However, Clark emphasizes that much more was at stake with NAFTA than just the growth of trade among the three nations. House defeat of NAÏTA, he notes, would have soured U.S. relations with Mexico and other Latin American countries—many of whom also want into NAFTA. It would take years to repair the damage. And business opportunities in Mexico that now will be open to U.S. firms would have gone to Japanese and European companies. A NAFTA defeat, Clark adds, also
would have cast a pall over the ongoing critical Uruguay round of multilateral trade negotiations, in which the chemical industry has a big stake. By passing NAFTA, he believes, the House has breathed new life into the General Agreement on Tariffs & Trade (GATT), which is sponsoring the Uruguay round trade talks. 'The whole world needs an economic shot in the arm/' Clark says. Passing NAFTA will provide it, he thinks. Earl Anderson
Biodegradable copolymer eyed as tissue matrix What one scientist calls "a milestone in the development of Ο Ο Ο Q Il II Il II more tissuelike matériau' was _/ 0 _ CH-C-O-CH-C O-CH-C-NH-CH-C reported last week by research\ I I ChL ChL ChL ers at Massachusetts Institute of Technology. NhL The MIT team for the first time synthesized a biodegradable coPoly (L-lactic acid-co-L-lysine) polymer and chemically attached a biologically active peptide to it. The co- as the amino acids are denoted). This polymer potentially could function as a key sequence latches onto an adhesion matrix to hold mammalian cells, and receptor on a cell membrane, enabling thus serve in the body as an artificial tis- the cell to stick to the polymer surface. sue or organ. Another research group has shown The new material could have broad that a surface density of only 1 χ 10"1"1 applications in efforts to develop biolog- mole per sq cm of an RGD peptide ical substitutes for damaged tissues, "effectively promotes cell adhesion to notes Robert Langer, professor of chemi- an otherwise nonadherent surface," cal and biomedical engineering at MIT, Langer notes. Other peptides that regu who led the research. Creation of such late cell functions—such as wound artificial tissues is being hotly pursued healing—could also be attached to the because the critical shortage of organ do- copolymer in the same way, he adds. nors severely limits transplantations. The work on the lactic acid/lysine A major challenge, Langer says, is to copolymer was carried out in Langer's find matrix materials that are biode- lab by former students Denise A. Bar gradable, are compatible with cell func- rera and Eric Zylstra, and associate tion, have tightly controlled properties, professor of chemistry Peter T. Lansand can be manufactured in large bury Jr. The results were published last quantities. week in the Journal of the American The new material developed in his Chemical Society [115,11010 (1993)1. laboratory—a copolymer of lactic acid Langer's group is now investigating [CH,CH(OH)COOH] and lysine whether the copolymer will fulfill its [H2N(CH2)4CH(NH2)COOH]—may fit potential. "We think this approach can the bill. Structurally, it is similar to offer a new dimension to tissue engi polylactic acid and related polymers neering," Langer tells C&EN. It will en that are used, for instance, in dissolv- able scientists to take the cell-regulat able sutures and drug-releasing im- ing sequences that occur in natural plants. But unlike polylactic acid, the polymers like proteins, and put them new copolymer has lysine residues, into synthetic polymers like polylactic whose terminal amino groups allow a acid. The eventual result, he says, could bioactive ligand to be attached. be creation of artificial tissues such as The ligand that Langer and cowork- liver, nerve, or cartilage. ers grafted to the lysine residues is a In working toward that goal, Langer pentapeptide containing an arginine- and coworkers already have found ways glycine-aspartic acid sequence (or RGD, to process biocompatible polymers into
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