Alternate Soaking Research Articles

Effect of protein adsorption layers and solution treatments on hydroxyapatite deposition on polystyrene plate surfaces in simulated body fluids.

We have developed a method to functionalize polystyrene (PS) cell culture plates with hydroxyapatite (HAp) via protein adsorption layers such as human serum albumin (HSA) in simulated body fluids (SBFs). In order to investigate the versatility the method, in this study the effect of protein adsorption layers on HAp deposition on PS plate surfaces in SBF was evaluated. Pretreatments with alternate soaking process (ASP) using solutions containing calcium ions and phosphate ions followed by incubation with SBF for 24 h resulted in HAp deposition on PS plates with adsorption layers of HSA, type I collagen, hen egg white lysozyme, and poly L-glutamic acid, an acidic protein analogue: the deposition behaviors were correlated with adsorption ability and charge state of proteins. We also demonstrated that commercially available tissue culture-treated PS (TCPS) were directly coated with bone-like HAp using the same ASP and SBF processes. Human mesenchymal stem cells adhered and stretched on the HAp-coated TCPS plates in a similar manner to the case of the HAp-coated PS plates prepared via HSA adsorption layers. The results indicate that the present methods are useful for preparing bone-like HAp-coated cell culture plates that can be utilized function of adsorbed proteins and that are obtainable conveniently and at low-cost.

Fabrication and characterization of water-dispersed chitosan nanofiber/poly(ethylene glycol) diacrylate/calcium phosphate-based porous composites.

We evaluated the capacity of chitosan nanofiber (CNF)- and poly(ethylene glycol) (PEG)-based hydrogel/calcium phosphate hybrid (CNF-PEG/CaP) composites to act as scaffolding materials. CNF-PEG/CaP composites were fabricated by mineralization of CNF-PEG hydrogels using an alternate soaking method. The amount of CaP mineralized on CNF-PEG hydrogels increased as the ratio of CNF in the CNF-PEG hydrogel increased. Young's modulus of CNF-PEG/CaP hydrogels was enhanced by increase in CNF ratio. It was further confirmed that osteoblasts embedded on the CNF-PEG/CaP composites were viable after incubation for 5days and firmly attached to the CaP porous layer, forming an extensive cell-scaffold leading to cell-cell interactions. These results indicated that the micro-porous structure of CNF-PEG hydrogels is suitable for CaP to be utilized as a scaffold for bone regeneration.

Effect of different mineralization processes on in vitro and in vivo bone regeneration and osteoblast-macrophage cross-talk in co-culture system using dual growth factor mediated non-mulberry silk fibroin grafted poly (Є-caprolactone) nanofibrous scaffold

This study evaluates mineralized nanofibrous polymeric scaffolds at supporting in vitro osteogenic differentiation of human mesenchymal stem cells (hMSCs) and in vivo bone tissue regeneration. Co-electrospin, alternative soaking, and electrodeposition were used to introduce hydroxyapatite in non-mulberry silk fibroin grafted poly(Є-caprolactone) nanofibrous scaffolds. Bone morphogenic protein-2 and Transforming growth factor-β, at a potency ratio of 1:1, are covalently coupled onto the scaffolds. hMSCs proliferation and interactions are studied through MTT and Alamar blue assay and scanning electron and confocal microscopy. Alkaline phosphatase activity, mineralization assays, and real-time PCR studies substantiate hMSCs’ osteogenic differentiation. Co-cultures of human macrophages and osteoblasts exhibit insignificant pro-inflammatory cytokines production. In vivo trials are conducted in rabbit femur (distal metaphysis region). Bone regeneration ability of the scaffolds’ is assessed using chronological radiography, micro-CT analysis, host tissue immuno-compatibility, histology, scanning electron microscope imagery, and fluorochrome labelling. In vitro and in vivo characterizations for osteogenesis and osseointegration show best results for scaffolds mineralized by electrodeposition, followed by alternate soaking and co-electrospinning. Non-mulberry silk fibroin grafted poly(Є-caprolactone) nanofibrous scaffold, mineralized by electrodeposition, could provide promising platform for bone healing and regeneration.

