Antibacterial and Antifungal Properties of Polyester, Polylactide, and Cotton Nonwovens and Fabrics, by Means of Stable Aqueous Dispersions Containing Copper Silicate and Some Metal Oxides

Literature reviews have described the applications of silver, copper, and zinc ions and metallic particles of Cu, Ti, and Zn oxides, which have been found to be useful antimicrobial reagents for the biofunctionalization of various materials and their surfaces. For this purpose, compositions of water dispersions containing emulsions of synthetic copolymers based on acrylic and vinyl monomers, polysaccharides (hydroxyethyl cellulose and starch), and various additives with wetting and stabilizing properties were used. Many stable water dispersions of different chemical compositions containing bioactive chemical compounds (copper silicate hydrate, titanium dioxide, and zinc oxide (and other auxiliary substances)) were developed. They were used for the preparation of thin hybrid coatings having good antimicrobial properties against Gram-negative bacteria (Escherichia coli), Gram-positive bacteria (Staphylococcus aureus), and yeast fungus (Candida albicans). Polyester (PES) and polylactide (PLA) nonwovens were modified using the dip-coating method, while PES and cotton fabrics were biofunctionalized by means of dip-coating and coating methods. The antimicrobial (antibacterial and antifungal) properties of the textile materials (nonwovens and fabrics) biofunctionalized with the above-mentioned bioactive agents exhibiting antimicrobial properties (CuSiO3, TiO2, ZnO, or ZnO∙SiO2) were strongly dependent on the agents' content in the water dispersions. The PES and PLA nonwovens, modified on the surface with water compositions containing copper silicate hydrate, showed good antibacterial properties against the Gram-negative bacteria Escherichia coli, even at a content of 1 wt.% CuSiO3∙xH2O, and against the Gram-positive bacteria Staphylococcus aureus, at the content of at least 5 wt.% CuSiO3∙xH2O. The bacterial growth reduction factor (R) was greater than 99% for most of the samples tested. Good antifungal properties against the fungus Candida albicans were found for the PES and PLA nonwoven fabrics modified with dispersions containing 5-7 wt.% CuSiO3∙xH2O and 4.2-5.0 wt.% TiO2. The addition of TiO2 led to a significant improvement in the antifungal properties of the PES and PLA nonwovens modified in this way. For the samples of PES WIFP-270 and FS F-5 nonwovens, modified with water dispersions containing 5.0 wt.% CuSiO3∙xH2O and 4.2-5.0 wt.% TiO2, the growth reduction factor for the fungus Candida albicans (R) reached values in the range of 80.9-98.0%. These new biofunctionalized polymeric nonwoven textile materials can find practical applications in the manufacture of filters for hospital air-conditioning systems and for the automotive industry, as well as in air purification devices. Moreover, similar antimicrobial modification of fabrics with the dip-coating or coating methods can be applied, for example, in the fabrication of fungi- and mold-resistant garden furniture.

Experimental study on fabrication, biocompatibility and mechanical characterization of polyhydroxybutyrate-ball clay bionanocomposites for bone tissue engineering

The poly (3-hydroxybutyrate) (PHB)/ball clay nanocomposites (B1-B10) were synthesized using solvent casting method with different weight percentage of ball clay in PHB matrix. Scanning electron microscope (SEM) showed maximum root mean square roughness (188.73 μm) for 10% ball clay loading. Fourier transforms infrared spectroscopy (FT-IR) and X-ray diffraction (XRD) showed establishment of intercalated structure and formation of hydrogen bond between ball clay and PHB matrix. Contact angle values (67.3 - 51.3°) exhibited that the nanocomposites (B1-B10) are more hydrophilic than neat PHB (70.30°). Thermogravimetric (TGA) and differential scanning calorimetry (DSC) revealed maximum T_max (278 °C) and T_m (175 °C) for the nanocomposite B10 (PHB/PEG/ball clay: 80%/10%/10%). Maximum tensile strength (38.21 ± 0.15 MPa) and Young's modulus (1.74 ± 0.016 GPa) was observed for B10 nanocomposite. The values of protein adsorption, platelet adhesion, PT, APTT and complement activation for B10 nanocomposites were 165 ± 2 μg/cm², 72 ± 3 × 10⁹ platelets/cm², 23 ± 1 s, 44 ± 2 s, 102 ± 2 mg/dL and 631 ± 3 mg/dL, respectively. Hydroxyapatite formation was also observed for nanocomposite (B10) in in vitro simulated body fluid (SBF) study. Finally, the nanocomposite (B10) showed no harmful effect on MG-63 cells, indicating that they are physiologically safe.

