Abstract

Lab-on-a-chips (LOCs), alternatively called micro total analysis systems (μTAS) are miniaturized chemical or biological analytical devices that integrate one or several laboratory functions on a single chip. LOCs handle small amount of sample volume and enable the analysis and detection with enhanced performances in short time.
This thesis focuses on developing LOC platforms for the detection of growth hormones such as bovine somatotropin (bST) and recombinant bovine somatotropin (rbST) in milk. Bovine somatotropin is a polypeptide growth hormone naturally produced by the anterior pituitary gland in mammals, which has strong influences on the biological effects such as growth, developments and reproductive functions. The bST is useful to increase the milk and meat production. With the emergence of the recombinant DNA technology, large quantities of artificial hormones called recombinant bovine somatotropin (rbST) are produced and used for the production of milk and meat in dairy industry. Use of growth hormones for the production of milk and meat is still controversial due to its potential effects on animal and human health. Hence, there is a huge demand for highly sensitive, rapid and low cost devices for the detection of growth hormones. Currently, the growth hormones are detected by large equipment which needs large amounts of reagents and bio-liquids in addition to longer analysis time. In this context, there is a large demand for developing a miniaturized bio-analytical platform for the rapid and precise screening of growth hormones in milk. In this thesis, development of LOC platforms for the labeled and label-free detection of growth hormone is attempted.
The labeled detection of the rbST was demonstrated in a low cost lab-on-a-chip platform fabricated by integrating an optical microfluidic system on silica-on-silicon (SOS) waveguide with a PDMS (polydimethylsiloxane) microfluidic chip. In order to achieve higher sensitivity and specificity, a novel cascaded waveguide coupler (CWC) system is designed and fabricated on the silica-on-silicon platform. A novel method of fabricating nano-island morphology is developed for the label-free detection of bovine growth hormone. Experimental and theoretical analysis of tuning the gold nano-island morphology is investigated and implemented for the label-free detection of growth hormone. Subsequently, the nano-island morphology is integrated into a PDMS microfluidic chip and a LOC is realized. A low cost, all polymer lab-on-a-chip is developed by integrating silver-PDMS nanocomposite by in-situ synthesis of nano-composite inside the microfluidic chip and detection of growth hormone is also demonstrated. The nano-islands are integrated into silica-on-silicon waveguides for the development of a nano-enhanced evanescent wave sensor for the detection of rbST. Extraction of growth hormone from milk by solid phase extraction and its detection are also demonstrated. Finally, a monolithically integrated LOC on silica-on-silicon (SOS) comprising of microfluidics, optical waveguides and Echelle grating based spectrometer is realized. The simulation and integration process of a micro-spectrometer with the optical waveguide and microfluidic channel are also presented.