A Facile and Universal Method for Preparing Polyethylene Glycol-Metal Hybrid Nanoparticles and Their Application in Tumor Theranostics.

Metal ions are of widespread interest owing to their brilliant biomedical functions. However, a simple and universal nanoplatform designed for assembling a range of functional metal ions has not been explored. In this study, a concept of polyethylene glycol (PEG)-mediated transport of metal ions is proposed. 31 types of PEG-metal hybrid nanoparticles (P-MNPs) are successfully synthesized through anionic ring-opening polymerization (ROP), "thiol-ene" click reaction, and subsequent incorporation with multiple metal ions. Compared with other methods, the facile method proposed in this study can provide a feasible approach to design MNPs (mostly <200 nm) containing different metal ions and thus to explore their potential for cancer theranostics. As a proof-of-concept demonstration, four types P-MNPs, i.e., PEG-metal hybrid copper nanoparticles (PEG-Cu NPs), ruthenium nanoparticles (PEG-Ru NPs), and manganese nanoparticles (PEG-Mn NPs) or gadolinium nanoparticles (PEG-Gd NPs), are proven to be tailored for chemodynamic therapy, photothermal therapy, and magnetic resonance imaging of tumors, respectively. Overall, this study provides several metal ions-based nanomaterials with versatile functions for broad applications in cancer theranostics. Furthermore, it offers a promising tool that can be utilized for processing other metal-based nanoparticles and exploring their potential in the biomedical field.

Fabrication and in vitro evaluation of PCL/gelatin hierarchical scaffolds based on melt electrospinning writing and solution electrospinning for bone regeneration.

As an emerging 3D printing technique, melt electrospinning writing (MEW) has been used to fabricate scaffolds with controllable structure and good mechanical strength for bone regeneration. However, how to further improve MEW scaffolds with nanoscale extracellular matrix (ECM) mimic structure and bioactivity is still challenging. In this study, we proposed a simple composite process by combining MEW and solution electrospinning (SE) to fabricate a micro/nano hierarchical scaffold for bone tissue engineering. The morphological results confirmed the hierarchical structure with both well-defined MEW microfibrous grid structure and SE random nanofiber morphology. The addition of gelatin nanofibers turned the scaffolds to be hydrophilic, and led to a slight enhancement of mechanical strength. Compared with PCL MEW scaffolds, higher cell adhesion efficiency, improved cell proliferation and higher osteoinductive ability were achieved for the MEW/SE composite scaffolds. Finally, multilayer composite scaffolds were fabricated by alternately stacking of MEW layer and SE layer and used to assess the effect on cell ingrowth in the scaffolds. The results showed that gelatin nanofibers did not inhibit cell penetration, but promoted the three-dimensional growth of bone cells. Thus, the strategy of the combined use of MEW and SE is a potential method to fabricate micro/nano hierarchical scaffolds to improve bone regeneration.

Micro/nanostructured TiO2/ZnO coating enhances osteogenic activity of SaOS-2 cells.

Although titanium implants account for a large proportion of the commercial dental market, their bioactivity are inadequate in many applications. A micro- and nano- scale hierarchical surface topography of the implant is suggested for rapid osseointegration from the biomimetic perspective. Moreover, Zinc (Zn) is an essential element in the skeletal system. Thus, a micro/nanostructured TiO2/ZnO coating, produced by micro-arc oxidation, and hydrothermal treatment, and heat treatment, was designed to endow the implant surface with enhanced osteogenic capacity. Physiochemical properties and biological effects of this coating were investigated in our study. The annealed micro/nanostructured TiO2/ZnO coating exhibited higher hydrophilicity and fibronectin adsorption ability compared to the micro-arc oxidation modified TiO2 coating. SaOS-2 cells grown on the annealed micro/nanostructured TiO2/ZnO coating showed increased alkaline phosphatase activity and collagen secretion, and immunofluorescence labeling revealed an upregulation of osteopontin, collagen type ι and osteocalcin. The micro/nanostructure and incorporation of Zn were considered to perform positive effect on the enhanced osteogenic activity of SaOS-2 cells. In conclusion, the micro/nanostructured TiO2/ZnO structure is simple, stable, and easy to produce and scale up, has promising applications in the surface modification of titanium implants.

