Polymer nanoassemblies with solvato- and halo-fluorochromism for drug release monitoring and metastasis imaging

Carfilzomib-Loaded Ternary Polypeptide Nanoparticles Stabilized by Polycationic Complexation

Carfilzomib (CFZ) is a second-generation proteasome inhibitor showing great efficacy in multiple myeloma treatment, yet its clinical applications for other diseases such as solid cancers are limited due to low aqueous solubility and poor biostability. Ternary polypeptide nanoparticles (tPNPs) are drug carriers that we previously reported to overcome these pharmaceutical limitations by entrapping CFZ in the core of the nanoparticles and protecting the drugs from degradation in biological media. However, preclinical studies revealed that tPNPs would require further improvement in particle stability to suppress initial burst drug release and thus achieve prolonged inhibition of proteasome activity with CFZ against tumor cells in vivo. In this study, CFZ-loaded tPNPs are stabilized by polycations which have varying pKa values and thus differently modulate nanoparticle stability in response to solution pH. Through polyion complexation, the polycations appeared to stabilize the core of tPNPs entrapping CFZ-cyclodextrin inclusion complexes while allowing for uniform particle size before and after freeze drying. Interestingly, CFZ-loaded tPNPs (CFZ/tPNPs) showed pH-dependent drug release kinetics, which accelerated CFZ release as solution acidity increased (pH < 6) without compromising particle stability at the physiological condition (pH 7.4). In vitro cytotoxicity and proteasome activity assays confirmed that tPNPs stabilized with cationic polymers improved bioactivity of CFZ against CFZ-resistant cancer cells, which would be greatly beneficial in combination with pH-dependent drug release for treatment of solid cancers with drug resistance and tumor microenvironment acidosis by using CFZ and other proteasome inhibitors.

Ternary Polypeptide Nanoparticles with Improved Encapsulation, Sustained Release, and Enhanced In Vitro Efficacy of Carfilzomib

PURPOSE

To develop a new nanoparticle formulation for a proteasome inhibitor Carfilzomib (CFZ) to improve its stability and efficacy for future in vivo applications.

METHODS

CFZ-loaded ternary polypeptide nanoparticles (CFZ/tPNPs) were prepared by using heptakis(6-amino-6-deoxy)-β-cyclodextrin(hepta-hydrochloride) (HaβCD) and azido-poly(ethylene glycol)-block-poly(L-glutamic acid sodium salt) (N₃-PEG-PLE). The process involved ternary (hydrophobic/ionic/supramolecular) interactions in three steps: 1) CFZ was entrapped in the cavity of HaβCD by hydrophobic interaction, 2) the drug-cyclodextrin inclusion complexes were mixed with N₃-PEG-PLE to form polyion complex nanoparticles, and 3) the nanoparticles were modified with fluorescent dyes (AFDye 647) for imaging and/or epithelial cell adhesion molecule (EpCAM) antibodies for cancer cell targeting. CFZ/tPNPs were characterized for particle size, surface charge, drug release, stability, intracellular uptake, proteasome inhibition, and in vitro cytotoxicity.

RESULTS

tPNPs maintained an average particle size of 50 nm after CFZ entrapment, EpCAM conjugation, and freeze drying. tPNPs achieved high aqueous solubility of CFZ (>1 mg/mL), sustained drug release (t_1/2 = 6.46 h), and EpCAM-mediated cell targeting, which resulted in increased intracellular drug accumulation, prolonged proteasome inhibition, and enhanced cytotoxicity of CFZ in drug-resistant DLD-1 colorectal cancer cells.

CONCLUSIONS

tPNPs improved stability and efficacy of CFZ in vitro, and these results potentiate effective cancer treatment using CFZ/tPNPs in future vivo studies.

Modeling of Nanotherapy Response as a Function of the Tumor Microenvironment: Focus on Liver Metastasis

The tumor microenvironment (TME) presents a challenging barrier for effective nanotherapy-mediated drug delivery to solid tumors. In particular for tumors less vascularized than the surrounding normal tissue, as in liver metastases, the structure of the organ itself conjures with cancer-specific behavior to impair drug transport and uptake by cancer cells. Cells and elements in the TME of hypovascularized tumors play a key role in the process of delivery and retention of anti-cancer therapeutics by nanocarriers. This brief review describes the drug transport challenges and how they are being addressed with advanced in vitro 3D tissue models as well as with in silico mathematical modeling. This modeling complements network-oriented techniques, which seek to interpret intra-cellular relevant pathways and signal transduction within cells and with their surrounding microenvironment. With a concerted effort integrating experimental observations with computational analyses spanning from the molecular- to the tissue-scale, the goal of effective nanotherapy customized to patient tumor-specific conditions may be finally realized.

Tethered polymer nanoassemblies for sustained carfilzomib release and prolonged suppression of proteasome activity

AIM

Proteasome inhibitors, such as carfilzomib (CFZ), have shown potential to treat various types of cancers in preclinical models, but clinical applications are limited likely due to formulation and delivery issues. Results & methodology: Tethered polymer nanoassemblies (TNAs) were synthesized by tethering hydrophilic polymers and hydrophobic groups to charged polymer scaffolds, and then end-capping remaining amines on scaffold. Drug entrapment and drug release half-lives increased as charge was removed from scaffold. TNAs with sustained CFZ release maintained drug efficacy after preincubation and increased duration of proteasome inhibition in cancer cells compared with free CFZ.

CONCLUSION

TNAs fine-tuned CFZ release as charge was removed from polymer scaffold, which allowed for sustained proteasome inhibition in cancer cells and potentially enhanced anticancer efficacy.

Development of Halofluorochromic Polymer Nanoassemblies for the Potential Detection of Liver Metastatic Colorectal Cancer Tumors Using Experimental and Computational Approaches

PURPOSE

To develop polymer nanoassemblies (PNAs) modified with halofluorochromic dyes to allow for the detection of liver metastatic colorectal cancer (CRC) to improve therapeutic outcomes.

METHODS

We combine experimental and computational approaches to evaluate macroscopic and microscopic PNA distributions in patient-derived xenograft primary and orthotropic liver metastatic CRC tumors. Halofluorochromic and non-halofluorochromic PNAs (hfPNAs and n-hfPNAs) were prepared from poly(ethylene glycol), fluorescent dyes (Nile blue, Alexa546, and IR820), and hydrophobic groups (palmitate), all of which were covalently tethered to a cationic polymer scaffold [poly(ethylene imine) or poly(lysine)] forming particles with an average diameter < 30 nm.

RESULTS

Dye-conjugated PNAs showed no aggregation under opsonizing conditions for 24 h and displayed low tissue diffusion and cellular uptake. Both hfPNAs and n-hfPNAs accumulated in primary and liver metastatic CRC tumors within 12 h post intravenous injection. In comparison to n-hfPNAs, hfPNAs fluoresced strongly only in the acidic tumor microenvironment (pH < 7.0) and distinguished small metastatic CRC tumors from healthy liver stroma. Computational simulations revealed that PNAs would steadily accumulate mainly in acidic (hypoxic) interstitium of metastatic tumors, independently of the vascularization degree of the tissue surrounding the lesions.

CONCLUSION

The combined experimental and computational data confirms that hfPNAs detecting acidic tumor tissue can be used to identify small liver metastatic CRC tumors with improved accuracy.