Nanostructure‐Dependent Ratiometric NIR Fluorescence Enabled by Ordered Dye Aggregation

Abstract

Nanocarriersi ncorporating therapeutic and imaging agentsw ithin as ingle nanostructure are emergingt ools for drug development and treatment planning. Additional information can be provided using activatable fluorescence that dynamically reports nanocarrier disruption and drugr elease. Dual-wavelengtha ctivation encodes au nique fluorescence signal for each nanocarrier state, enabling use of ratiometric imaging to measure the proportion of intact and disrupted nanocarriers within tissues. Here we investigate dualwavelength activation using as ingle dyew hose optical properties are intricately linked to the nanocarrier structure. Naturalb acteriochlorophyll incorporated within ac ompact lipoprotein nanocarrier forms ordered dye aggregates with red-shifted fluorescencee missionf rom 765 nm to 825 nm. We demonstrate that bacteriochlorophyll-ordered aggregation is af easible strategy to distinguish intact and disrupted theranostic nanocarriers by ratiometric fluorescence imaging.

Tailoring Porphyrin Conjugation for Nanoassembly-Driven Phototheranostic Properties

“…Both B­(P)-HDL and P­(B)-HDL nanoparticles consisted of mixtures of discoidal and spherical populations (<50 nm) characteristic of both native HDLs and established pyropheophorbide and BChl-containing lipoproteins. − Size distributions of B­(P)-HDL and P­(B)-HDL were obtained by ImageJ analysis of >400 particles across TEM images (Figure S5). The mean size of B­(P)-HDL was 32 nm and that of P­(B)-HDL was 25 nm, consistent with established literature describing lipoprotein mimetic nanoparticles. , Control B-HDL and P-HDL nanoparticles consisted of monodisperse spherical structures with well-defined cores. (B)-HDL and (P)-HDL nanoparticles morphologies, similar to B­(P)-HDL and P­(B)-HDL, were characterized as a heterogeneous mixture of discoidal and spherical species, demonstrating a clear effect of porphyrin-oleylamide aggregation on the nanostructure shape.…”

“…The core/shell architecture of native lipoproteins naturally allows for the incorporation of various porphyrin conjugates into different nanoparticle subunits (shell or core). Our group has explored porphyrin loading into a lipoprotein shell by introducing amphiphilicity to the porphyrin molecule through lipid conjugation , or into a lipoprotein core by enhancing porphyrin hydrophobicity through oleylamide or bis­(oleate) conjugation . Synthetic HDL-like nanoparticles recapitulate the structure of native lipoproteins; therefore, porphyrin conjugates of varying hydrophobicity can be easily incorporated into their structure …”

“…More specifically, lipoproteins consist of a phospholipid shell and a hydrophobic core, formed by cholesteryl esters, that are stabilized by various apolipoproteins . The natural ability of lipoproteins to integrate molecules of varying hydrophobicity has inspired scientists to reverse engineer a range of lipoprotein-like agents for both biomedical applications and fundamental studies. − From an application standpoint, their long plasma circulation time, non-immunogenicity, core and shell loading, and receptor targeting capabilities make them promising delivery vehicles for small-molecule drugs, − therapeutic siRNA, − and imaging agents. − From a fundamental standpoint, lipoprotein-like structures provide a unique way of studying supramolecular interactions, particularly the effects of nanostructures on dye–dye interactions, such as self-quenching and aggregation. − …”

“…To facilitate porphyrin incorporation into lipoproteins and thereby take advantage of their capacity for long circulation and receptor-targeted delivery, a variety of porphyrin conjugation strategies have been applied. Specifically, introduction of amphiphilicity to the porphyrin molecule through lipid conjugation enables porphyrin loading into the lipid shell of these lipoproteins. , Our group has developed porphyrin-containing high-density lipoprotein (HDL)-like nanoparticles in which amphiphilic pyropheophorbide-lipid was incorporated into the nanoparticle shell for activatable fluorescence imaging and photodynamic therapy (PDT). , In an alternative approach, highly hydrophobic porphyrin-fatty acid esters were successfully loaded into the HDL hydrophobic core . Recently, Harmatys and coauthors synthesized a series of hydrophobic chlorin derivatives that were encapsulated into a biomimetic HDL core, wherein the spatial constraints created by an ApoA-1 mimetic peptide resulted in dye J-aggregation characterized by a strong bathochromic shift (654 to 715 nm), enabling photoacoustic imaging .…”

Multipronged Biomimetic Approach To Create Optically Tunable Nanoparticles

“…[11] Our group has explored porphyrin J-aggregation in lipid-based nanoparticles for multimodality [12] and responsive imaging. [13] These structures are assembled from ap hospholipid-conjugated porphyrin building block that restricts the location of the aggregate to either the lipid bilayer or monolayer outer shell, where it is more likely to form J-aggregates without disruption from environmental influences.N atural chlorosomes contain as table three-dimensional porphyrin supramolecular assembly,s o the design of ac hlorosome mimetic requires freedom of porphyrin molecule interaction for self-assembly without external templated assistance that would be structurally confining.T herefore,a na lternative dye-nanoparticle system must be implemented. High-density lipoproteins (HDL) are endogenous nanoparticles involved in the metabolism and transport of fatty biomolecules [14] and HDL mimetics are widely studied nanocarriers for delivery of chemotherapeutics,s iRNA, and imaging agents.…”