Abstract
BackgroundGold nanorods (GNRs) display unique capacity to absorb and scatter near infrared light, which arises from their peculiar composition of surface plasmon resonances. For this reason, GNRs have become an innovative material of great hope in nanomedicine, in particular for imaging and therapy of cancer, as well as in photonic sensing of biological agents and toxic compounds for e.g. biomedical diagnostics, forensic analysis and environmental monitoring. As the use of GNRs is becoming more and more popular, in all these contexts, there is emerging a latent need for simple and versatile protocols for their modification with targeting units that may convey high specificity for any analyte of interest of an end-user.ResultsWe introduce protein G-coated GNRs as a versatile solution for the oriented immobilization of antibodies in a single step of mixing. We assess this strategy against more standard covalent binding of antibodies, in terms of biocompatibility and efficiency of molecular recognition in buffer, serum and plasma, in the context of the development of a direct immunoenzymatic assay. In both cases, we estimate an average of around 30 events of molecular recognition per particle. In addition, we disclose a convenient protocol to store these particles for months in a freezer, without any detrimental effect.ConclusionsThe biocompatibility and efficiency of molecular recognition is similar in either case of GNRs that are modified with antibodies by covalent binding or oriented immobilization through protein G. However, protein G-coated GNRs are most attractive for an end-user, owing to their unique versatility and ease of bioconjugation with antibodies of her/his choice.
Highlights
Gold nanorods (GNRs) display unique capacity to absorb and scatter near infrared light, which arises from their peculiar composition of surface plasmon resonances
After PEGylation, GNRs were conjugated with IgG anti-PCB28 (100 μg/mL) by chemical immobilization, incubated with PCB28-alkaline phosphatase (AP) and assessed by the spectrophotometric detection of the enzymatic product upon addition of the enzymatic substrate
Conjugation of PEGylated GNRs with antibodies and immunoenzymatic assay By covalent binding PEGylated GNRs were conjugated with IgG anti-PCB28 or anti-PCB169 by chemical binding and incubated with PCB28-AP
Summary
Gold nanorods (GNRs) display unique capacity to absorb and scatter near infrared light, which arises from their peculiar composition of surface plasmon resonances. GNRs exhibit two SPR bands that reflect their anisotropic shape: plasmonic oscillations along their longer axis correspond to a so-called longitudinal SPR peak, while those along their shorter axes to a so-called transverse SPR peak The latter typically falls at wavelengths between 510 and 530 nm and weakly depends on the size of the GNRs have emerged as an innovative material of great hope in nanomedicine, in particular for imaging and therapy of cancer, because of their remarkable capacity to absorb and scatter NIR light [4,5,6,7,8]. All these features make GNRs a promising platform for applications at the crossroads of nanomedicine and biomedical optics
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