Dae Hyeok Yang

Photo-cured hyaluronic acid-based hydrogels containing simvastatin as a bone tissue regeneration scaffold

We describe in this study the positive influences on in vitro and in vivo osteogenesis of photo-cured hyaluronic acid (HA) hydrogels loaded with simvastatin (SIM). Prior to loading SIM, we first characterized the HA hydrogels for their mechanical properties and swelling ratios. The results from this testing indicated that these two factors improved as the substitution degree of 2-aminoethyl methacrylate (AEMA) increased. MTT and live/dead assays showed that the HA hydrogels have good biocompatibility for use as scaffolds for bone tissue regeneration. Moreover, another MTT assay showed that the photo-cured HA hydrogels III fabricated with 30% AEMA (300 mg) conjugated HA (HA-AEMA iii) loaded with between 0.1 and 1 mg of SIM had a similar cytotoxicity as compared to the HA hydrogel III itself. The sustained release of SIM was observed to occur in the HA hydrogel III loaded with 1 mg of SIM. In vitro and in vivo experiments showed that the HA hydrogel III loaded with 1 mg of SIM had a significant influence on osteogenesis.

Improving osteoblast functions and bone formation upon BMP-2 immobilization on titanium modified with heparin.

The aim of this study was to develop bone morphogenetic protein-2 (BMP-2) immobilization on titanium (Ti) modified by heparin for improving osteoblast function in vitro and bone formation in vivo. The Ti surface was first modified with heparin and then immobilized with BMP-2 (BMP-2/Hep-Ti). The Ti and modified Ti were characterized by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and contact angle. In vitro studies demonstrated that osteoblasts cultured on BMP-2/Hep-Ti substrate increased ALP activity, calcium deposition, osteocalcin (OCN) and osteopontin (OPN) levels as compared to those cultured on Ti or BMP-2/Ti. In addition, intra-thread bone density and bone to implant contact ratio of BMP-2/Hep-Ti were significantly greater than those of Ti in the in vivo study. In conclusion, BMP-2 immobilized Ti modified heparin implants seemed to be a suitable delivery system for BMP-2 to improve osteoblast functions and new bone formation at the defect area around an implant.

The effect of titanium with heparin/BMP-2 complex for improving osteoblast activity.

The objective of this study was to investigate the enhanced osteoblast activity of MG-63 cells cultured on titanium (Ti) with a heparin/BMP-2 (Hep/BMP-2) complex. The Ti substrates were initially modified by chemical grafting poly-L-lysine (PLL) using condensing agent, followed by immobilizing the heparin/BMP-2 complex to the PLL-grafted Ti substrate via electrostatic interactions. The surface modification of Ti substrates with PLL and/or Hep/BMP-2 complex were confirmed with scanning electron microscopy, contact angle measurements, and X-ray photoelectron spectroscopy. Immobilized BMP-2 was released from the Hep/BMP-2/Ti substrate in a sustained manner. In vitro studies revealed that osteoblasts grown on Hep/BMP-2/Ti substrate increased ALP activity, calcium deposition, ALP and osteocalcin levels as compared to those grown on pristine Ti or PLL-Ti. These results indicated that heparin/BMP-2 complex immobilized Ti substrate can be useful to effectively improve osteoblast activity.

Glycol Chitosan-Based Fluorescent Theranostic Nanoagents for Cancer Therapy

Theranostics is an integrated nanosystem that combines therapeutics with diagnostics in attempt to develop new personalized treatments with enhanced therapeutic efficacy and safety. As a promising therapeutic paradigm with cutting-edge technologies, theranostic agents are able to simultaneously deliver therapeutic drugs and diagnostic imaging agents and also monitor the response to therapy. Polymeric nanosystems have been intensively explored for biomedical applications to diagnose and treat various cancers. In recent years, glycol chitosan-based nanoagents have been developed as dual-purpose materials for simultaneous diagnosis and therapy. They have shown great potential in cancer therapies, such as chemotherapeutics and nucleic acid and photodynamic therapies. In this review, we summarize the recent progress and potential applications of glycol chitosan-based fluorescent theranostic nanoagents for cancer treatments and discuss their possible underlying mechanisms.

