Bio-Hybrid Hydrogels Incorporated into a System of Salicylic Acid-pH/Thermosensitive Nanocarriers Intended for Cutaneous Wound-Healing Processes.

In this paper, the preparation method of bio-hybrid hydrogels incorporated into a system of salicylic acid-pH/thermosensitive nanocarriers to speed up the wound-healing process was developed. This combination creates a dual drug delivery system, which releases the model hydrophobic active substance-salicylic acid-in a gradual and controlled manner for an extended time. Our research team has determined the various properties of bio-hybrid hydrogels based on their physicochemical (swelling degree, and degradation), structural (FT-IR), morphological (SEM), and mechanical (elongation tests) traits. Moreover, empty pH/thermosensitive nanocarriers and their salicylic acid-containing systems were characterized using the following methods: DLS, TG/DTG, and DSC. Additionally, salicylic acid release profiles directly from thermosensitive nanocarriers were compared to the bio-hybrid matrix. These studies were conducted in PBS (pH = 7.4) for 7 days using the USP4 method. To evaluate the antibacterial properties of the obtained materials, the inhibition of growth of Staphylococcus aureus, Escherichia coli, Candida albicans, and Aspergillus niger-as the main microorganisms responsible for human infections-were tested. The obtained results indicated that the pH/thermosensitive nanocarrier-salicylic acid system and bio-hybrid hydrogels are characterized by antibacterial activity against both S. aureus and E. coli.

The Effect of Glycerin Content in Sodium Alginate/Poly(vinyl alcohol)-Based Hydrogels for Wound Dressing Application.

The impact of different amounts of glycerin, which was used in the system of sodium alginate/poly(vinyl alcohol) (SA/PVA) hydrogel materials on the properties, such as gel fraction, swelling ability, degradation in simulated body fluids, morphological analysis, and elongation tests were presented. The study shows a significant decrease in the gel fraction from 80.5 ± 2.1% to 45.0 ± 1.2% with the increase of glycerin content. The T5 values of the tested hydrogels were varied and range from 88.7 °C to 161.5 °C. The presence of glycerin in the matrices significantly decreased the thermal resistance, which was especially visible by T10 changes (273.9 to 163.5 °C). The degradation tests indicate that most of the tested materials do not degrade throughout the incubation period and maintain a constant ion level after 7-day incubation. The swelling abilities in distilled water and phosphate buffer solution are approximately 200-300%. However, we noticed that these values decrease with the increase in glycerin content. All tested matrices are characterized by the maximum elongation rate at break in a range of 37.6-69.5%. The FT-IR analysis exhibits glycerin changes in hydrogel structures, which is associated with the cross-linking reaction. Additionally, cytotoxicity results indicate good adhesion properties and no toxicity towards normal human dermal fibroblasts.

Investigation on Green Synthesis, Biocompatibility, and Antibacterial Activity of Silver Nanoparticles Prepared Using Cistus incanus.

This paper describes the plant-mediated preparation of silver nanoparticles with aqueous extract and infusion of Cistus incanus leaves. To evaluate aqueous extract and infusion antioxidant capacity and total phenolic content the DPPH and Folin-Ciocalteau methods were utilized. The antioxidant capacity and total phenolic content of extract and infusion were equal to 85.97 ± 6.54 mg gallic acid equivalents per gram of dry weight.; 10.76 ± 0.59 mg/mL and 12.65 ± 1.04 mg gallic acid equivalents per gram of dry weight.; 3.10 ± 0.14 mg/mL, respectively. The formed nanoparticles displayed the characteristic absorption band in the 380-450 nm wavelength range. The average size of particles was in the 68.8-71.2 nm range. Morphology and phase composition analysis revealed the formation of spherical nanoparticles with a face-centred cubic structure. Immune compatibility tests of nanoparticles and plant extracts showed no activation of the THP1-XBlue™ monocyte. Cytotoxicity tests performed with L929 mice fibroblasts showed that nanoparticles should be utilized at a concentration of 16 ppm. The minimum inhibitory concentrations determined with the microdilution method for nanoparticles prepared with plant infusion for S. aureus and S. epidermidis were 2 ppm and 16 ppm, respectively.