Chitosan/Hyaluronic acid/Alginate and an assorted polymers loaded with honey, plant, and marine compounds for progressive wound healing-Know-how

Biomaterials are being extensively used in regenerative medicine including tissue engineering applications, as these enhance tissue development, repair, and help in the process of angiogenesis. Wound healing is a crucial biological process of regeneration of ruptured tissue after getting injury to the skin and other soft tissue in humans and animals. Besides, the accumulation of microbial biofilms around the wound surface can increase the risk and physically obstruct the wound healing activity, and may even lead to amputation. Hence, in both acute and chronic wounds, prominent biomaterials are required for wound healing along with antimicrobial agents. This review comprehensively addresses the antimicrobial and wound healing effects of chitosan, chitin, cellulose acetate, hyaluronic acid, pullulan, bacterial cellulose, fibrin, alginate, etc. based wound dressing biomaterials fabricated with natural resources such as honey, plant bioactive compounds, and marine-based polymers. Due to their excellent biocompatibility and biodegradability, bioactive compounds derived from honey, plants, and marine resources are commonly used in biomedical and tissue engineering applications. Different types of polymer-based biomaterials including hydrogel, film, scaffold, nanofiber, and sponge dressings fabricated with bioactive agents including honey, curcumin, tannin, quercetin, andrographolide, gelatin, carrageenan, etc., can exhibit significant wound healing process in, diabetic wounds, diabetic ulcers, and burns, and help in cartilage repair along with good biocompatibility and antimicrobial effects. Among the reviewed biomaterials, carbohydrate polymers such as chitosan-based biomaterials are prominent and widely used for wound healing applications followed by hyaluronic acid and alginate-based biomaterials loaded with honey, plant, and marine compounds. This review first provides an overview of the vast natural resources used to formulate different biomaterials for the treatment of antimicrobial, acute, and chronic wound healing processes.

The Polymer-Based Technology in the Endovascular Treatment of Abdominal Aortic Aneurysms

An abdominal aortic aneurysm (AAA) is a dilatation of the abdominal aorta that progressively grows until it ruptures. Treatment is typically recommended when the diameter is more than 5 cm. The EVAR (Endovascular aneurysm repair) is a minimally invasive procedure that involves the placement of an expandable stent graft within the aorta to treat aortic disease without operating directly on the aorta. For years, stent grafts' essential design was based on metallic stent frames to support the fabric. More recently, a polymer-based technology has been proposed as an alternative method to seal AAA. This review underlines the two platforms that are based on a polymer technology: (1) the polymer-filled endobags, also known as Endovascular Aneurysm Sealing (EVAS) with Nellix stent graft; and (2) the O-ring EVAR polymer-based proximal neck sealing device, also known as an Ovation stent graft. Polymer characteristics for this particular aim, clinical applications, and durability results are hereby summarized and commented critically. The technique of inflating endobags filled with polymer to exclude the aneurysmal sac was not successful due to the lack of an adequate proximal fixation. The platform that used polymer to create a circumferential sealing of the aneurysmal neck has proven safe and effective.

Correlation between physicochemical properties of superparamagnetic iron oxide nanoparticles and their reactivity with hydrogen peroxide

The present study focuses on the effects of the physicochemical properties of superparamagnetic PEG-modified, positively charged, and negatively charged iron oxide nanoparticles (SPIONs) on their reactivity with hydrogen peroxide. Our hypothesis was that the reactivity of SPIONs in this reaction would depend on their surface properties. The comparative study of the nanoparticles with DLS and TEM revealed the average sizes of PEG-modified, positively charged, and negatively charged SPIONs. We observed that the reactivity of negatively charged SPIONs with hydrogen peroxide was less than that of positively charged SPIONs and that of these second nanoparticles was less than that of PEG-modified SPIONs. This difference in the reactivity of these SPIONs with hydrogen peroxide was attributed to the presence of carboxyl or amine groups on their surface. However, the values of the rate constants of the reactions of PEG-modified, positively charged, and negatively charged SPIONs with hydrogen peroxide showed that the reaction of negatively charged SPIONs with hydrogen peroxide was more rapid than that of PEG-modified SPIONs and the reaction of these second SPIONs with hydrogen peroxide was more rapid than that of positively charged SPIONs. The surface study of the SPIONs using XPS showed that the high-resolution spectra of these nanoparticles changed after reaction with hydrogen peroxide, which indicates their surface modifications. These investigations can help develop more appropriate nanoparticles with controlled physicochemical properties.

