Degradation In Phosphate Buffered Saline Research Articles

Exploring the potential of magnesium oxychloride, an amorphous magnesium phosphate, and newberyite as possible bone cement candidates.

Magnesium phosphate-based bone cements, particularly struvite (MgNH4PO4∙6H2O)-forming cements, have attracted increased scientific interest in recent years because they exhibit similar biocompatibility to hydroxyapatite while degrading much more rapidly in vivo. However, other magnesium-based minerals which might be promising are, to date, little studied. Therefore, in this study, we investigated three magnesium-based bone cements: a magnesium oxychloride cement (Mg3(OH)5Cl∙4H2O), an amorphous magnesium phosphate cement based on Mg3(PO4)2, MgO, and NaH2PO4, and a newberyite cement (MgHPO4·3H2O). Because it is not sufficiently clear from the literature to what extent these cements are suitable for clinical use, all of them were characterized and optimized regarding setting time, setting temperature, compressive strength and passive degradation in phosphate-buffered saline. Because the in vitro properties of the newberyite cement were most promising, it was orthotopically implanted into a partially weight-bearing tibial bone defect in sheep. The cement exhibited excellent biocompatibility and degraded more rapidly compared to a hydroxyapatite reference cement; after 4months, 18% of the cement was degraded. We conclude that the newberyite cement was the most promising candidate of the investigated cements and has clear advantages over calcium phosphate cements, especially in terms of setting time and degradation behavior.

In Vitro Biocompatibility of Hydrogel Polyvinyl Alcohol/Moringa oleifera Leaf Extract/Graphene Oxide for Wound Dressing.

Hydrogel-based wound dressings are often chosen for healing diabetic foot ulcers (DFU) in combination with herbal extracts. Moringa oleifera leaf (MOL) extract is a potent herb containing antimicrobial and anti-inflammatory bioactive substances. In this work, wound dressings based on polyvinyl alcohol (PVA), MOL extract, and graphene oxide (GO) were developed for DFU wound dressing. The PVA/MOL/GO hydrogel was synthesized using four cycles of a freeze-thaw process with varying concentrations of MOL extract. All hydrogels showed a water content of 83-88% and an equilibrium swelling ratio between 155-171%. After degradation in phosphate-buffered saline, the hydrogels showed a more open porous structure. We observed a degradation rate of 26-28%. Although the increase in MOL extract reduced the tensile strength of the hydrogel, the addition of GO increased the tensile strength. The PVA/MOL/GO hydrogel showed the highest antibacterial activity, with a reduction of 94% Gram-positive S. aureus and 82% Gram-negative E. coli. Finally, all samples possessed appropriate cytocompatibility with cell viability reaching 83-135% in 3T3L1 mouse fibroblast cells. This result was verified by in vitro wound-healing analysis performed by scratch assay. This study presents the potency of combined PVA, MOL, and GO as a biocompatible DFU wound dressing.

Ingestible capsules carrying 3D printed springs: a possible future prospective for SBS treatment?

Background Short Bowel Syndrome (SBS) is a malabsorption syndrome characterised by a severe reduction of the absorbent surface of the intestinal mucosa. Treatment of this condition needs multi-professional teams and different therapies, which are not always enough to ensure enteral autonomy. New techniques are being explored, particularly distraction enterogenesis, which can allow the lengthening of the residual intestines of these patients. This study aims to demonstrate the possibility of using biodegradable materials to design ingestible capsules which carry 3D-printed springs capable of reaching the patient’s intestine. These devices could be used as a slightly invasive distraction enterogenesis technique, stimulating cell proliferation and intestinal elongation without surgery. Materials and methods Capsules were realised with gelatin from pigskin type A from Sigma-Aldrich mixed with regenerated silk fibroin (RS) obtained by reverse engineering on Bombyx Mori cocoons. Springs are composed of a structure of regenerated silk (RS) modified with graphene nanoplatelets (GNP) externally covered with a biodegradable polyhydroxybutyrate-valerate (PHBV) shell. Springs were realised with 3D printing, through which, with an extruder, PHBV and RS compounds are deposited simultaneously in a 3D structure. The springs’ capsules were then analysed with solvents simulating the gastric and intestinal environment to verify their resistance to degradation. PBS (Phosphate Buffered Saline), composed of calcium chloride and magnesium chloride (CaCl 2 + MgCl 2 ), with a pH value of 7.4, was used as a degradative agent; for the gastric tract, we chose the acetic acid, CH 3 COOH, at 12% with a pH value of 2.3. Results While the gelatin-only capsules showed poor resistance to degradation in PBS, the new compound based on gelatin and regenerated silk showed excellent resistance in gastric and intestinal environments, allowing the pills to reach the intestine without dissolving. In addition, the results show variability in the release times of the springs as a function of the pH values and the elastic constants of the springs used: the latter determined that in acetic acid, the release time is increased at an increase of the elastic constant. In contrast, in PBS, an opposite trend was observed. Conclusions Our results confirm the possibility of using gelatin, silk fibroin and PHBV to design devices capable of transporting implantable endoluminal 3D structures, drugs, or growth factors, laying the foundations for a new approach to distraction enterogenesis in SBS patients.