Formulation of Biocompatible Targeted ECO/siRNA Nanoparticles with Long-Term Stability for Clinical Translation of RNAi.

Nanoparticle based siRNA formulations often suffer from aggregation and loss of function during storage. We in this study report a frozen targeted RGD-polyethylene glycol (PEG)-ECO/siß3 nanoparticle formulation with a prolonged shelf life and preserved nanoparticle functionality. The targeted RGD-PEG-ECO/siß3 nanoparticles are formed by step-wised self-assembly of RGD-PEG-maleimide, ECO, and siRNA. The nanoparticles have a diameter of 224.5 ± 9.41 nm and a zeta potential to 45.96 ± 3.67 mV in water and a size of 234.34 ± 3.01 nm and a near neutral zeta potential in saline solution. The addition of sucrose does not affect their size and zeta potential and substantially preserves the integrity and biological activities of frozen and lyophilized formulations of the targeted nanoparticles. The frozen formulation with as low as 5% sucrose retains nanoparticle integrity (90% siRNA encapsulation), size distribution (polydispersity index [PDI] ≤20%), and functionality (at least 75% silencing efficiency) at -80°C for at least 1 year. The frozen RGD-PEG-ECO/siß3 nanoparticle formulation exhibits excellent biocompatibility, with no adverse effects on hemocompatibility and minimal immunogenicity. As RNAi holds the promise in treating the previously untreatable diseases, the frozen nanoparticle formulation with the low sucrose concentration has the potential to be a delivery platform for clinical translation of RNAi therapeutics.

Pretreatment with γ-Valerolactone/[Mmim]DMP and Enzymatic Hydrolysis on Corncob and Its Application in Immobilized Butyric Acid Fermentation.

Corncob is a widely available raw material with high carbohydrate and low lignin content. To improve corncob conversion to the fermentable sugars, a novel method encompassing pretreatment using the γ-valerolactone (GVL)/1-methyl-3-methylimidazolium dimethylphosphite ([Mmim]DMP) system integrated with cellulase hydrolysis was developed and optimized. It is confirmed that lignin was extracted efficiently after combined pretreatment and that the subsequent enzymatic saccharification efficiency could be significantly enhanced, resulting in the yield of 94.9% glucose from cellulose and 53.3% xylose from xylan, respectively. Furthermore, the above fermentable sugars were used as carbon source for Clostridium tyrobutyricum immobilized in macroporous Ca-alginate-lignin beads with the extracted lignin as the active ingredient to evaluate the fermentability of butyric acid. The results showed that high butyrate productivity of 0.47 g/L/h and yield of 0.45 g/g were obtained after 10 repeated batches of fermentation, demonstrating an effective process for the production of butyric acid from abundant corncob waste-biomass.

The immunomodulatory effects of Zn-incorporated micro/nanostructured coating in inducing osteogenesis.

Micro/nanostructured TiO2/ZnO coating has been shown to possess multiple functions, including antibacterial activity and bioactivity. Osteoblast-like SaOS-2 cells were employed for evaluating the in vitro osteogenic capacity of this coating and positive results were obtained. However, traditional principles of osseointegration focus only on the osteogenic differentiation alone. The effects of immunomodulation on the osteogenic activity have been largely ignored. In this study, the inflammatory responses of macrophages on the micro/nanostructured TiO2/ZnO coating were investigated. The extract media of macrophage cell line RAW264.7 cultured on the TiO2/ZnO coating were collected as indirect co-culture conditioned media. The osteogenic activity of SaOS-2 cells in the conditioned media was investigated. Adhesion, ALP activity and extracellular mineralization of cells grown in the conditioned media extracted from the micro/nanostructured TiO2/ZnO coating were found to be enhanced, compared to those grown in the conditioned media extracted from the macroporous TiO2 coating. The immune microenvironment produced by the micro/nanostructured TiO2/ZnO coating showed excellent capacity to promote osteogenesis, indicating that this coating could be a promising candidate for implant surface modification in orthopaedic and dental applications. Furthermore, this work could help us understand the interplay between the host immune system and the osteoimmunomodulatory properties of the biomaterials, and optimize the design for coating biomaterials.

