Novel biosensing platforms for a fast screening of milk contaminants and prostate cancer

Abstract

Throughout the past decades, the rapid and prosperous development in analytical sciences has allowed scientists to take a deeper insight into more difficult multi-disciplinary research problems. One of the best outcomes of such multidimensionality lies in the evolvement of the concept of biosensor, a major research area among contemporary analytical scientists. Some fundamentals on this discipline will be given in Chapter One. Research and development never stop and scientists keep on designing different types of biosensing techniques for addressing different existing analytical problems. Similarly, this work aims to address two important public health concerns, particularly in food-safety and clinical area, by developing rapid biosensing methods through a smart design and application of small particles with specific properties. The first public concern is related to milk safety. In China, the milk safety issue has aroused citizens’ high concern due to the detection of different harmful contaminants present in milk. A recent notorious incident was the adulterant melamine scandal in 2008, which melamine was illegally abused to boost nitrogen levels during protein tests. Other than that, different undesired preservatives, synthetic hormones, antibiotics, bacteria and pathogens were reported to be food hazards to citizens. To ensure milk safety, a lot of monitoring works are needed and therefore a fast and multiplex screening method is in demand by food regulatory units. In Chapter Two, the development of a sensing method towards melamine based on the use of magnetic microspheres and flow cytometric immunoassay is reported. Detection can be achieved in a simple, sensitive, specific, high-through put and organic solvent-free manner. Another public health concern is related to prostate cancer (PCa), one of the commonest male-related cancers in the world with an increasing incidence rate. Hong Kong is no exception in this public health issue. Nevertheless, current screening methods towards PCa are not perfect enough. We have an urgent demand for more sensitive and accurate diagnostic biomarkers or methods to detect early PCa and improve the treatment outcome, given the latency of early, treatable PCa and the lethality of its late, discernible stage. In Chapter Three, it reports and discusses the results of our large-cohort study on urinary polyamine levels of suspected PCa patients. A useful biomarker, urinary spermine, was discovered and its usefulness in PCa detection was demonstrated. Based on this finding, Chapter Four focuses on the development of a rapid sensing method towards this novel biomarker via the use of DNA and gold nanoparticles. Any aggregations of gold nanoparticles induced by spermine would shift its absorption band and results in a distinct color change, which can be observed directly by naked eyes and acts as a mean of simple and indirect sensing of urinary spermine. This design would certainly help in diagnosing PCa in the future. Overall, this work takes a step towards in tackling the abovementioned public health problems.