BIOLOGICAL BEHAVIOUR OF CHITOSAN ELECTROSPUN NANOFIBROUS MEMBRANES AFTER DIFFERENT NEUTRALISATION METHODS

Chitosan electrospun nanofibres were synthesised in two different trifluoroacetic acid (TFA)/dichloromethane (DCM) solvent ratios and then neutralised in aqueous and ethanol sodium-based solutions (NaOH and Na2CO3) to produce insoluble materials with enhanced biological properties for regenerative and tissue engineering applications. Structural, electronic, and optical properties and the swelling capacity of the prepared nanofibre membrane were studied by scanning electron microscopy, Fourier-transform infrared spectroscopy, and photoluminescence. Cell viability (with the U2OS cell line) and antibacterial properties (against Staphylococcus aureus and Escherichia coli) assays were used to assess the biomedical potential of the neutralised chitosan nanofibrous membranes. A 7:3 TFA/DCM ratio allows for an elaborate nanofibrous membrane with a more uniform fibre size distribution. Neutralisation in aqueous NaOH only maintains a partial fibrous structure. At the same time, neutralisation in NaOH ethanol-water maintains the structure during 1 month of degradation in phosphate-buffered saline and distilled water. All membranes demonstrate high biocompatibility, but neutralisation in ethanol solutions affects cell proliferation on materials made with 9:1 TFA/DCM. The prepared nanofibrous mats could constrain the growth of both gram-positive and gram-negative microorganisms, but 7:3 TFA/DCM membranes inhibited bacterial growth more efficiently. Based on structural, degradation, and biological properties, 7:3 TFA/DCM chitosan nanofibrous membranes neutralised by 70% ethanol/30% aqueous NaOH exhibit potential for biomedical and tissue engineering applications.

Synthesis, characterization, thermal stability, and in vitro and in vivo degradation study of polycaprolactone and polyglycolide block copolymers

Biodegradable polymer materials are attractive in various biomedical applications. Herein, we report a block aliphatic copolymer, polycaprolactone-block-polyglycolide (PCL-b-PGA, denoted as PCLGA), and explored the polymer composition effect on the thermal and degradation behaviors. Three copolymers with different PCL/PGA weight ratios were obtained by a two-step ring opening polymerization. The chemical structures and compositions of copolymers were studied by NMR and FT-IR. The thermal behaviors were investigated by DSC and TGA. The in vitro degradation in phosphate buffer saline and in vivo degradation as an implant in rats were evaluated and the hygroscopic rate and polymer weight loss changes were monitored in an eight-week period. PCLGA with a higher PCL composition showed a slower degradation in vitro and in vivo. These PCLGAs with different degradation rates could be used as biomedical implants for potential application in drug delivery and tissue repair.

Functionally Graded Bioactive Composites Based on Poly(vinyl alcohol) Made through Thiol-Ene Click Reaction.

