TY - JOUR
T1 - Chemical Orthogonality in Surface-Patterned Poly(ethylene glycol) Microgels
AU - Teng, Feiyue
AU - Wu, Xinpei
AU - Libera, Matthew
N1 - Publisher Copyright:
Copyright © 2020 American Chemical Society.
PY - 2020/9/8
Y1 - 2020/9/8
N2 - Because of its widely known antifouling properties, a variety of lithographic approaches has been used to pattern surfaces with poly(ethylene glycol) (PEG) to control surface interactions with biomolecules and cells over micro- and nanolength scales. Often, however, particular applications need additional functions within PEG-patterned surfaces. Monofunctional films can be generated using PEG modified to include a chemically functional group. We show that patterning with focused electron beams, in addition to cross-linking a monofunctional PEG homopolymer thin-film precursor and grafting the resulting patterned microgels to an underlying substrate, induces additional chemical functionality by radiation chemistry along the polymer main chain and that this second functionality can be orthogonal to the initial one. Specifically, we explore the reactivity of biotin-terminated PEG (PEG-B) as a function of electron dose using 2 keV electrons. At low doses (∼4-10 μC/cm2), the patterned PEG-B microgels are reactive with streptavidin (SA). As dose increases, the SA reactivity decays as biotin is damaged by the incident electrons. Independently, amine reactivity appears at higher doses (∼150-500 μC/cm2). At both extremes, the patterned PEG microgels retain their ability to resist fibronectin adsorption. We confirm that the amine reactivity derives from the PEG main chain by demonstrating similar dose response in hydroxy-terminated PEG (PEG-OH), and we attribute this behavior to the formation of ketones, aldehydes, and/or carboxylic acids during and after electron-beam (e-beam) patterning. Based on relative fluorescent intensities, we estimate that the functional contrast between the differentially patterned areas is about a factor of six or more. This approach provides the ability to easily pattern biospecific functionality while preserving the ability to resist nonspecific adsorption at length scales relevant to controlling protein and cell interactions.
AB - Because of its widely known antifouling properties, a variety of lithographic approaches has been used to pattern surfaces with poly(ethylene glycol) (PEG) to control surface interactions with biomolecules and cells over micro- and nanolength scales. Often, however, particular applications need additional functions within PEG-patterned surfaces. Monofunctional films can be generated using PEG modified to include a chemically functional group. We show that patterning with focused electron beams, in addition to cross-linking a monofunctional PEG homopolymer thin-film precursor and grafting the resulting patterned microgels to an underlying substrate, induces additional chemical functionality by radiation chemistry along the polymer main chain and that this second functionality can be orthogonal to the initial one. Specifically, we explore the reactivity of biotin-terminated PEG (PEG-B) as a function of electron dose using 2 keV electrons. At low doses (∼4-10 μC/cm2), the patterned PEG-B microgels are reactive with streptavidin (SA). As dose increases, the SA reactivity decays as biotin is damaged by the incident electrons. Independently, amine reactivity appears at higher doses (∼150-500 μC/cm2). At both extremes, the patterned PEG microgels retain their ability to resist fibronectin adsorption. We confirm that the amine reactivity derives from the PEG main chain by demonstrating similar dose response in hydroxy-terminated PEG (PEG-OH), and we attribute this behavior to the formation of ketones, aldehydes, and/or carboxylic acids during and after electron-beam (e-beam) patterning. Based on relative fluorescent intensities, we estimate that the functional contrast between the differentially patterned areas is about a factor of six or more. This approach provides the ability to easily pattern biospecific functionality while preserving the ability to resist nonspecific adsorption at length scales relevant to controlling protein and cell interactions.
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U2 - 10.1021/acs.langmuir.0c02172
DO - 10.1021/acs.langmuir.0c02172
M3 - Article
C2 - 32787029
AN - SCOPUS:85090508125
SN - 0743-7463
VL - 36
SP - 10622
EP - 10627
JO - Langmuir
JF - Langmuir
IS - 35
ER -