Synthesis of AgCl Mineralized Thin Film Composite Polyamide Membranes To Enhance Performance and Antifouling Properties in Forward Osmosis

This is the first report using an alternate soaking process (ASP) to mineralize the surfaces of thin film composite (TFC) polyamide membranes with silver chloride (AgCl) for forward osmosis (FO). Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) analysis confirmed even distribution of AgCl particles on the top of the membrane surfaces. Surface roughness, contact angle, and zeta potential measurements show that the AgCl mineralized membranes have smoother, more hydrophilic, and more negatively charged surfaces than unmodified membranes. Under FO operation (with deionized water feed and 1 M NaCl draw), we found that the mineralized membranes exhibit higher salt rejection and water flux than the original membranes. Fouling experiments with bovine serum albumin (BSA) show that the mineralized membranes have lower water flux decline ratios in BSA aqueous solution and higher water flux recovery ratios after simple hydraulic washing than unmodified TFC membranes.

Investigating the potential of combined growth factors delivery, from non-mulberry silk fibroin grafted poly(ɛ-caprolactone)/hydroxyapatite nanofibrous scaffold, in bone tissue engineering

Mineralized scaffolds have the advantage of better mimicking the natural bone structure and thus show an improved potential for bone tissue engineering. This study uses cycles of alternative soaking to deposit hydroxyapatite (HAp) layers upon non-mulberry silk fibroin (from Antheraea mylitta) grafted poly(ɛ-caprolactone) nanofibrous matrices. Alternate soaking, of one through three cycles, is used due to its simplicity and deposition efficiency. HAp deposition improved mechanical strength of the scaffolds up to two cycles of soaking (by nearly 75%). Analysis of mechanical properties, bioactivity and in vitro study results (with MG-63 cell line) showed scaffolds fabricated using two-cycle soaking to be the most suitable. These constructs were loaded with growth factors (transforming growth factor beta (TGF-β) 4ng and bone morphogenic protein-2 (rhBMP-2) 100ng) using carbodiimide-coupling reaction. The following three different combinations of growth factor loaded composites were analyzed: solely rhBMP-2, solely TGF-β and rhBMP-2-TGF-β combinations. Scaffolds with both growth factors supported cellular activity and proliferation better (p<0.01), generated greater calcium deposits (p<0.01), facilitated early cell differentiation and yielded significantly better expression of genes linked to bone growth (p<0.05). These dual growth factor loaded scaffolds are mechanically robust and enhance cell proliferation and early differentiation of osteoblast-like cells. They thus show potential of being further optimized for use in bone tissue engineering.

Crystallisation of hydroxyapatite in phosphorylated poly(vinyl alcohol) as a synthetic route to tough mechanical hybrid materials

Partially phosphorylated poly(vinyl alcohol) was prepared by treating poly(vinyl alcohol) with 100% phosphoric acid, and 5, 10 and 20% of the hydroxyl groups were converted to phosphoric acid ester. Addition of Ca2+ to an aqueous solution of phosphorylated poly(vinyl alcohol) gave a transparent gel. Five cycles of alternate soaking of the gel in aqueous CaCl2 and aqueous (NH4)2HPO4 were carried out to crystallise hydroxyapatite (HAP) in the phosphorylated poly(vinyl alcohol) matrix. The X-ray diffraction peaks of HAP formed in 5% phosphorylated PVA were sharp, while those of HAP formed in 20% phosphorylated PVA were broad. The contents of inorganic phase in the hybrid powder were increased from 58 to 76wt% as the fraction of phosphate groups in the gel was decreased from 20% to 5%. The hybrid powder was first subjected to uniaxial pressing, followed by cold isostatic pressing (CIP) and warm isostatic pressing (WIP) at 120°C at pressures of 300–980MPa, to obtain the specimens for three-point bending test. These hybrid specimens showed bending strengths of 15–53MPa. The hybrid compacts prepared from 10% phosphorylated poly(vinyl alcohol) showed the smallest Young's modulus, the largest displacement at break, and the largest fracture energy, showing that it has the highest toughness among the hybrid materials prepared from poly(vinyl alcohol) with varying degrees of phosphorylation.