The Cu-containing TiO2 coatings with modulatory effects on macrophage polarization and bactericidal capacity prepared by micro-arc oxidation on titanium substrates.

The implant materials with both osteogenic and anti-bacterial properties are promising for orthopedic and dental applications. Moreover, the inflammatory response induced by biomaterials has been recently recognized as one of the critical factors in determining implantation fate. A new generation of implant materials should have modulatory effects on the local inflammatory environment such that it favors osteogenesis and osteointegration instead of being bio-inert. In this study, the micro-arc oxidation (MAO) technique was employed to fabricate Cu-containing ceramic coatings on titanium substrates. The macrophages cultured on Cu-containing MAO-fabricated surfaces were polarized to M1 phenotype, evidenced by the high expression levels of inducible nitric oxide synthase (iNOS), low expression levels of arginase1 (Arg1), enhanced pro-inflammatory cytokine interleukin-6 (IL-6) release and inhibited IL-4 and IL-10 (anti-inflammatory cytokines) release. The MAO-treated surface incorporated with larger amounts of Cu (referred as Cu(h)-MAO) could modulate a favorable inflammatory microenvironment for osteoblast-like cell differentiation. Moreover, the macrophages cultured on Cu(h)-MAO surface exhibited enhanced bacteria uptake and killing rate, indicating that the Cu(h)-MAO surface promoted the bactericidal capacity of macrophages. Together, Cu could be used as a promising modulatory agent for macrophage functions. The integration of Cu in biomaterials could lead to enhanced macrophage-mediated osteogenesis and bactericidal capacity.

The osteogenic, inflammatory and osteo-immunomodulatory performances of biomedical Ti-Ta metal-metal composite with Ca- and Si-containing bioceramic coatings.

It is known that good mechanical properties, low modulus to reduce stress-shielding effect, favorable osteogenic activity and limited inflammatory response are critical factors for orthopedic implants to induce excellent osteointegration. In this study, Ti-20% Ta metal-metal composite (referred as Ti-Ta) which consisted of Ti- and Ta-rich phases was fabricated via the strategy of powder metallurgy. Micro-arc oxidation (MAO) was employed to modify the surface of Ti-Ta composite. The surfaces of Ti-Ta composite after MAO treatment at an applied voltage of 250 (referred as MAO-250 V) or 300 V (referred as MAO-300 V) exhibited three distinct zones with significantly different morphological features and surface chemistry. Osteoblast-like SaOS-2 cells were found to be preferential to attach on the Ta-rich phase and its surrounding areas, exhibiting an area-dependent adhesion tendency. However, the attachment of Raw 264.7 macrophages was found to be insensitive to the surface characteristics. The proliferation and differentiation of SaOS-2 cells cultured on various surfaces basically followed the trend: MAO-modified surfaces > Ti-Ta surface > Ti surface. The Ti-Ta and MAO-modified surfaces were found to inhibit the inflammatory response and polarize macrophages to anti-inflammatory M2 phenotype compared to Ti surface. Moreover, the microenvironments created by Ti-Ta, MAO-250 V and MAO-300 V/macrophage interactions promoted the proliferation and differentiation of SaOS-2 cells compared to that created by Ti/macrophage interactions. MAO-300 V surface exhibited further enhanced positive osteo-immunomodulatory effects compared to Ti-Ta surface. Together, the Ti-20% Ta metal-metal composite modified by MAO at an applied voltage of 300 V is considered as a promising implant material for orthopedic applications.

A cyclo-trimer of acetonitrile combining fluorescent property with ability to induce osteogenesis and its potential as multifunctional biomaterial.

