Ming-Fa Hsieh

Hydroxyapatite coating on Ti6Al4V alloy using a sol-gel derived precursor

A simple rapid-heating method was successfully developed for calcium phosphate coatings on Ti6Al4V substrates deposited by using a sol–gel derived precursor. After five repetitions of coating procedures and heat treatment at 600 ◦ C, the formation of hydroxyapatite (HA) has been confirmed by X-ray diffractometry (XRD) analyses and the substrate material was found to be slightly oxidized. The residual organics, as revealed by X-ray photoelectron spectroscopy (XPS) spectra of a coating calcined at 400 ◦ C, might retard the formation of calcium phosphate phase, thus only small amount of calcium phosphate phase is present. After calcining at 600 ◦ C, calcium phosphate phase is the only one identifiable by XPS spectra. The adhesive strength of the five-coating layer on the substrate is around 60 MPa. The surface morphology of the thick HA film, calcined at 400 ◦ C and then consolidated at 600 ◦ C, displays porous structure arisen from rapid-heating of the bulk precursor.

Eradication of drug resistant Staphylococcus aureus by liposomal oleic acids

Staphylococcus aureus (S. aureus) represents a major threat to a broad range of healthcare and community associated infections. This bacterium has rapidly evolved resistance to multiple drugs throughout its antibiotic history and thus it is imperative to develop novel antimicrobial strategies to enrich the currently shrinking therapeutic options against S. aureus. This study evaluated the antimicrobial activity and therapeutic efficacy of oleic acid (OA) in a liposomal formulation as an innate bactericide against methicillin-resistant S. aureus (MRSA). In vitro studies showed that these OA-loaded liposomes (LipoOA) could rapidly fuse into the bacterial membranes, thereby significantly improving the potency of OA to kill MRSA compared with the use of free OA. Further in vivo tests demonstrated that LipoOA were highly effective in curing skin infections caused by MRSA bacteria and preserving the integrity of the infected skin using a mouse skin model. Moreover, a preliminary skin toxicity study proved high biocompatibility of LipoOA to normal skin tissues. These findings suggest that LipoOA hold great potential to become a new, effective, and safe antimicrobial agent for the treatment of MRSA infections.

Phase purity of sol–gel-derived hydroxyapatite ceramic

Calcium oxide was reported in the sol-gel-derived hydroxyapatite (HA) as an unavoidable major impurity. In this study phase purity of HA synthesized by sol-gel route was explored using precursors of calcium nitrate tetrahydrate and triethyl phosphate. Two different drying methods, the fast drying of as-prepared precursors and the slow drying of aged precursors were adopted as major processing variables. The dried gels were subsequently calcined up to 600 degrees C. In the calcined powder from fast-dried gel, X-ray diffraction (XRD) patterns revealed an intense CaO peak. For the slow-dried gel, thermogravimetric analysis revealed a 2-step weight-loss behavior during heating. XRD analysis of the calcined powder, corresponding to the second weight-loss step, showed major peaks of hydroxyapatite and a very weak CaO peak. P-31 NMR analysis indicated formation of calcium phosphate complex during aging. Complete incorporation of Ca(NO3)2 into the complex due to proper aging therefore diminishes CaO formation. It was also found that the minor CaO derived in the slow drying method can be easily and completely washed out just by distilled water.

Targeted delivery of doxorubicin to human breast cancers by folate-decorated star-shaped PEG–PCL micelle

