Screening of nucleic acid agents via particle display

A pool of aptamer particles, the pool comprising aptamer particles comprising DNA aptamer sequences, the pool of aptamer particles comprising:

• from about 1×102 to about 1×1014 aptamer particles,
• wherein each aptamer particle of the pool of aptamer particles comprises from about 1×102 to about 1×1010 copies of one or more DNA aptamer sequences bound thereto,
• wherein each of the aptamer particles has at least one dimension of from about 50 nm to about 100 μm, and
• wherein a plurality of the aptamer particles comprise aptamer sequences bound thereto which are capable of binding the target with a Kd of from about 1 pM to about 100 μM.

An aptamer screening method, the method comprising:

• exposing a plurality of aptamer particles to one or more fluorescently labeled targets, wherein each of the aptamer particles comprises two or more copies of one or more candidate DNA aptamer sequences bound thereto;
• wherein one or more of the one or more fluorescently labeled targets associate to a higher level with particles including one or more candidate DNA aptamer sequences having a first desired property and associate to a lower level with particles which do not include one or more candidate DNA aptamer sequences having the first desired property, or
• wherein one or more of the one or more fluorescently labeled targets associate to a lower level with particles including one or more candidate DNA aptamer sequences having a second desired property and associate to a higher level with particles which do not include one or more candidate DNA aptamer sequences having the second desired property;
• and
• isolating aptamer particles that display candidate DNA aptamer sequences having the first or second desired property based on a quantitated fluorescence intensity for each aptamer particle.