Ratiometric in vivo auditioning of targeted silver nanoparticles

Abstract

Attaching affinity ligands to nanoparticles (NPs) increases selectivity for targeting cells and tissues, and can result in improved sensitivity and reduced off-target toxicity in diagnostic and therapeutic systems. The decision over key features – NP size, shape, coating strategies and targeting ligands for clinical translation is often hampered by a lack of quantitative in vivo NP homing assays. Sensitive, internally controlled assays are needed which allow for quantitative comparisons (auditions) among various formulations of targeted NPs. We recently reported the development of peptide-functionalized, isotopically-barcoded silver NPs (AgNPs) for ultrasensitive studies centered on measuring relative ratios of NP internalization into cultured cells. Here we evaluated the application of this technology for NP homing studies in live mice using peptides with previously described tissue tropism; one peptide that favors vascular beds of the normal lungs (RPARPAR; receptor neuropilin-1, or NRP-1) and another that is selective for central nervous system vessels (CAGALCY). Equimolar mixtures of the peptide-targeted Ag107-NPs and Ag109 control particles were mixed and injected intravenously. Distribution profiles of Ag107 and Ag109 in tissue extracts were determined simultaneously through inductively coupled plasma mass spectrometry (ICP-MS). Compared to non-targeted particles up to ~9-fold increased lung accumulation was seen for RPARPAR-OH AgNPs (but not for AgNPs functionalized with RPARPAR-NH2, which does not bind to NRP-1). Similarly, AgNPs functionalized with the brain-homing CAGALCY peptide were overrepresented in brain extracts. Spatial distribution (mapping) analysis by laser ablation ICP-MS (LA-ICP-MS) was used to determine the ratio Ag107/Ag109 in tissue cryosections. The mapping demonstrated preferential accumulation of the RPARPAR-AgNPs in the perivascular areas around pulmonary veins, and CAGALCY AgNPs accumulated in discrete areas of the brain (e.g. in the vessels of cerebellar fibrillary tracts). Based on these results, the internally controlled ratiometric AgNP system is suitable for quantitative studies of the effect of targeting ligands on NP biodistribution, at average tissue concentration and distribution at the microscopic level. The platform might be particularly relevant for target sites with high local variability in uptake, such as tumors.

Preparation of oxymatrine n-butyl polycyanoacrylate nanoparticles and its hepatoprotective effects in ob/ob mice

“…For passively targeted preparations, the size of the particle s directly affects the distribution of the drug in vivo. Nanoparticles with different sizes have different in vivo distribution characteristics (24). From the perspective of medication safety, the smallest capillary diameter of the human body is about 4 µm, so the size of the intravenously injected nanoparticles should be less than this limit.…”

In vivophage display: identification of organ-specific peptides using deep sequencing and differential profiling across tissues

“…To validate our approach to in vivo homing peptide identification, we decided to perform a model screen focused on the enrichment and tissue distribution analyses of a known brainselective peptide, CAGALCY (20,21), spiked into a low complexity peptide phage library. We showed that by using the differential binding approach we can not only select for CAGALCY as a brain homing peptide, which would be possible by conventional enrichment analysis, but also profile its biodistribution and selectivity across organs.…”

“…Moreover, healthy organs can be specifically targeted with homing peptides. Examples are brain homing peptide CAGALCY (20,21) and prototypic C-end Rule (CendR) peptide RPARPAR that upon intravenous administration accumulates in lungs and heart (7).…”

Peptides as drug delivery vehicles across biological barriers

“…Structure-activity relationship analysis of CAGALCY peptide demonstrated the free carboxylic acid side chain and N-tyrosine as the key pharmacophore of the peptide (Fan et al 2007). CAGALCY coupled to silver NPs improved their brain homing effect in vivo (Toome et al 2017). Finally, Urich et al identified RLSSVDSDLSGC by next-generation sequencing (NGS) of T7 display phage library screened against in-vivo BBB model (rat).…”