Heparin-gold nanoparticles for enhanced microdialysis sampling

Cerebral microdialysis is a sampling technique which offers much potential for understanding inflammatory pathophysiology following traumatic brain injury (TBI). At present, the recovery of cytokines via microdialysis in clinical studies is not straightforward primarily due to their size, steric properties and low concentrations. Heparin and heparin-coated microspheres have previously shown promise as cytokine-binding agents for enhanced microdialysis sampling in animal models (Duo and Stenken in Anal Bioanal Chem 399(2):773–82, 2011; Anal Bioanal Chem 399(2):783–93, 2011). However, there are several factors limiting application for microdialysis in patients. The aim of this study was to produce heparin-coated gold nanoparticles as cytokine capture agents for enhanced microdialysis sampling, potentially applicable to a clinical setting. Gold nanoparticles (AuNP) were chemically conjugated to heparin via a bifunctional polyethylene glycol (PEG) linker. The heparin-AuNP (AuNP-Hep) were characterised, demonstrating the successful addition of heparin to the gold surface. The performance of the AuNP-Hep during in vitro testing was compared both to current methodology (Helmy et al. in J Neurotrauma 26(4):549–61, 2009) and to the heparin-coated microspheres developed by Duo and Stenken (Anal Bioanal Chem 399(2):773–82, 2011; Anal Bioanal Chem 399(2):783–93, 2011). The AuNP-Hep yielded a higher recovery of cytokines compared to current methodology and heparin-coated microspheres, during in vitro testing designed to mimic the human environment and the intensive care unit. In this study, AuNP-Hep were developed for enhanced microdialysis sampling of cytokines, potentially applicable in a clinical setting. Based on the success of the AuNP-Hep in vitro, the proposed method offers an alternative to the use of current protocols that rely on a blood product (albumin) for microdialysis sampling of cytokines in patients. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s00216-017-0447-y) contains supplementary material, which is available to authorized users.