Surface functionalization of tissue culture polystyrene plates with hydroxyapatite under body fluid conditions and its effect on differentiation behaviors of mesenchymal stem cells

The surfaces of polystyrene (PS) cell culture plates were functionalized with hydroxyapatite (HAp) under body fluid conditions utilizing protein adsorption layers and a pretreatment with an alternate soaking process (ASP) using solutions containing calcium and phosphate ions. Adsorption layers of human serum albumin (HSA) formed on the surface of each well of commercial 24-well PS plates by solution processes. CaCl2 and K2HPO4 solutions were alternately added to the wells, the plates were incubated to form the precursors, and this was followed by the addition of simulated body fluid (SBF) and a further incubation for 24h. These treatments resulted in the surfaces of the PS cell culture plates being completely covered with bone-like HAp. The coating of PS plates with HAp promoted the adhesion of mesenchymal stem cells (MSCs) and maintained cell growth that was as fast as that on tissue culture-treated PS (TCPS) plates. Osteogenic differentiation was greater, whereas adipogenic and chondrogenic differentiation was less in the culture on HAp-coated PS plates than in that on TCPS plates. The present method is useful for preparing HAp-coated PS plates at clean benches without the need for any expensive apparatus. HAp coated on PS plates by this method was a bone-like apatite with high bioactivity; therefore, the present HAp-coated PS plates are promising materials for assays of bone-related cells in the bone remodeling process.

Effect of Calcium Phosphate-Hybridized Tendon Graft in Anatomic Single-Bundle ACL Reconstruction in Goats.

Background:We previously developed a novel technique using an alternate soaking process that improves tendon-bone healing by hybridizing the tendon graft with calcium phosphate (CaP). However, the effects of the CaP-hybridized tendon graft on anatomic single-bundle anterior cruciate ligament (ACL) reconstruction remain unclear.Purpose:To determine the effects of CaP-hybridized tendon grafts compared with untreated tendon grafts 6 months after anatomic single-bundle ACL reconstruction using a goat model.Study Design:Controlled laboratory study.Methods:Animals were divided into a CaP group (n = 5 goats) and a control group (n = 5 goats), and we analyzed (1) knee kinematics and in situ forces under applied anterior tibial loads of 50 N and internal tibial torque of 2.0 N·m in the grafts at full extension and at 60° and 90° of knee flexion, (2) the mean percentage of bone tunnel enlargement using computed tomography (CT), and (3) the histology of the tendon-bone interface.Results:The in situ forces under applied anterior tibial loads of 50 N at 60° and 90° of knee flexion in the CaP group were greater than those in the control group (P < .05). The red safranin-O–stained area, indicating glycosaminoglycans in the cartilage layers at the joint aperture sites of the anterior femoral and posterior tibial bone tunnel, was greater in the CaP group than that in the control group (P < .05). The lengths of the nonbonding gap area between the anterior femoral and posterior tibial bone tunnels in the control group were greater than those in the CaP group (P < .05). No significant difference could be detected in the mean percentage of bone tunnel enlargement between the 2 groups.Conclusion:The CaP-hybridized tendon graft enhanced tendon-bone healing at the joint aperture site in both anterior femoral and posterior tibial tunnels 6 months after anatomic single-bundle ACL reconstruction in goats. The in situ forces under applied anterior tibial loads at greater flexion angles in the CaP group increased compared with controls.Clinical Relevance:Anatomic single-bundle ACL reconstruction using CaP-hybridized tendon grafts may lead to better postoperative knee function.

Nanohydroxyapatite-coated hydroxyethyl cellulose/poly (vinyl) alcohol electrospun scaffolds and their cellular response

ABSTRACTThe present study focused on the preparation of nanohydroxyapatite (nHA)-coated hydroxyethyl cellulose/polyvinyl alcohol (HEC/PVA) nanofibrous scaffolds for bone tissue engineering application. The electrospun HEC/PVA scaffolds were mineralized via alternate soaking process. FESEM revealed that the nHA was formed uniformly over the nanofibers. The nHA mineralization enhanced the tensile strength and reduced the elongation at breakage of scaffolds. The wettability of the nanofibrous scaffolds was significantly improved. The in vitro biocompatibility of scaffolds was evaluated with human osteosarcoma cells. nHA-coated scaffolds had a favorable effect on the proliferation and differentiation of osteosarcoma cell and could be a potential candidate for bone regeneration.