Impact of the Type of Crosslinking Agents on the Properties of Modified Sodium Alginate/Poly(vinyl Alcohol) Hydrogels.

Here, we report on studies on the influence of different crosslinking methods (ionic and chemical) on the physicochemical (swelling ability and degradation in simulated body fluids), structural (FT-IR spectra analysis) and morphological (SEM analysis) properties of SA/PVA hydrogels containing active substances of natural origin. First, an aqueous extract of Echinacea purpurea was prepared using a Soxhlet apparatus. Next, a series of modified SA/PVA-based hydrogels were obtained through the chemical crosslinking method using poly(ethylene glycol) diacrylate (PEGDA, Mn = 700 g/mol) as a crosslinking agent and, additionally, the ionic reaction in the presence of a 5% w/v calcium chloride solution. The compositions of SA/PVA/E. purpurea-based hydrogels contained a polymer of natural origin-sodium alginate (SA, 1.5% solution)-and a synthetic polymer-poly(vinyl alcohol) (PVA, Mn = 72,000 g/mol, 10% solution)-in the ratio 2:1, and different amounts of the aqueous extract of E. purpurea-5, 10, 15 or 20% (v/v). Additionally, the release behavior of echinacoside from the polymeric matrix was evaluated in phosphate-buffered saline (PBS) at 37 °C. The results indicate that the type of the crosslinking method has a direct impact on the release profile. Consequently, it is possible to design a system that delivers an active substance in a way that depends on the application.

Advanced SA/PVA-based hydrogel matrices with prolonged release of Aloe vera as promising wound dressings.

This work focuses on the influence of different amounts (5, 10, 15, 20 and 25%, v/v) of solution of Aloe vera on the chemical structure and properties of sodium alginate/poly(vinyl alcohol) hydrogel films. The polymeric matrix was prepared following the chemical cross-linking method using poly(ethylene glycol) diacrylate (PEGDA, Mn = 700 g/mol) as a cross-linking agent. First, the gel fractions of the modified hydrogels were determined and their swelling behavior in distilled water and phosphate-buffered saline (PBS) was tested. Subsequently, the following properties of the modified hydrogel materials were studied: structural (FT-IR spectra analysis), morphological (SEM analysis) and mechanical (tensile strength, elongation at break and hardness). Moreover, a thermal analysis (TG/DTG and DSC) confirmed that the SA/PVA hydrogels containing Aloe vera exhibited slightly higher thermal stability than the unmodified hydrogels, which allows concluding that a rigid and thermally stable three-dimensional structure had been obtained. Additionally, the release profile of polysaccharides from the hydrogel matrix was evaluated in PBS at 37 °C. The results show that the active substance was released in a prolonged manner, gradually, even for a week. It was found that the presence of Aloe vera inside the cross-linked polymeric network improved the active substance delivery properties of the hydrogel films. When greater amounts of Aloe vera were applied, the hydrogel had an irregular surface structure, as revealed by SEM images. The chemical structure was confirmed on the basis of an FT-IR spectral analysis. Concluding, SA/PVA/Aloe vera matrices are promising compounds and deserve further studies towards application in interactive wound dressings. Additionally, the cytotoxicity of the materials was studied and the results indicated good adhesion properties and no toxicity. In vitro experiments performed on normal human dermal fibroblasts proved excellent cell attachment on the Aloe vera hydrogel discs, which promoted cells spreading and proliferation.

Assessment of cytotoxicity and immune compatibility of phytochemicals-mediated biosynthesised silver nanoparticles using Cynara scolymus.

The study was focused on the phytochemicals-mediated biosynthesis of silver nanoparticles using leaf extracts and infusions from Cynara scolymus. To identify the antioxidant activity and total phenolic content, the 1,1-diphenyl-1-picrylhydrazyl and Folin-Ciocalteau methods were applied, respectively. The formation and stability of the reduced silver ions were monitored by UV-vis spectrophotometer. The particle sizes of the silver nanoparticles were characterised using the dynamic light scattering technique and scanning electron microscope. The phase composition of the obtained silver nanoparticles was characterised by X-ray diffraction. The silver nanoparticles suspension, artichoke infusion, and silver ions were separately tested towards potential cytotoxicity and pro-inflammatory effect using mouse fibroblasts and human monocytes cell line, respectively. The total phenolic content and antioxidant activity of ethanol extract and infusion were found significantly higher as compared to aqueous extract and infusion. The UV-visible spectrophotometric analysis revealed the presence of the characteristic absorption band of the Ag nanoparticles. Moreover, it was found that with the increasing volume of plant extract, the average size of particles was increased. Biocompatibility results evidently showed that silver nanoparticles do not induce monocyte activation, however in order to avoid their cytotoxicity suspension at a concentration <2 ppm should be applied.

