Abstract: The present disclosure relates generally to compositions and methods for generating hydrogel coatings on features. In some embodiments, hydrogel-coated features are prepared by horseradish peroxidase-mediated gelation of microspheres. Some embodiments relate to methods for generating hydrogel coatings using particle templated emulsification. The disclosure also relates to the use of hydrogel-coated features in arrays for spatial analysis of biological analytes in biological samples.

Abstract: The disclosure provides systems and methods for droplet processing. For example, a method can include providing a first droplet and a second droplet. In some cases, the first droplet may have a first concentration of a reagent and the second droplet may have a second concentration of the reagent. The second droplet may comprise a bead or a biological particle. The method can also include subjecting the first droplet and the second droplet to conditions sufficient to transfer the reagent from the first droplet to the second droplet, thereby decreasing the first concentration in the first droplet and increasing the second concentration in the second droplet.

Abstract: Multiple-emulsion nucleic acid amplification allows nucleic acids contained in biological systems to be detected, quantitated and/or sorted based on their sequence as detected with nucleic acid amplification techniques, e.g., PCR. The nucleic acids can be free floating or contained within living or nonliving structures, including particles, viruses, and cells. The nucleic acids can include, e.g., DNA or RNA. Systems and devices for use in practicing methods of the disclosure are also provided.