# Gold Nanoparticles Coated With Hydrophobin‐ProteinA Fusion Protein: Development of a Versatile Immunosensing Platform

## TL;DR

A new immunosensing platform uses gold nanoparticles coated with a fusion protein to anchor antibodies, enabling sensitive and selective detection of various targets.

## Contribution

A novel fusion protein of hydrophobin and protein A enables spontaneous functionalization of gold nanoparticles for biosensing.

## Key findings

- The fusion protein spontaneously adheres to gold nanoparticles without chemical modification.
- The platform effectively detects targets like mesothelin and SARS-CoV-2 spike protein.
- A two-step method using HCl-induced aggregation enhances detection through spectral analysis.

## Abstract

Advancing immunosensing technologies hinges on the development of next‐generation surface functionalization methods, as the precise anchoring of antibodies on transducer interface is essential for achieving high sensitivity and selectivity. Among the diverse methodologies explored, bioengineered materials have shown significant potential to improve antibody orientation, stability, and functional performance. In this study, we present a chimeric protein created by fusing the adhesive Class I hydrophobin Vmh2 from Pleurotus ostreatus, with the Fc‐binding region of protein A from Staphylococcus aureus (SpA). This fusion protein spontaneously adheres on gold nanoparticles (AuNPs) without requiring chemical modification, forming a robust bio‐interactive layer for antibody attachment. The platform's adaptability and effectiveness were assessed using an immunoglobulin specific to a fungal laccase to establish the performance of the system, and antibodies against two clinically significant targets‐ mesothelin, a tumor‐associated glycoprotein, and the SARS‐CoV‐2 spike protein‐ to showcase the diagnostic potential of the system. A two‐step method based on the induced aggregation of the AuNps not bound to the analyte allows underscoring the platform's promise in biosensing applications. Overall, this approach represents a sustainable, versatile, and low‐cost route for fabricating biologically active surfaces, with wide‐ranging relevance in medical diagnostics, environmental analysis, and biotechnological innovation.

The biosensor uses a two‐step method involving Ab‐Vmh2/SpA‐AuNPs. Gold nanoparticles are functionalized with Vmh2/SpA, antibodies and then mixed with analytes. HCl induces aggregation in unbound particles enabling detection through spectral analysis based on analyte interaction and nanoparticle aggregation behavior.