Eco-friendly approach to the synthesis of silver nanoparticles and their antibacterial activity against Staphylococcus spp. and Escherichia coli.

The aim of this study was to assess bactericidal properties of nanosilver obtained with ascorbic acid (vitamin C) as a reducing substance, against environmental strains of Gram-positive (Staphylococcus) and Gram-negative bacteria (Escherichia coli). Silver nanoparticles were obtained by a simple and fast method of chemical reduction in mild synthesis condition using substrates not classified as dangerous and commonly found in plants. Bacterial susceptibility to nanosilver was determined using the disk-diffusion method. Gram-positive bacteria were less susceptible to bactericidal action of nanosilver and minimum inhibitory concentration was higher for these bacteria. However, susceptibility of individual isolates of different species to nanosilver was very diverse. The range of growth inhibition zones indicates that the resistance to different concentrations of nanosilver was a strain-characteristic, not species-related feature. The study of effective nanomaterials synthesis and applicability appears to be an extremely important element in the development of nanotechnology, especially in terms of the risks assessment. Obtained results have a real chance to be an important step toward creating a new generation of disinfectants without toxic effects on the environment and higher organisms.

Bioactivity tests of calcium phosphates with variant molar ratios of main components.

Calcium phosphates constitute attractive materials of biomedical applications. Among them particular attention is devoted to bioactive hydroxyapatite (HAp) and bioresorbable tricalcium phosphate (TCP) that possess ability to bind to living bones and can be used clinically as important bone substitutes. Notably, in vivo bone bioactivity can be predicted from apatite formation of bone immersed in SBF fluids. Thus, analyses of behavior of calcium phosphates immersed in various bio fluids are of great importance. Recently, stoichiometric HAp and TCP structures have been widely studied, whereas only limited number of publications have been devoted to analyses of nonstoichiometric calcium phosphates. Here, we report physicochemical analysis of natural and synthetic phosphates with variable Ca/P molar ratios. Subsequently attained structures were subjected to incubation in either artificial saliva or Ringer's fluids. Both pH and conductivity of such fluids were determined before and after incubation. Furthermore, the influence of the Ca/P values on such parameters was exemplified. Physicochemical analysis of received materials was performed by XRD and FT-IR characterization techniques. Their potential antibacterial activity and behavior in the presence of infectious microorganisms as Escherichia coli and Staphylococcus aureus was also evaluated. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 1941-1950, 2018.

Silver nanoparticles toxicity against airborne strains of Staphylococcus spp.

The aim of this study was to explore the toxicity of silver nanoparticles (AgNPs) synthesized by chemical reduction method assessment with regard to airborne strains of Staphylococcus spp. The first step of the experiment was the preparation of silver nanoparticle suspension. The suspension was obtained by a fast and simple chemical method involving the reduction of silver ions through a reducing factor in the presence of the suitable stabilizer required to prevent the aggregation. In the second stage, varied instrumental techniques were used for the analysis and characterization of the obtained nanostructures. Third, the bacteria of the Staphylococcus genus were isolated from the air under stable conditions with 47 sports and recreational horses, relatively. Next, isolated strains were identified using biochemical and spectrophotometric methods. The final step was the evaluation of the Staphylococcus genus sensitivity to nanosilver using the disk diffusion test. It has been proven that prepared silver nanoparticles exhibit strong antibacterial properties. The minimum inhibitory concentration for tested isolates was 30 µg/mL. It has been found that the sensitivity of Staphylococcus spp. isolated from six identified species differs considerably. The size distribution of bacterial growth inhibition zones indicates that resistance to various nanosilver concentrations is an individual strain feature, and has no connection with belonging to a specific species.

Magnetic nanomaterials and sensors for biological detection.