A biomaterial combining fluorescent property with ability to induce osteogenesis can serve as an ideal multifunctional scaffold in bone tissue engineering. However, the frequently used fluorescent agents can only serve as imaging probes. The polymer or oligomer with a conjugated system containing nitrogen atoms will fulfill these criteria. In this study, a cyclo-trimer of acetonitrile is synthesized using a facile method, which is proved to be 4-amino-2,6-dimethylpyrimidine. The cyclo-trimer of acetonitrile demonstrates strong intrinsic photoluminescence and has the potential for in vivo imaging. The cyclo-trimer of acetonitrile shows no toxicity both in vitro and in vivo. Moreover, the cyclo-trimer of acetonitrile significantly promotes the osteogenesis of SaOS-2 cells by improving alkaline phosphatase activity, collagen type I and osteocalcin expression, as well as expressions of osteoblastic genes, and enhances the matrix mineralization of rBMSCs. Thus, the cyclo-trimer of acetonitrile synthesized in present study illustrates the employment of this kind multifunctional biomaterial in bone tissue engineering and may offer great potential in biomedical applications where bioimaging and osteogenesis are both required. STATEMENT OF SIGNIFICANCE: A conjugated cyclo-trimer of acetonitrile combining intrinsic fluorescent property with ability to induce osteogenesis was reported. Different from the traditional fluorescent dye or quantum dots, which are just "imaging agents", the cyclo-trimer of acetonitrile can serve as a multifunctional biomaterial and offer great potential in biomedical applications where bioimaging and osteogenesis are both required. To our best knowledge, the fluorescent property, especially fluorescent property in vivo and the ability of this molecule to induce osteogenesis have not been reported before. Our work illustrates the employment of this kind multifunctional biomaterial in bone tissue engineering and will highlight the importance of multifunctional biomaterial in biomedical applications.

A tissue-engineered scale model of the heart ventricle.

Laboratory studies of the heart use cell and tissue cultures to dissect heart function yet rely on animal models to measure pressure and volume dynamics. Here, we report tissue-engineered scale models of the human left ventricle, made of nanofibrous scaffolds that promote native-like anisotropic myocardial tissue genesis and chamber-level contractile function. Incorporating neonatal rat ventricular myocytes or cardiomyocytes derived from human induced pluripotent stem cells, the tissue-engineered ventricles have a diastolic chamber volume of ~500 µl (comparable to that of the native rat ventricle and approximately 1/250 the size of the human ventricle), and ejection fractions and contractile work 50-250 times smaller and 104-108 times smaller than the corresponding values for rodent and human ventricles, respectively. We also measured tissue coverage and alignment, calcium-transient propagation and pressure-volume loops in the presence or absence of test compounds. Moreover, we describe an instrumented bioreactor with ventricular-assist capabilities, and provide a proof-of-concept disease model of structural arrhythmia. The model ventricles can be evaluated with the same assays used in animal models and in clinical settings.

Injectable hyaluronan-methylcellulose composite hydrogel crosslinked by polyethylene glycol for central nervous system tissue engineering.

Spontaneous recovery ability of central nerves has inspired researchers to focus on tissue engineering techniques, especially scaffolds. To obtain a material with an appropriate degrading rate, an injectable composite hydrogel HAMC consisting of hyaluronic acid and methylcellulose was prepared using polyethylene glycol as a cross linker in this study. HAMC combined the advantages of two components to be fast-gelling, injectable, degradable, biocompatible, and it was able to meet some special shape requirement for injured tissue by in-situ forming. Moreover, due to the crosslinking effects polyethylene glycol brought to methylcellulose, the rheological properties and stability of HAMC were greatly improved, which could prolong the residence time of this hydrogel effectively. Cell viability results showed HAMC was cytocompatible for further applications in vivo, and would be a promising choice for neural tissue engineering in the future.

Zero-order controlled release of BMP2-derived peptide P24 from the chitosan scaffold by chemical grafting modification technique for promotion of osteogenesis in vitro and enhancement of bone repair in vivo.

