Surface modification of starch based biomaterials by oxygen plasma or UV-irradiation

Applications of Starch Biopolymers for a Sustainable Modern Agriculture

Protected cultivation in modern agriculture relies extensively on plastic-originated mulch films, nets, packaging, piping, silage, and various applications. Polyolefins synthesized from petrochemical routes are vastly consumed in plasticulture, wherein PP and PE are the dominant commodity plastics. Imposing substantial impacts on our geosphere and humankind, plastics in soil threaten food security, health, and the environment. Mismanaged plastics are not biodegradable under natural conditions and generate problematic emerging pollutants such as nano-micro plastics. Post-consumed petrochemical plastics from agriculture face many challenges in recycling and reusing due to soil contamination in fulfilling the zero waste hierarchy. Hence, biodegradable polymers from renewable sources for agricultural applications are pragmatic as mitigation. Starch is one of the most abundant biodegradable biopolymers from renewable sources; it also contains tunable thermoplastic properties suitable for diverse applications in agriculture. Functional performances of starch such as physicomechanical, barrier, and surface chemistry may be altered for extended agricultural applications. Furthermore, starch can be a multidimensional additive for plasticulture that can function as a filler, a metaphase component in blends/composites, a plasticizer, an efficient carrier for active delivery of biocides, etc. A substantial fraction of food and agricultural wastes and surpluses of starch sources are underutilized, without harnessing useful resources for agriscience. Hence, this review proposes reliable solutions from starch toward timely implementation of sustainable practices, circular economy, waste remediation, and green chemistry for plasticulture in agriscience

Antimicrobial Properties of the Ag, Cu Nanoparticle System

Microbes, including bacteria and fungi, easily form stable biofilms on many surfaces. Such biofilms have high resistance to antibiotics, and cause nosocomial and postoperative infections. The antimicrobial and antiviral behaviors of Ag and Cu nanoparticles (NPs) are well known, and possible mechanisms for their actions, such as released ions, reactive oxygen species (ROS), contact killing, the immunostimulatory effect, and others have been proposed. Ag and Cu NPs, and their derivative NPs, have different antimicrobial capacities and cytotoxicities. Factors, such as size, shape and surface treatment, influence their antimicrobial activities. The biomedical application of antimicrobial Ag and Cu NPs involves coating onto substrates, including textiles, polymers, ceramics, and metals. Because Ag and Cu are immiscible, synthetic AgCu nanoalloys have different microstructures, which impact their antimicrobial effects. When mixed, the combination of Ag and Cu NPs act synergistically, offering substantially enhanced antimicrobial behavior. However, when alloyed in Ag-Cu NPs, the antimicrobial behavior is even more enhanced. The reason for this enhancement is unclear. Here, we discuss these results and the possible behavior mechanisms that underlie them.

Bioinspired Modifications of PEEK Implants for Bone Tissue Engineering

In recent years, polyetheretherketone (PEEK) has been increasingly employed as an implant material in clinical applications. Although PEEK is biocompatible, chemically stable, and radiolucent and has an elastic modulus similar to that of natural bone, it suffers from poor integration with surrounding bone tissue after implantation. To improve the bioactivity of PEEK, numerous strategies for functionalizing the PEEK surface and changing the PEEK structure have been proposed. Inspired by the components, structure, and function of bone tissue, this review discusses strategies to enhance the biocompatibility of PEEK implants and provides direction for fabricating multifunctional implants in the future.

Hydrophilic Surface Functionalization of Electrospun Nanofibrous Scaffolds in Tissue Engineering

Electrospun polymer nanofibers have received much attention in tissue engineering due to their valuable properties such as biocompatibility, biodegradation ability, appropriate mechanical properties, and, most importantly, fibrous structure, which resembles the morphology of extracellular matrix (ECM) proteins. However, they are usually hydrophobic and suffer from a lack of bioactive molecules, which provide good cell adhesion to the scaffold surface. Post-electrospinning surface functionalization allows overcoming these limitations through polar groups covalent incorporation to the fibers surface, with subsequent functionalization with biologically active molecules or direct deposition of the biomolecule solution. Hydrophilic surface functionalization methods are classified into chemical approaches, including wet chemical functionalization and covalent grafting, a physiochemical approach with the use of a plasma treatment, and a physical approach that might be divided into physical adsorption and layer-by-layer assembly. This review discusses the state-of-the-art of hydrophilic surface functionalization strategies of electrospun nanofibers for tissue engineering applications. We highlighted the major advantages and drawbacks of each method, at the same time, pointing out future perspectives and solutions in the hydrophilic functionalization strategies.

