# Hydrogel as a Platform for Point-of-Care Calcium Determination in Blood

## TL;DR

A new hydrogel-based method allows quick and simple blood calcium testing at the point of care, using a finger-prick blood sample.

## Contribution

A novel hydrogel platform with an embedded calcium sensor enables rapid point-of-care calcium determination in blood plasma.

## Key findings

- Gelatin hydrogel is uniquely suitable among tested materials for separating blood and detecting calcium.
- The method allows photometric calcium concentration measurement in blood plasma with high accuracy.
- The platform is rapid, requires minimal sample preparation, and is suitable for clinical integration.

## Abstract

Calcium is a key macroelement involved in a range of physiological processes in the body, and its concentration in blood is an important diagnostic indicator in various diseases. This work presents a novel rapid method for the point-of-care determination of total calcium content in patient blood, by applying a drop of capillary blood from a finger onto a hydrogel. Gelatin hydrogel, modified with an optical sensor for calcium, Arsenazo III, was used as a platform for the separation of blood into plasma and erythrocytes. A comparative analysis of various types of hydrogel materials (polyacrylamide, PVA, Fmoc-FF, carbomer, carbopol, gelatin) was performed, demonstrating that among the studied systems, only gelatin hydrogel is suitable as a platform for the determination of calcium in blood plasma. The binding of calcium ions from blood plasma with the calcium sensor embedded in the hydrogel leads to a change in the absorption spectrum of the system, enabling photometric determination of calcium concentrations below and above the normal range in blood plasma. Therefore, this rapid assay allows monitoring of calcium metabolism disorders in the human organism. The method is characterized by its speed, simplicity of sample preparation, and potential for integration into clinical practice.