Desenvolvimento, caracterizacao e aplicacao da matriz FTO/POLI(3-aminofenol) na deteccao de marcador de lesao cardiaca por fotoluminescencia de quantum dots

Abstract

The heart is a vital organ propelling blood, that carries oxygen and nutrients throughout the body, but whenever these components do not reach it due to arterial obstruction, there is an electrical instability in the process of contraction of the muscle, causing arrhythmias that often, in less than an hour, causes acute myocardial infarction. The problem and cerebrovascular accident are the major cause of mortality worldwide. The diagnosis according to WHO meet three possibilities: clinical exam, electrocardiograph, and biochemistry. The former is slower while the others are inaccurate. Thus, there is much room for the development of analytical techniques that can generate quick results, specific, sensitive, and inexpensive. Polymers such as poly(aminophenols) are interesting platforms for these systems for the immobilization of biomolecules due the substituents on the benzene ring and its characteristics such as excellent permeability, selectivity, reproducibility and fast response time. To form these polymers the electrochemical synthesis is the most common procedure and where the interest is for the optical detection, vitreous substrates like tin fluorine doped tin oxide (FTO) become attractive as transducers for their excellent features such as: good electrical conductivity, high transparency, chemical inertness, high reproducibility and adherence to glass. The optical detection via indirect markers increases the sensitivity of diagnosis, and the quantum dots have been shown to be superior to conventional fluorophores such as cyanine, rhodamine and alexa fluor, based on their outstanding photophysical properties such as broad absorption spectrum, narrow emission spectrum, high photostability and decay time. In this work was electropolymerized on FTO by cyclic voltammetry in 3- aminophenol, whose ultra-violet spectrum in the visible region showed between 300 and 350 nm, proportional to the amount of material formed. Ion exchange of iron redox probes / ferricyanide of potassium and hexaammineruthenium (II) chloride showed that the material attracts cationic structures and repels anionic structures. Scanning electron microscopy with field emission and atomic force microscopy showed almost total polymer coating rough FTO surface whose thickness by laser interferometry was estimated at 375 ± 75 nm. Electrical characterization and electrochemical impedance spectroscopy (EIE) showed that the material has a high passivating character. That can be applied as matrix for building the diagnostic platform for cardiac injury through stable amide bonds among the NH2 groups of poly(3-aminophenol) and end carboxyls (Fc) of antitroponin T via EDC/NHS. Addionaly, this antibody was modified with biotin being strepavidin its affinity, such as the specificity between antibody and antigen investigated in the design of this system. Selective detection of troponin T was performed qualitatively (dot blot) and quantitatively by (EIE); and quantum dot photoluminescence (PL), at 0.5 μM. The results are promising to develop immunosensors for marker cardiac injuries.