Haibo Qu

Purpose Polymer-xerogel composite materials have been introduced to better optimize local anesthetics release kinetics for the pain management. In a previous study, it was shown that by adjusting various compositional and nano-structural properties of both inorganic xerogels and polymers, zero-order release kinetics over 7 days can be achieved in vitro. In this study, in vitro release properties are confirmed in vivo using a model that tests for actual functionality of the released local anesthetics. Methods Composite materials made with tyrosine-polyethylene glycol(PEG)-derived poly(ether carbonate) copolymers and silica-based sol–gel (xerogel) were synthesized. The in vivo release from the composite controlled release materials was demonstrated by local anesthetics delivery in a rat incisional pain model. Results The tactile allodynia resulting from incision was significantly attenuated in rats receiving drug-containing composites compared with the control and sham groups for the duration during which natural healing had not yet taken place. The concentration of drug (bupivacaine) in blood is dose dependent and maintained stable up to 120 h post-surgery, the longest time point measured. Conclusions These in vivo studies show that polymer-xerogel composite materials with controlled release properties represent a promising class of controlled release materials for pain management.

In this article we describe a simple but effective biomimetic method to prepare dense apatite/collagen nanocomposites. Collagen‐containing simulated body fluid was used to mimic the natural bone formation environment. The apatite/collagen films were formed at the air–solution interface under physiological conditions (40°C and pH=6.3). Transmission electron microscopy, scanning electron microscopy, thermal gravimetric analysis, X‐ray diffraction, western blot analysis, and energy‐dispersive X‐ray were used to characterize the apatite/collagen composites. It was revealed that the nanosized apatite particles formed into a platelet shape with 100 nm in width and length and

Bovine serum albumin (BSA) was employed as a model protein to study its loading efficiency into a calcium phosphate (CaP) coating on titanium substrates. It is found that the protein loading efficiency can be adjusted by varying the specific configurations of the coating system such as simulated body fluid (SBF) volume, solution height and container selection for the SBF. A BSA loading efficiency as high as 90% was achieved when the ratio of the substrate surface area to modified SBF (m-SBF) volume was as high as 0.072. The release of BSA from the biomimetic coatings was also investigated in vitro. A sustained release was achieved although a large quantity of BSA was still trapped in the coating after 15 days of immersion in a phosphate buffer solution. A much faster release rate would be expected when the coating is implanted in vivo due to the active involvement of osteoclast cells and enzymes.

Bone‐like apatite coatings were prepared using a biomimetic method in a simulated body fluid (SBF). The effect of initial pH values and immersing temperatures on biomimetic apatite coating formation was studied. Three different temperatures were used in this study: 24 (room temperature), 40, and 60°C. At each temperature, SBF solutions with three different initial pHs were chosen: low, medium, and high. The total inorganic carbon (TIC) content and pH‐time profile of each coating system were recorded during the coating formation. The apatite coatings were characterized using X‐ray diffraction (XRD), field emission scanning electron microscope (FESEM), and Fourier transform infra‐red (FTIR). It has been found that SBF temperature has a great effect on the bicarbonate decomposition rate. The bicarbonate ions tend to decompose faster as the temperature increases. The decomposition of bicarbonate ions results in a pH increase in the SBF. With different initial SBF pHs, the decomposition of different amounts of bicarbonate ions is required to reach the critical pH range of apatite formation. With different amounts of bicarbonate ions in the SBF, the surface morphology of the biomimetic apatite coating formed is different. Therefore, the initial pH of the SBF solution plays a vital role in controlling the surface morphology of the biomimetic apatite coating. Also, it was found that as the SBF temperature increased, the critical pH range at which biomimetic apatite coating forms decreased. The critical pH range for the SBF prepared at 24, 40, and 60°C was 6.65–6.71, 6.55–6.65, and 6.24–6.42, respectively. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2008

Bone‐like apatite coatings were prepared using a biomimetic method in a modified simulated body fluid (m‐SBF). The effect of the m‐SBF volume on the apatite coating quality was studied. Three m‐SBF volumes, 50, 100, and 200 mL, were employed to immerse titanium substrates in a sealed container so as to produce apatite coatings with different properties, namely types I, type II, and type III apatite coatings, respectively. The coatings were characterized using X‐ray diffraction and environmental scanning electron microscope. The bonding between the coating and the Ti substrate was evaluated using an adhesive strength test. All three apatite coatings demonstrated a poorly crystallized structure, and the coatings formed exhibited a uniformed surface morphology. Further increasing the m‐SBF volume, small globules of apatite started to form on the surface of the coating. The bonding strength for the three coating systems were 8.52 ± 2.41, 10.36 ± 2.78, and 17.23 ± 2.55 MPa for types I, II, and III apatite coatings, respectively. The failure analyses suggested that type III coating failed mostly at the interface between the coating and the substrate, while type I and II coatings failed mostly within the apatite coating. Our study revealed that a dense, thick, well‐adhered apatite coating could be achieved by carefully controlling the volume of m‐SBF. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2008