Fabrication and evaluation of hydroxyapatite-chitosan scaffold via simulated body fluid biomimetic mineralization

This research aimed to fabricate a hydroxyapatite (HA)-chitosan scaffold via simulated body fluid (SBF) biomimetic mineralization and determine how mineralization time affects scaffold construction and cell compatibility. The HA-chitosan scaffolds were fabricated by freeze-drying technique and then subjected to precalcification, also known as alternative soaking method. Afterward, precalcificated scaffolds were placed into the SBF to conduct the mineralization process. Mineralization time was set at 7, 14, and 21 days, corresponding to three experimental groups. Pure chitosan scaffolds acted as the control group, and the physical and chemical properties of the four groups were tested. Osteogenic-induced adipose-derived stem cells (ADSCs) were seeded into the scaffolds to investigate the scaffolds' cell compatibility. The mineral substance of the 14-day group exhibited a uniform distribution. The crystal composition of the mineral substance suited the HA's features. The compressive elastic modulus increased along with the extension of mineralization time. The 21-day group showed a statistically significant increase in compressive elastic modulus compared with the control group (P < 0.05). The cell proliferation level of the 14-day group was significantly the highest among the three experimental groups (P < 0.05). The calcium ion and the type I collagen had the highest secretion amount when the cells were seeded into the 14-day group. The SBF biomimetic mineralization method can be used to fabricate HA-chitosan bone-tissue-engineering scaffolds. The biological compatibility, as well as the chemical and physical properties, reached the optimum levels at day 14.

Nacrelike-structured multilayered polyelectrolyte/calcium carbonate nanocomposite membrane via Ca-incorporated layer-by-layer-assembly and CO2-induced biomineralization

The separation of metallic ions in particular heavy metallic ions in aqueous solution is a great challenge in membrane science. Herein, a simple and facile strategy—Ca2+-incorporated layer-by-layer (LbL) assembly and CO2-induced biomineralization was developed and applied to the preparation of nacrelike-structured multilayered PEI/PSS-CaCO3 nanocomposite membrane on PAN substrate. These nanocomposite membranes showed higher rejection (≥99.3%) and permeable flux (≥49.1Lm−2MPa−1h−1) for divalent metallic ions such as Mg2+, Cu2+, Ca2+, Ni2+, Zn2+, and Cd2+ in aqueous solution compared to the multilayer PEI/PSS or PEI/PSS-CaCO3 membrane prepared by alternate soaking process. High rejection and flux can be attributed to the following three aspects: (i) The incorporation of Ca2+ into PEI and PSS greatly reduces the formation of crosslinked structure of PEI and PSS and probably induces the ordered arrays of amine and sulfonate groups from PEI and PSS on membrane; (ii) Due to limited Ca2+ ions source and spatial limitation of crosslinking of PEI/PSS phase the nanostructured CaCO3 was in-situ formed after CO2-induced biomineralization and created some additional short paths (the bulgy section of PEI/PSS layer) that are beneficial to the permeability of membrane; (iii) Due to the calcification of incorporated Ca2+ ions the formed H+ ions makes amine and sulfonate groups further protonation that improves surface hydrophilicity of membrane. On the basis of a long-term performance stability, high rejection and flux, the nacrelike-structured multilayered PEI/PSS-CaCO3 nanocomposite membrane can be used as a promising membrane in industry for the separation of metallic ions in aqueous solution.

