Effect of stearic acid modified HAp nanoparticles in different solvents on the properties of Pickering emulsions and HAp/PLLA composites.

Stearic acid (Sa) was used to modify the surface properties of hydroxyapatite (HAp) in different solvents (water, ethanol or dichloromethane(CH2Cl2)). Effect of different solvents on the properties of HAp particles (activation ratio, grafting ratio, chemical properties), emulsion properties (emulsion stability, emulsion type, droplet morphology) as well as the cured materials (morphology, average pore size) were studied. FT-IR and XPS results confirmed the interaction occurred between stearic acid and HAp particles. Stable O/W and W/O type Pickering emulsions were prepared using unmodified and Sa modified HAp nanoparticles respectively, which indicated a catastrophic inversion of the Pickering emulsion happened possibly because of the enhanced hydrophobicity of HAp particles after surface modification. Porous materials with different structures and pore sizes were obtained using Pickering emulsion as the template via in situ evaporation solvent method. The results indicated the microstructures of cured samples are different form each other when HAp was surface modified in different solvents. HAp particles fabricated using ethanol as solvent has higher activation ratio and grafting ratio. Pickering emulsion with higher stability and cured porous materials with uniform morphology were obtained compared with samples prepared using water and CH2Cl2 as solvents. In conclusion, surface modification of HAp in different solvents played a very important role for its stabilized Pickering emulsion as well as the microstructure of cured samples. It is better to use ethanol as the solvent for Sa modified HAp particles, which could increase the stability of Pickering emulsion and obtain cured samples with uniform pore size.

Factors influencing the stability and type of hydroxyapatite stabilized Pickering emulsion.

Hydroxyapatite (HAp) nanoparticle stabilized Pickering emulsion was fabricated with poly(l-lactic acid) dissolved in dichloromethane (CH2Cl2) solution as oil phase and HAp aqueous dispersion as aqueous phase. Pickering emulsion was cured via in situ solvent evaporation method. Effect of PLLA concentrations, pH value, HAp concentrations, oil-water ratio, emulsification rates and times were studied on emulsion stability and emulsion type, etc. The results indicated emulsion stability increased with the increase of HAp concentration, emulsification rate and time; it is very stable when pH value of aqueous phase was adjusted to 10. Stable W/O and O/W emulsions were fabricated successfully using as-received HAp particles as stabilizer by adjusting the fabricating parameters. The interaction between HAp and PLLA played an important role to stabilize Pickering emulsions. SEM results indicated that both microsphere and porous materials were fabricated using emulsion stabilized by unmodified HAp nanoparticles, implying that both W/O and O/W emulsion type were obtained.

Development of PLGA nanoparticles simultaneously loaded with vincristine and verapamil for treatment of hepatocellular carcinoma.

Hepatocellular carcinoma (HCC) is one of the malignant tumors with poor chemo-sensitivity to vincristine sulfate (VCR) due to multi-drug resistance (MDR). Combinations of encapsulated VCR and verapamil hydrochloride (VRP, a chemo-sensitizer) might be a potential strategy to improve HCC therapeutic efficacy of VCR. PLGA nanoparticles (PLGANPs) simultaneously loaded with VCR and VRP (CVn) were prepared. The entrapment efficiencies of VCR and VRP were 70.92 ± 3.78% and 85.78 ± 3.23%, respectively (n = 3). The HCC therapeutic activity of CVn was assessed using MTT assay. In BEL7402 and BEL7402/5-FU human hepatocarcinoma cell lines, CVn had the same antitumor effect as one free drug/another agent-loaded PLGANPs (C + Vn or Cn + V) combination and coadministration of two single-agent-loaded PLGANPs (Cn + Vn), which was slightly higher than that of the free VCR/VRP combination (C - V). CVn might cause lower normal tissue drug toxicity by the enhanced permeation and retention effect in vivo. Additionally, CVn might cause fewer drug-drug interaction and be the most potential formulation to simultaneously deliver VCR and VRP to the target cell in vivo than the other three nanoparticle formulations (C + Vn, Cn + V, and Cn + Vn). Therefore, we speculate that CVn might be the most effective preparation in the treatment of drug-resistant human HCC in vivo.

[Cr-Ti-Al-N complex coating on titanium to strengthen Ti/porcelain bonding].

OBJECTIVE: To study the feasibility of magnetron sputtering Cr-Ti-Al-N complex coating as an interlayer on titanium to enhance the titanium-ceramic binding strength. METHODS: With a three-point bending test according to ISO 9693, the binding strength of Duceratin (Degussa) to titanium substrate prepared with 4 different surface treatments (polishing, polishing and megnetron sputtering Cr, Ti, Al, and N complex coating, sandblasting, sandblasting and coating) was evaluated. Ti/porcelain interface and fractured Ti surface were examined using scanning electron microscopy with energy-dispersive spectrometry (EDS). RESULTS: The binding strength of polished and coated titanium/Duceratin was significantly higher than polished titanium group (P<0.05). The binding strength of sandblasted and coated titanium/Duceratin did not differ significantly from that of sandblasted titanium group (P>0.05), and the strength in the two sandblasted titanium groups was significantly higher than that in polished and coated titanium group (P<0.05). CONCLUSION: Megnetron sputtering Cr-Ti-Al-N complex on polished titanium can increase the titanium/porcelain binding strength. Megnetron sputtering coating is a promising Ti/porcelain interlayer.