Simulated Physiological Fluids Research Articles

Physicochemical properties and biological activities of new berberine-based salts with syringic acid as well as 3,5-dimethoxybenzoic acid as anions: Effect of temperature, concentration and anion

Two novel berberine-based salts (berberine syringate ([BBR][SA]) and berberine 3,5-dimethoxybenzote ([BBR][DA])) were prepared and characterized. Their thermal stability, solubility and octanol–water partition coefficient in aqueous solution and simulated physiological fluids (simulated gastric, simulated body, simulated intestinal fluids) were determined. Self-aggregation and association behaviors of two salts in aqueous solution have been investigated by conductimetric method at different temperatures and limiting molar conductivity, critical aggregation concentration, etc for [BBR][SA] and [BBR][DA] were calculated. The minimum inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) values of two salts were assessed to evaluate their antibacterial effects on four strains (Staphylococcus aureus, Bacillus subtilis, Candida albicans, and Streptococcus mutans). The effect of two synthetic salts on the esterase-like activity of BSA and their cytotoxicity evaluation against B16-F10 cancer cell line were also carried out. The obtained results were evaluated with regard to the influence of such parameters as temperature, concentration and the nature of the anion.

Improvement in corrosion resistance of AZ91D Mg alloy in simulated body fluid by cerium-based/stearic acid composite coatings

Magnesium alloys have attracted attention due to their biocompatibility and biodegradability. In this work, composite coatings are developed to potentially improve the corrosion resistance of AZ91D Mg alloy in simulated physiological fluid. Cerium-based/stearic acid coatings were prepared by electrodeposition combined with a simple immersion method. The effect of stearic acid bath concentration on the contact angle and corrosion resistance of the composite coatings was evaluated. The results showed that the stearic acid treatment increased the hydrophobicity of the surfaces of the cerium-based simple coatings. The use of an appropriate stearic acid concentration is a key for the fabrication of hydrophobic surfaces. The duplex coatings were demonstrated to protect the substrate from corrosion in Ringer solution.

Synthesis and characterization of chitosan/polyvinylpyrrolidone hydrogels for controlled amoxicillin release

Hybrid crosslinked hydrogel-based drug delivery systems can deliver therapeutically beneficial drug release effects through controlled release on a temporal and spatial scale. Due to their tuneable physicochemical properties and the ability to prevent drug degradation, these systems facilitate different physicochemical interactions that control drug release. This research aims to synthesize a potent pH-sensitive crosslinked chitosan/polyvinylpyrrolidone hydrogel using different ratios of both the polymers and varying the glutaraldehyde crosslinking agent amount by the solution casting technique for controlled amoxicillin-release properties to mitigate gastrointestinal tract bacterial infection. The effect of polymer ratios and glutaraldehyde amount is investigated by the developing porosity, gel fraction, and extent of swelling in simulated physiological fluids of pH 1.2, 6.8, and 7.4 and in vitro biodegradation at pH 7.4. Interaction between the polymers with the formation of crosslinked structures, good stability, amorphous phase nature, and honeycomb-like structures of the hydrogels is revealed by Fourier-transform infrared spectroscopy, thermogravimetric analysis, X-ray diffraction, and scanning electron microscopy. Based on these properties, a chitosan/polyvinylpyrrolidone hydrogel (ratio of 60:40) crosslinked with 600 μL glutaraldehyde in 8 g of the polymers displaying adequate swelling in acidic to basic pH and in vitro biodegradation at pH 7.4 is chosen for the in situ loading of 200 mg of the drug amoxicillin. The cumulative drug release in simulated physiological fluids and the drug release kinetics using different models show that the best-fit Korsmeyer-Peppas model suggests amoxicillin release from the matrix follows diffusion and swelling-controlled time-dependent non-Fickian transport related to hydrogel erosion. This composition displays excellent antimicrobial activity against Streptococcus pyogenes and Escherichia coli.

