Tuning the surface properties of hydrogel at the nanoscale with focused ion irradiation

Abstract

With the site-specific machining capability of Focused Ion Beam (FIB) irradiation, we aim to tailor the surface morphology and physical attributes of biocompatible hydrogel at the nano/micro scale particularly for tissue engineering and other biomedical studies. Thin films of Gtn-HPA/CMC-Tyr hydrogels were deposited on a gold-coated substrate and were subjected to irradiation with a kiloelectronvolt (keV) gallium ion beam. The sputtering yield, surface morphology and mechanical property changes were investigated using Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM) and Monte Carlo simulations. The sputtering yield of the hydrogel was found to be approximately 0.47 μm(3) nC(-1) compared with Monte-Carlo simulation results of 0.09 μm(3) nC(-1). Compared to the surface roughness of the pristine hydrogel at approximately 2 nm, the average surface roughness significantly increased with the increase of ion fluence with measurements extended to 20 nm at 100 pC μm(-2). Highly packed submicron porous patterns were also revealed with AFM, while significantly decreased pore sizes and increased porosity were found with ion irradiation at oblique incidence. The Young's modulus of irradiated hydrogel determined using AFM force spectroscopy was revealed to be dependent on ion fluence. Compared to the original Young's modulus value of 20 MPa, irradiation elevated the value to 250 MPa and 350 MPa at 1 pC μm(-2) and 100 pC μm(-2), respectively. Cell culture studies confirmed that the irradiated hydrogel samples were biocompatible, and the generated nanoscale patterns remained stable under physiological conditions.

Robust antigen-specific tuning of the nanoscale barrier properties of biogels using matrix-associating IgG and IgM antibodies

“…Bulk changes to the matrix microstructure, either by changing the crosslinker concentration in covalently linked gels or by relying on environmental stimuli (e.g. light or enzymes, respectively) to polymerize or degrade matrix constituents [20][21][22][23][24][25], only facilitate selectivity based on size and are generally irreversible. Alternatively, covalent crosslinking of antigen-specific molecules to the matrix [16][17][18][19]25] is cumbersome in practice, is limited in the number of species that can be simultaneously immobilized, and may not efficiently immobilize diffusive species [26].…”

Nano and Microscale Patterning on Soft Matters with Ion Beam Irradiation

“…Compared to the original Young's modulus value of 20 MPa, irradiation elevated the value to 250 MPa and 350 MPa at 1 pC µm -2 and 100 pC µm -2 respectively. Cell culture studies confirmed that the irradiated hydrogel samples were biocompatible, with stable nanoscale patterns under physiological conditions [4]. This patterning approach can also be extended to other soft samples such as tumour tissues (Figure 2a).…”

Fabrication and Applications of Micro/Nanostructured Devices for Tissue Engineering

“…Yet, this kind of nanolithography is successfully used also for biomedical milling tasks, such as tune hydrogel surface morphology and modulus. During irradiation, unique nanoscale porous features in regular formation were observed and the pore parameters were found to be dependent on ion incident angles [ 51 ]. Modern FIB instruments, equipped with electrostatic optics and a liquid metal ion source, can achieve a resolution comparable to that of EBL [ 52 ].…”