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<p>Hydrogel microneedle patches offer minimally invasive access to interstitial fluid, yet on-patch immunoassays are often limited by surface-confined probe immobilization and multi-step conjugation workflows. Here, a PEGDA hydrogel microneedle platform is introduced that integrates fluid extraction and transfer-free immunoassays through linker-free antibody immobilization within a three-dimensional network. Antibodies are reduced with tris(2-carboxyethyl)phosphine to expose thiols, which undergo thiol–ene coupling with residual acrylates in the PEGDA matrix under mild aqueous conditions, enabling post-functionalization without additional linkers. The resulting patches insert reliably into ex vivo porcine skin and exhibit capillary-driven uptake with intramatrix access for protein-sized tracers in an agarose model, supporting intramatrix accessibility for protein-sized analytes within the microneedle interior. Using neutrophil gelatinase-associated lipocalin as a proof-of-concept target, the on-patch assay shows a concentration-dependent fluorescence response with a linear regime below 100 pg/mL and a limit of detection of 1.57 pg/mL. By performing capture and readout directly on the patch without sample transfer, the workflow shortens time-to-result to ~ 2&#xa0;h 40&#xa0;min while retaining high analytical sensitivity. This platform provides a practical route to scalable, transfer-free microneedle immunoassays enabled by intramatrix analyte accessibility and three-dimensional probe presentation.</p> Graphic abstract <p>Linker-free thiol–ene conjugation transforms PEGDA hydrogel microneedles into a three-dimensionalsensing matrix for fluid extraction and transfer-free on-patch immunoassays. The platform supportsdirect NGAL detection with high sensitivity, simplifying microneedle-based point-of-care diagnostics.</p> <p></p>

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Hydrogel microneedle patch with linker-free antibody conjugation for simplified, transfer-free on-patch immunoassays

  • 期刊论文

  • 发表日期：

    2026年6月30日

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  • Mina Kim,
  • Eun Ji Son,
  • Hojeong Jeon,
  • Nakwon Choi,
  • Seok Chung,
  • Tae Soup Shim

摘要

Hydrogel microneedle patches offer minimally invasive access to interstitial fluid, yet on-patch immunoassays are often limited by surface-confined probe immobilization and multi-step conjugation workflows. Here, a PEGDA hydrogel microneedle platform is introduced that integrates fluid extraction and transfer-free immunoassays through linker-free antibody immobilization within a three-dimensional network. Antibodies are reduced with tris(2-carboxyethyl)phosphine to expose thiols, which undergo thiol–ene coupling with residual acrylates in the PEGDA matrix under mild aqueous conditions, enabling post-functionalization without additional linkers. The resulting patches insert reliably into ex vivo porcine skin and exhibit capillary-driven uptake with intramatrix access for protein-sized tracers in an agarose model, supporting intramatrix accessibility for protein-sized analytes within the microneedle interior. Using neutrophil gelatinase-associated lipocalin as a proof-of-concept target, the on-patch assay shows a concentration-dependent fluorescence response with a linear regime below 100 pg/mL and a limit of detection of 1.57 pg/mL. By performing capture and readout directly on the patch without sample transfer, the workflow shortens time-to-result to ~ 2 h 40 min while retaining high analytical sensitivity. This platform provides a practical route to scalable, transfer-free microneedle immunoassays enabled by intramatrix analyte accessibility and three-dimensional probe presentation.

Graphic abstract

Linker-free thiol–ene conjugation transforms PEGDA hydrogel microneedles into a three-dimensionalsensing matrix for fluid extraction and transfer-free on-patch immunoassays. The platform supportsdirect NGAL detection with high sensitivity, simplifying microneedle-based point-of-care diagnostics.