We have developed a combinatorial method for screening cell-biomaterial interactions in a 3D format. Previous highthroughput approaches for screening cell-material interactions have focused on planar 2D surfaces or films. However, biomaterials are commonly used in a 3D scaffold format and cells behave more physiologically when cultured in 3D. Hence, combinatorial scaffold libraries were fabricated in 96-well plates in which polymeric, salt-leached scaffolds of varied composition and properties were present in each well. Libraries were fabricated from two biodegradable tyrosinederived polycarbonates: poly(desaminotyrosyl-tyrosine ethyl ester carbonate) (pDTEc) and poly(desaminotyrosyl-tyrosine octyl ester carbonate) (pDTOc). During culture, osteoblast adhesion and proliferation into scaffolds were enhanced as the pDTEc content of the scaffolds increased. To our knowledge, this is the first demonstration of a method for fabricating combinatorial arrays of large-pore scaffolds (diameter (d) > 0.1 mm) for screening cell-material interactions in a 3D format.Despite significant investments, few profitable tissueengineering products have come to market.[1] As a result, combinatorial methods, which have accelerated pharmaceutical research, [2,3] are beginning to impact biomaterials research. [4][5][6][7][8][9][10][11] However, methods for screening cell-biomaterial interactions are mostly limited to 2D films or surfaces, [4][5][6][7][8][9][10][11][12][13][14] despite the facts that biomaterials are frequently used to fabricate 3D scaffolds, [15] cells exist in vivo in a 3D environment, and cells cultured in vitro in a 3D environment typically behave more physiologically than those cultured on a 2D surface. [16][17][18][19][20] Films and surfaces typically display a ''nanoscale'' roughness, [11,21] while processing of biomaterials into 3D scaffolds yields structures with a topographical roughness at multiple size scales. Cells are very sensitive to material topography and the large difference in structure between 2D films and 3D scaffolds should be considered when screening materials. For these reasons, a combinatorial approach in which cell-biomaterial interactions are screened using a 3D polymer-scaffold configuration will provide more relevant information regarding cell responses to test biomaterials. We have developed a method for fabricating combinatorial libraries of polymer scaffolds where the materials are presented to cells as 3D, porous, salt-leached polymer scaffolds and many scaffold compositions can be tested in a single experiment. The libraries are designed for screening cell response so that scaffold formulations that promote or suppress cellular activity can rapidly be identified. In the current study, we have used the combinatorial approach to fabricate scaffold libraries of varying composition of two amorphous, biodegradable, biocompatible, tyrosine-derived polycarbonates: pDTEc [poly(desaminotyrosyl-tyrosine ethyl ester carbonate)] and pDTOc [poly(desaminotyrosyl-tyrosine octyl ester carbonate)]. [22] ...

We have developed a combinatorial method for determining optimum tissue scaffold composition for several X-ray imaging techniques. X-ray radiography and X-ray microcomputed tomography enable non-invasive imaging of implants in vivo and in vitro. However, highly porous polymeric scaffolds do not always possess sufficient X-ray contrast and are therefore difficult to image with X-ray-based techniques. Incorporation of high radiocontrast atoms, such as iodine, into the polymer structure improves X-ray radiopacity but also affects physicochemical properties and material performance. Thus, we have developed a combinatorial library approach to efficiently determine the minimum amount of contrast agent necessary for X-ray-based imaging. The combinatorial approach is demonstrated in a polymer blend scaffold system where X-ray imaging of poly(desaminotyrosyl-tyrosine ethyl ester carbonate) (pDTEc) scaffolds is improved through a controlled composition variation with an iodinated-pDTEc analog (pI 2 DTEc). The results show that pDTEc scaffolds must include at least 9%, 16%, 38% or 46% pI 2 DTEc (by mass) to enable effective imaging by microradiography, dental radiography, dental radiography through 0.75 cm of muscle tissue or micro-computed tomography, respectively. Only two scaffold libraries were required to determine these minimum pI 2 DTEc percentages required for X-ray imaging, which demonstrates the efficiency of this new combinatorial approach for optimizing scaffold formulations.

The cloud-point temperatures (T clo 's) of poly(N-isopropyl acrylamide) (PNI-PAM)/water solutions with NaCl, NaBr, or NaI were measured. All these salts reduced the T clo 's of PNIPAM/water solutions to different extents, in the following order: NaCl Ͼ NaBr Ͼ NaI. The higher the concentration of the added salt was, the more greatly T clo dropped. A dynamic viscoelasticity investigation of the PNIPAM/water solutions with the salts indicated that during phase separation, the system changed from a homogeneous fluid into a physically crosslinked network, and the addition of salts also reduced the temperature at which this change began. The gelation temperature (T gel ) and the scaling exponent of the PNIPAM/water solutions with NaBr were obtained with dynamic scaling theory, and T gel was found to be close to T clo . That the addition of salts to the solution decreased T clo and T gel to the same extent further proved that the network structure was formed with the phase separation in the PNIPAM/water solutions.

Gradients and arrays have become very useful to the fields of tissue engineering and biomaterials. Both gradients and arrays make efficient platforms for screening cell response to biomaterials. Graded biomaterials also have functional applications and make useful substrates for fundamental studies of cell phenomena such as migration. This article will review the use of gradients and arrays in tissue engineering and biomaterials research, with a focus on cellular and biologic responses.

We report here that by good design, polyaniline (PANI) can be cytocompatible and formed into usable scaffolds for bio-medical applications. By adjusting the ratio of two monomers, aniline (AN) and metanilic acid (MA), a series of copolymers with different sulfonation degrees have been synthesized. Four-probe conductivity measurements showed that as the sulfonation degree increased, the conductivity decreased. XPS analysis was used to determine the sulfur/nitrogen ratio. In vitro cell culture study was conducted with human osteosarcoma (HOS) cells. Microscopic observation did not show abnormal cellular behavior when sulfonated polyaniline (SPAN) was put in direct contact with HOS cells. Cells growing on the non-transparent dark green SPAN films were observed with fluorescence by laser scanning cytometry (LSC). In proliferation studies more than 70% of cells were found viable on SPAN compared to 88% for poly(L-lactic acid) with the number of cells growing on glass as a control, indicating generally good biocompatibility. We expect these polymers would have great potential in biological applications of conducting polymers as we determine that a variety of physical and chemical properties can be controlled through synthesis.