Development of double crosslinked sodium alginate/chitosan based hydrogels for controlled release of metronidazole and its antibacterial activity

Double network sodium alginate/chitosan hydrogels were prepared using calcium chloride (CaCl2) and glutaraldehyde as the crosslinking agents by the ionotropic interaction method for controlled metronidazole release. The effect of polymer ratios and CaCl2 amount is investigated by the developing porosity, gel fraction, and extent of swelling in simulated physiological fluids. Interaction between the polymers with the formation of crosslinked structures, good stability, phase nature, and morphology of the hydrogels is revealed by Fourier-transform infrared spectroscopy, thermogravimetric analysis, X-ray diffraction, and scanning electron microscopy. A sodium alginate/chitosan hydrogel (weight ratio of 75:25) crosslinked with two percent CaCl2 is chosen for the in-situ loading of 200 mg of metronidazole. The drug release kinetics using different models show that the best-fit Korsmeyer-Peppas model suggests metronidazole release from the matrix follows diffusion and swelling-controlled time-dependent non-Fickian transport related to hydrogel erosion. This composition displays enhanced antimicrobial activity against Staphylococcus aureus and Escherichia coli.

Fabrication of pH‐sensitive double cross‐linked sodium alginate/chitosan hydrogels for controlled release of amoxicillin

AbstractThis research aims to fabricate a potent pH‐sensitive double network sodium alginate/chitosan hydrogel cross‐linked by calcium chloride (CaCl2) and glutaraldehyde for the controlled release of amoxicillin (AMX) to mitigate gastrointestinal tract bacterial infection. The effect of polymer ratios and CaCl2 concentration is investigated by the developing porosity, gel fraction, and swelling ratios in simulated physiological fluids of different pH and in vitro biodegradation at pH 7.4. Interaction between the polymers with the formation of cross‐linked structures, amorphous phase nature, good thermal stability, and transition from porous, fibrous structures to highly densified structures of the hydrogels is revealed by scanning electron microscopy, Fourier‐transform infrared spectroscopy, x‐ray diffraction, and thermogravimetric analysis. Based on structure–property relationships, a sodium alginate/chitosan hydrogel (weight ratio 75:25) cross‐linked with 2% CaCl2 and soaked in 2% (25 wt/v% solutions) glutaraldehyde is chosen for the incorporation of 200 mg of the drug. The percent cumulative AMX release in physiological fluids and the drug release kinetics using different models reveal that the most appropriate Korsmeyer–Peppas model suggests AMX release from the matrix follows diffusion coupled with swelling‐regulated time‐dependent non‐Fickian transport process related to hydrogel erosion. Excellent antibacterial against Streptococcus pyogenes and Escherichia coli is exhibited by this composition.

Artificial Organelles with Digesting Characteristics: Imitating Simplified Lysosome- and Macrophage-Like Functions by Trypsin-Loaded Polymersomes.

Defects in cellular protein/enzyme encoding or even in organelles are responsible for many diseases. For instance, dysfunctional lysosome or macrophage activity results in the unwanted accumulation of biomolecules and pathogens implicated in autoimmune, neurodegenerative, and metabolic disorders. Enzyme replacement therapy (ERT) is a medical treatment that replaces an enzyme that is deficient or absent in the body but suffers from short lifetime of the enzymes. Here, this work proposes the fabrication of two different pH-responsive and crosslinked trypsin-loaded polymersomes as protecting enzyme carriers mimicking artificial organelles (AOs). They allow the enzymatic degradation of biomolecules to mimic simplified lysosomal function at acidic pH and macrophage functions at physiological pH. For optimal working of digesting AOs in different environments, pH and salt composition are considered the key parameters, since they define the permeability of the membrane of the polymersomes and the access of model pathogens to the loaded trypsin. Thus, this work demonstrates environmentally controlled biomolecule digestion by trypsin-loaded polymersomes also under simulated physiological fluids, allowing a prolonged therapeutic window due to protection of the enzyme in the AOs. This enables the application of AOs in the fields of biomimetic therapeutics, specifically in ERT for dysfunctional lysosomal diseases.

