Tumor Retention of Enzyme-Responsive Pt(II) Drug-Loaded Nanoparticles Imaged by Nanoscale Secondary Ion Mass Spectrometry and Fluorescence Microscopy

Abstract

In nanomedicine, determining the spatial distribution of particles and drugs, together and apart, at high resolution within tissues, remains a major challenge because each must have a different label or detectable feature that can be observed with high sensitivity and resolution. We prepared nanoparticles capable of enzyme-directed assembly of particle therapeutics (EDAPT), containing an analogue of the Pt(II)-containing drug oxaliplatin, an 15N-labeled monomer in the hydrophobic block of the backbone of the polymer, the near-infrared dye Cy5.5, and a peptide that is a substrate for tumor metalloproteinases in the hydrophilic block. When these particles reach an environment rich in tumor associated proteases, the hydrophilic peptide substrate is cleaved, causing the particles to accumulate through a morphology transition, locking them in the tumor extracellular matrix. To evaluate the distribution of drug and EDAPT carrier in vivo, the localization of the isotopically labeled polymer backbone was compared to that of Pt by nanoscale secondary ion mass spectrometry (NanoSIMS). The correlation of NanoSIMS with super-resolution fluorescence microscopy revealed the release of the drug from the nanocarrier and colocalization with cellular DNA within tumor tissue. The results confirmed the dependence of particle accumulation and Pt(II) drug delivery on the presence of a Matrix Metalloproteinase (MMP) substrate and demonstrated antitumor activity. We conclude that these techniques are powerful for the elucidation of the localization of cargo and carrier, and enable a high-resolution assessment of their performance following in vivo delivery.

SIMS imaging in neurobiology and cell biology

“…In drug delivery technology, a nanocarrier is designed to contain a platinum drug for cancer treatment. 50 It contains a polymer backbone coupled with a uorescence dye Cy5.5 and labeled with 15 N, and a substrate peptide for matrix metalloproteinase (MMP) (Fig. 3B).…”

Biomedical nanoparticle design: What we can learn from viruses

“… Stimulus Effect Target NP In vivo Therapy/Cargo Ref. Enzymatic Ligand unveiling MMP-2 PEG-PCL NPs A549 tumor (mouse) Curcumin [ 182 ] MMP-7 PEG NPs – siRNA [ 183 ] MMP-9 PEG Quantum dots BxPC-3 tumor (mouse) GEM [ 184 ] MMP-2 PEG NPs lung tumor (mouse) PTX [ 185 ] “-” PEG Liposomes – – [ 186 ] Legumain Liposomes 4 T1 tumor (mouse) DOX [ 191 ] Ligand activation ACE PEG-PLA/PLGA NPs – – [ 74 , 175 ] Morphology change MMP Peptide NPs HT-1080 tumor (mouse) Pt(II) [ 187 ] MMP-2/9 Peptide/Polymer NPs Myocardial infarct (rat) – [ 188 ] MMP Norbornene/Peptide NPs HT-1080 tumor (mouse) PTX [ 189 ] Bacterial PGA/BLA Polymer NPs – Antibiotics [ 192 ] Bacterial elastase PEI-Pep...…”

“…The enzymes most commonly addressed are the matrix metalloproteinases (MMPs) [ 181 ], which can be found in the extracellular tumor medium for example. They have been used to unveil PEG-shielded ligands protected during circulation [ [182] , [183] , [184] , [185] , [186] ], or to induce a morphology change [ [187] , [188] , [189] ], increasing the targeting potential of NPs. Other enzymes, such as legumain, which is upregulated in tumors in correlation with their malignancy [ 190 ], have also been targeted to unveil shielded ligands, like TAT [ 191 ], in a site-specific manner.…”

Approaching sites of action of drugs in clinical pharmacology: New analytical options and their challenges

“…Finally, SIMS and nanoSIMS are also used for metal-containing drug imaging. 163,165 SIMS can also be used to map a larger panel of pharmaceuticals in tissue sections such as dexamethasone in ovine eyes 166 and topically applied drugs on mouse skin. 167 In Table 1, In the context of MS imaging, highly sensitive instrumentation is necessary for the quantification of low drug concentrations.…”