Mechanical property and biocompatibility of PLLA coated DCPD composite scaffolds

Indiana University-Purdue University Indianapolis (IUPUI)Dicalcium phosphate dihydrate (DCPD) cements have been used for bone repair due to its excellent biocompatibility and resorbability. However, DCPD cements are typically weak and brittle. To overcome these limitations, the sodium citrate used as a setting regulator and the coating of poly-L-lactide acid (PLLA) technique have been proposed in this study. The first purpose of this thesis is to develop composite PLLA/DCPD scaffolds with enhanced toughness by PLLA coating. The second purpose is to examine the biocompatibility of the scaffolds. The final purpose is to investigate the degradation behaviors of DCPD and PLLA/DCPD scaffolds. In this experiment, DCPD cements were synthesized from monocalcium phosphate monohydrate (MCPM) and -tricalcium phosphate ( –TCP) by using deionized water and sodium citrate as liquid components. The samples were prepared with powder to liquid ratio (P/L) at 1.00, 1.25 and 1.50. To fabricate the PLLA/DCPD composite samples, DCPD samples were coated with 5 % PLLA. The samples were characterized mechanical properties, such as porosity, diametral tensile strength, and fracture energy. The mechanical properties of DCPD scaffolds with and without PLLA coating after the in vitro static degradation (day 1, week1, 4, and 6) and in vitro dynamic degradation (day 1, week 1, 2, 4, 6, and 8) were investigated by measuring their weight loss, fracture energy, and pH of phosphate buffer solution. In addition, the dog bone marrow stromal stem cells (dBMSCs) adhesion on DCPD and PLLA/DCPD composite samples were examined by scanning electron microscopy. The cell proliferation and differentiation in the medium conditioned with DCPD and PLLA/DCPD composite samples were studied by XTT (2,3-Bis(2-methoxy-4- nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide inner salt), and alkaline phosphatase (ALP) assay, respectively. The addition of sodium citrate and PLLA coating played a crucial role in improving the mechanical properties of the samples by increasing the diametral tensile strength from 0.50 ± 0.15 MPa to 2.70 ± 0.54 MPa and increasing the fracture energy from 0.76 ± 0.18 N-mm to 12.67 ± 4.97 N-mm. The DCPD and PLLA/DCPD composite samples were compatible with dBMSCs and the cells were able to proliferate and differentiate in the conditioned medium. The degradation rate of DCPD and PLLA/DCPD samples were not significant different (p > 0.05). However, the DCPD and PLLA/DCPD composite samples those used sodium citrate as a liquid component was found to degrade faster than the groups that use deionized water as liquid componen

Mechanical Property and Biocompatibility of PLLA Coated DCPD Composite Scaffolds

poster abstractIntroductions: Dicalcium phosphate dehydrate (DCPD) cements have been used for bone repair due to its excellent biocompatibility and resorability. However, DCPD cements are typically weak and brittleness. To address these limitations, the addition of sodium citrate as a regulator and polylactic acid (PLLA) as reinforcing agent has been proposed in this study. Objectives: 1) To develop composite PLLA/ DCPD scaffolds with enchanted toughness by PLLA coating. 2) To examine cell proliferation on the scaffolds. 3) To investigate the degradation behaviors of DCPD and PLLA/DCPD scaffolds. Materials and Methods: DCPD cements were synthesized with a 1:1 ratio of monocalcium phosphate monohydrate and -tricalcium phosphate with and without 100 mM sodium citrate in the mixing liquid. The specimens were prepared with powder to liquid ratio (P/L) of 1.00, 1.25 and 1.50. To fabricate the PLLA/DCPD composite scaffolds, DCPD scaffolds were coated with 5 % PLLA. The chemical and mechanical properties of DCPD scaffolds with and without PLLA coating after the in-vitro degradation (day 1, week 1, 4, and 6) were investigated by measuring their porosity, diametral tensile strength, and energy to fracture. In addition, cell adhesion and proliferation on these scaffolds were examined by scanning electron microscopy. Results: the addition of sodium citrate and the infiltration of PLLA significantly increased the mechanical properties of DCPD scaffolds (p < 0.05). The range of diametral tensile strength was 0.50-2.70 MPa and the range of energy to fracture was 0.80 to 9.90 N-mm. The most effective improvement of tensile strength and energy to fracture was achieved with P/L of 1.50. Moreover, incorporating PLLA to DCPD scaffolds slowed down the weight loss in the vitro degradation. Conclusion: a combination of template-casting and polymer impregnation methods can be applied to fabricate a cement/polymer biodegradable scaffold for bone tissue regeneration with significantly slow down degradation and excellent biocompatibility

