# Development of an SPRi Immune Method for the Quantitative Detection of Osteopontin

## TL;DR

A new SPRi biosensor method was developed to quickly and accurately detect osteopontin in blood plasma without complex sample preparation.

## Contribution

The development of a sensitive SPRi biosensor using monoclonal antibodies for osteopontin detection in biological fluids.

## Key findings

- The biosensor achieved detection limits of 0.014–0.018 ng/mL for osteopontin using mouse or rabbit antibodies.
- The method showed good agreement with ELISA results when testing blood plasma samples.
- The SPRi biosensor allows rapid and simple osteopontin detection without signal enhancement or complex sample preparation.

## Abstract

SPRi biosensors for osteopontin determination have been developed.

The bioreceptors are mouse or rabbit monoclonal anti-osteopontin antibodies attached to the gold surface of a chip via a cysteamine linker.

The biosensors have sufficient sensitivity to determine osteopontin at levels characteristic of this protein in blood plasma without any signal enhancement.

Osteopontin (OPN) is a protein that plays many essential functions in the human body. It is present in most tissues and body fluids. OPN, among other things, participates in wound healing, the formation and remodeling of bone, immune response, inflammation, angiogenesis, and tumor formation. A new analytical method, based on SPRi (surface plasmon resonance imaging) biosensors, has been developed to determine osteopontin in biological fluids. OPN was captured from a solution by an immobilized antibody (mouse or rabbit), a bioreceptor in the SPRi sensor. A separate validation process was carried out for each antibody used. The LOD and LOQ values obtained for the biosensor with mouse antibody were 0.014 ng mL−1 and 0.043 ng mL−1, respectively, and those obtained for the biosensor with rabbit antibody were 0.018 ng mL−1 and 0.055 ng mL−1, respectively. The response ranges of both biosensors were in a similar range: 0.05–1.00 ng mL−1. OPN was determined in blood plasma to demonstrate the sensor potential, showing good agreement with the data obtained using an ELISA test and reported in the literature. The presented method is characterized by ease and speed of measurement, and the process does not require special preparation of samples.