Whey valorization for sustainable polyhydroxyalkanoate production by Bacillus megaterium: Production, characterization and in vitro biocompatibility evaluation

Polyhydroxyalkanoates (PHAs) are biodegradable biopolymers acclaimed as an eco-friendly substitute of hazardously polluting petrochemical plastics. Using industrial by-products as PHA feedstocks could improve its process economics and market implementation. Valorizing the plenteous, nutritive pollutant whey as PHA production feedstock would be an excellent whey management strategy. This study aimed at whole/crude whey valorization for value-added PHA production using B. megaterium Ti3 innate protease, alleviating pretreatments. Response surface methodology (RSM) media optimization ascertained whey (%) as the key influential factor (p < 0.05). The optimized and validated RSM model (R², 0.991; desirability, 1) facilitated 12.2, 11.5 folds increased PHA yield (2.20 ± 0.11 g/L) and productivity (0.05 gPHA/L/h). A positive correlation (r², 0.95 and 0.87) was observed amid the innate enzymes (protease and lipase) and PHA production. The PHA was characterized by ¹H and ¹³C NMR, GPC, TGA, and was identified as poly (3-hydroxybutyrate) (P3HB) by NMR. A significantly reduced roughness (110 ± 5.6 nm); increased hydrophilicity (8.6 ± 0.3 and 8.7 ± 0.5%), protein adsorption (68.75 ± 2.55 μg/cm²) and 1.6 folds higher biocompatibility achieved on poly (ethylene glycol) (PEG) blending compared to neat P3HB films. This is the first report on B. megaterium innate enzyme based whey valorization to PHAs also demonstrating its biomedical applicability.

Biosynthesis of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) in Bacillus aryabhattai and cytotoxicity evaluation of PHBV/poly(ethylene glycol) blends

The study described poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) accumulation in Bacillus aryabhattai PHB10 for the first time and evaluated the polymer induced cytotoxicity in-vitro with PHBV/poly(ethylene glycol) (PEG) blends. The B. aryabhattai strain produced 2.8 g/L PHBV, equivalent to 71.15% of cell dry mass in a medium supplemented with propionic acid, after 48 h incubation. The optimum temperature and pH for the copolymer accumulation was 31 °C and 7, respectively. The gas chromatography-mass spectrometry and nuclear magnetic resonance analyses confirmed the polymer obtained as PHBV. The differential scanning calorimetry analysis revealed that the melting point of the material as 90 °C and its thermal stability up to 220 °C. The average molecular weight (Mn) and polydispersity index of the sample was estimated by gel permeation chromatography analysis and observed as 128.508 kDa and 2.82, respectively. The PHBV showed tensile strength of 10.3 MPa and elongation at break of 13.3%. The PHBV and their blends with PEG were tested for cytotoxicity on human keratinocytes (HaCaT cells) and the cells incubated with PHBV/PEG2kDa blends were 99% viable, whereas with the PHBV alone showed comparatively higher cytotoxicity. The significant improvement in the cell viability of PHBV/PEG2kDa blends indicates its potential as a candidate for skin graft applications.

Dental Implants with Anti-Biofilm Properties: A Pilot Study for Developing a New Sericin-Based Coating

Aim: several strategies have been tested in recent years to prevent bacterial colonization of dental implants. Sericin, one of the two main silk proteins, possesses relevant biological activities and also literature reports about its potential antibacterial properties, but results are discordant and not yet definitive. The aim of this study was to evaluate the effectiveness of different experimental protocols in order to obtain a sericin-based coating on medical grade titanium (Ti) able to reduce microbial adhesion to the dental implant surface. Materials and Methods: different strategies for covalent bonding of sericin to Ti were pursued throughout a multi-step procedure on Ti-6Al-4V disks. The surface of grade 5 Ti was initially immersed in NaOH solution to obtain the exposure of functional -OH groups. Two different silanization strategies were then tested using aminopropyltriethoxysilane (APTES). Eventually, the bonding between silanized Ti-6Al-4V and sericin was obtained with two different crosslinking processes: glutaraldehyde (GLU) or carbodiimide/N-Hydroxy-succinimide (EDC/NHS). Micro-morphological and compositional analyses were performed on the samples at each intermediate step to assess the most effective coating strategy able to optimize the silanization and bioconjugation processes. Microbiological tests on the coated Ti-6Al-4V disks were conducted in vitro using a standard biofilm producer strain of Staphylococcus aureus (ATCC 6538) to quantify the inhibition of microbial biofilm formation (anti-biofilm efficacy) at 24 hours. Results: both silanization techniques resulted in a significant increase of silicon (Si) on the Ti-6Al-4V surfaces etched with NaOH. Differences were found between GLU and EDC/NHS bioconjugation strategies in terms of composition, surface micro-morphology and anti-biofilm efficacy. Ti-6Al-4V samples coated with GLU-bound sericin after silanization obtained via vapor phase deposition proved that this technique is the most convenient and effective coating strategy, resulting in a bacterial inhibition of about 53% in respect to the uncoated Ti-6Al-4V disks. Conclusions: The coating with glutaraldehyde-bound sericin after silanization in the vapor phase showed promising bacterial inhibition values with a significant reduction of S. aureus biofilm. Further studies including higher number of replicates and more peri-implant-relevant microorganisms are needed to evaluate the applicability of this experimental protocol to dental implants.