Nanointeraction: The profound influence of nanostructured and nano-drug delivery biomedical implant surfaces on cell behavior

Nanostructured surfaces feature promising biological properties on biomaterials attracting large interest at basic research, implant industry development, and bioengineering applications. Thou, nanoscale interactions at a molecular and cellular level are not yet completely understood and its biological and clinical implications need to be further elucidated. As follows, the aim of this comprehensive review was to evaluate nanostructured surfaces at biomedical implants focusing on surface development, nanostructuration, and nanoengineered drug delivery systems that can induce specific cell interactions in all relevant aspects of biological, reparative, anti-bacterial, anti-inflammatory and clinical processes. The methods and the physio-chemical properties involved in nanotopography performance, the main cellular characteristics involved at surface/cell interaction, and a summary of results and outlooks reported in studies applying nanostructured surfaces and nano-drug delivery systems is presented. The future prospects and commercial translation of this developing field, particularly concerning multifunctional nanostructured surfaces and its clinical implications are further discussed. At a cellular level, nanostructured biomedical implant surfaces can enhance osteogenesis by targeting osteoblasts, osteocytes, and mesenchymal cells, stimulate fibroblast/epithelial cells proliferation and adherence, inhibit bacterial cell proliferation and biofilm accumulation, and act as immune-modulating surfaces targeting macrophages and reducing pro-inflammatory cytokine expression. Moreover, several methodological options to create drug-delivery systems on metallic implant surfaces are available, however, the clinical translation is yet incomplete. The efficiency of which nanostructured/nano-delivery surfaces may target specific cell interactions and favor clinical outcomes needs to be further elucidated in pre-clinical and clinical studies, along with engineering solutions for commercial translation and approval of controlling agencies.

Physicochemical properties of partially α-glucan-coated normal corn starch formed by amylosucrase from Neisseria polysaccharea

Amylosucrase (AS) is a glycosyltransferase that produces linear α-1,4 glucans using sucrose as the sole substrate. In this study, for various applications, α-glucan-coated starch (α-GCS) was produced by AS (20 U/L_reactant) from Neisseria polysaccharea to improve the physicochemical properties of raw normal corn starch (NCS) by applying different reaction conditions (i.e., varying the substrate concentration, pH, and temperature). Field-emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD) showed that raw NCS was successfully coated by α-glucan. Differential scanning calorimetry (DSC) and rapid viscosity analyses (RVA) of the α-GCS confirmed that the α-glucan coating decreased the degree of retrogradation. Notably, compared to raw NCS as a control, starch retrogradation was significantly (p < 0.05) decreased by 13.7% after five weeks. Therefore, the novel α-GCS can be applied as a functional material for controlled retrogradation in the starch-based food industry for shelf-life extension.

Tuning surface properties of bone biomaterials to manipulate osteoblastic cell adhesion and the signaling pathways for the enhancement of early osseointegration

