The accurate quantification of nucleic acids is of utmost importance for clinical diagnostics, drug discovery, and basic science research. These applications require the concurrent measurement of multiple targets while demanding high-throughput analysis, high sensitivity, specificity between closely related targets, and a wide dynamic range. In attempt to create a technology that can simultaneously meet these demands, we recently developed a method of multiplexed analysis using encoded hydrogel particles. Here, we demonstrate tuning of hydrogel porosity with semi-interpenetrating networks of poly(ethylene glycol), develop a quantitative model to understand hybridization kinetics, and use the findings from these studies to enhance particle design for nucleic acid detection. With an optimized particle design and efficient fluorescent labeling scheme, we demonstrate subattomole sensitivity and single-nucleotide specificity for small RNA targets.