impact on the material performance, affecting cell, bacterial, and biomolecular adhesion. Thin films of chitosan and carboxymethyl cellulose were produced by layer-by-layer deposition at different pH values and had their surface growth process studied throughout roughness measurements. Both polymers are nontoxic and biocompatible to the human biological system, with biomedical applications from tissue engineering to drug delivery. Growth exponents are presented, and it is suggested that fractal-based growth models are suitable for describing surface evolution and morphology of carboxymethyl cellulose/chitosan layer-by-layer thin film growth during deposition, primarily nonlinear models.

Achieving low-fouling surfaces with oppositely charged polysaccharides via LBL assembly

The aim of this work is to understand and achieve low fouling surfaces by mixing two oppositely charged polysaccharides through layer-by-layer (LBL) assembly. Diethylaminoethyl-dextran hydrochloride and alginate were employed as a model system to build LBL films. A surface plasmon resonance (SPR) biosensor was used to measure quantitatively the adsorption behavior of charged macromolecules during LBL buildup and the protein adsorption behavior of each deposited bilayer in situ in real time accordingly. Results show that LBL films have lower protein adsorption as the films are constructed above the substrate surface. These LBL films eventually reach very low fouling when they are sufficiently far from the substrate surface, where the substrate surface effect is minimized and bilayers consisting of positively and negatively charged marcromolecules are uniformly mixed. Single proteins, undiluted human blood serum and plasma and cells were tested for adsorption to LBL films with similar trends. To verify the generality of these findings, alginates of low and high molecular weights and carboxymethylcellulose as a substitute to alginate were studied with similar trends observed. These results demonstrate that oppositely charged polymers, when uniformly mixed, are able to achieve low fouling properties. Findings from this work will provide a fundamental understanding of and design principles on how to build nonfouling LBL films.

STATEMENT OF SIGNIFICANCE

We demonstrate that protein adsorption decreases with the increase of bilayer numbers. Results indicate that oppositely charged components tend to be uniformly mixed and distinct change layers in classical layer-by-layer (LBL) theories no longer exist as LBL films are sufficiently far from the substrate surface. Findings from this work provide a fundamental understanding of and design principles on how to build nonfouling LBL films.

Recent Developments in Antimicrobial Polymers: A Review

Antimicrobial polymers represent a very promising class of therapeutics with unique characteristics for fighting microbial infections. As the classic antibiotics exhibit an increasingly low capacity to effectively act on microorganisms, new solutions must be developed. The importance of this class of materials emerged from the uncontrolled use of antibiotics, which led to the advent of multidrug-resistant microbes, being nowadays one of the most serious public health problems. This review presents a critical discussion of the latest developments involving the use of different classes of antimicrobial polymers. The synthesis pathways used to afford macromolecules with antimicrobial properties, as well as the relationship between the structure and performance of these materials are discussed.