Functionally graded materials (FGMs) composed of a polymer matrix embedded with calcium phosphate particles are preferred for bone tissue engineering, as they can mimic the hierarchical and gradient structure of bones. In this study, we report the design and development of a FGM based on thiolated poly(vinyl alcohol) (TPVA) and nano-hydroxyapatite (nano-HA) with graded bioactivity, cell compatibility, and degradability properties that are conducive for bone regeneration. The polymer matrix comprises crosslinked poly(vinyl alcohol) with ester and thioether linkages formed via the thiol–ene click reaction, avoiding undesired additives and byproducts. Freshly precipitated and spray-dried HA was mixed with the TPVA hydrogel, and layers of varying concentrations were cast. Upon lyophilization, the hydrogel structure yielded porous sheets of the graded composite of TPVA and nano-HA. The new FGM showed higher values of tensile strength and degradation in phosphate buffer saline (PBS) in vitro, compared to bare TPVA. The bioactive nature of the FGM was confirmed through bioactivity studies in simulated body fluid (SBF), while cytocompatibility was demonstrated with human periodontal ligament cells in vitro. Cumulatively, our results indicate that based on the composition, mechanical properties, bioactivity, and cytocompatibility, the fabricated TPVA-HA composites can find potential use as guided bone regeneration (GBR) membranes.

Injectable Hydrogels Based on Inter-Polyelectrolyte Interactions between Hyaluronic Acid, Gelatin, and Cationic Cellulose Nanocrystals.

The present work dealt with the development of physically cross-linked injectable hydrogels with potential applications in tissue engineering. The hydrogels were composed of a ternary mixture of a polyanion and a polyampholyte, hyaluronic acid (HA) and gelatin, respectively, bridged by cationic cellulose nanocrystals (cCNCs). A 3D network is formed by employing attractive electrostatic interactions and hydrogen bonding between these components under physiological conditions. The hydrogels demonstrated low viscosity at high stresses, enabling easy injection, structural stability at low stresses (<15 Pa), and nearly complete structure recovery within several minutes. Increasing the cCNC content (>3%) reduced hydrogel swelling and decelerated the degradation in phosphate-buffered saline as compared to that in pure HA and HA-gelatin samples. Biological evaluation of the hydrogel elutions showed excellent cell viability. The proliferation of fibroblasts exposed to elutions of hydrogels with 5% cCNCs reached ∼200% compared to that in the positive control after 11 days. Considering these results, the prepared hydrogels hold great potential in biomedical applications, such as injectable dermal fillers, 3D bioprintable inks, or 3D scaffolds to support and promote soft tissue regeneration.

High-Throughput Assessment of the Abiotic Stability of Test Chemicals in In Vitro Bioassays.

Abiotic stability of chemicals is not routinely tested prior to performing in vitro bioassays, although abiotic degradation can reduce the concentration of test chemicals leading to the formation of active or inactive transformation products, which may lead to misinterpretation of bioassay results. A high-throughput workflow was developed to measure the abiotic stability of 22 test chemicals in protein-rich aqueous media under typical bioassay conditions at 37 °C for 48 h. These test chemicals were degradable in the environment according to a literature review. The chemicals were extracted from the exposure media at different time points using a novel 96-pin solid-phase microextraction. The conditions were varied to differentiate between various reaction mechanisms. For most hydrolyzable chemicals, pH-dependent degradation in phosphate-buffered saline indicated that acid-catalyzed hydrolysis was less important than reactions with hydroxide ions. Reactions with proteins were mainly responsible for the depletion of the test chemicals in the media, which was simulated by bovine serum albumin (BSA) and glutathione (GSH). 1,2-Benzisothiazol-3(2H)-one, 2-methyl-4-isothiazolinone, and l-sulforaphane reacted almost instantaneously with GSH but not with BSA, indicating that GSH is a good proxy for reactivity with electrophilic amino acids but may overestimate the actual reaction with three-dimensional proteins. Chemicals such as hydroquinones or polyunsaturated chemicals are prone to autoxidation, but this reaction is difficult to differentiate from hydrolysis and could not be simulated by the oxidant N-bromosuccinimide. Photodegradation played a minor role because cells are exposed in incubators in the dark and simulations with high light intensities did not yield realistic degradation. Stability predictions from various in silico prediction models for environmental conditions can give initial indications of the stability but were not always consistent with the experimental stability in bioassays. As the presented workflow can be performed in high throughput under realistic bioassay conditions, it can be used to provide an experimental database for developing bioassay-specific stability prediction models.

