Graphene oxide-decorated hyrogel inverse opal photonic crystal improving colorimetric and fluorescent responses for rapid detection of lipocalin-1

In this paper, the colorimetric and fluorescent biosensors prepared from polyethylene glycol diacrylate (PEGDA)based inverse opal photonic crystal (IOPC) decorated with graphene oxide (GO) (termed as GO-modified PEGDAbased IOPC) have been explored for simple and rapid semi-quantitative and quantitative detections of biomarker lipocaline-1 (LCN1) in tear at low level, respectively. We found that only after the concentration of GO (CGO) was sufficiently high to create a thin GO layer due to intermolecular interactions between neighboring GO molecules on the PEGDA surface, the red-shift of the reflection peak position (lambda stb) became effective. This widening of the shift in lambda stb became significant when GO-modified PEGDA-based IOPC was selectively attached with LCN1 via the immunoassay, because the attachment with LCN1 caused a reverse shift in lambda stb. Correspondingly, the visualizable photonic color could vary in wider range depending on the concentration of LCN1 (CLCN1), from orange color of blank solution to light blue color of solution containing LCN1 at CLCN1 of 0.06 mg/mL using CGO = 2.5 mg/mL. For quantification, CGO and enrichment time of LCN1 were optimized for getting the maximum fluorescence microscopy intensity. The diagram for the relationship between fluorescence intensity and CLCN1 showed various advantages of GO-modified PEGDA-based IOPC over non-GO-modified PEGDA-based IOPC. Those were higher fluorescence intensity, wider linear range and higher detection sensitivity. Thus, our results revealed potential applications of GO-modified PEGDA-based IOPC in screening patients with diabetic retinopathy (DR) in early stage.