Conventional nanocarriers are associated with systemic toxicity and poor bioavailability of the anti-tumor drugs due to undesired specificity. The objective of this study is to introduce a folic targeting ligand on the surface of a polymeric nanocarrier to enhance the delivery of the doxorubicin (DOX) via ligand-mediated endocytosis. Hence, the folate decorated-micelle based on the star-shape FOL–PEG–PCL copolymer was synthesized. The chemical structure of the copolymer was characterized by proton nuclear magnetic resonance spectroscopy, gel permeation chromatography and differential scanning calorimetry, respectively. A generalized biocompatibility test of the micelle was evaluated using MTT assay, in vitro hemolytic test, nitric oxide production and reactive oxygen species generation, respectively. When DOX was encapsulated in the micelle, the drug loading efficiency and drug loading content were found to be 90% and 13%, respectively. The average particle size of the DOX-loaded micelle, determined by dynamic light scattering was 148.2 nm. The intracellular uptake experiments showed that human breast cancer cells (MCF-7) could uptake a similar amount of DOX from two dosage forms: free DOX and DOX-loaded FOL–PEG–PCL micelle. The uptake of DOX-loaded FOL–PEG–PCL micelle was higher than that of free DOX in MCF-7/adr cells, adriamycin-resistant cell line. The uptake of the micelle in MCF-7 was found to be time-dependent; e.g.caveolae/lipid-raft mediated endocytosis and then folate receptor-mediated endocytosis was observed. This study demonstrates that the FOL–PEG–PCL micelle was non-toxic and the DOX-loaded FOL–PEG–PCL micelle could be a potential carrier for cancer treatments.

Doxorubicin-Loaded PEG-PCL-PEG Micelle Using Xenograft Model of Nude Mice: Effect of Multiple Administration of Micelle on the Suppression of Human Breast Cancer

The triblock copolymer is composed of two identical hydrophilic segments Monomethoxy poly(ethylene glycol) (mPEG) and one hydrophobic segment poly(ε-caprolactone) (PCL); which is synthesized by coupling of mPEG-PCL-OH and mPEG-COOH in a mild condition using dicyclohexylcarbodiimide and 4-dimethylamino pyridine. The amphiphilic block copolymer can self-assemble into nanoscopic micelles to accommodate doxorubixin (DOX) in the hydrophobic core. The physicochemical properties and in vitro tests, including cytotoxicity of the micelles, have been characterized in our previous study. In this study, DOX was encapsulated into micelles with a drug loading content of 8.5%. Confocal microscopy indicated that DOX was internalized into the cytoplasm via endocystosis. A dose-finding scheme of the polymeric micelle (placebo) showed a safe dose of PEG-PCL-PEG micelles was 71.4 mg/kg in mice. Importantly, the circulation time of DOX-loaded micelles in the plasma significantly increased compared to that of free DOX in rats. A biodistribution study displayed that plasma extravasation of DOX in liver and spleen occurred in the first four hours. Lastly, the tumor growth of human breast cancer cells in nude mice was suppressed by multiple injections (5 mg/kg, three times daily on day 0, 7 and 14) of DOX-loaded micelles as compared to multiple administrations of free DOX.

The essentiality of α‐2‐macroglobulin in human salivary innate immunity against new H1N1 swine origin influenza A virus

A novel strain of influenza A H1N1 emerged in the spring of 2009 and has spread rapidly throughout the world. Although vaccines have recently been developed that are expected to be protective, their availability was delayed until well into the influenza season. Although anti‐influenza drugs such as neuraminidase inhibitors can be effective, resistance to these drugs has already been reported. Although human saliva was known to inhibit viral infection and may thus prevent viral transmission, the components responsible for this activity on influenza virus, in particular, influenza A swine origin influenza A virus (S‐OIV), have not yet been defined. By using a proteomic approach in conjunction with beads that bind α‐2,6‐sialylated glycoprotein, we determined that an α‐2‐macroglobulin (A2M) and an A2M‐like protein are essential components in salivary innate immunity against hemagglutination mediated by a clinical isolate of S‐OIV (San Diego/01/09 S‐OIV). A model of an A2M‐based “double‐edged sword” on competition of α‐2,6‐sialylated glycoprotein receptors and inactivation of host proteases is proposed. We emphasize that endogenous A2M in human innate immunity functions as a natural inhibitor against S‐OIV.

Fabrication of synthesized PCL‐PEG‐PCL tissue engineering scaffolds using an air pressure‐aided deposition system

Purpose – Bone tissue engineering is an emerging field providing viable substitutes for bone regeneration. Poly(e‐caprolactone) (PCL) is a good candidate for scaffold fabrication due to its high mechanical strength and excellent resistance under moist conditions, but its hydrophobicity causes cell‐attached difficulties, thus limiting its clinical application. The paper aims to develop an air pressure‐aided deposition system for fabricating scaffolds made of synthesized PCL‐PEG‐PCL copolymers and to validate the biocompatibility and hydrophilicity improvement of fabricated scaffolds.Design/methodology/approach – An air pressure‐aided deposition system that involves rapid prototyping technique has been developed to fabricate scaffolds for tissue engineering (TE) application. Poly(ethylene glycol) (PEG), a hydrophilic non‐ionic polymer, is adopted to reduce the hydrophobicity of PCL alone. The synthesis process of PCL‐PEG‐PCL copolymer is briefly introduced. Effect of viscosity in regard to scanning speed on...