A Complex In Vitro Degradation Study on Polydioxanone Biliary Stents during a Clinically Relevant Period with the Focus on Raman Spectroscopy Validation.

Biodegradable biliary stents are promising treatments for biliary benign stenoses. One of the materials considered for their production is polydioxanone (PPDX), which could exhibit a suitable degradation time for use in biodegradable stents. Proper material degradation characteristics, such as sufficient stiffness and disintegration resistance maintained for a clinically relevant period, are necessary to ensure stent safety and efficacy. The hydrolytic degradation of commercially available polydioxanone biliary stents (ELLA-CS, Hradec Králové, Czech Republic) in phosphate-buffered saline (PBS) was studied. During 9 weeks of degradation, structural, physical, and surface changes were monitored using Raman spectroscopy, differential scanning calorimetry, scanning electron microscopy, and tensile and torsion tests. It was found that the changes in mechanical properties are related to the increase in the ratio of amorphous to crystalline phase, the so-called amorphicity. Monitoring the amorphicity using Raman spectroscopy has proven to be an appropriate method to assess polydioxanone biliary stent degradation. At the 1732 cm−1 Raman peak, the normalized shoulder area is less than 9 cm−1 which indicates stent disintegration. The stent disintegration started after 9 weeks of degradation in PBS, which agrees with previous in vitro studies on polydioxanone materials as well as with in vivo studies on polydioxanone biliary stents.

Synthesis and Antiplatelet Adhesion Behavior of a Poly(L-lactide-co-glycolide)-Poly(1,5-dioxepan-2-one) Multiblock Copolymer.

Platelet adhesion and denaturation on artificial medical implants induce thrombus formation. In this study, bioabsorbable copolymers composed of poly(l-lactide-co-glycolide) (PLGA) and poly(1,5-dioxepan-2-one) (PDXO) were synthesized and evaluated for their antiplatelet adhesive properties. The PLGA–PXO multiblock copolymer (PLGA–PDXO MBC) and its random copolymer (PLGA–PDXO RC) showed effective antiplatelet adhesive properties, and the number of adhered platelets was similar to those adhered on poly(2-methoxyethylacrylate), a known antiplatelet adhesive polymer, although a large number of denatured platelets were observed on a PLGA–poly(ε-caprolactone) multiblock copolymer (PLGA–PCL MBC). Using monoclonal antifibrinogen IgG antibodies, we also found that both αC and γ-chains, the binding sites of fibrinogen for platelets, were less exposed on the PLGA–PDXO MBC surface compared to PLGA–PCL MBC. Furthermore, free-standing films of PLGA–PDXO MBC were prepared by casting the polymer solution on glass plates and showed good tensile properties and slow hydrolytic degradation in phosphate-buffered saline (pH = 7.4). We expect that the unique properties of PLGA–PDXO MBC, i.e., antiplatelet adhesive behavior, good tensile strength, and hydrolytic degradation, will pave the way for the development of new bioabsorbable implanting materials suitable for application at blood-contacting sites.

Development of Antibacterial, Degradable and pH-Responsive Chitosan/Guar Gum/Polyvinyl Alcohol Blended Hydrogels for Wound Dressing.

