A resonance light scattering sensor based on bioinspired molecularly imprinted polymers for selective detection of papain at trace levels

• A MIPs-based RLS sensor is developed for the first time to recognize protein.
• The bio-inspired PDA coated SiO2 NPs reduce the cytotoxicity in protein detection.
• Highly selective and sensitive are obtained and the detection limit is 0.63 nM.
• The sensor can be applied to some systems that can't be detected by fluorescence.

A novel resonance light scattering sensor based on the molecularly imprinted polymers (MIPs) technique was developed for specific recognition of the trace quantities of papain (Pap). In this sensor, as the specific recognition element, an excellent biocompatibility of protein-imprinted polymer without fluorescent materials was easily prepared, which based on the effective synthesis of mussel-inspired bionic polydopamine (PDA) on the surface of SiO2 nanoparticles (SiO2@PDA NPs). This recognition element could capture the target protein selectively, which led to the enhancement of resonance light scattering intensity with the increasing of the target protein concentration. The sensor was applied to determine Pap in the linear concentration range of 2.0–20.0 nM with a correlation coefficient r = 0.9966, and a low detection limit of 0.63 nM. The relative standard deviation for 14 nM of Pap was 1.02% (n = 7). In addition, the specificity study confirmed the resultant Pap-imprinted SiO2@PDA NPs had a high-selectivity to Pap, and the practical analytical performance was further examined by evaluating the detection of Pap in the dietary supplement with satisfactory results, with good recoveries of 97.5–105.3%.

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