Fluorescence response of CdS nanoparticles to serum of cardiac patients: towards the development of a real time sensor for heart failure detection.
Subject: Enfermedades del corazon (Investigacion cientifica)
Enfermedades del corazon (Prevencion)
Enfermedades del corazon (Analisis de casos)
Nanotecnologia (Historia)
Nanotecnologia (Investigacion cientifica)
Nanotecnologia (Analisis de casos)
Authors: Ferrer, Edmy
Zayas, Francisco
Latorre, Elena
Castro, Miguel E.
Pub Date: 09/01/2009
Publication: Name: Puerto Rico Health Sciences Journal Publisher: Universidad de Puerto Rico, Recinto de Ciencias Medicas Language: Spanish Audience: Academic Format: Magazine/Journal Subject: Health Copyright: COPYRIGHT 2009 Universidad de Puerto Rico, Recinto de Ciencias Medicas ISSN: 0738-0658
Issue: Date: Sept, 2009 Source Volume: 28 Source Issue: 3
Geographic: Geographic Name: Puerto Rico
Accession Number: 206864576
Full Text: Nanotechnology may represent a tool for the improvement in our quality of life by providing a platform for new sensors or sensing elements--components that can be integrated into functional sensors to monitor chemicals closely related to health issues. A sensor is a device that receives and responds to a signal or stimulus indicative of a real-world condition. The aim of the work presented here is to evaluate the response of US semiconductor nanoparticles to the serum of patients that have been evaluated for cardiac troponin, a protein that has been the subject of previous works related to its value in the prognosis, risk stratification and management of patients with acute coronary syndromes and myocardial necrosis (1-5). These conditions are major health issues, costing consumers millions of dollars through high insurance premiums and health care. Development of a real time sensor that targets the detection of cardiac troponin in the blood is a major technological challenge that can reduce mortality and as well as health care costs.

In a typical semiconductor, electrons can be excited by light from the valence band into the conduction band. The minimum energy required to promote electrons from the valence band into the conduction band represents the band gap of the semiconductor, which is inversely proportional to the nanoparticle size (6). Photo-excited electrons in the conduction band are energetically relaxed to lower energy states or traps, which are states resulting from defects in the structure of the nanoparticle or from the adsorption of chemicals on their surface. Emission of light results from relaxation of electrons from trap states into the valence band. When the trap states arise from the adsorption of molecules on the particle surface, the resulting luminescence is very sensitive to the chemical environment of the semiconductor nanoparticle: a potential sensor element to the specific chemical that created the trap state.


The inset in Figure 1 shows the absorbance spectrum of the US nanoparticles in dimethylsulfoxide (DMSO) employed for the work described here. The absorbance decreases with wavelength until the band edge of the semiconductor nanoparticle reaches around 515 nm. Based on the absorbance cutoff it is possible to estimate a nanoparticle diameter of about 2.4 nm (6). Serum samples of patients obtained from the Perea Hospital's Clinical Laboratory were analyzed for cardiac troponin levels using the Abbott method. A typical emission spectrum of a solution prepared by adding 90 [micro]L of the serum of a patient with no detectable cardiac troponin to a solution containing the US nanoparticles is labeled as Patient 1 on Figure 1. No new emission bands besides those associated with the emission of the US nanoparticle appear in the spectrum. On the other hand, the photoluminescence of a mixture containing US nanoparticles and 90 [micro]L, of serum of a patient with a troponin level of 1.8 mg/mL, labeled as Patient 2 on Figure 1, exhibits bands around 545 nm, a low wavelength shoulder between 500 and 540 nm, and a high wavelength peak around 580 nm. The light emission intensity decreases linearly with dilution in this example as well as in four other serum samples containing troponin indicating that the emission is from the mixture and not an experimental artifact. Control experiments with troponin containing serum do not show these bands in the absence of the CdS particles. The number and chemical nature of other biomarkers that may be present in the serum samples limits the interpretation of the results in terms of specific troponin-CdS nanoparticle interaction (7). However, the results encourage pursuing further work focused on the use of CdS nanoparticles for the detection of cardiac troponin and other biomarkers related to coronary syndromes.


EF acknowledges a PhD scholarship from the Sloan Foundation and a scholarship from the Puerto Rico Infrastructure Development Company (PRIDCO). FZ and ET acknowledge undergraduate student scholarships from the UPRM Biominds Program and the National Institutes of Health Minority Access to Research Careers (MARC) Program. Partial financial support from Dupont Electronic Technologies and the UPRM Department of Chemistry is gratefully acknowledged.


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Edmy Ferrer, MS; Francisco Zayas, Elena Latorre; Miguel E. Castro, Ph D, Chemical Imaging Center, Department of Chemistry, University of Puerto Rico at Mayaguez, Mayaguez, Puerto Rico 00680.
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