Fabrication of pH-Responsive Chitosan/Polyvinylpyrrolidone Hydrogels for Controlled Release of Metronidazole and Antibacterial Properties

This research focused on preparing hydrogels with controlled drug release properties to control gastrointestinal tract bacterial infection. Chitosan (CS) and polyvinylpyrrolidone (PVP) were used as the base polymers, with the CS component crosslinked by glutaraldehyde for hydrogel preparation using the solution casting technique. The effect of varying glutaraldehyde content in the hydrogels was characterized by the extent of swelling in simulated physiological fluids of pH 1.2, 6.8, and 7.4; the development of porosity; and gel fraction. Functional groups and covalent and hydrogen bonds formed, thermal stability, phase structure, and morphology were characterized by Fourier-transform infrared spectroscopy, thermogravimetric analysis, X-ray diffraction, and scanning electron microscopy. The results show that the components in the hydrogels have good compatibility and formed honeycomb-like structures. In vitro studies confirmed that the hydrogels have good biodegradability at pH 7.4. Based on these properties, a CS/PVP hydrogel of the ratio of 60 : 40 crosslinked with 600 μL glutaraldehyde was selected for the in-situ loading of 200 mg of the drug metronidazole (MTZ). The hydrogel was characterized for cumulative drug release in the simulated physiological fluids and drug release kinetics using different models and for its antibacterial activity. The best-fit Korsmeyer–Peppas model suggests that MTZ release followed diffusion and swelling-controlled time-dependent non-Fickian transport related to hydrogel erosion. This hydrogel displays enhanced antimicrobial activity against Staphylococcus aureus, and Escherichia coli showed substantial inhibition zones indicating the produced CS/PVP hydrogels are promising candidates for controlled drug release applications.

Synthesis and Characterization of Sol–Gel‐Derived SiO2–CaO Particles: Size Impact on Glass (Bio)Properties

AbstractFour highly bioactive glasses in a binary SiO2–CaO system are prepared following a sol−gel method using Ca(OH)2 as a calcium precursor. In the synthesis of glass according to the modified Stöber method, Ca(OH)2 suspended in polyethylene glycol allows the elimination of the presence of calcite and the increase of ammonia concentration causes formation of spherical particles with different sizes in the range of 26–266 nm. The relation among the size and properties, including bioactivity, of the glass particles is evaluated. New glasses that vary in composition (10–25 wt% CaO), porosity (15–113 m2 g−1), and hydroxyl groups content greatly enhance the formation process of hydroxyapatite (HA) in simulated physiological fluids. For all glasses, superior apatite‐mineralization ability in time as short as 2 h in the physiological‐like buffer is achieved, thus exceeding the bioactivity of the known bioactive glasses, including 45S5 glass (Bioglass). The assessment of the safety and toxicity profile of the obtained glasses is verified in a wide range of concentrations (1–1000 µg mL−1) against human dermal fibroblasts and MC3T3 mouse osteoblast precursors, but also to human erythrocytes by determining hemocompatibility. Two glasses of different sizes, 73 and 266 nm, are promising and warrant further research.

Graphene Nanoplatelets-Based Textured Polymeric Fibrous Fabrics for the Next-Generation Devices.

Graphene is a 2D crystal composed of carbon atoms in a hexagonal arrangement. From their isolation, graphene nanoplatelets (nCD) have revolutionized material science due to their unique properties, and, nowadays, there are countless applications, including drug delivery, biosensors, energy storage, and tissue engineering. Within this work, nCD were combined with PLA, a widely used and clinically relevant thermoplastic polymer, to produce advanced composite texturized electrospun fabric for the next-generation devices. The electrospinning manufacturing process was set-up by virtue of a proper characterization of the composite raw material and its solution. From the morphological point of view, the nCD addition permitted the reduction of the fiber diameter while the texture allowed more aligned fibers. After that, mechanical features of fabrics were tested at RT and upon heating (40 °C, 69 °C), showing the reinforcement action of nCD mainly in the texturized mats at 40 °C. Finally, mats' degradation in simulated physiological fluid was minimal up to 30 d, even if composite mats revealed excellent fluid-handling capability. Moreover, no toxic impurities and degradation products were pointed out during the incubation. This work gains insight on the effects of the combination of composite carbon-based material and texturized fibers to reach highly performing fabrics.

