Related Experiment Video
Updated: Apr 28, 2026
Preparation and Characterization of Individual and Multi-drug Loaded Physically Entrapped Polymeric Micelles
Published on: August 28, 2015
Selective intracellular delivery of proteasome inhibitors through pH-sensitive polymeric micelles directed to
Abstract:
The ubiquitin-proteasome system is central in the regulation of cellular proteins controlling cell cycle progression and apoptosis, drawing much interest for developing effective targeted cancer therapies. Herein, we developed a novel pH-responsive polymeric-micelle-based carrier system to effectively deliver the proteasome inhibitor MG132 into cancer cells. MG132 is covalently bound to the block copolymer composed of polyethylene glycol (PEG) and polyaspartate through an acid-labile hydrazone bond. This bond is stable at physiological condition, but hydrolytically degradable in acidic compartments in the cell, such as late-endosomes and lysosomes, and thus, it was used for controlled release of MG132 after EPR-mediated preferential accumulation of the micelles into the tumor. MG132-loaded micelles have monodispersed size distribution with an average diameter of 45nm, and critical micelle concentration is well below 10(-7)M. In vitro studies against several cancer cell lines confirmed that MG132-loaded micelles retained the cytotoxic effect, and this activity was indeed due to the inhibition of proteasome by released MG132 from the micelles. Real-time in vitro confocal-microscopy experiments clearly indicated that MG132-conjugated micelles disintegrated only inside the target cells. By intravital confocal micro-videography, we also confirmed the prolonged circulation of MG132 loaded micelles in the bloodstream, which lead to tumor specific accumulation of micelles, as confirmed by in vivo imaging 24h after injection. These micelles showed significantly lower in vivo toxicity than free MG132, while achieving remarkable antitumor effect against a subcutaneous HeLa-luc tumor model. Our findings create a paradigm for future development of polymeric-micelle-based carrier system for other peptide aldehyde type proteasome inhibitors to make them effective cohort of the existing cancer therapeutic regiments.
Insights
This study introduces pH-responsive polymeric micelles for targeted cancer therapy, delivering the proteasome inhibitor MG132 effectively into cancer cells with reduced toxicity. The novel carrier system demonstrates significant antitumor effects in preclinical models.
Area of Science:
- Biomedical Engineering
- Nanotechnology
- Cancer Therapy
Background:
- The ubiquitin-proteasome system regulates key cellular processes like cell cycle and apoptosis, making it a target for cancer therapy.
- Proteasome inhibitors, such as MG132, show therapeutic potential but require effective delivery systems to enhance efficacy and reduce toxicity.
Purpose of the Study:
- To develop a novel pH-responsive polymeric-micelle-based carrier for targeted delivery of the proteasome inhibitor MG132 into cancer cells.
- To evaluate the controlled release, cellular uptake, in vitro cytotoxicity, and in vivo antitumor efficacy and toxicity of the developed carrier system.
Main Methods:
- Covalent conjugation of MG132 to a polyethylene glycol (PEG)-polyaspartate block copolymer via an acid-labile hydrazone bond.
- Formation of pH-responsive polymeric micelles with a 45nm average diameter and low critical micelle concentration.
- In vitro evaluation of cytotoxicity and proteasome inhibition in cancer cell lines.
- In vivo studies using confocal micro-videography for circulation and tumor accumulation, and assessment of antitumor effects in a subcutaneous HeLa-luc tumor model.
Main Results:
- MG132-loaded micelles demonstrated sustained release in acidic cellular compartments and retained cytotoxic activity against cancer cells.
- Confocal microscopy confirmed micelle disintegration and drug release exclusively within target cells.
- In vivo imaging revealed prolonged circulation and preferential tumor accumulation of the micelles.
- The developed micelles exhibited significantly lower toxicity compared to free MG132 and achieved remarkable antitumor efficacy.
Conclusions:
- pH-responsive polymeric micelles offer a promising platform for targeted delivery of proteasome inhibitors like MG132, enhancing their therapeutic index.
- This approach provides a paradigm for developing similar carrier systems for other peptide aldehyde proteasome inhibitors in cancer therapy.
Related Concept Videos
01:24Site-Targeted Drug Delivery Systems: Polymeric Carriers
01:24Modified-Release Drug Delivery Systems: Site-Targeted
02:57Targeted Cancer Therapies
There are several types of targeted therapies against...