Narrow Absorption NIR Wavelength Organic Nanoparticles Enable Multiplexed Photoacoustic Imaging

Abstract

Photoacoustic (PA) imaging is an emerging hybrid optical-ultrasound based imaging technique that can be used to visualize optical absorbers in deep tissue. Free organic dyes can be used as PA contrast agents to concurrently provide additional physiological and molecular information during imaging, but their use in vivo is generally limited by rapid renal clearance for soluble dyes and by the difficulty of delivery for hydrophobic dyes. We here report the use of the block copolymer directed self-assembly process, Flash NanoPrecipitation (FNP), to form series of highly hydrophobic optical dyes into stable, biocompatible, and water-dispersible nanoparticles (NPs) with sizes from 38 to 88 nm and with polyethylene glycol (PEG) surface coatings suitable for in vivo use. The incorporation of dyes with absorption profiles within the infrared range, that is optimal for PA imaging, produces the PA activity of the particles. The hydrophobicity of the dyes allows their sequestration in the NP cores, so that they do not interfere with targeting, and high loadings of >75 wt % dye are achieved. The optical extinction coefficients (ε (mL mg(-1) cm(-1))) were essentially invariant to the loading of the dye in NP core. Co-encapsulation of dye with vitamin E or polystyrene demonstrates the ability to simultaneously image and deliver a second agent. The PEG chains on the NP surface were functionalized with folate to demonstrate folate-dependent targeting. The spectral separation of different dyes among different sets of particles enables multiplexed imaging, such as the simultaneous imaging of two sets of particles within the same animal. We provide the first demonstration of this capability with PA imaging, by simultaneously imaging nontargeted and folate-targeted nanoparticles within the same animal. These results highlight Flash NanoPrecipitation as a platform to develop photoacoustic tools with new diagnostic capabilities.

Nanoparticle targeting of Gram-positive and Gram-negative bacteria for magnetic-based separations of bacterial pathogens

“…This is especially important for optimizing cell targeting, as increasing ligand densities can improve binding in some instances, but excessively high-ligand densities can also result in decreased cell binding (Allen 2002;Cabral et al 2011;Cheng et al 2012;D'Addio et al 2013;Elias et al 2013;Kathleen et al 2007;Lee et al 2010). The FNP process enables the simultaneous encapsulation of several hydrophobic actives, including imaging modalities and hydrophobic drugs, to create theranostic NPs for novel antimicrobial treatments (Lu et al 2015(Lu et al , 2016(Lu et al , 2017Pansare et al 2012Pansare et al , 2014. We here present the development and characterization of FNPbased NPs that target Gram-negative and Gram-positive bacteria, and demonstrate proof-of-concept applications where bacteria are separated from media using commercially available and easily scalable magnetic separation setups.…”

Enhanced Performance of a Molecular Photoacoustic Imaging Agent by Encapsulation in Mesoporous Silicon Nanoparticles

“…[1-3] In PA imaging, laser pulses are directed at tissues containing a molecular or nanoparticle chromophore with a strong optical absorbance at the laser wavelength, typically in the near infrared (NIR) region of the spectrum. Non-radiative relaxation converts the optical excitation into a thermoacoustic wave [1, 4, 5] which is detected with audio transducers and reconstructed into a three-dimensional image. [6] Since light is used only to excite the target molecules and the generated acoustic waves are less efficiently scattered than photons in biological tissues, images can be obtained at greater depths and with higher spatial resolution than can be achieved with more conventional fluorescence imaging.…”

Performances of a Pristine Graphene–Microbubble Hybrid Construct as Dual Imaging Contrast Agent and Assessment of Its Biodistribution by Photoacoustic Imaging

“…Here, we show the in vivo multiplexed PA imaging of hybrid graphene PVA microbubbles, due to the well separated absorbance profiles as proved by the in vitro study. The ability to simultaneously distinguish the PA signals of endogenous and exogenous contrast agents in the same image is necessary for multiplexed imaging . Hence, the wavelength choice based on the comparison of the PA spectral features of each components, i.e., oxy, deoxy hemoglobins both present in the blood and G/PVA–PEGDA2000, as illustrated in Figure , favors the G/PVA–PEGDA2000 PA contrast at 720 nm.…”