Combination of tissue-engineered bone scaffolds with cell-adhesive, osteoconductive, or osteoinductive biomolecules is a critical strategy to improve their properties that significantly influence cellular behaviors, such as adhesion, proliferation, and differentiation, which is beneficial for critical-sized bone defects repairing. However, the traditional surface modification techniques, such as physical adsorption, coating, and plasma treatment, et al, have great limitations for immobilization of bioactive molecules due to undesirable controlled delivery performance or overly complex multistep procedures. In this study, we functionalized the chitosan/hydroxyapatite (CS/HA) biomimetic composite scaffold for controlled delivery of BMP2-derived peptide (P24) by the chemical grafting modification technique: firstly, P24 was conjugated with a thiolated chitosan, chitosan-4-thiobutylamidine (CS-TBA); secondly, the resultant CS-P24 was then combined with HA to prepare CS-P24/HA scaffolds. The effect of CS-P24/HA scaffolds on bone regeneration was evaluated, along with the underlying biological mechanisms responsible in vitro and in vivo. In vitro, the controlled and sustained release of bioactive P24 could last up to 90 days, furthermore, the release profiles of CS-5%P24/HA and CS-10%P24/HA were linear and could be fitted according to zero-order kinetic model (R2=0.9929; R2=0.9757); P24 on the scaffold significantly promoted cell adhesion, proliferation, osteodifferentiation, and mineralization with synergistic effects. Bone marrow stromal cells (BMSCs) revealed spindle-shaped surface morphology, indicating the CS-P24/HA scaffolds supported cell adhesion and possessed a high proliferation rate that varied according to the P24 concentration levels. Furthermore, mRNA levels for OCN, Runx2, and collagen I were significantly up-regulated on CS-P24/HA scaffolds compared with cells grown on CS/HA scaffolds in vitro (p < 0.05). Similarly, the BMSCs exhibited a higher ALP expression and calcium deposition level on CS-P24/HA scaffolds compared with CS/HA scaffolds (p < 0.05). In vivo, osteoinductive studies revealed a significantly higher ectopic osteogenesis level of CS-10%P24/HA scaffolds in rat dorsal muscle pockets compared with that of CS/HA scaffolds. Finally, CS-P24/HA scaffolds showed superior performance in the reconstruction of rat calvarial bone defects. This novel CS-P24/HA scaffold is deemed a strong potential candidate for the repair of bone defects in human bone tissue engineering.

Mithramycin-loaded mPEG-PLGA nanoparticles exert potent antitumor efficacy against pancreatic carcinoma.

Previous studies have shown that mithramycin A (MIT) is a promising candidate for the treatment of pancreatic carcinoma through inhibiting transcription factor Sp1. However, systemic toxicities may limit its clinical application. Here, we report a rationally designed formulation of MIT-loaded nanoparticles (MIT-NPs) with a small size and sustained release for improved passive targeting and enhanced therapeutic efficacy. Nearly spherical MIT-NPs with a mean particle size of 25.0±4.6 nm were prepared by encapsulating MIT into methoxy poly(ethylene glycol)-block-poly(d,l-lactic-co-glycolic acid) (mPEG-PLGA) nanoparticles (NPs) with drug loading of 2.11%±0.51%. The in vitro release of the MIT-NPs lasted for >48 h with a sustained-release pattern. The cytotoxicity of MIT-NPs to human pancreatic cancer BxPC-3 and MIA Paca-2 cells was comparable to that of free MIT. Determined by flow cytometry and confocal microscopy, the NPs internalized into the cells quickly and efficiently, reaching the peak level at 1-2 h. In vivo fluorescence imaging showed that the prepared NPs were gradually accumulated in BxPC-3 and MIA Paca-2 xenografts and retained for 168 h. The fluorescence intensity in both BxPC-3 and MIA Paca-2 tumors was much stronger than that of various tested organs. Therapeutic efficacy was evaluated with the poorly permeable BxPC-3 pancreatic carcinoma xenograft model. At a well-tolerated dose of 2 mg/kg, MIT-NPs suppressed BxPC-3 tumor growth by 96%. Compared at an equivalent dose, MIT-NPs exerted significantly higher therapeutic effect than free MIT (86% versus 51%, P<0.01). Moreover, the treatment of MIT and MIT-NPs reduced the expression level of oncogene c-Myc regulated by Sp1, and notably, both of them decreased the protein level of CD47. In summary, the novel formulation of MIT-NPs shows highly therapeutic efficacy against pancreatic carcinoma xenograft. In addition, MIT-NPs can downregulate CD47 expression, implying that it might play a positive role in cancer immunotherapy.