Formation and properties of polyelectrolytes/TiO2 composite coating on wood surfaces through layer-by-layer assembly method

Abstract A transparent and protective multilayer coating composed of poly(allylamine hydrochloride) (PAH), poly(styrene sulfonic acid) sodium salt (PSS), and nano-TiO2 films was fabricated on wood surfaces by layer-by-layer assembly method. The coating was formed through pre-immobilization of cationic PAH layer on wood substrate, followed by alternate soaking cycles in pH-controlled anionic PSS solution and TiO2 colloidal solution. The structure and properties of the assembled coating were characterized through scanning electron microscopy (SEM), energy disperse X-ray analysis (EDXA), UV reflection and absorption, colorimetry, and contact angle (CA) measurement. Results revealed that the coverage uniformity and thickness were improved with increasing number of PSS/TiO2 bilayers. The coating masked the cell wall ultrastructure while leaving the microscale features intact. The anatase TiO2 in the assembled coating enhanced the UV stability of wood and resulted in a lowered photochromism. Furthermore, the photocatalytic capability of the nano-TiO2 films in degrading dyes of rhodamine B and methylene blue was verified. The nano-TiO2 film on the top surface of the coating embodied a superhydrophilicity, showing self-cleaning and anti-fog capabilities. Stearic acid modification altered the superhydrophilicity to hydrophobicity with CA of 140°.

Composite of porous starch-silk fibroin nanofiber-calcium phosphate for bone regeneration

New bioactive nanobiocomposite scaffolds based on silk fibroin nanofiber-porous starch are presented for potential bone tissue regeneration. The silk fibroin nanofibers were fabricated directly via wet electrospinning using methanol coagulation bath and then the chopped electrospun nanofibers were incorporated into the starch matrix, followed by particulate leaching and freeze-drying. To achieve bioactivity, the calcium phosphate was then deposited throughout the fabricated scaffolds via alternate soaking in saturated calcium and phosphate solutions at 37°C. The morphology, structure, swelling, and calcium phosphate forming ability of the scaffolds were evaluated and the results indicated that addition of silk fibroin nanofibers into the starch matrix reduced the mean pore size, porosity, and water uptake of the fabricated scaffolds. Moreover, the deposited calcium phosphate layer consists of both brushite and apatitic calcium phosphate. The highest amount of formed calcium phosphate is evident in the starch matrix and increasing the amount of silk fibroin nanofibers decreases calcium phosphate formation. Cell culture experiments with osteoblast-like cells (MG63) on the scaffolds coated with calcium phosphate demonstrated that incorporation of SF nanofibers into the starch hydrogel improves cell viability, proliferation, and attachment.

Hydrogel-free alternate soaking technique for micropatterning of bioactive ceramics on wettability-patterned substrates around room temperature

Abstract We discuss a hydrogel-free alternate soaking technique for the micropatterning of bioactive ceramics on wettability-patterned substrates around room temperature. Wettability-patterned substrates were fabricated by partly removing self-assembled monolayers on glass plates using mask exposure of UV–Ozone. Hydroxyapatite scaffolds or calcium carbonate films were formed selectively on the hydrophilic surface of the wettability-patterned substrates by alternate soaking of the wettability-patterned substrates in two kinds of calcifying solutions. The wettability-patterned substrates formed with hydroxyapatite scaffolds were immersed in hydroxyapatite precursor for the growth of hydroxyapatite crystals. The c plates of hydroxyapatite crystals were highly aligned parallel to the substrates in the initial stage. This technique allow for the micropatterning of bioactive ceramics with low cost, low energy and short time because this technique does not require bioactive glasses which require calcination process for activation, or hydrogels which need long diffusion time of hydroxyapatite precursor, contributing to the application to templates for bio-living culture cells and cell arrays for medical diagnosis with environmentally-friendly fabrication process in the future.

Hydroxyapatite agarose composite gels as a biochemical material for the repair of alveolar bone defects due to cleft lip and palate

