地域性知識交換理論強調創新活動者在空間的聚集特性，認為面對面的知識交換助於該地區的創新能量，近年由於全球勞力分工形態的轉變與資訊傳播科技的突破，開啟以「網路」為基礎的地理創意與創新發展模式。學者開始主張城市的創新能量立基於活動者的關係連結，透過網路建構彼此的合作創新模式，網路鄰近性逐漸改變傳統上地理鄰近性的知識交換行為。本研究以社會網路分析方法，檢視美國生物技術共同專利（biotechnology co-patents）之發明人居住城市在1979年至2009年，每10年的跨區域合作創新網路的變化情形，並以核心—邊陲的關係性假說來驗證2009年跨區域的網路體系與都市階層。結果顯示隨著生物技術共同專利活動的增加，發明人已逐步建立跨區合作的知識交換模式，城市相互連結日益頻繁，網路結構漸趨複雜，知識傳遞與交換的路徑更加多元，雖然生物技術專利的跨區域合作模式已具全國性之規模，然而地方和區域的連結模式仍明顯存在，其中，舊金山（San Francisco）和紐約（New York）扮演東、西兩岸的生物技術創新核心，波士頓（Boston）、聖地牙哥（San Diego）和洛杉磯（Los Angeles）也在創新系統中扮演關鍵性之角色，這些生物技術重鎮均包括重要的研究型大學、強大的科技基礎建設，以及生物技術關連性產業群聚等特性。

Theories of localized knowledge exchange emphasize geographical concentration of inventive firms, research institutions, and creative individuals. Knowledge transfer is bounded in space because human interaction relies on face-to-face exchange of tacit knowledge. Although distance-based clustering of economic agents remains a pillar in the geography of invention and innovation, and alternative perspective focuses on interregional collaborative networks in which individuals and groups are embedded in wide-ranging webs of relationships. This research uses social network analysis to explore the changing structures of collaborative networks of international co-patenting in 1979, 1989, 1999 and 2009. Networks are identified by tracking American inventors who obtained co-patents in biotechnology.After attributing each co-patent to the U.S. metropolitan area where the inventor resides, this study analyzed interregional co-patenting patterns to identify thekey relationships linking U.S. major urban areas, and compare properties of these collaborative network systems. Results show that interregional network complexity has broadened and deepened. While inventors in major centers, including San Francisco, New York, Boston, and San Diego are the foremost collaborators, a dense web of knowledge exchange has emerged that is not singularly controlled by a handful of intermediaries. Although national linkages have developed, intense local and regional ties persist.