Recent years have seen very strong increase in everyday application of biotechnology products as well as diagnostics shifting from centralized laboratories to distributed measurements. This also increases the need for quality control and suitable receptors for the respective sensor systems. Natural recognition systems fit perfectly in terms of sensitivity. However, in terms of technological application they are somewhat limited concerning stability and costs. Therefore, artificial recognition systems such as molecularly imprinted polymers (MIP) have attracted increasing attention. These materials aim to mimic natural recognition principles such as antibody-antigen interactions [
1,
2]. Imprinted polymers are typically cheap, straightforward to generate and effective in creating recognition systems for various types of analytes. Among others, MIP can be combined with mass-sensitive quartz micro balances (QCM) [
3] to create powerful sensors for various types of analytes [
4,
5,
6] that can also be applied in real life conditions [
7]. Although several imprinting techniques for creating protein MIPs have been developed [
8], there is not yet a systematic procedure for protein imprinting. This can be explained by several challenges one faces in protein imprinting [
9]: Diffusion of larger bio species into the polymer is inhibited. Proteins can change their steric properties depending on pH and temperature. Due to this fact the steric recognition property of MIP might be lost. Additionally, proteins of course are large molecules containing many functional groups on their surfaces. Depending on the exact orientation during imprinting they can result in a large number of different binding sites on their respective surface area with broadly distributed affinity. Also protein imprinting is mainly limited to aqueous solution, where water competes for the corresponding binding sites with the analyte [
10]. Considering this, rationally optimizing those polymers is the first important step on the way to protein MIP sensors. The aim of this paper is to systematically examine various polymer properties, such as cross linker ratio and functional monomer, and their influence on sensitivity and response time. For this purpose Bovine Serum Albumin (BSA) was chosen as model protein. BSA is a globular protein and extensively described in literature [
11]. We hence prepared albumin-imprinted polymers for mass-sensitive sensing. All sensor responses of imprinted polymers are compared to a non-imprinted polymer (NIP) to compensate for any physical influence or non-specific adsorption on the surface. As MIP and NIP are chemically identical, any difference in their respective sensor signals only correlates to the imprinting effect. A scheme of such a QCM coated with MIP and NIP, respectively, is shown in
Figure 1.
Figure 1.
Scheme of a two-electrode quartz coated with two different polymers; molecularly imprinted polymer (MIP) and non-imprinted polymer (NIP).