Photothermal Imaging and Measurement of Protein Shell Stoichiometry of Single HIV-1 Gag Virus-like Nanoparticles

Abstract

Virus life stages often constitute a complex chain of events, difficult to track in-vivo and in real-time. Challenges are associated with spatial and time limitations of current probes: most viruses are smaller than the diffraction limit of optical microscopes while the entire time-scale of virus dynamics spans over 8 orders of magnitude. Thus, virus processes such as entry, disassembly, and egress have generally remained poorly understood. Here we discuss photothermal heterodyne imaging (PHI) as a possible alternative to fluorescence microscopy in the study of single virus-like nanoparticle (VNP) dynamics, with relevance in particular to virus uncoating. Being based on optical absorption rather than emission, PHI could potentially surpass some of the current limitations associated with fluorescent labels. As proof-of-principle, single VNPs self-assembled from 60 nm DNA-functionalized gold nanoparticles (DNA-Au NPs) encapsulated in a Gag protein shell of the Human immunodeficiency virus (HIV-1) were imaged and their photothermal response compared with DNA-Au NPs. For the first-time, the protein stoichiometry of a single virus-like particle was estimated by a method other than electron microscopy.

Hybrid Nanoparticles for Detection and Treatment of Cancer

“…These gold‐labeled adenoviral vectors displayed similar luciferase expression to unmodified adenoviral vectors in MC38‐CEA‐2 cancer cells. Recently, additional examples of photo‐activatable viral nanoparticles have been developed for targeted photothermal heating/imaging by decorating a virus capsid with C 60 (“buckyballs”)201 or by encapsulating a gold nanoparticle with viral proteins 202…”

The Process of Wrapping Virus Revealed by a Force Tracing Technique and Simulations

“…They are similar to the authentic virus structurally and can mimic authentic virus to elicit strong and broad immune responses; therefore, they are noninfectious and safe for experimentation in ordinary labs . Many types of VLPs have been expressed and applied for clinical research, such as Influenza, Severe Acute Respiratory Syndrome (SARS) coronavirus and Hepatitis B virus, and to investigate the interactions between viruses and cells by colocalization and single‐particle tracking . Here, we use force tracing technique to directly record the endocytic force and wrapping time of single VLPs via cell membranes.…”

Imaging nano-objects by linear and nonlinear optical absorption microscopies

“…For example, to achieve high sensitivity solvents such as glycerol are needed, [48] although experiments can also be performed in water [47,121,126,128] and in biological samples. [17,36,87,88,90,91,163] 7 A diagram of the instrument used for SMS in our laboratory is shown in Figure 1(b). Unlike TAM and PHI, SMS is a single beam technique.…”