Localized surface plasmon resonance (LSPR) sensors are used in a broad range of detection applications across the chemical, biological, environmental, and medical disciplines. These types of sensors traditionally use the plasmon resonance wavelength of a nanoparticle array to detect changes in refractive index at the sensor surface and, therefore, require expensive spectroscopic instrumentation for readout. However, simple, portable, and low-cost LSPR sensors can be achieved by transitioning to colorimetric measurements, in which refractive index changes are quantified using the R, G, and B pixel intensities from digital nanoparticle images. In this study, we use R, G, and B pixel intensities to quantify color coordinates in the HSV, CIE L*a*b*, and rgb chromaticity color spaces. We show that for sensors comprising 115 nm diameter nanoparticles, hue (H) is the most sensitive color parameter, with a change per refractive index unit (Δhue/ΔRIU) of 0.71 and a figure of merit of 183 RIU–1. Furthermore, we compared hue figures of merit (FOM) for nanoparticles in four different diameters (34.1, 59.8, 81.5, and 115 nm) and showed that hue sensitivity peaks at a diameter of 81.5 nm, with a FOM of 222 RIU–1. In contrast, the spectroscopic sensitivity, quantified in units of Δnm/ΔRIU, increased continually with nanoparticle size. Therefore, the design requirements for colorimetric plasmonic sensors differ from those for spectroscopic plasmonic sensors. This difference in size dependence was explored further using Mie calculations to simulate nanoparticle extinction spectra. Our results revealed that, while λmax responds linearly to refractive index changes, hue responds in a sigmoidal fashion. As a result, the nanoparticle size used in colorimetric sensors relying on hue measurement should be carefully selected to achieve a linear sensor response. We provide general design rules for optimizing hue-based colorimetric sensors and demonstrate that our sensor can be used with a smartphone to detect antibody–antigen interactions.

Haspin is a histone kinase that promotes error-free chromosome segregation by recruiting the Chromosomal Passenger Complex (CPC) to mitotic and meiotic chromosomes. Haspin remains less well studied than other M-phase kinases and the models explaining Haspin function have been developed primarily in mitotic cells. Here, we generate strains containing new conditional or nonsense mutations in the C. elegans Haspin homologs hasp-1 and hasp-2 and characterize their phenotypes. We show that hasp-1 is responsible for all predicted functions of Haspin and that loss of function of hasp-1 using classical and conditional alleles produces defects in germline stem cell proliferation, spermatogenesis, and confirms its role in oocyte meiosis. Genetic analysis suggests hasp-1 acts downstream of the Polo-like kinase plk-2 and shows synthetic interactions between hasp-1 and two genes expected to promote recruitment of the CPC by a parallel pathway that depends on the kinase Bub1. This work adds to the growing understanding of Haspin function by characterizing a variety of roles in an intact animal.

Haspin is a histone kinase that promotes error-free chromosome segregation by recruiting the Chromosomal Passenger Complex (CPC) to mitotic and meiotic chromosomes. Haspin remains less well studied than other M-phase kinases and the models explaining Haspin function have been developed primarily in mitotic cells. Here, we generate new mutations in the C. elegans Haspin homologs hasp-1 and hasp-2 and characterize their phenotypes. We show that hasp-1 is responsible for all predicted functions of Haspin and that loss of function of hasp-1 using classical and conditional alleles produces defects in germline stem cell proliferation, spermatogenesis, and confirms its role in oocyte meiosis. Genetic analysis suggests hasp-1 acts downstream of the Polo-like kinase plk-2 and shows synthetic interactions between hasp-1 and two genes expected to promote recruitment of the CPC by a parallel pathway that depends on the kinase Bub1. This work adds to the growing understanding of Haspin function by characterizing a variety of roles in an intact animal.