Osteoblast cell adhesion is the initial step of early osseointegration responding to bone material implants. Enhancing the osteoblastic cell adhesion has become one of the prime aims when optimizing the surface properties of bone biomaterials. The traditional strategy focuses in improving the physical attachment of osteoblastic cells onto the surfaces of biomaterials. However, instead of a simple cell physical attachment, the osteoblastic cell adhesion has been revealed to be a sophisticated system. Despite the well-documented effect of bone biomaterial surface modifications on adhesion, few studies have focused on the underlying molecular mechanisms. Physicochemical signals from biomaterials can be transduced into intracellular signaling network and further initiate the early response cascade towards the implants, which includes cell survival, migration, proliferation, and differentiation. Adhesion is vital in determining the early osseointegration between host bone tissue and implanted bone biomaterials via regulating involving signaling pathways. Therefore, the modulation of early adhesion behavior should not simply target in physical attachment, but emphasize in the manipulation of downstream signaling pathways, to regulate early osseointegration. This review firstly summarized the basic biological principles of osteoblastic cell adhesion process and the activated downstream cell signaling pathways. The effects of different biomaterial physicochemical properties on osteoblastic cell adhesion were then reviewed. This review provided up-to-date research outcomes in the adhesion behavior of osteoblastic cells on bone biomaterials with different physicochemical properties. The strategy is optimised from traditionally focusing in physical cell adhesion to the proposed strategy that manipulating cell adhesion and the downstream signaling network for the enhancement of early osseointegration.

Evaluation of three different decontamination techniques on biofilm formation, and on physical and chemical properties of resin composites

OBJECTIVES

This study evaluated three different sterilization/disinfection techniques for resin composites on bacterial growth and surface modification after decontamination.

METHODS

Two resin composites were sterilized/disinfected with three different techniques: UV light, 1% chloramine T, and 70% ethanol. Four different times were used for each technique to determine the shortest time that the solution or UV light was effective. The influence of sterilization/disinfection technique on bacterial growth was evaluated by analyzing the metabolic activity, using the AlamarBlue™ assay, bacterial viability, and SEM images from biofilms of Streptococcus mutans. The surface change, after the process, was analyzed with ATR/FTIR and SEM images. The solutions used for decontamination (1% chloramine-T and 70% ethanol) were analyzed with ¹ H-NMR to identify any resin compounds leached during the process.

RESULTS

One minute of decontamination was efficient for all three methods tested. Chloramine-T increased the surface porosity on resin composites, no changes were observed for UV light and 70% ethanol, however, ¹ H-NMR identified leached monomers only when 70% ethanol was used. No chemical change of the materials was found under ATR/FTIR analyses after the decontamination process. Chloramine-T, with no previous wash, increased the bacterial viability for both resin composites and increased the bacterial metabolism for the resin composite without fluoride.

CONCLUSION

UV light had no interference on the resin composites properties tested using 1 min of exposure compared to the other decontamination methods. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 945-953, 2018.

Inhibition of Salmonella typhimurium on radish sprouts using nitrogen-cold plasma

This study investigated the effects of cold plasma treatment (CPT) on the inhibition of Salmonella typhimurium on radish sprouts and the quality attributes of the sprouts. Radish sprouts were treated with nitrogen (N₂)-cold plasma at 900W and 667Pa for 0, 2, 5, 10, and 20min using a microwave-powered CPT system. The sensory attributes of the radish sprouts, appearance and odor, were evaluated before and after the treatment. The effects of N₂-CPT for 10min on microbial growth and the quality attributes of the radish sprouts were evaluated during storage for 12days at 4 and 10°C. N₂-CPT at 900W and 667Pa for 20min reduced the number of S. typhimurium by 2.6±0.4logCFU/g. The moisture content of the radish sprouts decreased with treatment time. The appearance and odor of the radish sprouts were not altered by CPT (p>0.05) and this treatment did not affect the quality attributes of the sprouts in terms of color, ascorbic acid concentration, or antioxidant activity during storage at both 4 and 10°C. These findings suggest that CPT has the potential to improve the microbiological safety of radish sprouts with reference to S. typhimurium during cold storage without significant detriment to its quality properties.