Fabrication of Poly-l-lactic Acid/Dicalcium Phosphate Dihydrate Composite Scaffolds with High Mechanical Strength-Implications for Bone Tissue Engineering

Scaffolds were fabricated from poly-l-lactic acid (PLLA)/dicalcium phosphate dihydrate (DCPD) composite by indirect casting. Sodium citrate and PLLA were used to improve the mechanical properties of the DCPD scaffolds. The resulting PLLA/DCPD composite scaffold had increased diametral tensile strength and fracture energy when compared to DCPD only scaffolds (1.05 vs. 2.70 MPa and 2.53 vs. 12.67 N-mm, respectively). Sodium citrate alone accelerated the degradation rate by 1.5 times independent of PLLA. Cytocompatibility of all samples were evaluated using proliferation and differentiation parameters of dog-bone marrow stromal cells (dog-BMSCs). The results showed that viable dog-BMSCs attached well on both DCPD and PLLA/DCPD composite surfaces. In both DCPD and PLLA/DCPD conditioned medium, dog-BMSCs proliferated well and expressed alkaline phosphatase (ALP) activity indicating cell differentiation. These findings indicate that incorporating both sodium citrate and PLLA could effectively improve mechanical strength and biocompatibility without increasing the degradation time of calcium phosphate cement scaffolds for bone tissue engineering purposes

3D bioactive composite scaffolds for bone tissue engineering

Bone is the second most commonly transplanted tissue worldwide, with over four million operations using bone grafts or bone substitute materials annually to treat bone defects. However, significant limitations affect current treatment options and clinical demand for bone grafts continues to rise due to conditions such as trauma, cancer, infection and arthritis. Developing bioactive three-dimensional (3D) scaffolds to support bone regeneration has therefore become a key area of focus within bone tissue engineering (BTE). A variety of materials and manufacturing methods including 3D printing have been used to create novel alternatives to traditional bone grafts. However, individual groups of materials including polymers, ceramics and hydrogels have been unable to fully replicate the properties of bone when used alone. Favourable material properties can be combined and bioactivity improved when groups of materials are used together in composite 3D scaffolds. This review will therefore consider the ideal properties of bioactive composite 3D scaffolds and examine recent use of polymers, hydrogels, metals, ceramics and bio-glasses in BTE. Scaffold fabrication methodology, mechanical performance, biocompatibility, bioactivity, and potential clinical translations will be discussed

Novel Microfluidic Colon with an Extracellular Matrix Membrane

Collagen is a key element of basal lamina in physiological systems that participates in cell and tissue culture. Its function is for cell maintenance and growth, angiogenesis, disease progression, and immunology. The goal of our present study was to integrate a micrometer resolution membrane that is synthesized out of rat-tail type I collagen in a microfluidic device with apical and basolateral chambers. The collagen membrane was generated by lyophilization. In order to evaluate the compatibility of the resulting membrane with organs-on-chips technology, it was sandwiched between layers of polydimethylsiloxane (PDMS) that had been prepared by replica molding, and the device was used to culture human colon caco 2 cells on the top of the membrane. Membrane microstructure, transport, and cell viability in the organs-on-chips were observed to confirm the suitability of our resulting membrane. Through transport studies, we compared diffusion of two different membranes: Transwell and our resulting collagen membrane. We found that mass transport of 40 kDa dextran was an order of magnitude higher through the collagen membrane than that through the Transwell membrane. Human colon caco 2 cells were cultured in devices with no, Transwell, or ECM membrane to evaluate the compatibility of cells on the ECM membrane compared to the other two membranes. We found that caco 2 cells cultured on the collagen membrane had excellent viability and function for extended periods of time compared to the other two devices. Our results indicate a substantial improvement in establishing a physiological microenvironment for in vitro organs-on-chips