Muco-adhesion Evaluation of Polysaccharides in Simulated Physiological Fluids

Gellan gum is a microbial exopolysaccharide, water-soluble polymers secreted by microorganisms during fermentation. The biopolymer gellan gum is a relatively recent addition to the family of microbial polysaccharides that is gaining much importance in food, pharmaceutical and chemical industries due to its novel properties. The purpose of this work is to investigate the impact of physiological fluids on both the physical and chemical properties of gellan gum, and to understand the role of polymers gel in muco-adhesion and drug delivery to prolong the residence time of the drug inside the body. Muco-adhesion measurements of retention time were performed using bespoke retention apparatus to determine the retention of labelled gellan gum dose. The physiological fluids used in this work are artificial gastric juice, artificial saliva fluid, and artificial tears fluid. Results of this work show that in general the viscosity of gellan increased with high concentration and the gel formation is strong with artificial gastric juice (HCL) and weak gel formation with artificial saliva and tears but the retention time is longer with saliva and tears than with artificial gastric juice.

Bioactive nanoglasses and xerogels (SiO2–CaO and SiO2–CaO–P2O5) as promising candidates for biomedical applications

A binary and ternary system of highly bioactive nanoparticles of xerogel (88SiO2–12CaO (wt.%), solvXG88, 78SiO2–16CaO–6P2O5, solvXG78P6) and glass (69SiO2–25CaO–6P2O5, solvBG69P6) were prepared following an unconventional solvothermal path of the synthesis. These nanosized (<50 nm), non-spherical in shape and mesoporous materials with different compositions greatly enhanced the formation process of hydroxyapatite (HA) in simulated physiological fluids compared to reference 45S5 glass, commonly used in orthopedics and dentistry. The deposition of a HA layer on the glasses was analyzed by various techniques, namely XRD, IR-ATR, 31P CP-MAS NMR, EDS analyses, SEM, and HR-TEM imaging. For both types of nanoparticles (glass and obtained at lower temperature xerogels) superior apatite-mineralization ability in time as short as 4 h in the physiological-like buffer was achieved thus, exceeded the bioactivity of the 45S5 glass. This unique bioactivity was complemented by biocompatibility with human dermal fibroblasts and MC3T3 mouse osteoblast precursors, verified in a wide range of concentrations, as well as hemocompatibility studies. The most promising candidate which can compete with clinically used Bioglass is solvXG78P6.

PH‐sensitive folic acid/poly(vinyl pyrrolidone) functionalized MnFe2O4/single‐walled carbon nanotubes for release of a natural anticancer agent: Chlorogenic acid

AbstractDespite promising features of chlorogenic acid (CGA) as an antioxidant and anticancer agent, short pharmacological half‐life constrains its application in cancer treatment. This work was aimed at developing a new nanocarrier with pH‐sensitive release behavior for CGA. In this direction, a porous nanohybrid, poly(vinyl pyrrolidone)/MnFe2O4/single‐walled carbon nanotube–folic acid (PVP/MnFe2O4/SWCNT–FA) was prepared by in situ coprecipitation of manganese and iron salts in the oxidized SWCNT suspension, followed by wrapping of PVP and then conjugating of FA on the magnetic SWCNTs. Afterward, the nanohybrid was loaded with CGA to form a carrier. The PVP/MnFe2O4/SWCNT–FA was characterized using Fourier transform infrared spectra, X‐ray diffraction, FE‐SEM/energy dispersive X‐Ray analysis spectroscope, TGA, and BET, confirming a well‐defined porous structure consisting of numerous functional groups. The CGA loading was carried out through the adsorption process. Adsorption equilibrium was reached within 60 min at pH 5.0. The experimental adsorption data showed an excellent nonlinear correlation coefficient with the simplified Elovich kinetic model and two‐step isotherm model. The CGA release was studied in simulated normal physiological fluid (pH 7.4) and simulated acidic tumor fluid (pH 5.6) over 6 h. The release rate from CGA loaded PVP/MnFe2O4/SWCNT–FA achieved 79.5% at pH 5.6, which was much higher than at pH 7.4 (37.2%), reflecting the acidic medium could markedly improve drug release. In addition, the Peppas–Sahlin model was more appropriate than the Higuchi and Korsmeyer–Peppas models to describe CGA release kinetics from the nanocarrier. In vitro cell viability studies indicated that PVP/MnFe2O4–SWCNT–FA had better biocompatibility in comparison with SWCNTs. Our findings indicate that the designed magnetic nanocarrier has acceptable performance to be used as a pH‐sensitive drug system with low toxicity for targeted drug delivery applications.