Modulating cell adhesion to polybutylene succinate biotextile constructs for tissue engineering applications

Textile-based technologies are powerful routes for the production of three-dimensional porous architectures for tissue engineering applications because of their feasibility and possibility for scaling-up. Herein, the use of knitting technology to produce polybutylene succinate fibre-based porous architectures is described. Furthermore, different treatments have been applied to functionalize the surface of the scaffolds developed: sodium hydroxide etching, ultraviolet radiation exposure in an ozone atmosphere and grafting (acrylic acid, vinyl phosphonic acid and vinyl sulphonic acid) after oxygen plasma activation as a way to tailor cell adhesion. A possible effect of the applied treatments on the bulk properties of the textile scaffolds has been considered and thus tensile tests in dry and hydrated states were also carried out. The microscopy results indicated that the surface morphology and roughness were affected by the applied treatments. The X-ray photoelectron spectroscopy and contact angle measurements showed the incorporation of oxygen-containing groups and higher surface free energy as result of the surface treatments applied. The DNA quantification and scanning electron microscopy analysis revealed that these modifications enhanced cell adhesion and altered cell morphology. Generally, sodium hydroxide treatment altered most significantly the surface properties, which in turn resulted in a high number of cells adherent to these surfaces. Based on the results obtained, the proposed surface treatments are appropriate to modify polybutylene succinate knitting scaffolds, influencing cell adhesion and its potential for use in tissue engineering applications. Copyright © 2016 John Wiley & Sons, Ltd.

Slow chlorine releasing compounds: A viable sterilisation method for bioabsorbable nanocomposite biomaterials

Objective

Selection of the appropriate sterilisation method for biodegradable materials has been a challenging task. Many conventional sterilisation methods are not suitable for the next generation of biomaterials, mainly due to their complex composition, based on nanomaterials, often incorporating bioactive moieties. In this study, we investigate sterilisation efficacy of slow chlorine releasing compound sodium dichloroisocyanurate dihydrate (SDIC) for polyhedral oligomeric silsesquioxane (POSS)-poly(caprolactone urea-urethane) (PCL) scaffolds in comparison with conventional sterilisation methods.

Methods

POSS-PCL scaffolds were subjected to 70% ethanol, UV, and SDIC sterilisation methods. Samples were immersed in tryptone soya broth (TSB) and thioglycollate medium (THY) and after seven days visually inspected for signs of microbial growth. Bulk and surface properties and molecular weight distribution profiles of the scaffolds after sterilization were investigated using FTIR analysis, surface hydrophilicity, scanning electron microscopy analysis, tensile strength testing, and gel-permeation chromatography (GPC). Adipose-derived stem cells (ADSC) were seeded on the scaffolds and AlamarBlue® viability assay was performed to investigate cell metabolic activity. Confocal imaging of rhodamine phalloidin and Dapi stained ADSC on scaffolds was used to demonstrate cell morphology.

Results

GPC results showed that autoclaving led to a significant decrease in the molecular weight of POSS-PCL, whereas ethanol caused visible deformation of the polymer 3D structure and UV radiation did not effectively sterilise the scaffolds. AlamarBlue® analysis showed metabolic activity close to that of tissue culture plastic for ethanol and SDIC.

Conclusion

SDIC sterilisation can be safely applied to biodegradable scaffolds unsuitable for the more common sterilisation methods.

Surface modification of electrospun poly(methyl methacrylate) (PMMA) nanofibers for the development of in vitro respiratory epithelium model

Scaffold design is an important aspect of in vitro model development. In this study, nanoscaffold surface modification, namely UV radiation and genipin cross-linking to immobilize collagen on the surface of electrospun poly (methyl methacrylate) (PMMA) nanofiber sheet was investigated. Samples were divided into four groups; PMMA nanofibers (PMMA), collagen-coated PMMA nanofibers (PMMACOL), genipin cross-linked collagen-coated PMMA nanofibers (PMMAGEN), and UV-irradiated collagen-coated PMMA nanofibers (PMMAUV). 6 h of UV radiation significantly reduced the hydrophobicity of PMMA nanofibers from (131.88° ± 1.33°) to (110.04° ± 0.27°) (p < 0.05). The amount of collagen immobilized was significantly higher in PMMAGEN group (239.36 ± 16.63 μg collagen/mg nanofibers) (p < 0.05) compared to the other groups. RECs on all scaffold expressed epithelial cell-specific markers (CK18 and CK14), mucin-producing cell marker (MUC5Ac) and were actively proliferating, based on the positive expression of Ki67. Total number of attached cells was significantly the highest in PMMAUV group on day 9 (6.44 × 10(4) ± 2.77 × 10(4) cells/cm(2)) and it has the highest proliferation rate from day 4 to 9 (0.005 ± 0.003 h(-1)) compared to the other groups. Even though PMMAGEN group showed the highest collagen adsorption, in terms of cells attachment and proliferation, PMMAUV group showed a better outcome compared to the other groups. Thus, PMMAUV scaffold is more suitable to be used in the construction of in vitro respiratory epithelial model.

