From Genes to Biomarkers: Understanding the Biology of Malaria Gametocytes and Their Detection

Each year, approximately 230 million malaria cases and 400,00 malaria deaths are reported worldwide. Malaria is a life-threatening disease caused by Plasmodium parasites that are transmitted from one individual to another through the bites of infected female Anopheles mosquitoes. Malaria parasites replicate asexually in the human host, and, in each replication cycle, a portion of the asexual stages develops into sexual gametocytes that permit transmission. The proportion of infections that carries gametocytes and the infectivity of gametocytes are indicators of human-to-mosquito transmission potential. In P. falciparum, gametocytes appear 10–14 days after infection, whereas in P. vivax gametocytes appear simultaneously with asexual schizonts. Such difference in development not only increases the length of time that an individual is infectious, but also increases the likelihood of transmission before treatment. The conversion from asexual parasites to gametocytes is also highly variable between infections. Differences in age, host immune response, parasite genetic composition, density of red blood cells, presence of co-infecting parasite strains, and antimalarial drug use could affect gametocytes production. In P. vivax, the unique ability to produce hypnozoites, a dormant liver stage of the parasite, may allow gametocytes to be produced periodically from relapse and contribute to transmission. In this chapter, we will provide an overview of the biology of Plasmodium gametocytes, existing tools for gametocyte detection, and features of gametocyte genes. The biological insights and genetic findings are essential to developing better detection biomarkers and effective strategies to reduce transmission in malaria-endemic countries

Raman spectroscopy: techniques and applications in the life sciences

Raman spectroscopy is an increasingly popular technique in many areas including biology and medicine. It is based on Raman scattering, a phenomenon in which incident photons lose or gain energy via interactions with vibrating molecules in a sample. These energy shifts can be used to obtain information regarding molecular composition of the sample with very high accuracy. Applications of Raman spectroscopy in the life sciences have included quantification of biomolecules, hyperspectral molecular imaging of cells and tissue, medical diagnosis, and others. This review briefly presents the physical origin of Raman scattering explaining the key classical and quantum mechanical concepts. Variations of the Raman effect will also be considered, including resonance, coherent, and enhanced Raman scattering. We discuss the molecular origins of prominent bands often found in the Raman spectra of biological samples. Finally, we examine several variations of Raman spectroscopy techniques in practice, looking at their applications, strengths, and challenges. This review is intended to be a starting resource for scientists new to Raman spectroscopy, providing theoretical background and practical examples as the foundation for further study and exploration

Recent Advancement in the Surface-Enhanced Raman Spectroscopy-Based Biosensors for Infectious Disease Diagnosis

Diagnosis is the key component in disease elimination to improve global health. However, there is a tremendous need for diagnostic innovation for neglected tropical diseases that largely consist of mosquito-borne infections and bacterial infections. Early diagnosis of these infectious diseases is critical but challenging because the biomarkers are present at low concentrations, demanding bioanalytical techniques that can deliver high sensitivity with ensured specificity. Owing to the plasmonic nanomaterials-enabled high detection sensitivities, even up to single molecules, surface-enhanced Raman spectroscopy (SERS) has gained attention as an optical analytical tool for early disease biomarker detection. In this mini-review, we highlight the SERS-based assay development tailored to detect key types of biomarkers for mosquito-borne and bacterial infections. We discuss in detail the variations of SERS-based techniques that have developed to afford qualitative and quantitative disease biomarker detection in a more accurate, affordable, and field-transferable manner. Current and emerging challenges in the advancement of SERS-based technologies from the proof-of-concept phase to the point-of-care phase are also briefly discussed

Ligand Exchange on Gold Nanorods: Going Back to the Future

Ligand exchange on gold nanorods (NRs) is still too often dismissed or not given the importance it should deserve. The many applications of gold NRs, mainly in plasmonics, biological imaging, and sensing, are made possible by fi nely tuning not only the optical properties of the metallic core but also the tethered functional groups. Gold NRs are mainly synthesized by using CTAB as the morphology-guiding surfactant, and an intimate relationship between the crystallographic facets of the rod and the CTAB bilayer exists. Because of this, it is imperative to fully understand the ligand exchange mechanisms that allow replacing CTAB with functional ligands, including the energetic contri- butions. Here, the major applications of gold NRs are briefly overviewed, and what is known about ligand exchange mechanisms is summarized, as well as why it is important to achieve complete removal of CTAB, including the techniques that are used to characterize the exchange reaction products. The concept of interface in gold NRs is briefly examined, and explained why the scientific community should focus more on understanding and characterizing it. Starting from the published literature, the reader is guided through the reasons why it is thought that ligand exchange on gold NRs is perhaps the next grand challenge in the nanoparticle field