Inhalable Formulation Based on Lipid-Polymer Hybrid Nanoparticles for the Macrophage Targeted Delivery of Roflumilast.

Here, novel lipid–polymer hybrid nanoparticles (LPHNPs), targeted to lung macrophages, were realized as potential carriers for Roflumilast administration in the management of chronic obstructive pulmonary disease (COPD). To achieve this, Roflumilast-loaded fluorescent polymeric nanoparticles, based on a polyaspartamide-polycaprolactone graft copolymer, and lipid vesicles, made from 1,2-dipalmitoyl-sn-glycero-3-phosphocholine and 1,2-distearoyl-sn-glycero-phosphoethanolamine-N-(polyethylene glycol)-mannose, were properly combined using a two-step method, successfully obtaining Roflumilast-loaded hybrid fluorescent nanoparticles (Man-LPHFNPs@Roflumilast). These exhibit colloidal size and a negative ζ potential, 50 wt % phospholipids, and a core–shell-type morphology; they slowly release the entrapped drug in a simulated physiological fluid. The surface analysis also demonstrated their high surface PEG density, which confers mucus-penetrating properties. Man-LPHFNPs@Roflumilast show high cytocompatibility toward human bronchial epithelium cells and macrophages and are uptaken by the latter through an active mannose-mediated targeting process. To achieve an inhalable formulation, the nano-into-micro strategy was applied, encapsulating Man-LPHFNPs@Roflumilast in poly(vinyl alcohol)/leucine-based microparticles by spray-drying.

Assessing Mg/Si3N4 biodegradable nanocomposites for osteosynthesis implants with a focus on microstructural, mechanical, in vitro corrosion and bioactivity aspects

Magnesium-based biodegradable implant materials for the osteosynthesis process (fixation or stabilizing of a fractured bone) are on the verge of being used clinically. However, the rapid degradation of magnesium-based materials in the physiological environment results in a loss of mechanical integrity before the complete healing of the fracture site. To address this issue, the present study used Silicon Nitride (Si3N4) nanoparticles to improve the in-vitro degradation resistance along with the mechanical strength and ductility of Magnesium. The Si3N4 nanoparticles were homogeneously reinforced in the pure Magnesium matrix through the ultrasonic-assisted stir casting method. Moreover, the effect of Si3N4 nanoparticles on microstructure, mechanical, in-vitro corrosion and bioactivity response of Mg/Si3N4 nanocomposites was studied. Notably, the inclusion of 1.0 vol% Si3N4 nanoparticles increased tensile strength by 1.4 times and ductility by two times. In addition, the elastic modulus of Mg/Si3N4 nanocomposites is within the range of local cortical bone elastic modulus. In-vitro immersion experiments in simulated physiological fluids revealed a 2.2-fold reduction in degradation rate compared to pure Magnesium. Moreover, the addition of Si3N4 nanoparticles enhanced the in-vitro bioactivity, as the surface of the nanocomposites showed a high needle-like Ca–P apatite layer with a 1.41 Ca/P ratio of the deposited layer close to hydroxyapatite's Ca/P ratio (1.64). Overall, this study provides the basis for the fabrication of stable yet completely biodegradable Mg/Si3N4 nanocomposite bone implants for the osteosynthesis process.