Nanoparticle-based bioactive agent release systems for bone and cartilage tissue engineering

The inability to deliver bioactive agents locally in a transient but sustained manner is one of the challenges on the development of bio-functionalized scaffolds for tissue engineering (TE) and regenerative medicine. The mode of release is especially relevant when the bioactive agent is a growth factor (GF), because the dose and the spatiotemporal release of such agents at the site of injury are crucial to achieve a successful outcome. Strategies that combine scaffolds and drug delivery systems have the potential to provide more effective tissue regeneration relative to current therapies. Nanoparticles (NPs) can protect the bioactive agents, control its profile, decrease the occurrence and severity of side effects and deliver the bioactive agent to the target cells maximizing its effect. Scaffolds containing NPs loaded with bioactive agents can be used for their local delivery, enabling site-specific pharmacological effects such as the induction of cell proliferation and differentiation, and, consequently, neo-tissue formation. This review aims to describe the concept of combining NPs with scaffolds, and the current efforts aiming to develop highly multi-functional bioactive agent release systems, with the emphasis on their application in TE of connective tissues.

Influence of different surface modification treatments on silk biotextiles for tissue engineering applications

Biotextile structures from silk fibroin have demonstrated to be particularly interesting for tissue engineering (TE) applications due to their high mechanical strength, interconnectivity, porosity, and ability to degrade under physiological conditions. In this work, we described several surface treatments of knitted silk fibroin (SF) scaffolds, namely sodium hydroxide (NaOH) solution, ultraviolet radiation exposure in an ozone atmosphere (UV/O3) and oxygen (O2) plasma treatment followed by acrylic acid (AAc), vinyl phosphonic acid (VPA), and vinyl sulfonic acid (VSA) immersion. The effect of these treatments on the mechanical properties of the textile constructs was evaluated by tensile tests in dry and hydrated states. Surface properties such as morphology, topography, wettability and elemental composition were also affected by the applied treatments. The in vitro biological behavior of L929 fibroblasts revealed that cells were able to adhere and spread both on the untreated and surface-modified textile constructs. The applied treatments had different effects on the scaffolds' surface properties, confirming that these modifications can be considered as useful techniques to modulate the surface of biomaterials according to the targeted application.

Surface charge and carbon contamination on an electron-beam-irradiated hydroxyapatite thin film investigated by photoluminescence and phase imaging in atomic force microscopy

The surface properties of hydroxyapatite, including electric charge, can influence the biological response, tissue compatibility, and adhesion of biological cells and biomolecules. Results reported here help in understanding this influence by creating charged domains on hydroxyapatite thin films deposited on silicon using electron beam irradiation and investigating their shape, properties, and carbon contamination for different doses of incident injected charge by two methods. Photoluminescence laser scanning microscopy was used to image electrostatic charge trapped at pre-existing and irradiation-induced defects within these domains, while phase imaging in atomic force microscopy was used to image the carbon contamination. Scanning Auger electron spectroscopy and Kelvin probe force microscopy were used as a reference for the atomic force microscopy phase contrast and photoluminescence laser scanning microscopy measurements. Our experiment shows that by combining the two imaging techniques the effects of trapped charge and carbon contamination can be separated. Such separation yields new possibilities for advancing the current understanding of how surface charge influences mediation of cellular and protein interactions in biomaterials.

