Rapid biofabrication of tubular tissue constructs by centrifugal casting in a decellularized natural scaffold with laser-machined micropores.

Centrifugal casting allows rapid biofabrication of tubular tissue constructs by suspending living cells in an in situ cross-linkable hydrogel. We hypothesize that introduction of laser-machined micropores into a decellularized natural scaffold will facilitate cell seeding by centrifugal casting and increase hydrogel retention, without compromising the biomechanical properties of the scaffold. Micropores with diameters of 50, 100, and 200 mum were machined at different linear densities in decellularized small intestine submucosa (SIS) planar sheets and tubular SIS scaffolds using an argon laser. The ultimate stress and ultimate strain values for SIS sheets with laser-machined micropores with diameter 50 mum and distance between holes as low as 714 mum were not significantly different from unmachined control SIS specimens. Centrifugal casting of GFP-labeled cells suspended in an in situ cross-linkable hyaluronan-based hydrogel resulted in scaffold recellularization with a high density of viable cells inside the laser-machined micropores. Perfusion tests demonstrated the retention of the cells encapsulated within the HA hydrogel in the microholes. Thus, an SIS scaffold with appropriately sized microholes can be loaded with hydrogel encapsulated cells by centrifugal casting to give a mechanically robust construct that retains the cell-seeded hydrogel, permitting rapid biofabrication of tubular tissue construct in a "bioreactor-free" fashion.

Tannic acid mimicking dendrimers as small intestine submucosa stabilizing nanomordants.

Chemical stabilization resulting in increased resistance to proteolytic degradation is one of the approaches in prevention of post-implantational aneurysm development in decellularized natural vascular scaffolds. Recently, tannic acid (TA) and tannic acid mimicking dendrimers (TAMD) have been suggested as potential stabilization agents for collagen and elastin. The aim of this work was to determine the stabilizing effects of TAMD on decellularized natural scaffolds. Vascular scaffolds fabricated from small intestine submucosa (SIS) and SIS plane sheets (Cook Biotech Inc.) were used. The biomechanical properties of the SIS vascular graft segments treated with TA and TAMD were tested. The effect of TAMD treatment on resistance to proteolytic degradation was evaluated by measuring biomechanical properties of TAMD stabilized and non-stabilized SIS specimens after incubation in collagenase solution. It was shown that treatment with TA as well as with TAMD increased the strength of tubular SIS as well as their resistance to proteolytic biodegradation manifested by preservation of biomechanical properties after collagenase treatment. Transmission electron microscopy demonstrated that treatment with TAMD increased the periodical pattern typical of collagen fiber ultrastructure as a result of the "mordant" effect. The possible collagen cross-linking effect of TAMD on SIS was investigated by differential scanning calorimetry (DSC). The treatment with TAMD induced a small, but detectable cross-linking effect, suggesting that TAMD do not establish extensive covalent cross links within the extracellular matrix but rather interact with collagen, thus rendering SIS scaffolds more resistant to proteolytic degradation.

Osteogenic protein-1 enhances osseointegration of titanium implants coated with peri-apatite in rabbit femoral defect.

This study evaluated the effect of osteogenic protein-1 (OP-1) carried by Peri-Apatite (PA) on bone healing in the gap surrounding implants in a rabbit model. Cylindrical titanium implants (3 x 9 mm) were uniformly coated with PA precipitated from a calcium and phosphate solution. OP-1 solution containing 60 microg OP-1 was directly loaded on the implants immediately before implantation for the experimental group, whereas buffer solution was loaded on the implants for the control. The implant was placed in the distal femur and surrounded by a 1-mm gap. The implants were retrieved and examined 6 weeks after implantation. Mechanical testing (push-out) data showed that OP-1 enhanced implant fixation by 80%. Histomorphometric measurements indicated that bone ingrowth in the initial gap expressed as a percentage of the whole gap was significantly higher in the specimens treated with OP-1 than the control group (25.4% vs. 8.9%, p < 0.05). The percentage of the surface of implants, which was covered by bone, was significantly higher in the OP-1-treated group compared to the control group (65% vs. 25%, p < 0.05). This study suggests that OP-1 can be loaded on orthopedic implants through PA to enhance the osseointegration of orthopedic implant.