Surface modification of titanium with hydroxyapatite-heparin-BMP-2 enhances the efficacy of bone formation and osseointegration in vitro and in vivo.

Surface‐modified titanium (Ti) samples with hydroxyapatite (HAp) and heparin (Hep)–bone morphogenetic protein‐2 (BMP‐2) complex (Ti/HAp/Hep/BMP‐2) were prepared, and their efficacies on the enhancements of bone formation and osseointegration in vitro and in vivo were examined as compared to Ti/HAp and Ti/Hep/BMP‐2. The modified surfaces were characterized by X‐ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and contact angle goniometry. In vitro studies revealed that MG‐63 human osteosarcoma cell lines grown on Ti/HAp/Hep/BMP‐2 increased the amounts of alkaline phosphatase (ALP) activity, calcium deposition and the levels of OCN mRNA gene expression as compared to those grown on Ti/HAp, Ti/Hep/BMP‐2 or pristine Ti. Moreover, Ti/HAp/Hep/BMP‐2 exhibited higher bone volume (BV), bone volume/tissue volume (BV/TV), removal torque value and bone–implant contact (BIC) than Ti/HAp, Ti/Hep/BMP‐2 or pristine Ti in vivo. Histological evaluations showed that many desirable features of bone remodelling existed at the interface between Ti/HAp/Hep/BMP‐2 and the host bone. Consequently, Ti/HAp/Hep/BMP‐2 may have potential for clinical use as dental or orthopaedic implants. Copyright

Evaluations of chitosan/poly(D,L-lactic-co-glycolic acid) composite fibrous scaffold for tissue engineering applications

AbstractThe objective of the present study was to evaluate non-woven chitosan/poly(lactic-co-glycolic acid) fibrous scaffold (chitosan/PLGA FS) prepared by a co-electrospinning process for tissue engineering applications, as compared to chitosan and PLGA FSs. The morphological, structural, and mechanical properties of the FSs were assessed by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy-attenuated total reflection mode (FTIR-ATR), and a universal testing machine (UTM). The biocompatibility of the FSs was also evaluated in vitro in cultures of mouse fibroblasts and in vivo by subcutaneous implantation studies in rats. SEM image of the chitosan/PLGA FS showed morphological similarities to the natural ECM, characterized by high surface-to-volume ratio, high porosity, and variable pore size distributions. The FTIR-ATR spectrum of chitosan/PLGA FS revealed incorporation of the characteristic bands of chitosan and PLGA, indicating the co-existence of two fibrous structures. The poor mechanical properties of chitosan FS was improved by co-electrospinning with PLGA. In vitro L929 cell proliferation assay revealed that the cytocompatibility of chitosan/PLGA FS was increased compared to that of PLGA. In addition, chitosan/PLGA FS showed the improved ability to resolve foreign body reactions compared to PLGA FS due to the presence of chitosan.

ZrO2 surface chemically coated with hyaluronic acid hydrogel loading GDF-5 for osteogenesis in dentistry

The objective of this study was to modify zirconium dioxide (ZrO(2)) with photo-cured hyaluronic acid hydrogel (pcHAgel), and to subsequently evaluate the bone regeneration potential of the modified ZrO(2). In the present study, HA grafted onto a ZrO(2) substrate was investigated for its biocompatibility and other properties. We describe the positive influences of ZrO(2) surface-modified with pcHAgel (Zr-3) containing two different loads of growth and differentiation factor-5 (GDF-5) to aid new bone formation as compared to the same amount of BMP-2 (Zr-4-7). We characterized the Zr-3 for their surface morphology and chemical properties. Atomic force microscopy (AFM), scanning electron microscope (SEM), and X-ray photoelectron spectroscopy (XPS) showed that the pcHAgel was successfully grafted onto the ZrO(2) surface. The sustained release of GDF-5 and BMP-2 were observed to occur in the Zr-4-7. In vitro cell tests showed a higher level of MG63 cell proliferation and differentiation on Zr-4-7 than on Zr-3. The Zr-3 is a good biomaterial to deliver osteogenic differentiation factors such as BMP-2 and GDF-5, and GDF-5 can be useful as an effective alternative to aid new bone formation as compared to BMP-2.

