Xiupeng Wang

MBG/PLGA composite microspheres with prolonged drug release

Mesoporous bioactive glass (MBG) and composite microspheres with MBG particles embedded in biodegradable poly(D,L-lactide-co-glycolide) (PLGA) matrix have been prepared and used to load gentamicin (GS). The in vitro drug release experiments from both MBG and composite microspheres were conducted in distilled water and phosphate buffered saline (PBS) solution at 37 degrees C for more than 30 days. In both water and PBS, GS release from the MBG was very fast with about 60 wt % of the loaded drug released in the first 24 h, and more than 80 wt % released in two days. MBG/PLGA composite microspheres showed an initial release of about 33 wt % in the first day, and 48 wt % in 2 days, and a subsequent sustained release lasting for more than 4 weeks in PBS. MBG/PLGA composite microspheres may be used as an alternative drug release system, especially as a bone void filler for bone repair due to their combined advantages of sustained release of antibiotics and apatite-forming ability.

Microstructure and Properties of A Calcium Phosphate Cement Tissue Engineering Scaffold Modified with Collagen and Chitosan

In this study, an ACP-DCPD based Calcium phosphate cement (CPC) scaffold with a porosity of 88% was prepared by using Na3PO4 as a poregen and then modified by collagen and chitosan. The results showed that collagen and chitosan obviously increased the compressive strength. Cell culture showed that the cell can migrate, attach, proliferate and differentiate on the surface of the materials and the pores walls. This CPC scaffold modified with collagen or chitosan was a promising material to be used in bone tissue engineering.

Improvement of Anti-Washout Performance of Calcium Phosphate Cement Using Modified Starch

Calcium phosphate cements (CPCs) are well-known orthopedic materials for filling bone. However, CPC pastes tend to disintegrate immediately when contacting with blood or other aqueous (body) fluids, which is a main limitation of its clinical applications in bone repairing, reconstruction and augmentation. To improve the anti-washout performance of CPC, modified starches such as pre-gelatinized starch, etherified starch, and esterified starch were added to the liquid phase of CPC in this work. CPC with good anti-washout performance was prepared and the effects of the modified starches on the properties of CPC were investigated. The results showed that the CPC with the modified starches were more stable in simulated body fluid than that without modified starch, especially the CPC with the etherified starch (II). X-ray diffraction analysis revealed that the modified starches did not inhibit CPC components from converting to hydroxyapatite. Furthermore, the anti-washout mechanism of the modified starches in CPC was discussed. It is concluded that the addition of the modified starches such as pre-gelatinized starch, etherified starch, and esterified starch to CPC can improve its anti-washout performance and should be of value in clinical surgery where the cement is exposed to blood.

Development of a New Injectable Calcium Phosphate Cement That Contains Modified Starch

In this study modified starch were used as anti-washout promoters of injectable calcium phosphate cement (CPC) and the effects of the modified starch on the injectability, anti-washout performance, setting time, compressive strength, phase evolution and microstructure of this cement were investigated. The injectability of the cement was improved by adding the modified starch (0.5-2.0%). After mixing with modified starch (0.5-2.0%), the cement showed better anti-washout performance than that without modified starch after immersed and shaken in SBF. Especially, when the content of the modified starch was 1.0%, the remaining percentage of the cement was reached to 92.6%, but only 5.9% of the CPC paste remained and set for the sample without modified starch after shaken for 2 hrs. The compressive strength of cements significantly increased from 44 MPa to 54 MPa when 0.5% of modified starch was added. And a slight increase on the mechanical strength can be observed for other concentrations. Powder X-ray diffraction analysis revealed no significant difference for the conversion of the cement to hydroxyapatite for any concentrations of modified starches. The influence of the modified starch on the microstructure of the set cement was also studied. The results showed the modified starch would reduce the acicular crystal size of hydroxyapatite accompanied with little flaky crystals generation and made a compact structure. It is concluded that modified starch, a suitable anti-washout promoter, improved the performance of CPC.

Effect of Carbonate on the Properties of Bone Cement Containing PCCP and DCPA

A novel calcium phosphate cement (CPC) was prepared by mixing partially crystallized calcium phosphate (PCCP) containing carbonate and dicalcium phosphate anhydrous (DCPA) in this work. The effects of the carbonate content on the phase composition, strength, prosity, and degradation of the set bodies were studied. The results showed that the cement formed into hydroxyapatite (HAp) after setting, in which carbonate doped into the HAp crystal lattice. With the increase of the carbonate to phosphate ratio in PCCP, the compressive strength of the cement declined and the setting of the cement accelerated. Furthermore, the calcium phosphate cement formed a more porous structure with the increase of the carbonate to phosphate ratio in PCCP. The results also indicated that the degradation of CPC may be speeded up by introducing carbonate to the cement.

Rheological Properties of an Injectable Calcium Phosphate Bone Cement and their Relationship with the Phase Evolution

An injectable calcium phosphate bone cement was prepared by combining amorphous calcium phosphate (ACP) and dicalcium phosphate dihydrate (DCPD) for use in non-invasive surgery in this work. The effect of the conserving time on the viscosity, yield stress and injectability of the calcium phosphate cement (CPC) pastes were studied. The results showed that as the conserving time of the pastes prolonged, the viscosity and the yield stress of the pastes increased exponentially, and the injectability of the pastes decreased. This resulted from the transformation of DCPD and ACP into hydroxyapatite via hydration reaction. The results also indicated that the pastes still exhibited good injectability in even 15 min after preparation of the CPC pastes.