The present research is based on the fabrication preparation of CS/PVA/GG blended hydrogel with nontoxic tetra orthosilicate (TEOS) for sustained paracetamol release. Different TEOS percentages were used because of their nontoxic behavior to study newly designed hydrogels’ crosslinking and physicochemical properties. These hydrogels were characterized using Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and wetting to determine the functional, surface morphology, hydrophilic, or hydrophobic properties. The swelling analysis in different media, degradation in PBS, and drug release kinetics were conducted to observe their response against corresponding media. The FTIR analysis confirmed the components added and crosslinking between them, and surface morphology confirmed different surface and wetting behavior due to different crosslinking. In various solvents, including water, buffer, and electrolyte solutions, the swelling behaviour of hydrogel was investigated and observed that TEOS amount caused less hydrogel swelling. In acidic pH, hydrogels swell the most, while they swell the least at pH 7 or higher. These hydrogels are pH-sensitive and appropriate for controlled drug release. These hydrogels demonstrated that, as the ionic concentration was increased, swelling decreased due to decreased osmotic pressure in various electrolyte solutions. The antimicrobial analysis revealed that these hydrogels are highly antibacterial against Gram-positive (Staphylococcus aureus and Bacillus cereus) and Gram negative (Pseudomonas aeruginosa and Escherichia coli) bacterial strains. The drug release mechanism was 98% in phosphate buffer saline (PBS) media at pH 7.4 in 140 min. To analyze drug release behaviour, the drug release kinetics was assessed against different mathematical models (such as zero and first order, Higuchi, Baker–Lonsdale, Hixson, and Peppas). It was found that hydrogel (CPG2) follows the Peppas model with the highest value of regression (R2 = 0.98509). Hence, from the results, these hydrogels could be a potential biomaterial for wound dressing in biomedical applications.

The interphase degradation in a nanobiosensor including biopolymers and carbon nanotubes

In this paper, a degradation nanobiosensor comprising two biopolymers as poly (lactic acid) (PLA) and poly (ethylene oxide) (PEO) as well as carbon nanotubes (CNT) is developed. The electrical conductivity of the samples for the period of degradation in phosphate-buffered saline (PBS) solution is analyzed focusing on interphase degradation. Furthermore, a model for the conductivity of examples is advanced by CNT properties, filler wettability by polymer medium, interphase depth, degradation portion and tunneling distance. The model’s calculations are linked to the experimental facts and all parameters’ impacts on the conductivity of the decayed examples are described. The predictions of the suggested model sufficiently follow the empirical data. The interphase thickness dwindles during degradation and a high content of CNT largely eliminates the polymer and interphase region, because CNT accelerate the degradation. Both thick interphase and short tunnels obtain the high conductivity, while either thin interphase or a large tunnel causes an insulated example, since thin interphase or a big tunnel prevents the electron transferring. This study can provide a simple approach to calculate and optimize the conductivity to predict the behavior of a degradation nanobiosensor.

In Vitro Macrophage Immunomodulation by Poly(ε-caprolactone) Based-Coated AZ31 Mg Alloy.

Due to its excellent bone-like mechanical properties and non-toxicity, magnesium (Mg) and its alloys have attracted great interest as biomaterials for orthopaedic applications. However, their fast degradation rate in physiological environments leads to an acute inflammatory response, restricting their use as biodegradable metallic implants. Endowing Mg-based biomaterials with immunomodulatory properties can help trigger a desired immune response capable of supporting a favorable healing process. In this study, electrospun poly(ε-caprolactone) (PCL) fibers loaded with coumarin (CM) and/or zinc oxide nanoparticles (ZnO) were used to coat the commercial AZ31 Mg alloy as single and combined formulas, and their effects on the macrophage inflammatory response and osteoclastogenic process were investigated by indirect contact studies. Likewise, the capacity of the analyzed samples to generate reactive oxygen species (ROS) has been investigated. The data obtained by attenuated total reflection Fourier-transform infrared (FTIR-ATR) and X-ray photoelectron spectroscopy (XPS) analyses indicate that AZ31 alloy was perfectly coated with the PCL fibers loaded with CM and ZnO, which had an important influence on tuning the release of the active ingredient. Furthermore, in terms of degradation in phosphate-buffered saline (PBS) solution, the PCL-ZnO- and secondary PCL-CM-ZnO-coated samples exhibited the best corrosion behaviour. The in vitro results showed the PCL-CM-ZnO and, to a lower extent, PCL-ZnO coated sample exhibited the best behaviour in terms of inflammatory response and receptor activator of nuclear factor kappa-B ligand (RANKL)-mediated differentiation of RAW 264.7 macrophages into osteoclasts. Altogether, the results obtained suggest that the coating of Mg alloys with fibrous PCL containing CM and/or ZnO can constitute a feasible strategy for biomedical applications.

Calcium-siRNA Nanocomplexes Optimized by Bovine Serum Albumin Coating Can Achieve Convenient and Efficient siRNA Delivery for Periodontitis Therapy.

