Multiplexed protein quantification with barcoded hydrogel microparticles

Ultrasensitive multiplexed microRNA quantification on encoded gel microparticles using rolling circle amplification

There is great demand for flexible biomolecule analysis platforms that can precisely quantify very low levels of multiple targets directly in complex biological samples. Herein we demonstrate multiplexed quantification of microRNAs (miRNAs) on encoded hydrogel microparticles with subfemtomolar sensitivity and single-molecule reporting resolution. Rolling circle amplification (RCA) of a universal adapter sequence that is ligated to all miRNA targets captured on gel-embedded probes provides the ability to label each target with multiple fluorescent reporters and eliminates the possibility of amplification bias. The high degree of sensitivity achieved by the RCA scheme and the resistance to fouling afforded by the use of gel particles are leveraged to directly detect miRNA in small quantities of unprocessed human serum samples without the need for RNA extraction or target-amplification steps. This versatility has powerful implications for the development of rapid, noninvasive diagnostic assays.

Hydrogel microparticles from lithographic processes: novel materials for fundamental and applied colloid science

In recent years there has been a surge in methods to synthesize geometrically and chemically complex microparticles. Analogous to atoms, the concept of a "periodic table" of particles has emerged and continues to be expanded upon. Complementing the natural intellectual curiosity that drives the creation of increasingly intricate particles is the pull from applications that take advantage of such high-value materials. Complex particles are now being used in fields ranging from diagnostics and catalysis to self-assembly and rheology, where material composition and microstructure are closely linked with particle function. This is especially true of polymer hydrogels, which offer an attractive and broad class of base materials for synthesis. Lithography affords the ability to engineer particle properties a priori and leads to the production of homogenous ensembles of particles. This review summarizes recent advances in synthesizing hydrogel microparticles using lithographic processes and highlight a number of emerging applications. We discuss advantages and limitations of current strategies, and conclude with an outlook on future trends in the field.