Effects of microalloying on the microstructure, tribological and electrochemical properties of novel Ti-Mo based biomedical alloys in simulated physiological solution

ABSTRACT The tribological characteristics of Ti alloys containing beta stabilisers such as Mo, Nb, Ta, Zr, and Sn have seldom been explored despite their applicability for metallic biomaterials requiring good wear and surface degradation resistance. Using sliding wear contact, the influence of these alloying components on Ti-Mo biomedical alloys in simulated physiological fluid was examined. Microalloying influences microstructure, hardness, and wear. Nb-microalloyed samples with metastable -phase increased anti-wear and frictional resistance while keeping frictional resistance. Orthorhombic α′′phase-rich samples were the least wear resistance. The findings contribute to a better understanding of the interaction between Ti-based biomaterials' micro-alloying and their tribological properties. The stabilised TiMo (Nb,Ta, Zr, or Sn) alloys outperformed CP-Ti, the original Ti92Mo8, and the regularly used biomedical Ti6Al-4V alloys in terms of corrosion resistance. This indicates that alloying tuning may be used to enhance biomedical prosthesis and increase the service life of bio-implants and components.

Rapid response electrowetting on dielectric of Ag-ZnO@STA nanocomposite coatings with antibacterial properties and the application for diabetes detection

Electrowetting on dielectric (EWOD) has been developed dynamic blood glucose detection in many special areas of life. However, there are still disadvantages such as slow responsiveness, low sensitivity and poor reproducibility, even no bactericidal function. Herein, the superhydrophobic Ag-ZnO@STA/Zn composite device has been prepared by simple sol-gel and spin-coating techniques, in which Ag@STA nanoparticles are embedded into the interspaces of flower-like ZnO@STA nanosheets and formed the micro-nano hierarchical structure with large surface roughness. The EWOD performance of Ag-ZnO@STA/Zn device is optimized to achieve large contact angle (CA) modulation of 100° and superlow threshold voltage less than 1 V, which completely ensure the success application for the diabetes detection. The CA under voltage is used as a strategy for sensor response, the simulated physiological fluids are used as test liquid in EWOD, the prepared Ag-ZnO@STA/Zn device is endowed with high sensitivity detection ability to glucose with low concentration. More importantly, as the diabetes sensor, the Ag-ZnO@STA/Zn device has excellent anti-corrosion and bactericidal functions.

Electrochemical behavior of open-cellular structured Ti-6Al-4V alloy fabricated by electron beam melting in simulated physiological fluid: the significance of pore characteristics

The cellular structured titanium alloys have attracted significant attention for implants because of their lower Youngʼs modulus, which is comparable to human bone and has the capability of providing space for bone tissue in-growth. However, there is a gap in the knowledge in regard to the relationship between the pore characteristics and the electrochemical performance of open-cellular structured titanium alloys. In this study, we elucidate the influence of pore characteristics on the electrochemical performance of open-cellular structured Ti-6Al-4V alloys produced by electron beam melting (EBM). Intriguingly, the passive film formed on cellular structured Ti-6Al-4V alloy with a larger pore size was more stable and protective, and the corrosion performance was superior compared to the samples with a smaller pore size in phosphate buffered saline (PBS), mainly because of relatively smaller exposed surface area and unlimited flow of electrolyte. However, in acidic PBS containing fluoride ions, the pore characteristics did not play an important role in the corrosion resistance. It was considered that the protective film breaks down such that the corrosion performance of cellular structured alloys was comparable to each other in this harsh environment.

Biomedical PEVA Nanocomposite with Dual Clay Nanofiller: Cytotoxicity, Mechanical Properties, and Biostability.