PurposeReducing toxicity, immunogenicity, and costs of small interfering RNAs (siRNA) carrier materials are key goals for RNA interference (RNAi) technology transition from bench to bed. Recently, calcium ions (Ca2+) have garnered attention as a novel, alternative material for delivering siRNA to cells. However, the tolerance for Ca2+ concentration varies in different cell types, which has limited its applications in vivo. Bovine serum albumin (BSA) can bind to Ca2+ through chelation. Moreover, BSA is a favorable coating material for nanoparticles owing to its excellent biocompatibility. Therefore, we hypothesized that coating Ca2+-siRNA with BSA helps buffer Ca2+ toxicity in vivo.MethodsBSA-Ca2+-siRNA nanoparticles were prepared, and the size, shape, encapsulation, and release efficiency were characterized using atomic force microscopy, scanning electronic microcopy, and gel electrophoresis. Binding nanoparticles were evaluated using attenuated total reflection-Fourier-transform infrared spectroscopy. The cellular uptake, intracellular release, cytotoxicity, and gene knockdown of nanoparticles were evaluated in periodontal ligament stem cells (PDLSCs) using laser-scanning confocal microscope, flow cytometry, and real-time quantitative polymerase chain reaction.ResultsBSA and Ca2+-siRNA could form a stable nano-scale complex (~140 nm in diameter). The nanocomplexes could maintain siRNA release for more than 1 week in neutral phosphate-buffered saline (PBS) and could induce accelerated degradation in acidic PBS (pH 5.0). The nanoparticles were taken up by the cells, primarily through macropinocytosis, and were then released intracellularly through the acidification of endosomes/lysosomes. Importantly, the BSA-Ca2+ carrier had high transfection efficiency and biocompatibility both in vitro and in vivo. To demonstrate the therapeutic potential of our BSA coating-optimized Ca2+-siRNA technology, we showed that BSA-Ca2+-siWWP1 complexes strongly enhanced the osteogenic differentiation of inflammatory PDLSCs.ConclusionBSA-Ca2+ could potentially be used for siRNA delivery, which is not only highly efficient and cost-effective but also biocompatible to host tissues owing to the BSA coating.

A Regenerative Polymer Blend Composed of Glycylglycine ethyl ester-substituted Polyphosphazene and Poly (lactic-co-glycolic acid).

In the pursuit of continuous improvement in the area of biomaterial design, blends of mixed-substituent polyphosphazenes and poly (lactic acid-glycolic acid) (PLGA) were prepared, and their morphology of phase distributions for the first time was studied. The degradation mechanism and osteocompatibility of the blends were also evaluated for their use as regenerative materials. Poly [(ethyl phenylalanato)25(glycine ethyl glycinato)75phosphazene](PNEPAGEG) and poly [(glycine ethyl glycinato)75(phenylphenoxy)25phosphazene](PNGEGPhPh) were blended with PLGA at various weight ratios to yield different blends, namely PNEPAGEG-PLGA 25:75, PNEPAGEG-PLGA 50:50, PNGEGPhPh-PLGA 25:75, and PNGEGPhPh-PLGA 50:50. The molecular interactions, domain sizes, and phase distributions of the blends were confirmed by atomic force microscopy (AFM) as the PNEPAGEG-PLGA and PNGEGPhPh-PLGA blends showed different domain sizes and phase distributions. Due to the extensive hydrogen bonding within the two polymer components, PNEPAGEG-PLGA exhibited small-sized domains and well-distributed morphology. While for the PNGEGPhPh-PLGA blends, the presence of phenylphenol (PhPh) caused the formation of PLGA large-sized domains as the PLGA formed a continuous phase and PNGEGPhPh constituted a dispersed phase. In addition to AFM results, scanning electron microscopy-energy dispersive X-ray spectrometry (SEM-EDS), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and Fourier transform infrared spectroscopy (FTIR) results demonstrated the miscibility of the blends. The PNEPAGEG-PLGA and PNGEGPhPh-PLGA blends presented in situ 3D interconnected porous structures upon degradation in phosphate-buffered saline (PBS) media at 37°C. However, the blends showed different mechanistic pathways to the formations of the pores. The difference in the erosion patterns could be attributed to the nature of molecular attractions that exist in the blends. Furthermore, the novel blends were able to support cell growth as compared to PLGA, and accommodate cell infiltrations, which ultimately augmented surface area for better cell-material interactions.

