Biosensors

A biosensor device is defined by its biological or bioinspired receptor unit with specificities toward specific bio analytes. Analytes are often from biological origin like DNA, proteins generated from the immune system (antibodies, antigens), receptors at the cell membranes, entire living organisms (viruses, bacteria or blood cells) or simple molecules involved in a physiological process like glucose. Analysis of pollutants is also of our interest.  

Nanotechnology could revolutionize health care by enabling more efficient diagnostic devices. In our lab, we develop biosensing technologies for point of care and medical diagnosis taking advantage of optical and photonic properties of nanoparticles.

GOLD NPs FOR DETECTION AND IMAGING OF PROTEIN ASSOCIATED TO HEALTHCARE 

The incidence of an electromagnetic signal on a metallic nanoparticle produce an oscillation of electron density whose quantum unit is the localized surface plasmon resonance (LSPR). It depends on the oscillator strength (f), size and shape (r) and refractive index of the surrounding media (n). It is defined by the extinction coefficient composed by the absorption coefficient and scattering coefficient (Cext = Cabs + Cscat). For gold NPs f~105 compared to f~1 for a dye, while sabs a f and sscat a f2. This explains why metallic NPs are much better absorber and produce higher scattering, ideal for biosensors.

In our lab we synthesize gold NPs controlling size and shape to tune the LSPR and the dominance of absorption or scattering coefficient. It is functionalized with a receptor unit to guarantee to be attached only to a specific analyte. We are interested in the detection of over expressed proteins associated to few health problems, notably tuberculosis detection, prostate and breast cancer. We are also interested to imaging cancer cells over a tissue sample to localize the tumor area at early stage.

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SERS SUBSTRATE FOR SINGLE MOLECULE DETECTION.

Surface-enhanced raman scattering (SERS) is a two-photon process where the presence of metallic nanoparticles produce and enhancement of the local field of 104 to 108 plus the factor related to the geometry of the system. In our lab, we synthesize gold nanoparticles with different morphologies, specially star-like or spiky gold nanoparticles. Nanoparticles are distributed over soft and hard substrates forming complexes with an ideal separation between NPs of 2 nm and then functionalized for a specific analyte. We are interested in single molecule detection, especially overexpressed proteins in early stage cancer, glucose and therapeutic drug monitoring for personalized medication.

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PHOTOLUMINESCENSE OF NPs FOR DETECTION AND IMAGING OF PROTEIN ASSOCIATED TO HEALTHCARE.

We synthesize quantum dots and lanthanide doped ceramic and fluoride nanoparticles to produce fluorescence after UV and near infrared excitation (NIR, 980 nm), respectively. Excitation at 980 nm avoids fluorescence of analytes, compared to UV excitation, thus enhancing the contrast and then improving the limit of detection of the analytes. We are interested in the detection of overexpressed proteins associated with few health problems, in particular, tuberculosis, prostate and breast cancer. We are also interested in imaging cancer cells over a tissue sample to localize the tumor area at an early stage.

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