With continued discovery of gene function in humans, it is imperative to develop more rapid, inexpensive, and sensitive ways to target specific DNA sequences for the diagnosis of genetic diseases, mutations, and single-nucleotide polymorphisms (SNP's). Typically, biological detection is accomplished by measuring the fluorescence emission of organic dye molecules, radioactivity of isotopic labels, or color changes during enzymatic events. Due to their commercial availability and high sensitivity, organic dye molecules have found widespread use as fluorescent labels. However, strategies based mainly on organic fluorophores often suffer from short photobleaching, low signal intensities, and random intermittent emissions. These limitations have led to the development and utilization of more photostable probes such as natural fluorescent proteins and nanoparticle probes. Nanometer-sized particles are particularly attractive in biological applications due to both their size similarity with biomolecules and their unique optical, electronic, and magnetic properties. Latex nanospheres, semiconductor nanocrystals, and metal nanoparticles are three types of nanoparticles that have gained recent interest in many biological detection applications. This dissertation describes the conjugation of various proteins and oligonucleotides to fluorescent latex nanoparticles, semiconductor nanocrystals, and gold nanoparticles to form functional nanoparticle probes designed to target specific DNA sequences both in solution and on solid surfaces. Furthermore, we also developed a nanoparticle-biomolecular assembly that could be used to study the systematic cleavage events of exonuclease enzymes. These bioconjugated nanoparticle probes should have broad implications in a variety of areas including molecular biology, clinical diagnostics, biomedical engineering, and nanotechnology
