Genetic diversity, population structure, and selection of breeder germplasm subsets from the USDA sweetpotato (Ipomoea batatas) collection.

Sweetpotato (Ipomoea batatas) is the sixth most important food crop and plays a critical role in maintaining food security worldwide. Support for sweetpotato improvement research in breeding and genetics programs, and maintenance of sweetpotato germplasm collections is essential for preserving food security for future generations. Germplasm collections seek to preserve phenotypic and genotypic diversity through accession characterization. However, due to its genetic complexity, high heterogeneity, polyploid genome, phenotypic plasticity, and high flower production variability, sweetpotato genetic characterization is challenging. Here, we characterize the genetic diversity and population structure of 604 accessions from the sweetpotato germplasm collection maintained by the United States Department of Agriculture (USDA), Agricultural Research Service (ARS), Plant Genetic Resources Conservation Unit (PGRCU) in Griffin, Georgia, United States. Using the genotyping-by-sequencing platform (GBSpoly) and bioinformatic pipelines (ngsComposer and GBSapp), a total of 102,870 polymorphic SNPs with hexaploid dosage calls were identified from the 604 accessions. Discriminant analysis of principal components (DAPC) and Bayesian clustering identified six unique genetic groupings across seven broad geographic regions. Genetic diversity analyses using the hexaploid data set revealed ample genetic diversity among the analyzed collection in concordance with previous analyses. Following population structure and diversity analyses, breeder germplasm subsets of 24, 48, 96, and 384 accessions were established using K-means clustering with manual selection to maintain phenotypic and genotypic diversity. The genetic characterization of the PGRCU sweetpotato germplasm collection and breeder germplasm subsets developed in this study provide the foundation for future association studies and serve as precursors toward phenotyping studies aimed at linking genotype with phenotype.

Exosome isolation and purification via hydrophobic interaction chromatography using a polyester, capillary-channeled polymer fiber phase.

Extracellular vesicles, including microvesicles and exosomes, are lipidic membrane-derived vesicles that are secreted by most cell types. Exosomes, one class of these vesicles that are 30-100 nm in diameter, hold a great deal of promise in disease diagnostics, as they display the same protein biomarkers as their originating cell. For exosomes to become useful in disease diagnostics, and as burgeoning drug delivery platforms, they must be isolated efficiently and effectively without compromising their structure. Most current exosome isolation methods have practical problems including being too time-consuming and labor intensive, destructive to the exosomes, or too costly for use in clinical settings. To this end, this study examines the use of poly(ethylene terephthalate) (PET) capillary-channeled polymer (C-CP) fibers in a hydrophobic interaction chromatography (HIC) protocol to isolate exosomes from diverse matrices of practical concern. Initial results demonstrate the ability to isolate extracellular vesicles enriched in exosomes with comparable yields and size distributions on a much faster time scale when compared to traditional isolation methods. As a demonstration of the potential analytical utility of the approach, extracellular vesicle recoveries from cell culture milieu and a mock urine matrix are presented. The potential for scalable separations covering submilliliter spin-down columns to the preparative scale is anticipated.

Three-photon imaging using defect-induced photoluminescence in biocompatible ZnO nanoparticles.

BACKGROUND: Although optical spectroscopy promises improved lateral resolution for cancer imaging, its clinical use is seriously impeded by background fluorescence and photon attenuation even in the so-called two-photon absorption (2PA) imaging modality. An efficient strategy to meet the clinical cancer imaging needs, beyond what two-photon absorption (2PA) offers, is to use longer excitation wavelengths through three-photon absorption (3PA). A variety of fluorescent dyes and nanoparticles (NPs) have been used in 3PA imaging. However, their nonlinear 3PA coefficient is often low necessitating high excitation powers, which cause overheating, photodamage, and photo-induced toxicity. Doped wide band gap semiconductors such as Mn:ZnS NPs have previously been used for 3PA but suffer from poor 3PA coefficients. METHODS: Here, we prepared ZnO NPs with intrinsic defects with high 3PA coefficients using a polyol method. We functionalized them with peptides for selective uptake by glioblastoma U87MG cells and used breast cancer MCF-7 cells as control for 3PA studies. Uptake was measured using inductively coupled plasma-mass spectrometry. Biocompatibility studies were performed using reactive oxygen species and cell viability assays. RESULTS: We demonstrate that ZnO NPs, which have a band gap of 3.37 eV with an order of magnitude higher 3PA coefficients, can facilitate the use of longer excitation wavelengths 950-1,100 nm for bioimaging. We used the presence intrinsic defects (such as O interstitials and Zn vacancies) in ZnO NPs to induce electronic states within the band gap that can support strong visible luminescence 550-620 nm without the need for extrinsic doping. The peptide functionalization of ZnO NPs showed selective uptake by U87MG cells unlike MCF-7 cells without the integrin receptors. Furthermore, all ZnO NPs were found to be biocompatible for 3PA imaging. CONCLUSION: We show that defect-induced luminescence 550-620 nm in ZnO NPs (20 nm) due to 3PA at longer excitation (975 nm) can be used for 3PA imaging of U87MG glioblastoma cells with lower background noise.