Whispering gallery mode aptasensors for detection of blood proteins

Abstract

Whispering gallery mode resonators (WGMR), as silica microspheres, have been recently proposed as an efficient tool for the realisation of optical biosensors. In this work we present a functionalization procedure based on the DNA-aptamer sequence immobilization on WGMR, able to recognize specifically thrombin or VEGF protein, preserving a high Q factor. The protein binding was optically characterized in terms of specificity in buffer solution or in 10% diluted human serum. Simulation of the protein flow was found in good agreement with experimental data. The aptasensor was also chemically regenerated and tested again, demonstrating the reusability of our system.

Whispering gallery mode sensors

“…Examples of receptor molecules that have been used and studied in WGM biosensing applications include oligonucleotides, which bind (hybridize) sequence-specifically to single-stranded nucleic acids [4,277–281]. Other examples include antibodies, which are widely used for detecting proteins [282–286] and aptamers [285,287]. A particular challenge when working with antibodies lies in finding a functionalization protocol that attaches the antibodies to the sensor surface without impeding their specific binding capabilities, maintaining their preferred orientation, etc.…”

SPAD aptasensor for the detection of circulating protein biomarkers

“…In order to introduce thiol groups able to react with the 5' dithiol groups of the modified aptamer, the silicon oxide surface was functionalized in wet conditions with MPTMS, as previously described (Pasquardini et al, 2013). Briefly, SiO 2 substrates were cleaned with an argon plasma (6.8 W, one minute) to remove organic contaminants and to hydroxylate the surface and were then immersed in a 1% v/v solution of MPTMS in toluene anhydrous at 60°C for 10 min.…”

“…Due to their significance and consolidated use in clinics, protein biomarkers are also an attractive target of miniaturized biosensor-based assays. Examples of biomarkers detected with biosensors are present in the literature, with detection methods based on surface plasmon resonance (Liu et al, 2012, Cho et al, 2012, electrochemistry (Palchetti andMascini, 2012, Lee et al, 2009), optics (fluorescence) (Freeman et al, 2012, Wang et al, 2014, chemiluminescence (Zhang et al, 2014) or even labelfree detection (Byeon and Bailey, 2011, Luchansky and Bailey, 2012, Pasquardini et al, 2013. Among the optical detection techniques, chemiluminescence is one of the most promising for the development of miniaturized biosensors due to the simple setup required, not requiring illumination sources neither long optical paths (Myers and Lee, 2008).…”

Whispering Gallery Modes Microresonators for Sensing and Biosensing Applications

“…Q factor measurements, performed at 773 nm, revealed high values both after silanization process (4.2 × 10 6 ) and thrombin covalent binding in BRB solution (8 × 10 5 ). Moreover, after the injection of 5 μl of 0.3 mg/ml of thrombin in human serum, the sensorgram revealed a wavelength shift of about 14.6 ± 0.1 pm in about 20 min [5].…”