Protection of Nanostructures-Integrated Microneedle Biosensor Using Dissolvable Polymer Coating

Abstract

Real-time transdermal biosensing provides a direct route to quantify biomarkers or physiological signals of local tissues. Although microneedles (MNs) present a mini-invasive transdermal technique, integration of MNs with advanced nanostructures to enhance sensing functionalities has rarely been achieved. This is largely due to the fact that nanostructures present on MNs surface could be easily destructed due to friction during skin insertion. In this work, we reported a dissolvable polymer-coating technique to protect nanostructures-integrated MNs from mechanical destruction during MNs insertion. After penetration into the skin, the polymer could readily dissolve by interstitial fluids so that the superficial nanostructures on MNs could be re-exposed for sensing purpose. To demonstrate this technique, metallic and resin MNs decorated with vertical ZnO nanowires (vNWs) were employed as an example. Dissolvable poly­(vinyl pyrrolidone) was spray-coated on the vNW-MNs surface as a protective layer, which effectively protected the superficial ZnO NWs when MNs penetrated the skin. Transdermal biosensing of H2O2 biomarker in skin tissue using the polymer-protecting MNs sensor was demonstrated both ex vivo and in vivo. The results indicated that polymer coating successfully preserved the sensing functionalities of the MNs sensor after inserting into the skin, whereas the sensitivity of the MN sensor without a coating protection was significantly compromised by 3-folds. This work provided unique opportunities of protecting functional nanomodulus on MNs surface for minimally invasive transdermal biosensing.

Engineering Microneedles for Therapy and Diagnosis: A Survey

“…A gold layer has been used for improvement of the biocompatibility and mechanical strength of MNs [98]. Biocompatible molecules such as PVP are applied to protect the probe layer [44].…”

“…Although there are some MNs with a naked sensitive layer [116][117][118], physical deformation (e.g., nanostructure collapse, enzyme detachment) during puncture into skin is still supposed to be eliminated. Liu et al proposed a PVP barrier to protect MNs' surface during penetration ( Figure 4A) [44]. Raw stainless-steel MNs modified with ZnO nanowires (NWs) structure were used to improve surface specificity and enhance sensitivity.…”

“…(A) Schematic illustration of dissolvable polyvinylpyrrolidone (PVP) layer/ZnO NWs/Pt nanostructure modified stainless MN. PVP coating provides protection during skin penetration, and rapidly dissolves after penetration, exposing sensitive probe for detection (reproduced with permission from the authors of[44]). (B) Schematic of a continuous minimally invasive alcohol sensor.…”

Advances in the Formulations of Microneedles for Manifold Biomedical Applications

“…Reduced Pt/rGO nanoparticles were coated on the MNs via LbL assembly. The PVP layer was coated over the Pt/rGO layers to protect Pt/rGO layers from mechanical destruction during the skin penetration . Once in skin, PVP layer quickly dissolved and exposed the Pt/rGO layer to skin ISF for biosensing.…”

Microneedle-based bioassays

“…The sustained chemical reaction can be used to trigger an electrical signal, which can be interpreted by a detection instrument. [84][85][86] Wang's group developed an attractive skin-worn MN sensing device for the continuous detection of organophosphate (OP) nerve agents (Fig. 5).…”