Dexamethasone Degradation in Aqueous Medium and Implications for Correction of In Vitro Release from Sustained Release Delivery Systems.

The in vitro drug release in an aqueous medium is a critical performance metric for a sustained release drug product. During long-term release studies, drugs may degrade in the release medium, and such degradation can lead to errors in drug release quantitation. Using dexamethasone as a model drug and LC-MS/MS methods employing dexamethasone-d4 as an internal standard, this study identified that dexamethasone can degrade into 13 major degradation products in phosphate buffered saline (PBS) as a function of time, temperature (25, 37, and 45°C), and light exposure. A putative scheme for dexamethasone degradation pathways in PBS has been proposed. In proof-of-concept studies, the analytical method was used to quantitate dexamethasone and its degradation products during in vitro release studies with sustained release dexamethasone-poly(D,L-lactide-co-glycolide) (PLGA) implants incubated in phosphate buffer saline (PBS). Further, mathematical approaches were developed to estimate drug release from implants after accounting for drug degradation in PBS. The LC-MS/MS analytical method and the mathematical approaches developed could be used for assessing the stability and/or release of dexamethasone during manufacturing, storage, and use of various dosage forms.

Robust and Tunable Hybrid Hydrogels from Photo-Cross-Linked Soy Protein Isolate and Regenerated Silk Fibroin

Soy protein isolate (SPI), a plant derived protein, is emerging as a potential material for biomedical applications because of its abundance in nature, ease of isolation and processing, tailorable biodegradability, low cost, and low immunogenicity. Herein we report the development and structure−property relationship of photo-cross-linked SPI and SPI/silk fibroin (SF) hybrid hydrogels for the first time. The pristine SPI hydrogels were cross-linked at two different structural conformations (i.e., closed at pH 7 and open at pH 12), and SPI/SF hybrid hydrogels were co-cross-linked at pH 7 in three different weight ratios (3:1, 1:1, and 1:3). The fabricated hydrogels were characterized using electron microscopy, X-ray diffraction, Raman and infrared spectroscopy, thermal analysis, small- and ultrasmall-angle neutron scattering, rheology, water uptake, and in vitro degradation studies. The equilibrium water swollen SPI hydrogel cross-linked at pH 7 exhibited a specific microstructure, controlled degradation in phosphate-buffered saline, and a shear storage modulus of ∼7.7 kPa, which is in the range of human lumbar nucleus pulposus and significantly higher than soy hydrogels reported by thermal treatment, pressure treatment, salt-induced cold-setting, and enzymatic cross-linking. Conversely, the SPI hydrogel cross-linked at pH 12 exhibited ordered porous microstructure, higher water uptake of ∼1946%, poor water resistance, and low mechanical properties. Increase in SF content of the SPI/SF hybrid hydrogels demonstrated improved porosity, water swelling, molecular chain mobility, elastic, and water-resistant properties. An in-depth understanding of the effect of pH and composition on the hierarchical structure and physicochemical properties of the fabricated hydrogels was established. Moreover, the pristine SPI and SPI/SF hybrid inks used for hydrogel fabrication exhibited flow properties highly suitable for 3D-printing scaffolds for tissue engineering applications. The pr

Synthesis, Characterization and Physicomechanical Properties of Novel Water-based Biodegradable Polyurethane Dispersion

