Soft molecularly imprinted nanoparticles with simultaneous lossy mode and surface plasmon multi-resonances for femtomolar sensing of serum transferrin protein

Abstract

The simultaneous interrogation of both lossy mode (LMR) and surface plasmon (SPR) resonances was herein exploited for the first time to devise a sensor in combination with soft molecularly imprinting of nanoparticles (nanoMIPs), specifically entailed of the selectivity towards the protein biomarker human serum transferrin (HTR). Two distinct metal-oxide bilayers, i.e. TiO2–ZrO2 and ZrO2–TiO2, were used in the SPR–LMR sensing platforms. The responses to binding of the target protein HTR of both sensing configurations (TiO2–ZrO2–Au-nanoMIPs, ZrO2–TiO2–Au-nanoMIPs) showed femtomolar HTR detection, LODs of tens of fM and KDapp ~ 30 fM. Selectivity for HTR was demonstrated. The SPR interrogation was more efficient for the ZrO2–TiO2–Au-nanoMIPs configuration (sensitivity at low concentrations, S = 0.108 nm/fM) than for the TiO2–ZrO2–Au-nanoMIPs one (S = 0.061 nm/fM); while LMR was more efficient for TiO2–ZrO2–Au-nanoMIPs (S = 0.396 nm/fM) than for ZrO2–TiO2–Au-nanoMIPs (S = 0.177 nm/fM). The simultaneous resonance monitoring is advantageous for point of care determinations, both in terms of measurement’s redundancy, that enables the cross-control of the measure and the optimization of the detection, by exploiting the individual characteristics of each resonance.

Sensing Approaches Exploiting Molecularly Imprinted Nanoparticles and Lossy Mode Resonance in Polymer Optical Fibers

“…From the above figure, it is possible to observe that the LMR resonance wavelength decreases (blue shift) at increasing HTR concentrations. This blue shift is a well-known phenomenon when dealing with nanoMIPs since it was extensively demonstrated that the analyte-nanoMIPs interaction causes a shrinkage of the nanoparticles, reducing the measured refractive index at the sensitive surface [ 22 , 23 , 24 , 30 ].…”

“…In this method, it was possible to observe a multi-resonance phenomenon due to the simultaneous excitation of SPR and LMR [ 20 ]. These sensing platforms were recently coupled to molecularly imprinted nanoparticles (nanoMIPs) to conduct binding tests, comparing the obtained performance with the state-of-the-art SPR and LMR biochemical sensors [ 22 ].…”

“…This work developed different optical probes consisting of a ZrO 2 and TiO 2 combination bilayer deposited on the core of a D-shaped POF sensitive area. These kinds of platforms, unlike the ones extensively presented in [ 20 , 22 ], do not include the upper gold nanofilm in such a way as to exploit only the LMR phenomenon. These sensor configurations were experimentally tested for their binding behavior by coupling them with the nanoMIPs layer.…”

“…The optical platforms based on the bilayers (TiO 2 -ZrO 2 and ZrO 2 -TiO 2 ), which showed appropriate LMR performance in bulk sensitivity [ 20 ], were explored to evaluate the binding sensitivity using nanoMIPs as a recognition element. In this work, the nanoMIPs layer is in contact with MOs directly, without the gold nanofilm used in [ 22 ]. Currently, to the best of our knowledge, the LMR technique is infrequently implemented with nanoMIPs.…”

“…Currently, to the best of our knowledge, the LMR technique is infrequently implemented with nanoMIPs. In particular, by exploiting nanoMIPs, the binding sensitivity improves thanks to the high value of receptor efficiency [ 22 , 23 , 24 ]. In fact, when the NanoMIPs-analyte binding occurs, the capability to convert variations of analyte concentration into refractive index changes is ultra-efficiency [ 22 , 23 , 24 ].…”