Chemical derivatization and biofunctionalization of hydrogel nanomembranes for potential biomedical and biosensor applications

Abstract

Poly(ethylene glycol) based hydrogel nanomembranes (PHMs) are demonstrated to be able to host protein-specific receptors, providing, at the same time, stable, protein-repelling matrices with a characteristic mesh size up to 7-8 nm. The membranes were prepared by crosslinking of amino- and epoxy-terminated STAR-PEG precursors and maintained their hydrogel and protein-repelling properties even at a deviation of the precursor composition from the equilibrium value (1 : 1). The grafting density of the test avidin protein, specifically attached to the biotin moieties coupled to the free amine groups in the PHMs, varied from 0.45 × 10(12) to 1.3 × 10(12) proteins per cm(2) within the sampling depth of the experiments (∼11.5 nm), depending on the precursor composition, whereas the analogous values for the non-specifically adsorbed proteins were lower by a factor of 4-5. The engineering of PHMs with biomolecule-specific receptors and their loading with biomolecules are of potential interest for sensor fabrication and biomedical applications, including tissue engineering and regenerative therapy.

Elastic Properties of Poly(ethylene glycol) Nanomembranes and Respective Implications

“…Poly(ethylene glycol) (PEG) is a material that has distinct bioinert properties. It is frequently used for the suppression of adhesion and settlement of biomolecules and bio-organisms [ 1 , 2 , 3 , 4 , 5 , 6 ] as well as for the fabrication of biologically inert templates that can be decorated with bioactive functional groups and specific receptors [ 7 , 8 , 9 ]. For these applications, PEG moieties are used either as terminal parts of self-assembled monolayers (SAMs) or as the major or even only component of thin films.…”

“…These films exhibit pronounced bioinert and hydrogel properties and their characteristics could be flexibly tuned by varying the parameters of the preparation procedure [ 15 ] and the molecular weight of the precursors [ 16 ]. Further options are provided by the creation of hybrid materials on the basis of these films [ 15 ], their decoration with bioreceptors [ 8 ], and their modification by electron irradiation and UV light [ 17 , 18 ], paving the way to a variety of lithographic applications.…”

“…These membranes are quite stable and possess an exceptional elasticity, emphasized by a very small Young’s modulus of 2.1–5.2 MPa at a thickness of ~100 nm [ 16 ]. The value of Young’s modulus depends on the molecular weight of the STAR-NH 2 and STAR-EPX precursors [ 16 ], but is most likely a function of the membrane thickness and its composition at a deviation from the standard 1:1 ratio between STAR-NH 2 and STAR-EPX, which is useful for some applications [ 8 ]. It cannot also be excluded that the derived values of Young’s modulus are affected by the parameters of the experimental setup used for their measurement, which will strongly diminish their reliability.…”

Fabrication of Multifunctional Stimuli‐Responsive Hydrogels Susceptible to both pH and Metal Cation for Visual Detections

“…Recently, Khan et al prepared PEG‐based hydrogel films using commercially available epoxy/amine‐terminated four‐arm STAR‐PEGs with M n = 2000 gmol −1 which have thickness tuned between 4–200 nm. The unreacted epoxy/amino groups and hydroxyl groups in cross‐linking points were investigated for the attachment of specific receptors . Although the method is elegant, the high cost of multi‐arm PEG‐based polymers may limit the wide adaptability of this approach.…”

“…The unreacted epoxy/amino groups and hydroxyl groups in cross-linking points were investigated for the attachment of specific receptors. [27] Although the method is elegant, the high cost of multi-arm PEG-based polymers may limit the wide adaptability of this approach. Hence, simple, scalable, and cost-effective approaches to develop PEG-based reactive materials that can be easily functionalized are needed.…”