Biocompatible, Robust Free‐Standing Paper Composed of a TWEEN/Graphene Composite

Nonspecific binding (NSB), a random adsorption of biocomponents such as proteins and bacteria on noncomplementary materials,isoneofthebiggestproblemsinbiological applications including biosensors, protein chips, surgical instruments, drug delivery, and biomedicine. Polyoxyethylene sorbitan laurate (TWEEN), a commercially available chemical with aliphatic ester chains, has shown promise as a medical material and in overcomingproblems associated withNSB. [1‐4] However,stability during solution-based processing and uniformity of the materials that have TWEEN coating on flat substrates or nanomaterials using the selfassembled-monolayer (SAM) method has been an important issue. Further, biocompatible materials with high strength are important for several medical applications including stents, nail implants, and strong invasive instruments. Here, we present the production of a free-standing ‘‘paperlike’’ material composed of TWEEN and reduced graphene oxide (RGO) platelets and obtained by simple filtration of a homogeneous aqueous colloidal suspension of TWEEN/RGO hybrid. The ‘‘TWEEN paper’’ was highly stable in water without leakage of TWEEN and is compliant and sufficiently robust to be handled by hand without breaking. Furthermore, the TWEEN paper was noncytotoxic to three mammalian cell lines and biocompatible, inhibiting nonspecific binding of Gram-positive bacteria. [5] In contrast, RGO paper without TWEEN showed nonspecific bacterial binding. TWEEN is composed ofthree chemical parts (Fig. 1a): aliphatic esterchains that can prevent NSB ofbiomolecules, three-terminal hydroxyl groups that are hydrophilic and can be chemically modified for further applications, and an aliphatic chain that can easily be adsorbed on a hydrophobic surface by noncovalent interaction. Protein microarrays on flat substrates with SAM of TWEEN [4] and highly sensitive biosensors, [1‐3] built using field-effect transistor (FET) behavior of individual carbon nanotube (CNT) strands coated with TWEEN, have demonstrated that TWEEN can be effectively used to overcome NSB.