Physical and biological performance of a novel block copolymer nerve guide.

Although the ability to regenerate is evident in the nervous system, lesioned neurites are unable to cross gaps in neuronal pathways. In order to bridge gaps, guiding cues are essential to direct neurite regrowth. To overcome many of the shortcomings of polymer-based nerve guides, we developed a bioresorbable nerve guide composed of a novel trimethylene carbonate-caprolacton block copolymer (TMC-CL). Pore formation was controlled by using special solvent/precipitation media compositions in combination with the pore forming agent poly ethylene glycol (PEG). NMR spectroscopy, shear force-, compression-, and permeation assays were used for conduit characterization. The polymer conduit has a semipermeable wall with submicron pores to allow free metabolite/drug exchange. In order to investigate the principle of temporally controlled expression of therapeutic proteins in nerve guides, Neuro-2a cells were genetically engineered to express the reporter gene product green fluorescent protein (GFP) under the control of the Tet-On system. When these transduced cells were encapsulated in nerve guides, GFP expression could be induced for days by adding the antibiotic tetracycline derivative doxycycline to the nerve guide environment. Furthermore, encapsulated dorsal root ganglia (DRG) produced long neurites in vitro. In subsequent in vivo experiments, nerve guides filled with Schwann cells (SC) were implanted into lesioned spinal cords of adult rats. Regeneration of spinal cord axons into nerve guides was promoted by co-implanted Schwann cells. The data suggest that the novel TMC-CL nerve guides provide a promising tool for neuroregeneration.

Color as an indicator of the organization and compactibility of binary powder mixes.

The aim of this study was to relate the color of several binary mixes to their organization as observed by scanning electronic microscopy, and to their compactibility. Binary mixes of niflumic acid (yellow) with ethyl cellulose, hydroxypropylmethylcellulose, low-substituted hydroxypropylcellulose (L-HPC), and ibuprofen (all white) were prepared using different particle size ranges. Colors of the mixes were determined by diffuse reflectance spectroscopy using a chromameter. Linear correlation was observed between the yellowness index/whiteness index ratio (Y/W ratio) defined by the American Society for Testing and Materials (ASTM) standards and the mean particle size difference of the materials which governs the organization of the blend. Except for the least interacting mix, the niflumic acid/L-HPC series, the color of the blend was also related to the tensile strength of the tablets made from the binary mixes. Color could be an interesting indicator of the organization of a powder mix. Diffuse reflectance spectroscopy could be used as a quality control tool because any modification of the color of the mix may be an indicator of a modification of its compactibility.

A tumor-derived protein which provides T-cell costimulation through accessory cell activation.

A recently described tumor-derived glycoprotein, designated 90K, has been shown to have positive effects on the generation of cytotoxic effector cells (NK/LAK) from human PBMC. To determine the mechanism of these effects, we have examined the effects of 90K on cytokine production by human PBMC. A culture of normal PBMC with 90K alone did not result in IL-2 secretion; however, in coculture with suboptimal doses of ConA, 90K increased IL-2 secretion by PBMC. Coculture of PBMC with 90K and ConA also resulted in increased production of the cytokines IL-1, IL-6, GM-CSF, and TNF alpha. T cells depleted of accessory cells failed to respond to ConA alone, 90K alone, or the combination of ConA and 90K, suggesting that this protein does not have a direct effect on T cells. However, 90K alone was sufficient to induce cytokine production by unfractionated PBMC (IL-1, IL-6, GM-CSF, and TNF alpha) or by CD14-enriched PBMC (IL-1 and IL-6). In addition, expression of ICAM-1 was increased on a human monocytic cell line cultured with purified 90K in the absence of any other stimulus. This 90K-induced upregulation of ICAM-1 expression was accompanied by an increased accessory function of the monocytes, demonstrated by their ability to support ConA-induced activation of peripheral blood T cells. Based on the current data, we propose a model in which 90K activates accessory cells, resulting in the secretion of cytokines and the expression of adhesion molecules, which in turn act as costimulatory signals for T-cell activation. Activated T cells then produce cytokines such as IL-2, which lead to a more vigorous cell-mediated immune response to tumor cells and virus-infected cells. Thus, 90K shows promise as an immunotherapeutic reagent for diseases such as cancer and viral infection.