Effects of hierarchical micro/nano-topographies on the morphology, proliferation and differentiation of osteoblast-like cells.

Coating the surfaces of titanium-based implants with appropriate hierarchical micro/nano-topographies resembling the structure of natural bone significantly enhances their biological performance. However, the relationship between nanostructures surfaces and their effects on modulating cellular response is not clearly understood. Moreover, it is not clear whether the surface chemistry or topography is the main factor on modulating cellular behavior, because the commonly used surface modification techniques for titanium-based implants simultaneously modify surface topography and chemistry. The aim of this study is to investigate osteoblast-like cell adhesion, proliferation and differentiation on hierarchical micro/nano-topographies with similar surface chemistry but different nano-scale features. Micro-arc oxidation and post hydrothermal treatment were employed to fabricate micro/nano-topographies on titanium. According to the morphological features, they were classified as microcrater (micro-topography), nanoplate (hierarchical topography with nanoplates) and nanoleaf (hierarchical topography with nanoleaves). The response of osteoblast like cells (SaOS-2) was studied on each surface after sputtering with a thin layer of gold (Au) to minimize the influence of surface chemistry. The morphological evaluation after histochemical staining revealed that the adherent cells were polygonal-shaped on microcrater surface, roundish on nanoplate surface and elongated on nanoleaf surface. Additionally, compared to microcrater surface, nanoplate surface slowed down cell proliferation and exhibited no enhancement on cell differentiation. However, nanoleaf surface supported cell proliferation and promoted cell differentiation. The results indicate that tuning morphological features of nanostructures on micro-topography can serve as a promising strategy to specifically modulate cellular response, such as cell morphology, proliferation, differentiation and mineralization.

Preparation and characterization of TiO2/silicate hierarchical coating on titanium surface for biomedical applications.

In the current work, TiO2/silicate hierarchical coatings with various nanostructure morphologies were successfully prepared on titanium substrates through micro-arc oxidation (MAO) and subsequent hydrothermal treatment (HT). Moreover, the nucleation mechanism and growth behavior of the nanostructures, hydrophilicity, protein adsorption and apatite-inducing ability of various coatings were also explored. The novel TiO2/silicate hierarchical coatings comprised calcium silicate hydrate (CSH) as an outer-layer and TiO2 matrix as an inner-layer. According to the morphological features, the nanostructures were classified as nanorod, nanoplate and nanoleaf. The morphology, degree of crystallinity and crystalline phases of CSH nanostructures could be controlled by optimizing the HT conditions. The nucleation of CSH nanostructures is caused by release and re-precipitation mechanism. The TiO2/CSH hierarchical coatings exhibited some enhanced physical and biological performances compared to MAO-fabricated coating. The improvement of the hydrophilicity, fibronectin adsorption and apatite-inducing ability was found to be morphological dependent according to the following trend: nanoleaf coating>nanoplate coating>nanorod coating>MAO coating. The results indicate that the tuning of physical and morphological properties of nanostructures coated on biomaterial surface could significantly influence the hydrophilicity, protein adsorption and in vitro bioactivity of biomaterial.

SaOS-2 cell response to macro-porous boron-incorporated TiO2 coating prepared by micro-arc oxidation on titanium.

The aims of the present study were to develop boron-incorporated TiO2 coating (B-TiO2 coating) through micro-arc oxidation (MAO) and subsequently evaluate the effect of boron incorporation on the in vitro biological performance of the coatings. The physicochemical properties of B-TiO2 coating and its response to osteoblast like cells (SaOS-2) were investigated compared to the control group without boron (TiO2 coating). The morphological and X-ray diffraction results showed that both coatings exhibited similar surface topography and phase composition, respectively. However, the incorporation of B led to an enhancement in the surface hydrophilicity of B-TiO2 coating. The spreading of SaOS-2 cells on B-TiO2 coating was faster than that on TiO2 coating. The proliferation rate of SaOS-2 cells cultured on B-TiO2 decreased after 5days of culture compared to that on TiO2 coating. SaOS-2 cells cultured on B-TiO2 coating exhibited an enhanced alkaline phosphatase (ALP) activity, Collagen I synthesis and in vitro mineralization compared to those on TiO2 coating. The present findings suggest that B-TiO2 coating is a promising candidate surface for orthopedic implants.

