Introducing! X-Aptamer Selection Kit

Next generation aptamers that offer an array of modifications to increase specificity and affinity for the target molecule over traditional aptamers.

Try our X-Aptamer development program. Next generation sequencing and synthesis for


Equipment needed for performing the kit protocol.

X-Aptamer Selection Kit

• Effective

• Bead Based Process

• Not Selex

• One Selection Round

• Up to 5 targets

• Proteins & Small Molecules



X-Aptamers are the next step in the evolution of aptamer technology. They are synthetic affinity reagents that incorporate natural as well as chemically-modified DNA or RNA nucleotides. Common modifications include amino acid functional groups as well as small molecules in virtually any combination. For many years, aptamers were developed using one of several versions of the Systemic Evolution of Ligands by Exponential Enrichment (SELEX) process.

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Selection Process

Selection Process

AM Biotech uses a proprietary bead-based technology to select X-Aptamers. The single round, bead-based discovery process has significant advantages relative to Systematic Evolution of Ligands by Exponential Enrichment (SELEX) approaches. AM Biotech’s process eliminates the repeated rounds of PCR amplification that are required with SELEX. This eliminates problems associated with PCR bias, which disfavors recovery of the most structurally stable aptamers.

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Improve Existing Aptamers & siRNA

Improve Existing Aptamers & siRNA

The chemical modifications that AM Biotech uses improve existing aptamer and siRNA performance. DNA or RNA aptamer binding affinity can improve by orders of magnitude by using just one or two modified nucleotides in just one or two sequence locations – without adversely affecting specificity.

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X-Aptamers are game-changers because they are able to incorporate combinations of chemical functional groups that enhance the interaction with a target.


Customer Feedback

“Compared to aptamers selected through SELEX protocol, X-Aptamers generated through this kit demonstrated much higher affinity to their target molecules on our platform.”

“Using the prototype kit we were able to select nanomolar affinity X-Aptamers to a target candidate biomarker of Tuberculosis disease…that we failed to raise DNA aptamers to via conventional SELEX procedures and we believe that the chemical modification of the X-Aptamer library was key to this success.”

“Working in an aptamer research lab, I’m regularly approached by companies and researchers from all around the world for technical help with their aptamer selections. It seems to me that there has been a demand for aptamers-on-demand for quite some time and it is delightful to see it is finally becoming a reality!”

“The ease of use [of the kit] allowed my undergraduate researchers to be able to skillfully perform the selection experiments, and we have since identified one of the putative aptamers identified as a success – this aptamer binds with low nanomolar affinity and is being used to generate an electrochemical biosensor platform for the detection of botulism.”

Selected publications from our scientists and collaborators

Origins of the enhanced affinity of RNA-protein interactions triggered by RNA phosphorodithioate backbone modification

Posted on Oct 6, 2017

Abstract: The well-characterized interaction between the MS2 coat protein and its cognate RNA hairpin was used to evaluate changes in affinity as a result of phosphorodithioate (PS2) replacing phosphate by biolayer interferometry (BLI). A structure-based analysis of...Read More

Selection of PD1/PD-L1 X-Aptamers

Posted on Oct 6, 2017

Abstract: Specific, chemically modified aptamers (X-Aptamers) were identified against two immune checkpoint proteins, recombinant Programmed Death 1 (PD-1) and Programmed Death Ligand 1 (PD-L1). Selections were performed using a bead-based X-Aptamer (XA) library...Read More

X-Aptamer Selection and Validation

Posted on Aug 3, 2017

Abstract Aptamers and second generation analogs, such as X-Aptamers (XAs), SOMAmers, locked nucleic acids (LNAs), and others are increasingly being used for molecular pathway targeting, biomarker discovery, or disease diagnosis by interacting with protein targets on...Read More

Nano-SPRi Aptasensor for the Detection of Progesterone in Buffer.

Posted on Dec 17, 2016

Abstract Progesterone is a steroid hormone that plays a central role in the female reproductive processes such as ovulation and pregnancy with possible effects on other organs as well. The measurement of progesterone levels in bodily fluids can assist in early...Read More

Electrochemical aptamer scaffold biosensors for detection of botulism and ricin toxins.

Posted on Dec 17, 2016

Abstract Protein toxins present considerable health risks, but detection often requires laborious analysis. Here, we developed electrochemical aptamer biosensors for ricin and botulinum neurotoxins, which display robust and specific signal at nanomolar concentrations...Read More

X-aptamers: a bead-based selection method for random incorporation of druglike moieties onto next-generation aptamers for enhanced binding.

Posted on Dec 17, 2016

Abstract By combining pseudorandom bead-based aptamer libraries with conjugation chemistry, we have created next-generation aptamers, X-aptamers (XAs). Several X-ligands can be added in a directed or random fashion to the aptamers to further enhance their binding...Read More

Construction and selection of bead-bound combinatorial oligonucleoside phosphorothioate and phosphorodithioate aptamer libraries designed for rapid PCR-based sequencing.

Posted on Dec 17, 2016

Abstract Chemically synthesized combinatorial libraries of unmodified or modified nucleic acids have not previously been used in methods to rapidly select oligonucleotides binding to target biomolecules such as proteins. Phosphorothioate oligonucleotides (S‐ODNs) or...Read More

Evoking picomolar binding in RNA by a single phosphorodithioate linkage.

Posted on Dec 17, 2016

Abstract RNA aptamers are synthetic oligonucleotide-based affinity molecules that utilize unique three-dimensional structures for their affinity and specificity to a target such as a protein. They hold the promise of numerous advantages over biologically produced...Read More

Crystal structure, stability and Ago2 affinity of phosphorodithioate-modified RNAs

Posted on Jun 10, 2016

Abstract Small interfering RNAs (siRNAs) with phosphorodithioate modifications (PS2-RNA) possess favourable properties for use as RNAi therapeutics. Beneficial here is the combining of PS2 and 20 -O-methyl modifications (MePS2). SiRNAs with MePS2 moieties in the sense...Read More

2′-OMe-phosphorodithioate-modified siRNAs show increased loading into the RISC complex and enhanced anti-tumour activity.

Posted on Jun 9, 2016

Abstract Improving small interfering RNA (siRNA) efficacy in target cell populations remains a challenge to its clinical implementation. Here, we report a chemical modification, consisting of phosphorodithioate (PS2) and 2′-O-Methyl (2′-OMe) MePS2 on one nucleotide...Read More