Poly(ethylene-vinyl acetate) (PEVA) nanocomposite incorporating dual clay nanofiller (DCN) of surface modified montmorillonite (S-MMT) and bentonite (Bent) was studied for biomedical applications. In order to overcome agglomeration of the DCN, the S-MMT and Bent were subjected to a physical treatment prior to being mixed with the copolymer to form nanocomposite material. The S-MMT and Bent were physically treated to become S-MMT(P) and Bent(pH-s), respectively, that could be more readily dispersed in the copolymer matrix due to increments in their basal spacing and loosening of their tactoid structure. The biocompatibility of both nanofillers was assessed through a fibroblast cell cytotoxicity assay. The mechanical properties of the neat PEVA, PEVA nanocomposites, and PEVA-DCN nanocomposites were evaluated using a tensile test for determining the best S-MMT(P):Bent(pH-s) ratio. The results were supported by morphological studies by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Biostability evaluation of the samples was conducted by comparing the ambient tensile test data with the in vitro tensile test data (after being immersed in simulated body fluid at 37 °C for 3 months). The results were supported by surface degradation analysis. Our results indicate that the cytotoxicity level of both nanofillers reduced upon the physical treatment process, making them safe to be used in low concentration as dual nanofillers in the PEVA-DCN nanocomposite. The results of tensile testing, SEM, and TEM proved that the ratio of 4:1 (S-MMT(P):Bent(pH-s)) provides a greater enhancement in the mechanical properties of the PEVA matrix. The biostability assessment indicated that the PEVA-DCN nanocomposite can achieve much better retention in tensile strength after being subjected to the simulated physiological fluid for 3 months with less surface degradation effect. These findings signify the potential of the S-MMT(P)/Bent(pH-s) as a reinforcing DCN, with simultaneous function as biostabilizing agent to the PEVA copolymer for implant application.

The Effect of the Corrosion Medium on Silane Coatings Deposited on Titanium Grade 2 and Titanium Alloy Ti13Nb13Zr.

The present paper focuses on the fabrication of coatings based on vinyltrimethoxysilane and the influence of various corrosion media on the coatings produced. Coatings were deposited on two substrate materials, namely, titanium Grade 2 and titanium alloy Ti13Nb13Zr, by immersion in a solution containing vinyltrimethoxysilane, anhydrous ethyl alcohol, acetic acid and distilled water. The obtained coatings were characterized in terms of surface morphology, adhesion to the substrate and corrosion resistance. As corrosion solutions, four different simulated physiological fluids, which differed in the contents of individual ions, and a 1 mol dm−3 NaBr solution were used. The chloride ions contained in the simulated physiological fluids did not lead to pitting corrosion of titanium Grade 2 and titanium alloy Ti13Nb13Zr. This investigation shows that titanium undergoes pitting corrosion in a bromide ion medium. It is demonstrated that the investigated coatings slow down corrosion processes in all corrosion media examined.

Hydroxyapatite Obtained via the Wet Precipitation Method and PVP/PVA Matrix as Components of Polymer-Ceramic Composites for Biomedical Applications.

The aspect of drug delivery is significant in many biomedical subareas including tissue engineering. Many studies are being performed to develop composites with application potential for bone tissue regeneration which at the same provide adequate conditions for osteointegration and deliver the active substance conducive to the healing process. Hydroxyapatite shows a great potential in this field due to its osteoinductive and osteoconductive properties. In the paper, hydroxyapatite synthesis via the wet precipitation method and its further use as a ceramic phase of polymer–ceramic composites based on PVP/PVA have been presented. Firstly, the sedimentation rate of hydroxyapatite in PVP solutions has been determined, which allowed us to select a 15% PVP solution (sedimentation rate was 0.0292 mm/min) as adequate for preparation of homogenous reaction mixture treated subsequently with UV radiation. Both FT-IR spectroscopy and EDS analysis allowed us to confirm the presence of both polymer and ceramic phase in composites. Materials containing hydroxyapatite showed corrugated and well-developed surface. Composites exhibited swelling properties (hydroxyapatite reduced this property by 25%) in simulated physiological fluids, which make them useful in drug delivery (swelling proceeds parallel to the drug release). The short synthesis time, possibility of preparation of composites with desired shapes and sizes and determined physicochemical properties make the composites very promising for biomedical purposes.