Recent developments in the synthesis of poly(hydroxybutyrate) based biocomposites

Poly(hydroxybutyrate) (PHB) has become an attractive biomaterial in research and development for past few years. It is natural bio-based aliphatic polyester produced by many types of bacteria. Due to its biodegradable, biocompatible, and eco-friendly nature, PHB can be used in line with bioactive species. However, high production cost, thermal instability, and poor mechanical properties limit its desirable applications. So there is need to incorporate PHB with other materials or biopolymers for the development of some novel PHB based biocomposites for value addition. Many attempts have been employed to incorporate PHB with other biomaterials (or biopolymers) to develop sustainable biocomposites. In this review, some recent developments in the synthesis of PHB based biocomposites and their biomedical, packaging and tissue engineering applications have been focused. The development of biodegradable PHB based biocomposites with improved mechanical properties could be used to overcome its native limitations hence to open new possibilities for industrial applications.

Nanotechnologies in Pancreatic Cancer Therapy

Pancreatic cancer has been classified as a cancer of unmet need. After diagnosis the patient prognosis is dismal with few surviving over 5 years. Treatment regimes are highly patient variable and often the patients are too sick to undergo surgical resection or chemotherapy. These chemotherapies are not effective often because patients are diagnosed at late stages and tumour metastasis has occurred. Nanotechnology can be used in order to formulate potent anticancer agents to improve their physicochemical properties such as poor aqueous solubility or prolong circulation times after administration resulting in improved efficacy. Studies have reported the use of nanotechnologies to improve the efficacy of gemcitabine (the current first line treatment) as well as investigating the potential of using other drug molecules which have previously shown promise but were unable to be utilised due to the inability to administer through appropriate routes-often related to solubility. Of the nanotechnologies reported, many can offer site specific targeting to the site of action as well as a plethora of other multifunctional properties such as image guidance and controlled release. This review focuses on the use of the major nanotechnologies both under pre-clinical development and those which have recently been approved for use in pancreatic cancer therapy.

Preparation and characterization of biodegradable polyhydroxybutyrate-co-hydroxyvalerate/polyethylene glycol-based microspheres

The in vivo effectiveness of biomolecules may be limited by their rapid diffusion in the body and short half-life time. Encapsulation of these biomolecules allows protecting them against degradation and ensuring a controlled release over time. In this work, the production of polyhydroxybutyrate-co-hydroxyvalerate/polyethylene glycol-based microspheres loaded with heparin by double emulsion-solvent evaporation is investigated. Significant improvements are achieved after blending PHB-HV microspheres with PEG. First of all, an important decrease of the initial burst effect is ensured. Moreover, lower degradation of the microspheres is observed after 30days in the release medium. Finally, the release rate could be controlled using different PEG molecular weights and concentrations. A toxic effect of PHB-HV 30% PEG 1100gmol^-1 microspheres is observed whereas PHB-HV and PHB-HV 30% PEG 10,000gmol^-1 microspheres are not toxic. These microspheres seem to be most suited for further tissue engineering applications. The effectiveness of direct PEG blending to PHB-HV is proved, limiting the use of chemical reagents for PHB-HV/PEG copolymer synthesis and steps for chemical reagents removal from the copolymer.