Local delivery of recombinant human bone morphogenic protein-2 (rhBMP-2) from rhBMP-2/heparin complex fixed to a chitosan scaffold enhances osteoblast behavior

The objective of this study was to determine the effects on osteoblast activity of a recombinant human bone morphogenic protein (rhBMP)-2/heparin complex immobilized on a chitosan scaffold (Hep-C-rhBMP-2/chitosan) compared to a rhBMP-2-dipping chitosan (rhBMP-2/chitosan) and to a chitosan scaffold alone. Scanning electron microscopy (SEM) confirmed that the surface and cross morphologies of Hep-C-rhBMP-2/chitosan and rhBMP-2/chitosan were similar to those of the chitosan scaffold, and that the Hep-C-rhBMP-2/chitosan scaffold achieved sustained, controlled release of rhBMP-2 compared to the rhBMP-2/chitosan scaffold. We used measurements of alkaline phosphatase activity, calcium deposition, and real-time PCR to determine that significantly more MG-63 cells were successfully cultured on Hep-C-rhBMP-2/chitosan than on rhBMP-2/chitosan or the chitosan scaffold alone. These results suggest that the Hep-C-rhBMP-2/chitosan scaffold promotes osteoblast behavior beyond the other two scaffolds tested. This system may have advantages for dental and orthopedic applications to regenerate bone.

Evaluation of GENESIS-BCP™ scaffold composed of hydroxyapatite and β-tricalcium phosphate on bone formation

The purpose of this study was to evaluate the effects of a GENESIS-BCP™ scaffold composed of hydroxyapatite (HAp) and β-tricalcium phosphate (β-TCP) on bone formation. The relative ratio of components forming GENESIS-BCPTM was investigated by confirming the molar ratio of Ca/P through energy dispersive spectrometer (EDS) analysis. The results being that the scaffold is comprised of 60% HAp and 40% β-TCP. Moreover, scanning electron microscopy (SEM) images showed a unique surface morphology similar to a soccer ball. X-ray diffraction (XRD) analysis showed that the porosity, crystallinity, and Ca/P ratio were 65.5%, 84.9%, and 1.61%, respectively. In vitro tests including cytotoxicity and cell proliferation showed a good biocompatibility of GENESIS-BCP™. In vivo tests, including mouse skull test, and hematoxylin and eosin stains of GENESIS-BCP™ implanted in rabbit and human subjects showed that the bone graft is effective to accelerate new bone formation. It was concluded that GENESIS-BCP™ can be used as an effective alloplast bone graft.

Cellular behaviour of hepatocyte-like cells from nude mouse bone marrow-derived mesenchymal stem cells on galactosylated poly(D,L-lactic-co-glycolic acid)

Previously, the galactosylation of poly(d,l‐lactic‐co‐glycolic acid) (PLGA) surface was accomplished by grafting allylamine (AA), using inductively coupled plasma‐assisted chemical vapour deposition (ICP‐CVD) and conjugating lactobionic acid (LA) with AA via 1‐ethyl‐3‐(3‐dimethylaminopropyl) carbodiimide and N‐hydroxysuccinimide (EDC/NHS) activation for hepatic tissue‐engineering purposes. As a continuation study, the cellular behaviour of hepatocyte‐like cells (HLCs) on the surface of the galactosylated PLGA were investigated. Nude mouse bone marrow‐derived mesenchymal stem cells (MSCs) were cultured under hepatogenic conditions and the differentiated cells were characterized by reverse‐transcription polymerase chain reaction (RT–PCR), immunofluorescence and periodic acid–Schiff (PAS) staining. Galactosylated PLGA enhanced the proliferation rate of HLCs compared to the control; HLCs on the surface of the sample became aggregated and formed spheroids after 3 days of culture. A large number of cells on the surface of the sample exhibited increased liver‐specific functional activities, such as albumin and urea secretions. In addition, multicellular spheroids in the sample strongly expressed phospholyated focal adhesion kinase (pFAK) (cell–matrix interactions), E‐cadherin (cell–cell interactions) and connexin 32 (Cox32; gap junction). Copyright