PurposeHydroxyapatite agarose composite gel (HAp gel) is a radiolucent and absorbable bone–graft material that differs from hydroxyapatite ceramic; it is more rapidly absorbed and replaced by new bone than existing materials. This study examined the usefulness of HAp gel in the repair of alveolar bone defects due to cleft lip and palate. Materials and methodsHAp gel was prepared by an alternate soaking technique. HAp gel was mixed with an equal volume of autologous bone and applied to bone defects due to cleft lip and palate (mixture group). As a reference group, 10 cases were treated with autologous bone graft alone (bone group). To determine the presence of osteogenesis, bone density on X-ray film was measured at the transplanted site and surrounding normal bone, and the ratio was calculated. The marginal bone level was assessed by intraoral radiography. ResultsIn the mixture group, the bone density of the transplanted site increased on radiography 1 month postoperatively and was maintained thereafter. A similar increase in bone density was observed in the bone group. The marginal bone level in the alveolar cleft was similar between groups. There were no complications such as infection and prolonged inflammation of the transplanted bone in association with the use of HAp gel. ConclusionsThe mixture of HAp gel and autologous bone is as effective as autologous bone in the treatment of bone defects due to cleft lip and palate. HAp gel can reduce the weight of autologous bone required.

Response of human mesenchymal stem cells to intrafibrillar nanohydroxyapatite content and extrafibrillar nanohydroxyapatite in biomimetic chitosan/silk fibroin/nanohydroxyapatite nanofibrous membrane scaffolds.

Incorporation of nanohydroxyapatite (nHAP) within a chitosan (CS)/silk fibroin (SF) nanofibrous membrane scaffold (NMS) may provide a favorable microenvironment that more closely mimics the natural bone tissue physiology and facilitates enhanced osteogensis of the implanted cell population. In this study, we prepared pristine CS/SF NMS, composite CS/SF/nHAP NMS containing intrafibrillar nHAP by in situ blending of 10% or 30% nHAP before the electrospinning step, and composite CS/SF/nHAP NMS containing extrafibrillar nHAP by depositing 30% nHAP through alternative soaking surface mineralization. We investigated the effect of the incorporation of HAP nanoparticles on the physicochemical properties of pristine and composite NMS. We confirmed the presence of ~30 nm nHAP in the composite nanofibrous membranes by thermogravimetry analysis (TGA), X-ray diffraction (XRD), and scanning electron microscopy (SEM), either embedded in or exposed on the nanofiber. Nonetheless, the alternative soaking surface mineralization method drastically influenced the mechanical properties of the NMS with 88% and 94% drop in Young’s modulus and ultimate maximum stress. Using in vitro cell culture experiments, we investigated the effects of nHAP content and location on proliferation and osteogenic differentiation of human bone marrow mesenchymal stem cells (hMSCs). The proliferation of hMSCs showed no significant difference among pristine and composite NMS. However, the extent of osteogenic differentiation of hMSCs was found to be positively correlated with the content of nHAP in the NMS, while its location within the nanofiber played a less significant role. In vivo experiments were carried out with hMSCs seeded in CS/SF/30%nHAP NMS prepared by in situ blending and subcutaneous implantation in nude mice. Micro-computed tomography images as well as histological and immunohistochemical analysis of the retrieved hMSCs/NMS construct 1 and 2 months postimplantation indicated that NMS had the potential for bone regeneration and can be suggested as a promising scaffold for bone tissue engineering.

Preparation of composites of liquid-crystalline matrix of poly(p-phenylene-sulfoterephthalamide) and CaCO3byIn situmineralization

Liquid-crystalline (LC) hydrogels were obtained from an aqueous solution of poly(p-phenylene-sulfoterephthalamide) (PPST) by the addition of calcium ions (Ca2+). The critical hydrogel formation ratio of Ca2+ to the sulfonic acid group in PPST (crtRCa = [Ca2+]/[ ‐SO3−]) depended on the concentration of PPST, and was independent of the molecular weight of PPST. When the LC hydrogel was prepared at a concentration of 0.5 wt % and crtRCa = 0.6, and was exposed to ammonium carbonate vapor for 96 h, all Ca2+ in the LC hydrogel were converted into calcite crystals. The alternate soaking process for the LC hydrogel induced the formation of two mesocrystal morphologies on and in the Ca2+ cross-linked LC hydrogel. Plate-like calcite mesocrystals grew at the hydrogel/solution interface and cubic mesocrystals were present in the inner space of the hydrogel, thus composites with some ordered structures of LC matrix and CaCO3 have been prepared through in situ mineralization. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41455.