Modification of titanium surfaces by adding antibiotic-loaded PHB spheres and PEG for biomedical applications

Novel researches are focused on the prevention and management of post-operative infections. To avoid this common complication of implant surgery, it is preferable to use new biomaterials with antibacterial properties. Therefore, the aim of this work is to develop a method of combining the antibacterial properties of antibiotic-loaded poly(3-hydroxybutyrate) (PHB) nano- and micro-spheres and poly(ethylene glycol) (PEG) as an antifouling agent, with titanium (Ti), as the base material for implants, in order to obtain surfaces with antibacterial activity. The Ti surfaces were linked to both PHB particles and PEG by a covalent bond. This attachment was carried out by firstly activating the surfaces with either Oxygen plasma or Sodium hydroxide. Further functionalization of the activated surfaces with different alkoxysilanes allows the reaction with PHB particles and PEG. The study confirms that the Ti surfaces achieved the antibacterial properties by combining the antibiotic-loaded PHB spheres, and PEG as an antifouling agent.

Au-nanomaterials as a superior choice for near-infrared photothermal therapy

Photothermal therapy (PPT) is a platform to fight cancer by using multiplexed interactive plasmonic nanomaterials as probes in combination with the excellent therapeutic performance of near-infrared (NIR) light. With recent rapid developments in optics and nanotechnology, plasmonic materials have potential in cancer diagnosis and treatment, but there are some concerns regarding their clinical use. The primary concerns include the design of plasmonic nanomaterials which are taken up by the tissues, perform their function and then clear out from the body. Gold nanoparticles (Au NPs) can be developed in different morphologies and functionalized to assist the photothermal therapy in a way that they have clinical value. This review outlines the diverse Au morphologies, their distinctive characteristics, concerns and limitations to provide an idea of the requirements in the field of NIR-based therapeutics.

Invincible DNA tethers: covalent DNA anchoring for enhanced temporal and force stability in magnetic tweezers experiments

Magnetic tweezers are a powerful single-molecule technique that allows real-time quantitative investigation of biomolecular processes under applied force. High pulling forces exceeding tens of picoNewtons may be required, e.g. to probe the force range of proteins that actively transcribe or package the genome. Frequently, however, the application of such forces decreases the sample lifetime, hindering data acquisition. To provide experimentally viable sample lifetimes in the face of high pulling forces, we have designed a novel anchoring strategy for DNA in magnetic tweezers. Our approach, which exploits covalent functionalization based on heterobifunctional poly(ethylene glycol) crosslinkers, allows us to strongly tether DNA while simultaneously suppressing undesirable non-specific adhesion. A complete force and lifetime characterization of these covalently anchored DNA-tethers demonstrates that, compared to more commonly employed anchoring strategies, they withstand 3-fold higher pulling forces (up to 150 pN) and exhibit up to 200-fold higher lifetimes (exceeding 24 h at a constant force of 150 pN). This advance makes it possible to apply the full range of biologically relevant force scales to biomolecular processes, and its straightforward implementation should extend its reach to a multitude of applications in the field of single-molecule force spectroscopy.

Electrospun polyhydroxybutyrate and poly(L-lactide-co-ε-caprolactone) composites as nanofibrous scaffolds

Electrospinning can produce nanofibrous scaffolds that mimic the architecture of the extracellular matrix and support cell attachment for tissue engineering applications. In this study, fibrous membranes of polyhydroxybutyrate (PHB) with various loadings of poly(L-lactide-co-ε-caprolactone) (PLCL) were successfully prepared by electrospinning. In comparison to PLCL scaffolds, PLCL blends with PHB exhibited more irregular fibre diameter distributions and higher average fibre diameters but there were no significant differences in pore size. PLCL/PHB scaffolds were more hydrophilic (<120°) with significantly reduced tensile strength (ca. 1 MPa) compared to PLCL scaffolds (150.9 ± 2.8° and 5.8 ± 0.5 MPa). Increasing PLCL loading in PHB/PLCL scaffolds significantly increased the extension at break, (4-6-fold). PLCL/PHB scaffolds supported greater adhesion and proliferation of olfactory ensheathing cells (OECs) than those exhibiting asynchronous growth on culture plates. Mitochondrial activity of cells cultivated on the electrospun blended membranes was enhanced compared to those grown on PLCL and PHB scaffolds (212, 179, and 153%, resp.). Analysis showed that PLCL/PHB nanofibrous membranes promoted cell cycle progression and reduced the onset of necrosis. Thus, electrospun PLCL/PHB composites promoted adhesion and proliferation of OECs when compared to their individual PLCL and PHB components suggesting potential in the repair and engineering of nerve tissue.