It is becoming progressively more understandable that sensitivity and versatility of magnetic biosensors provides unique platform for high performance diagnostics in clinical settings. Confluence of information suggested that magnetic biosensors required well-tailored magnetic particles as probes for detection that generate large and specific biological signal with minimum possible nonspecific binding. However, there are visible knowledge gaps in our understanding of the strategies to overcome existing challenges related to even smaller size of intracellular targets and lower signal-to-noise ratio than that in whole-cell studies, therefore tool designing and development for intracellular measurement and manipulation is problematic. In this review we describe magnetic nanoparticles, synthesis and sensing principles of magnetic nanoparticles as well as surface functionalization and modification and finally magnetic nanoparticles for medical diagnostics. This review gathers important and up-to-date information and may help to develop the method of obtaining magnetic materials especially for medical application.

Kraft lignin/silica-AgNPs as a functional material with antibacterial activity.

Advanced functional silica/lignin hybrid materials, modified with nanosilver, were obtained. The commercial silica Syloid 244 was used, modified with N-(2-aminoethyl)-3-aminopropyltrimethoxysilane to increase its chemical affinity to lignin. Similarly, kraft lignin was oxidized using a solution of sodium periodate to activate appropriate functional groups on its surface. Silver nanoparticles were grafted onto the resulting silica/lignin hybrids. The systems obtained were comprehensively tested using available techniques and methods, including transmission electron microscopy, Fourier transform infrared spectroscopy, energy-dispersive X-ray spectroscopy, elemental analysis and atomic absorption spectroscopy. An evaluation was also made of the electrokinetic stability of the systems with and without silver nanoparticles. Conclusions were drawn concerning the chemical nature of the bonds between the precursors and the effectiveness of the method of binding nanosilver to the hybrid materials. The antimicrobial activity of the studied materials was tested against five species of Gram-positive and Gram-negative bacteria. The addition of silver nanoparticles to the silica/lignin hybrids led to inhibition of the growth of the analyzed bacteria. The best results were obtained against Pseudomonas aeruginosa, a dangerous human pathogen.

Studies on sintering process of synthetic hydroxyapatite.

In this study the effect of sintering process in different temperatures on microstructure and morphological properties of sintered hydroxyapatite (HAp) was investigated. HAp powder was prepared by wet precipitation method from following reagents: Ca(OH)2 + H3PO4 in an alkaline conditions. Thermal analysis (TA), X-Ray diffraction method (XRD), FT-IR spectrometry (FT-IR) and scanning electron microscopy (SEM) were used to elaborate the phase composition and properties of sintered HAp samples and raw HAp powder as well. The total and apparent density and total porosity of sintered compacts, shrinkage and weight loss during the sintering were also measured. The results show that there is a difference in sintering behavior of synthetic hydroxyapatites depending on sintering temperature. The main differences refer to the loss of mass, shrinkage, changes in porosity and density of the investigated materials.

Physicochemical and biological properties of hydrogel/gelatin/hydroxyapatite PAA/G/HAp/AgNPs composites modified with silver nanoparticles.

Composites comprising biodegradable polymer matrix, bioactive ceramic fillers and metallic nanoparticles can be applied in the substitution of bone tissue and many others medical and dental applications. Recently, fully resorbable composite materials applicable as bone substitutes are the subject of intensive studies in surgical reconstruction and bone tissue engineering. Biological composites, such as bone and teeth, contain hydroxyapatite (HAp), a mineral component with composition Ca10(PO4)6(OH)2. Silver nanoparticles or silver ions have long been known to have strong inhibitory and bactericidal effects as well as a broad spectrum of antimicrobial activities. In this study we applied natural origin hydroxyapatite obtained from pork bone sludge. As polymer matrix gelatin and poly(acrylic acid) were used. Composite materials were obtained with the use of microwave irradiation. The influence of metallic nanoparticles presence on the degradation process of composite materials was investigated by pH and conductivity analyses of water filtrates. In vitro tests in simulated body fluid (SBF) and artificial saliva confirmed that it is possible to produce hydroxyapatite/polymer composites doped with silver nanoparticles for medical applications. Tests proved that content of silver nanoparticles in composites had influence on degradation behaviour of HA/Polymer/AgNPs in artificial media such as simulated body fluid and saliva.