Surface mineralization of commercial thin-film composite polyamide membrane by depositing barium sulfate for improved reverse osmosis performance and antifouling property

In this study, a novel approach, namely surface mineralization, was adopted to modify the commercial thin-film composite (TFC) polyamide (PA) reverse osmosis (RO) membrane for improved membrane properties. BaSO4-based mineral coating was deposited on the surface of the PA-RO membrane by alternate soaking process (ASP) using aqueous solutions containing barium chloride (BaCl2) and sodium sulfate (Na2SO4), respectively. Membranes with different mineralization degrees were prepared by varying the number of ASP cycles. The mineralized TFC PA-RO membranes were characterized through FESEM microscopy, AFM analysis, EDX analysis, zeta-potential analysis, contact angle measurement and cross-flow permeation test. It was found that the mineral coating composed of BaSO4 particles distributed evenly on membrane surface. The surface of the membrane became more hydrophilic and negatively charged after mineralization and the membranes modified under certain conditions exhibited both increased water flux and salt rejection. Fouling experiments with bovine serum albumin (BSA) aqueous solution also demonstrated that the BaSO4-based surface coating layer could effectively alleviate the adsorption and deposition of foulant molecules on the membrane surface through enhancing electrostatic repulsion and lowing hydrophobic interaction between BSA molecules and membrane surface, and that the mineralized membrane possessed improved fouling resistance to BSA aqueous solution.

Directing osteogenesis of stem cells with hydroxyapatite precipitated electrospun eri–tasar silk fibroin nanofibrous scaffold

Stimulating stem cell differentiation without growth factor supplement offers a potent and cost-effective scaffold for tissue regeneration. We hypothesise that surface precipitation of nano-hydroxyapatite (nHAp) over blends of non-mulberry silk fibroin with better hydrophilicity and RGD amino acid sequences can direct the stem cell towards osteogenesis. This report focuses on the fabrication of a blended eri–tasar silk fibroin nanofibrous scaffold (ET) followed by nHAp deposition by a surface precipitation (alternate soaking in calcium and phosphate solution) method. Morphology, hydrophilicity, composition, and the thermal and mechanical properties of ET/nHAp were examined by field emission scanning electron microscopy, TEM, FT-IR, X-ray diffraction, TGA and contact angle measurement and compared with ET. The composite scaffold demonstrated improved thermal stability and surface hydrophilicity with an increase in stiffness and elastic modulus (778 ± 2.4 N/m and 13.1 ± 0.36 MPa) as compared to ET (160.6 ± 1.34 N/m and 8.3 ± 0.4 MPa). Mineralisation studies revealed an enhanced and more uniform surface deposition of HAp-like crystals, while significant differences in cellular viability and attachment were observed through 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and confocal microscopy study. The cell viability and expression of adhesion molecules (CD 44 and CD 29) are found to be optimum for subsequent stages of growth proliferation and differentiation. The rates of proliferation have been observed to decrease owing to the transition of MSC from a state of proliferation to a state of differentiation. The confirmation of improved osteogenic differentiation was finally verified through the alkaline phosphatase assay, pattern of gene expression related to osteogenic differentiation and morphological observations of differentiated cord blood human mesenchymal stem cells under fluorescence microscope. The results obtained showed the improved physicochemical and biological properties of the ET/nHAp scaffold for osteogenic differentiation without the addition of any growth factors.

In situ mineralization of hydroxyapatite on poly(vinyl alcohol) monolithic scaffolds for tissue engineering

A poly(vinyl alcohol) (PVA)/hydroxyapatite (HAp) composite monolithic scaffold is prepared via thermally impacted non-solvent induced phase separation method, successively followed by an alternate soaking process. The morphology of the resulting composite monolith is observed by scanning electron microscopy (SEM). The formation of hydroxyapatite is confirmed by X-ray diffraction, SEM in combination with energy dispersive X-ray analysis, and Fourier transform infrared spectroscopy. The effects of soaking cycle and soaking time upon the formation of hydroxyapatite on the monolith surface are systematically investigated. With the increase of soaking cycle and soaking time, the amount of the formed hydroxyapatite increases. As the soaking cycle increases, the water uptake of the composite monolith decreases. The PVA/HAp composite monolith greatly has a promising application as scaffold of bone tissue engineering.