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- Development of a sensitive ratiometric Imprinted hydrogel for the detection of matrix metalloproteinase 7 (MMP7) biomarkerPublication . Piloto, Ana Margarida L.; Ribeiro, David S.M.; Santos, João L.M.; Sales, GoretiA dual-emissive fluorescent probe was developed for the sensitive and selective detection of matrix metalloproteinase 7 (MMP7), a protein biomarker associated with pancreatic cancer. The ratiometric probe consisting of blue emitting carbon dots (CDs) and molecularly imprinted polymers (MIPs) previously assembled around red emitting quantum dots (QDs) was successfully combined for the detection of MMP7 protein. The concept is to use MIPs that function as the biorecognition elements, conjugated to cadmium telluride QDs, as the sensing system. The fluorescence intensity of red QDs is quenched with increasing concentrations of the analyte, acting as sensitive probes, while the fluorescence intensity of blue emitting CDs remains constant, acting as internal controls. The resultant fluorescence color changed from red to blue as a function of the MMP7 concentration, under a 365 nm UV lamp. The imprinted material MIP@QDs were successfully incorporated within a cellulose hydrogel containing CDs as reference probes. The resultant materials were designated as imprinted ratiometric hydrogels (imprinted rHGs). The fluorescence quenching of the imprinted rHGs occurred with increasing concentrations of MMP7, showing linearity in the range [1.49 × 10–11 – 1.92 × 10–9] g/mL, in 1000-fold diluted human serum. The imprinted rHGs showed an imprinting factor of 1.83 and a limit of detection of 4.11 × 10–12 g/mL. Overall, the imprinted rHGs developed in this work presented increased selectivity for the MMP7 protein over red emitting QDs nanoparticles and higher sensitivity comparatively to the non-imprinted rHGs.
- Sensitive ratiometric imprinted hydrogel for the detection of matrix metalloproteinase 7 (MMP7) biomarkerPublication . Piloto, Ana Margarida L.; Ribeiro, David S.M.; Santos, João L.M.; Sales, GoretiA dual-emissive fluorescent probe has been developed for the sensitive and selective detection of matrix metalloproteinase 7 (MMP7), a protein biomarker associated with pancreatic cancer1,2. The resultant materials were designated as imprinted ratiometric hydrogels (imprinted rHGs). The fluorescence quenching of the imprinted rHGs occurred with increasing concentrations of MMP7, showing linearity in the range [1.49 x 10-11 – 1.92 x 10-9] g/mL in 1000-fold diluted human serum in PBS 10mM pH 5.8. Overall, the imprinted rHGs developed in this work presented increased selectivity for the MMP7 protein over raw emitting QDs nanoparticles and higher sensitivity comparatively to the non-imprinted rHGs.
- Cellulose‑based hydrogel on quantum dots with molecularly imprinted polymers for the detection of CA19‑9 protein cancer biomarkerPublication . Piloto, Ana Margarida L.; Ribeiro, David S.M.; Rodrigues, S. Sofia M.; Santos, João L.M.; Sampaio, Paula; Sales, Maria Goreti FerreiraMolecularly imprinted polymers (MIPs), were successfully assembled around quantum dots (QDs), for the detection of the carbohydrate antigen CA19-9, a biomarker associated with pancreatic cancer (PC). The imprinted materials MIP@QDs were incorporated within cellulose hydrogels and designated as imprinted hydrogels (iHGs). The concept is to use MIPs which function as the biorecognition elements, conjugated to QDs as the sensing system. The fluorescence quenching of the iHGs occurred with increasing concentrations of CA19-9, showing linearity in the range 2.76 × 10−2 – 5.23 × 102 U/ml, in a 1000-fold diluted human serum. The iHGs show a linear response below the cutoff values for pancreatic cancer diagnosis (< 23 U/ml), a limit of detection of 1.58 × 10−3 U/ml and an imprinting factor (IF) of 1.76. Moreover, they exhibit stability and selectivity towards CA19-9, when compared with the non-imprinted controls, here designated as non-imprinted hydrogels (non-iHGs). In conclusion, this work demonstrates that the conjugation of MIPs to QDs increases the sensitivity and specificity of the developed sensing system for optical detection methods within clinical significance ranges. This fact shows potential for the iHGs to be applied as a sensitive, low-cost format for point-of-care tests (PoCTs).
- Label-free quantum dot conjugates for human protein IL-2 based on molecularly imprinted polymersPublication . Piloto, Ana Margarida L.; Ribeiro, David S.M.; Rodrigues, S. Sofia M.; Santos, João L.M.; Ferreira Sales, Maria GoretiHerein, the development of a fluorescent-based sensor by combining quantum dots (QDs) with molecularly-imprinted technology (MIT), intensively optimized to generate exceptional operating features is presented. This sensor is designed to target human interleukin-2 (IL-2) in synthetic human serum. IL-2 is a regulatory protein released as a triggered response from the immune system towards an inflammation. For this purpose, cadmium telluride (CdTe) QDs are prepared with 3-mercaptopropionic acid (MPA) and modified afterwards to produce an IL-2 imprinted polymer with methacrylic acid and N,N´-methylenebis(acrylamide), upon removal of the template under optimized conditions. During IL-2 rebinding, the fluorescence intensity of CdTe@MPA QDs is quenched in a concentration dependent manner. Using surface imprinting technology, the optimal fluorescence signals yielded a linear response versus logarithm of IL-2 concentration from 35 fg/ml to 39 pg/ml, in a 1000-fold diluted synthetic human serum. The limit of detection obtained is 5.91 fg/ml, lying below the concentration levels of IL-2 with clinical interest for cancer diagnosis (9.4–19.2 pg/ml). Overall, the method presented herein is a demonstration that the combination of MIP and QDs for protein detection constitutes a powerful tool in clinical analysis, providing low cost, sensitive and quick responses. The same concept may be further extended to other proteins of interest.