Introduction to Biotechnical and Biomedical Applications of Poly(Ethylene Glycol)

At first glance, the polymer known as poly(ethylene glycol) or PEG appears to be a simple molecule. It is a linear or branched, neutral polyether, available in a variety of MWs, and soluble in water and most organic solvents. Despite its apparent simplicity, % MathType!MTEF!2!1!+- % feaagCart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn % hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr % 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9 % vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x % fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaqbaeaabiqaaa % qaaabaaaaaaaaapeGaamisaiaad+eacqGHsisldaqadaWdaeaapeGa % am4qaiaadIeapaWaaSbaaSqaa8qacaaIYaaapaqabaGcpeGaam4qai % aadIeapaWaaSbaaSqaa8qacaaIYaaapaqabaGcpeGaam4taaGaayjk % aiaawMcaa8aadaWgaaWcbaWdbiaad6gaa8aabeaak8qacqGHsislca % WGdbGaamisa8aadaWgaaWcbaWdbiaaikdaa8aabeaak8qacaWGdbGa % amisa8aadaWgaaWcbaWdbiaaikdaa8aabeaak8qacaWGpbGaamisaa % WdaeaacaWGWbGaam4BaiaadYgacaWG5bGaaiikaiaadwgacaWG0bGa % amiAaiaadMhacaWGSbGaamyzaiaad6gacaWGLbGaaGPaVlaadEgaca % WGSbGaamyEaiaadogacaWGVbGaamiBaiaacMcaaaaaaa!5E2C!$${HO - {{\left( {C{H_2}C{H_2}O} \right)}_n} - C{H_2}C{H_2}OH} \hfill \\ {poly(ethylene\,glycol)}$$ this molecule is the focus of much interest in the biotechnical and biomedical communities. Primarily this is because PEG is unusually effective at excluding other polymers from its presence when in an aqueous environment. This property translates into protein rejection, formation of two-phase systems with other polymers, nonimmunogenicity, and nonantigenicity. In addition, the polymer is nontoxic and does not harm active proteins or cells although it interacts with cell membranes. It is subject to ready chemical modification and attachment to other molecules and surfaces, and when attached to other molecules it has little effect on their chemistry but controls their solubility and increases their size. These properties, which are described in more detail below, have led to a variety of important biotechnical and biomedical applications, a summary of which is also presented below.