Quantification of Cellular Drug Biodistribution Addresses Challenges in Evaluating In Vitro and In Vivo Encapsulated Drug Delivery

Abstract

Nanoencapsulated drug delivery to solid tumors is a promising approach to overcome the pharmacokinetic limitations of therapeutic drugs. However, encapsulation leads to complex drug biodistribution and delivery making analysis of delivery efficacy challenging. As proxies, nanocarrier accumulation or total tumor drug uptake in the tumor are used to evaluate delivery. Yet these measurements fail to assess the delivery of active, released drug to the target, and thus it commonly remains unknown if drug-target occupancy is achieved. Here, an approach to evaluate the delivery of encapsulated drug to the target is developed, where residual drug target vacancy is measured using a fluorescent drug analog. In vitro measurements reveal that burst release governs drug delivery independent of nanoparticle uptake, and highlight limitations of evaluating nanoencapsulated drug delivery in these models. In vivo, however, the approach captures successful nanoencapsulated delivery, showing that tumor stromal cells drive nanoparticle accumulation and mediate drug delivery to adjacent cancer cells. These results, and generalizable approach, provide a critical advance to evaluate delivery of encapsulated drugs to the drug target-the central objective of nanotherapeutics.

pH-Responsive Drug Delivery Nanoplatforms as Smart Carriers of Unsymmetrical Bisacridines for Targeted Cancer Therapy

“…To obtain the desired therapeutic response in the target site, the nanoencapsulated drug must be released from its nanoconjugate. Distinguishing the encapsulated and the released drug is often problematic and there are technical difficulties in quantifying them in the complex matrices [ 40 ]. Many methods reported in the literature for assaying the release profiles of drugs from nanoparticulate systems are based on HPLC with UV-Vis and/or mass spectrometric detection [ 41 , 42 , 43 ].…”

Cyanine Masking: A Strategy to Test Functional Group Effects on Antibody Conjugate Targeting

“…While intrinsically hydrophobic, these molecules can be synthetically modified with polar functional groups. Several prior studies, including those from our group, have examined the impact of modifications on the in vivo properties of mAb–fluorophore conjugates. − While these prior studies provided key insights, they are not systematic from a “functional group” perspective making it hard to draw larger lessons (see Figure S1 for previous molecules). Here, we address this issue with single-point alterations to substituents distal to the cyanine scaffold.…”

Cyanine Masking: A Strategy to Test Functional Group Effects on Antibody Conjugate Targeting

“…Several prior studies, including from our group, have examined the impact of modifications on the in vivo properties of mAb-fluorophore conjugates. [11][12][13][14][15][16]17,18,[19][20][21] While these prior studies provided key insights, they are not systematic from a "functional-group" perspective making it hard to draw larger lessons (See Figure S1 for previously tested molecules). Here we address this issue with single point alterations to substituents distal to the cyanine scaffold.…”