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Gene therapies have shown great promise for the potential treatment of a broad range of diseases. Adeno-associated viruses (AAVs) are popular gene vectors because of their ability to target specific tissues, and they have demonstrated high transduction efficiencies in multiple neurological targets. While these therapeutics hold great promise, their biomanufacturing has limited potential cost-reduction and more widespread adoption. Herein, we report the preliminary development of an immunosensor for measuring the titer of adeno-associated virus 2 (AAV2), which may be deployed for rapid quantification of product yield during AAV biomanufacturing. We functionalized an interdigitated electrode array with anti-AAV2 antibodies, and electrochemical impedance spectroscopy was employed to investigate the response to AAV2 titer. A Faradaic sensing principle was utilized, in which the charge transfer resistance (Rct) of an electrochemical reporter was monitored after capture of AAV2 on the surface of the sensor. A linear response was measured over titers 1012 - 1013 capsids/mL. 

In this study, we investigate the enhancement of exchange bias in core/shell/shell structures by synthesizing single inverted core/shell (Co-oxide/Co) and core/shell/shell (Co-oxide/Co/Co-oxide) nanostructures through a two-step reduction and oxidation method. We evaluate the magnetic properties of the structures and study the effect of shell thickness on the exchange bias by synthesizing various shell thicknesses of Co-oxide/Co/Co-oxide nanostructures. The extra exchange coupling formed at the shell–shell interface in the core/shell/shell structure leads to a remarkable increase in the coercivity and the strength of the exchange bias by three and four orders, respectively. The strongest exchange bias is achieved for the sample comprising the thinnest outer Co-oxide shell. Despite the general declining trend of the exchange bias with Co-oxide shell thickness, we also observe a nonmonotonic behavior in which the exchange bias oscillates slightly as the shell thickness increases. This phenomenon is ascribed to the dependence of the antiferromagnetic outer shell thickness variation at the expense of the simultaneous opposite variation in the ferromagnetic inner shell.