Pattern-based recognition of proteins by an array of fluorescent carbon-nanodot receptors

Protein types and concentrations in human body fluid environment have a direct correlation to health conditions, and can be used for primary screening and diagnostics of a great variety of diseases. Herein, we synthesized a series of fluorescent carbon nanodots (CDs) with various ratios of β-cyclodextrin doping, which can recognize proteins and adjust self-emission by combining both the cavity recognition effect of cyclodextrin and noncovalent bonding effect of carboxyl, amino and hydroxyl groups. The difference in β-cyclodextrin contents of various CDs will result in a differential response to various proteins, based on which a sensor array by four CDs was constructed to detect and discriminate six proteins with various subunit numbers. In order to improve the discriminative effect of the sensor array, CD-sensitive metal ions (Cu²⁺ and Fe³⁺) were introduced as sensing media to increase the action sites between the CDs and proteins, and these proteins were well discriminated by the CD@metal ion sensor array with a detection limit of 50 μM. The sensor array could work in physiological conditions (such as urine and serum) and realize multiple proteins detection. Combining with the good repeatable detection results and higher sensitivity, the sensor array based on the CDs and metal ions provides an efficient and accurate method to detect proteins, which is important for disease diagnosis through assessing protein levels.