Vimalkumar Balasubramanian

Nanomedicine in cancer therapy: challenges, opportunities, and clinical applications.

Cancer is a leading cause of death worldwide. Currently available therapies are inadequate and spur demand for improved technologies. Rapid growth in nanotechnology towards the development of nanomedicine products holds great promise to improve therapeutic strategies against cancer. Nanomedicine products represent an opportunity to achieve sophisticated targeting strategies and multi-functionality. They can improve the pharmacokinetic and pharmacodynamic profiles of conventional therapeutics and may thus optimize the efficacy of existing anti-cancer compounds. In this review, we discuss state-of-the-art nanoparticles and targeted systems that have been investigated in clinical studies. We emphasize the challenges faced in using nanomedicine products and translating them from a preclinical level to the clinical setting. Additionally, we cover aspects of nanocarrier engineering that may open up new opportunities for nanomedicine products in the clinic.

Biocompatible Functionalization of Polymersome Surfaces: A New Approach to Surface Immobilization and Cell Targeting Using Polymersomes

Vesicles assembled from amphiphilic block copolymers represent promising nanomaterials for applications that include drug delivery and surface functionalization. One essential requirement to guide such polymersomes to a desired site in vivo is conjugation of active, targeting ligands to the surface of preformed self-assemblies. Such conjugation chemistry must fulfill criteria of efficiency and selectivity, stability of the resulting bond, and biocompatibility. We have here developed a new system that achieves these criteria by simple conjugation of 4-formylbenzoate (4FB) functionalized polymersomes with 6-hydrazinonicotinate acetone hydrazone (HyNic) functionalized antibodies in aqueous buffer. The number of available amino groups on the surface of polymersomes composed of poly(dimethylsiloxane)-block-poly(2-methyloxazoline) diblock copolymers was investigated by reacting hydrophilic succinimidyl-activated fluorescent dye with polymersomes and evaluating the resulting emission intensity. To prove attachment of biomolecules to polymersomes, HyNic functionalized enhanced yellow fluorescent protein (eYFP) was attached to 4FB functionalized polymersomes, resulting in an average number of 5 eYFP molecules per polymersome. Two different polymersome-antibody conjugates were produced using either antibiotin IgG or trastuzumab. They showed specific targeting toward biotin-patterned surfaces and breast cancer cells. Overall, the polymersome-ligand platform appears promising for therapeutic and diagnostic use.

Protein delivery: from conventional drug delivery carriers to polymeric nanoreactors

Due to their low bioavailability, many naturally occurring proteins can not be used in their native form in diseases caused by insufficient amounts or inactive variants of those proteins. The strategy of delivering proteins to biological compartments using carriers represents the most promising approach to improve protein bioavailability. A large variety of systems have been developed to protect and deliver proteins, based on lipids, polymers or conjugates. Here we present the current progress of the carriers design criteria with the help of recent specific examples in the literature ranging from conventional liposomes to polymeric nanoreactors, with sizes from micrometer to nanometer scale, and having various morphologies. The design and optimisation of carriers in the dual way of addressing questions of a particular application and of keeping them very flexible and reliable for general applications represent an important step in protein delivery approaches, which influence considerably the therapeutic efficacy. We examine several options currently under exploration for creating suitable protein carriers, discuss their advantages and limitations that induced the need to develop alternative ways to deliver proteins to biological compartments. We consider that only tailored systems can serve to improve proteins bioavailability, and thus solve specific pathological situations. This can be accomplished by developing nanocarriers and nanoreactors based on biocompatible, biodegradable and non-toxic polymer systems, adapted sizes and surface properties, and multifunctionality to cope with the complexity of the in-vivo biological conditions.

pH‐Switch Nanoprecipitation of Polymeric Nanoparticles for Multimodal Cancer Targeting and Intracellular Triggered Delivery of Doxorubicin

Theranostic nanoparticles are emerging as potent tools for noninvasive diagnosis, treatment, and monitoring of solid tumors. Herein, an advanced targeted and multistimuli responsive theranostic platform is presented for the intracellular triggered delivery of doxorubicin. The system consists of a polymeric-drug conjugate solid nanoparticle containing encapsulated superparamagnetic iron oxide nanoparticles (IO@PNP) and decorated with a tumor homing peptide, iRGD. The production of this nanosystem is based on a pH-switch nanoprecipitation method in organic-free solvents, making it ideal for biomedical applications. The nanosystem shows sufficient magnetization saturation for magnetically guided therapy along with reduced cytotoxicity and hemolytic effects. IO@PNP are largely internalized by endothelial and metastatic cancer cells and iRGD decorated IO@PNP moderately enhance their internalization into endothelial cells, while no enhancement is found for the metastatic cancer cells. Poly(ethylene glycol)-block-poly(histidine) with pH-responsive and proton-sponge properties promotes prompt lysosomal escape once the nanoparticles are endocyted. In addition, the polymer-doxorubicin conjugate solid nanoparticles show both intracellular lysosomal escape and efficient translocation of doxorubicin to the nuclei of the cells via cleavage of the amide bond. Overall, IO@PNP-doxorubicin and the iRGD decorated counterpart demonstrate to enhance the toxicity of doxorubicin in cancer cells by improving the intracellular delivery of the drug carried in the IO@PNP.