Adhesion, growth, and maturation of vascular smooth muscle cells on low-density polyethylene grafted with bioactive substances

The attractiveness of synthetic polymers for cell colonization can be affected by physical, chemical, and biological modification of the polymer surface. In this study, low-density polyethylene (LDPE) was treated by an Ar(+) plasma discharge and then grafted with biologically active substances, namely, glycine (Gly), polyethylene glycol (PEG), bovine serum albumin (BSA), colloidal carbon particles (C), or BSA+C. All modifications increased the oxygen content, the wettability, and the surface free energy of the materials compared to the pristine LDPE, but these changes were most pronounced in LDPE with Gly or PEG, where all the three values were higher than in the only plasma-treated samples. When seeded with vascular smooth muscle cells (VSMCs), the Gly- or PEG-grafted samples increased mainly the spreading and concentration of focal adhesion proteins talin and vinculin in these cells. LDPE grafted with BSA or BSA+C showed a similar oxygen content and similar wettability, as the samples only treated with plasma, but the nano- and submicron-scale irregularities on their surface were more pronounced and of a different shape. These samples promoted predominantly the growth, the formation of a confluent layer, and phenotypic maturation of VSMC, demonstrated by higher concentrations of contractile proteins alpha-actin and SM1 and SM2 myosins. Thus, the behavior of VSMC on LDPE can be regulated by the type of bioactive substances that are grafted.

Directly created electrostatic micro-domains on hydroxyapatite: probing with a Kelvin Force probe and a protein

Micro-domains of modified surface potential (SP) were created on hydroxyapatite films by direct patterning by mid-energy focused electron beam, typically available as a microprobe of Scanning Electron Microscopes. The SP distribution of these patterns has been studied on sub-micrometer scale by the Kelvin Probe Force Microscopy method as well as lysozyme adsorption. Since the lysozyme is positively charged at physiological pH, it allows us to track positively and negatively charged areas of the SP patterns. Distribution of the adsorbed proteins over the domains was in good agreement with the observed SP patterns.

Protein interactions with nanoporous sol-gel derived bioactive glasses

Sol-gel derived bioactive glasses are excellent candidates for bone regenerative implant materials as they bond with bone, stimulate bone growth and degrade in the body. Their interactions with proteins are critical to understanding their performance after implantation. This study focuses on the interactions between fibrinogen and sol-gel glass particles of the 70S30C (70 mol.% SiO(2), 30 mol.% CaO composition). Sol-gel silica and melt-derived Bioglass® were also used for comparison. Fibrinogen penetration into the nanoporous glasses was observed by live tracking the fluorescent-labelled fibrinogen with confocal microscopy. The effect of pore size on protein penetration was investigated. Nanoporous networks with modal pore diameters larger than 6 nm were accessible to fibrinogen. When the modal nanopore diameter was decreased to 2 nm or less, the penetration of fibrinogen was inhibited. The surface properties of the glasses, which can be modulated by media pH, glass composition and final stabilisation temperature in the sol-gel process, have effects on fibrinogen adsorption via long-range Coulombic forces before the adsorption and via short-range interactions such as hydrogen bonding after the adsorption.

Plasma-assisted surface modification of organic biopolymers to prevent bacterial attachment

Despite many synthetic biomaterials having physical properties that are comparable or even superior to those of natural body tissues, they frequently fail due to the adverse physiological reactions they cause within the human body, such as infection and inflammation. The surface modification of biomaterials is an economical and effective method by which biocompatibility and biofunctionality can be achieved while preserving the favorable bulk characteristics of the biomaterial, such as strength and inertness. Amongst the numerous surface modification techniques available, plasma surface modification affords device manufacturers a flexible and environmentally friendly process that enables tailoring of the surface morphology, structure, composition, and properties of the material to a specific need. There are a vast range of possible applications of plasma modification in biomaterial applications, however, the focus of this review paper is on processes that can be used to develop surface morphologies and chemical structures for the prevention of adhesion and proliferation of pathogenic bacteria on the surfaces of in-dwelling medical devices. As such, the fundamental principles of bacterial cell attachment and biofilm formation are also discussed. Functional organic plasma polymerised coatings are also discussed for their potential as biosensitive interfaces, connecting inorganic/metallic electronic devices with their physiological environments.