The stimulatory effect of silica nanoparticles on osteogenic differentiation of human mesenchymal stem cells.

Silica-based materials with favourable biocompatibility are generally considered as excellent candidates for applications in biomedical fields. However, previous researches mainly focused on the safety of silica-based materials, their effects on osteogenic differentiation of human mesenchymal stem cells (hMSCs) still need further investigations. In this study, core-shell fluorescent silica nanoparticles (silica NPs) with three different sizes (S1 ~ 50 nm, S2 ~ 200 nm, S3 ~ 400 nm, respectively) were prepared according to the Stöber method. The silica NPs with different sizes did not affect the cell viability (even up to a concentration of 500 µg ml-1), showing size- and dose-independent cytocompatibility of silica NPs on hMSCs. Uptake of silica NPs significantly enhanced the activity of alkaline phosphatase (ALP) and the formation of bone-like nodules of hMSCs after osteogenic induction. At the concentration of 10 µg ml-1, after treating hMSCs with larger sized silica NPs (S2 and S3), higher ALP activity of hMSCs was measured and larger sized bone-like nodules were formed by hMSCs compared with that treated with smaller sized silica NPs (S1).The enhanced osteogenic potential of hMSCs treated with silica NPs may be attributed to the Si released from silica NPs due to the lysosomal degradation inside hMSCs. These results demonstrate the stimulatory effect of silica NPs on osteogenic differentiation of hMSCs and the application potential of silica NPs in bone tissue engineering.

In vitro BMP-2 peptide release from thiolated chitosan based hydrogel.

Thiolated chitosan based thermo-sensitive hydrogel is a water soluble system and the existing thiol groups are beneficial for the delivery of cysteine-rich peptides. In the present study, a kind of thiolated chitosan, i.e. chitosan-4-thio-butylamidine (CS-TBA) conjugate was characterized and used to prepare CS-TBA/hydroxyapatite (HA)/beta-glycerophosphate disodium (ß-GP) thermo-sensitive hydrogel. The cysteine terminated peptide 24 (P24) containing residues 73-92 of the knuckle epitope of BMP-2 (N→C: KIPKASSVPTELSAISTLYLSGGC) was synthesized and characterized. The release behavior of P24 from CS-TBA based hydrogel was investigated in vitro. The thiol groups in CS-TBA may react with thiol groups in P24, thus decreases the P24 release rate and maintains the peptide release for a longer time compared with unmodified chitosan based hydrogel. Moreover, the bioactivity of P24 is preserved during release process. These results indicate that P24 loaded CS-TBA based thermosensitive hydrogel is a potential material for minimally invasive surgery of bone repair.

A novel titania/calcium silicate hydrate hierarchical coating on titanium.

Recently, surface micron/nano-topographical modifications have attracted a great deal of attention because it is capable of mimicking the hierarchical characteristics of bone. In the current work, a novel titania/calcium silicate hydrate (CSH) bi-layer coating with hierarchical surface topography was successfully prepared on titanium substrate through micro-arc oxidation (MAO) and subsequent hydrothermal treatment (HT). MAO treatment could lead to a micron-scale topographical surface with numerous crater-like protuberances. The subsequent HT process enables the in situ nucleation and growth of CSH nanoplates on MAO-fabricated titania surface. The nucleation of CSH nanoplates is considered to follow a dissolution-precipitation mechanism. Compared to MAO-fabricated coating with single-scale surface topography, MAO-HT-fabricated coating with hierarchical surface topography exhibits enhanced hydrophilicity, fibronectin adsorption and initial MG-63 cell attachment. The process of cell-material interactions is considered to be triggered by surface properties of the coated layer and indirectly mediated by protein adsorption on coating surface. These results suggest that MAO-HT treatment is an efficient way to prepare coatings with hierarchical surface topography on titanium surface, which is essential for altering protein adsorption and initial cell attachment.