The use of hydrogel microparticles to sequester and concentrate bacterial antigens in a urine test for Lyme disease

Hydrogel biomarker capturing microparticles were evaluated as a biomaterial to amplify the sensitivity of urine testing for infectious disease proteins. Lyme disease is a bacterial infection transmitted by ticks. Early diagnosis and prompt treatment of Lyme disease reduces complications including arthritis and cardiac involvement. While a urine test is highly desirable for Lyme disease screening, this has been difficult to accomplish because the antigen is present at extremely low concentrations, below the detection limit of clinical immunoassays. N-isopropylacrylamide (NIPAm)-acrylic acid (AAc) microparticles were covalently functionalized with amine containing dyes via amidation of carboxylic groups present in the microparticles. The dyes act as affinity baits towards protein analytes in solution. NIPAm/AAc microparticles functionalized with acid black 48 (AB48) mixed with human urine, achieved close to one hundred percent capture and 100 percent extraction yield of the target antigen. In urine, microparticles sequestered and concentrated Lyme disease antigens 100 fold, compared to the absence of microparticles, achieving an immunoassay detection sensitivity of 700 pg/mL in 10 mL urine. Antigen present in a single infected tick could be readily detected following microparticle sequestration. Hydrogel microparticles functionalized with high affinity baits can dramatically increase the sensitivity of urinary antigen tests for infectious diseases such as Lyme disease. These findings justify controlled clinical studies evaluating the sensitivity and precision of Lyme antigen testing in urine.

Nanoparticle technology: amplifying the effective sensitivity of biomarker detection to create a urine test for hGH

Several clinical-grade immunoassays exist for the specific measurement of hGH or its isoforms in blood but there is an urgent need to apply these same reliable assays to the measurement of hGH in urine as a preferred 'non-invasive' biofluid. Unfortunately, conventional hGH immunoassays cannot attain the sensitivity required to detect the low concentrations of hGH in urine. The lowest limit of sensitivity for existing hGH immunoassays is >50 pg/mL, while the estimated concentration of urinary hGH is about 1 pg/m-50 times lower than the sensitivity threshold. We have created novel N-isopropylacrylamide (NIPAm)-based hydrogel nanoparticles functionalized with an affinity bait. When introduced into an analyte-containing solution, the nanoparticles can perform, in one step, (1) complete harvesting of all solution phase target analytes, (2) full protection of the captured analyte from degradation and (3) sequestration of the analyte, effectively increasing the analyte concentration up to a hundredfold. N-isopropylacrylamide nanoparticles functionalized with Cibacron Blue F3GA bait have been applied to raise the concentration of urinary hGH into the linear range of clinical grade immunoassays. This technology now provides an opportunity to evaluate the concentration of hGH in urine with high precision and accuracy.

Abstract 4575: Covalent incorporation of a new class of dye-based affinity baits in sieving hydrogel nanoparticles overcome roadblocks to cancer biomarker discovery

Cancer biomarker discovery and clinical application has been seriously hampered by low abundance, instability and complex formation with high abundance proteins (e.g. albumin). N-isopropylacrylamide (NIPA) based hydrogel particles, consisting of a bait-containing core and a protective shell, overcome these major issues associated to biomarker discovery and measurement. Particles perform in one step, in solution, a) total sequestration and concentration, b) size sieving and c) complete protection form degradation of LMW protein biomarkers in blood and urine. In this study, novel dye molecules were selected as affinity ligands for broad classes of biomarkers; dyes were chosen for their ability to bind proteins, glycoproteins and nucleic acid for tissue histology, to bind textile proteins for fabric staining or for their known property to bind allergens. Dyes containing primary amine group (e.g. Acid Black 48, Basic Red 9) were coupled to NIPA/acrylic acid (AAc) particles by condensation of the amine group the carboxylic group. The ability of particles to capture and concentrate analytes was tested against a panel of low abundance, labile tumor relevant biomarker that include angiogenic growth factors (bFGF, VEGF, PDGF), IGF-1 and IGF binding proteins, interleukins (IL-6, IL-8), chemokines (CXCL12, CCL24), pro-apoptotic Bcl-2 proteins (Bak, Bax), and nucleic acids. Technologies used to screen dye functionalized particles include 1 D gel electrophoresis, western blotting, immunoassay, and mass spectrometry.

Results showed that dye based baits have extremely high affinity for the target analytes so that particles capture all the analyte present in solution and that the affinity of biomarkers to the bait is unique and specific to the chemical structure of the bait molecule.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4575.