Novel water-based biodegradable polyurethane dispersions with an aim to develop environmentally friendly materials, including medicine, various industries, have been prepared in this study. Biodegradable ionic polyurethanes (IPU) were synthesized based on polyols from renewable resources, such as castor oil (CO), in the presence of a polyester polyol and polyethylene glycol (PEG) with hydrophilic property and 1,6-hexamethylene diisocyanate. 1,4-Butanediol and dibutyltin dilaurate, were used as a chain extender and catalyst, respectively. The comprehensive investigations of the structure and properties of five types of synthesized polyurethanes demonstrated biodegradability relationship of these polyurethanes with their structure and composition. In this research effects of different types and content of polyols on biodegradability and physico mechanical properties of prepared PUDs were investigated. The structure, properties and physico mechanical and application behavior of mentioned materials were characterized by 1H NMR, FTIR spectroscopy, thermogravimetric analysis (TG/DTG) and dynamic mechanical thermal analysis (DMTA). The adhesion properties were measured by pull off test as well. Particle size was measured by dynamic light scattering (DLS) methods. The biodegradability of prepared polyurethane dispersions was confirmed by water uptake, hydrolytic and enzymatic degradation in phosphate buffer saline (PBS) with lipase enzyme in PBS. Results showed that by the incorporation of natural components into the polymer chain, adjusting of hydrophilic and hydrolytic liability properties of soft segments and especial relevant designs, useful polyurethane can be synthesized with desirable property of biodegradability and dispersion stability. Except for one sample, other samples were decomposed totally in enzymatic media.

Variations of tunneling properties in poly (lactic acid) (PLA)/poly (ethylene oxide) (PEO)/carbon nanotubes (CNT) nanocomposites during hydrolytic degradation

The combination of poly (lactic acid) (PLA) with water-soluble poly (ethylene oxide) (PEO) and carbon nanotubes (CNT) presents interesting results during hydrolytic degradation. This paper investigates the conductivity of PLA/PEO/CNT nanocomposites during degradation in phosphate-buffered saline (PBS) solution. A simple model is suggested to express the conductivity of samples during degradation by CNT properties, degradation fraction, interphase thickness and tunneling properties. The calculations of developed model are compared to the experimental data and the variations of tunneling resistivity and tunneling distance are explained. Moreover, the parametric examinations are applied to confirm the developed model. The predictions of conductivity acceptably agree with the experimental data during degradation. The degradation reduces the tunneling resistivity and tunneling distance between neighboring CNT, due to the exclusion of polymer matrix. The results demonstrate the positive effects of high degradation fraction, thick interphase, large tunneling diameter, slight tunneling resistivity and short tunneling distance between adjacent CNT on the conductivity of degraded nanocomposites. The current study can provide useful guidelines for analysis of conductivity in nanocomposites during degradation.

Mechanically-competent and cytocompatible polycaprolactone-borophosphosilicate hybrid biomaterials.

Organic-inorganic class II hybrid materials have domain sizes at the molecular level and chemical bonding between the organic and inorganic phases. We have previously reported the synthesis of class II hybrid biomaterials from alkoxysilane-functionalized polycaprolactone (PCL) and borophosphosilicate (B2O3-P2O5-SiO2) glass (BPSG) through a non-aqueous sol-gel process. In the present study, the mechanical properties and degradability of these PCL/BPSG hybrid biomaterials were studied and compared to those of their conventional composite counterparts. The compressive strength, modulus and toughness of the hybrid biomaterials were significantly greater compared to the conventional composites, likely due to the covalent bonding between the organic and inorganic phases. A hybrid biomaterial (50wt% PCL and 50wt% BPSG) exhibited compressive strength, modulus and toughness values of 32.2 ± 3.5MPa, 573 ± 85MPa and 1.54 ± 0.03MPa, respectively; whereas the values for composite of similar composition were 18.8 ± 1.6MPa, 275 ± 28MPa and 0.76 ± 0.03MPa, respectively. Degradation in phosphate-buffered saline was slower for hybrid biomaterials compared to their composite counterparts. Thus, these hybrid materials possess superior mechanical properties and more controlled degradation characteristics compared to their corresponding conventional composites. To assess in vitro cytocompatibility, MC3T3-E1 pre-osteoblastic cells were seeded onto the surfaces of hybrid biomaterials and polycaprolactone (control). Compared to polycaprolactone, cells on the hybrid material displayed enhanced spreading, focal adhesion formation, and cell number, consistent with excellent cytocompatibility. Thus, based on their mechanical properties, degradability and cytocompatibility, these novel biomaterials have potential for use as scaffolds in bone tissue engineering and related applications.