On-chip multiplexed voltammetry using a universal antifouling hydrogel and porous gold foam interface for stress and inflammation monitoring

Affinity based electrochemical biosensing systems with integrated miniaturised interfaces has enabled key advancement toward rapid, sensitive, precise and deployable detection platforms. Translation of the biosensing tools for routine monitoring of dairy cows’ functional welfare through non-invasive methods may have implications for identifying welfare compromise and improving welfare on-farm. Our goal was to develop an onchip voltammetric device to evaluate measures of inflammation (haptoglobin) and stress (cortisol) in biofluids of dairy cows, i.e. milk. We demonstrate the straightforward fabrication of highly reproducible silicon devices designed for electrochemical interface, using an efficient scale-up process for batch manufacturing of sensitive multiplexed sensor arrays. Lift-off and passivation lithography are used subsequently to construct the electroactive arrays with excellent reproducibility allowing micro and nano-scale patterning. Then we address the non-specific binding challenge via a simple, rapid formation of a biocompatible antibiofouling coating onto several porous gold surfaces on a single chip – simultaneously - in approximately two minutes. The developed coating provides flexibility in the experimental design due to abundant functional groups (-COOH and –NH2). We combine the coating with glutaraldehyde cross-linked Protein A/G to achieve a universal matrix for anti-IgG based biosensing and validate by attainment of two sensors of cortisol and haptoglobin by using milk samples.