Doxorubicin-Loaded Nanosized Micelles of a Star-Shaped Poly(ε-Caprolactone)-Polyphosphoester Block Co-polymer for Treatment of Human Breast Cancer

Star-shaped co-polymers based on the backbone of poly(ε-caprolactone) were synthesized by a ring-opening reaction using pentaerythritol as initiator and Sn(Oct)2 as catalyst. The star-shaped poly(ε-caprolactone) polymer was then chain extended with a terminal block of poly(ethyl ethylene phosphate) to form a copolymer, poly(ε-caprolactone)-poly(ethyl ethylene phosphate), when using the cyclic ethyl ethylene phosphate monomer. The amphiphilic block co-polymers can self-assemble into nanoscopic micelles with a mean diameter of 150 nm and a spherical shape. Additionally, the prepared micelles did not induce hemolysis and nitric oxide production in vitro based on nitric oxide, hemolytic tests and MTT assays. The hydrophobic micellar cores encapsulated doxorubicin (DOX) in an aqueous solution with a loading efficiency of 55.2%. The in vitro release of DOX from DOX-loaded micelles was pH dependent. DOX-loaded micelles present significantly enhanced cytotoxicity to both MCF-7/drug-sensitive and MCF-7/drug-resistant cells after second incubation. Moreover, results of confocal microscopy and flow cytometry of DOX-loaded micelles demonstrate the feasibility of this delivery system for effective therapy of drug-resistant tumours.

Use of nanoparticles as therapy for methicillin-resistant staphylococcus aureus infections

Staphylococcal infection can cause a wide range of diseases resulting either from staphylococcal bacteria invasion or through toxin production. The majority of infections caused by staphylococci are due to Staphylococcus aureus. Moreover, methicillin-resistant Staphylococcus aureus has recently been considered to be one of the major causes of hospital-acquired infections. The treatment of staphylococci infections is difficult because increased antibiotic resistant strains have become more common, increasing the risk of serious health penalty. Delivery of antibiotics via nanoparticles is a promising therapy, as a drug delivery mechanism, particularly for controlled release or depot delivery of drugs to decrease the number of doses required to achieve a clinical effect. This review emphasized the potential of nanoparticles in the targeted antibiotics for therapy of staphylococcal infections.

The Osteogenesis of Bone Marrow Stem Cells on mPEG-PCL-mPEG/Hydroxyapatite Composite Scaffold via Solid Freeform Fabrication

The study described a novel bone tissue scaffold fabricated by computer-aided, air pressure-aided deposition system to control the macro- and microstructure precisely. The porcine bone marrow stem cells (PBMSCs) seeded on either mPEG-PCL-mPEG (PCL) or mPEG-PCL-mPEG/hydroxyapatite (PCL/HA) composite scaffold were cultured under osteogenic medium to test the ability of osteogenesis in vitro. The experimental outcomes indicated that both scaffolds possessed adequate pore size, porosity, and hydrophilicity for the attachment and proliferation of PBMSCs and the PBMSCs expressed upregulated genes of osteogensis and angiogenesis in similar manner on both scaffolds. The major differences between these two types of the scaffolds were the addition of HA leading to higher hardness of PCL/HA scaffold, cell proliferation, and VEGF gene expression in PCL/HA scaffold. However, the in vivo bone forming efficacy between PBMSCs seeded PCL and PCL/HA scaffold was different from the in vitro results. The outcome indicated that the PCL/HA scaffold which had bone-mimetic environment due to the addition of HA resulted in better bone regeneration and mechanical strength than those of PCL scaffold. Therefore, providing a bone-mimetic scaffold is another crucial factor for bone tissue engineering in addition to the biocompatibility, 3D architecture with high porosity, and interpored connection.