Polymersomes containing quantum dots for cellular imaging

Quantum dots (QDs) are highly fluorescent and stable probes for cellular and molecular imaging. However, poor intracellular delivery, stability, and toxicity of QDs in biological compartments hamper their use in cellular imaging. To overcome these limitations, we developed a simple and effective method to load QDs into polymersomes (Ps) made of poly(dimethylsiloxane)-poly(2-methyloxazoline) (PDMS-PMOXA) diblock copolymers without compromising the characteristics of the QDs. These Ps showed no cellular toxicity and QDs were successfully incorporated into the aqueous compartment of the Ps as confirmed by transmission electron microscopy, fluorescence spectroscopy, and fluorescence correlation spectroscopy. Ps containing QDs showed colloidal stability over a period of 6 weeks if stored in phosphate-buffered saline (PBS) at physiological pH (7.4). Efficient intracellular delivery of Ps containing QDs was achieved in human liver carcinoma cells (HepG2) and was visualized by confocal laser scanning microscopy (CLSM). Ps containing QDs showed a time- and concentration-dependent uptake in HepG2 cells and exhibited better intracellular stability than liposomes. Our results suggest that Ps containing QDs can be used as nanoprobes for cellular imaging.

Angiopep2-functionalized polymersomes for targeted doxorubicin delivery to glioblastoma cells

A targeted drug delivery nanosystem for glioblastoma multiforme (GBM) based on polymersomes (Ps) made of poly(dimethylsiloxane)-poly(2-methyloxazoline) (PDMS-PMOXA) diblock copolymers was developed to evaluate their potential to actively target brain cancer cells and deliver anticancer drugs. Angiopep2 was conjugated to the surface of preformed Ps to target the low density lipoprotein receptor-related protein 1 that are overexpressed in blood brain barrier (BBB) and glioma cells. The conjugation efficiency yield for angiopep2 was estimated to be 24%. The angiopep2-functionalized Ps showed no cellular toxicity after 24h and enhanced the cellular uptake around 5 times more in U87MG glioblastoma cells compared to the non-targeted Ps. The encapsulation efficiency of doxorubicin (DOX) in Ps was 13% by co-solvent method, compared to a film rehydration method (4%). The release profiles of the DOX from Ps showed a release of 42% at pH 5.5 and 40% at pH 7.4 after 24h, indicating that Ps can efficiently retain the DOX with a slow release rate. Furthermore, the in vitro antiproliferative activity of DOX-loaded Ps-Angiopep2 showed enhanced toxicity to U87MG glioblastoma cells, compared to non-targeted Ps. Overall, our in vitro results suggested that angiopep2-conjugated Ps can be used as nanocarriers for efficient targeted DOX delivery to glioblastoma cells.

Biocompatible polymer-Peptide hybrid-based DNA nanoparticles for gene delivery.

Currently, research on polymers to be used as gene delivery systems is one of the most important directions in both polymer science and biomedicine. In this report, we describe a five-step procedure to synthesize a novel polymer-peptide hybrid system for gene transfection. The block copolymer based on the biocompatible polymer poly(2-methyl-2-oxazoline) (PMOXA) was combined with the biocleavable peptide block poly(aspartic acid) (PASP) and finally modified with diethylenetriamine (DET). PMOXA-b-PASP(DET) was produced in high yield and characterized by (1)H NMR and FT-IR. Our biopolymer complexed plasmid DNA (pDNA) efficiently, and highly uniform nanoparticles with a slightly negative zeta potential were produced. The polymer-peptide hybrid system was able to efficiently transfect HEK293 and HeLa cells with GFP pDNA in vitro. Unlike the commonly used polymer, 25 kDa branched poly(ethylenimine), our biopolymer had no adverse effects on cell growth and viability. In summary, the present work provides valuable information for the design of new polymer-peptide hybrid-based gene delivery systems with biocompatible and biodegradable properties.

Drug-Loaded Multifunctional Nanoparticles Targeted to the Endocardial Layer of the Injured Heart Modulate Hypertrophic Signaling

Ischemic heart disease is the leading cause of death globally. Severe myocardial ischemia results in a massive loss of myocytes and acute myocardial infarction, the endocardium being the most vulnerable region. At present, current therapeutic lines only ameliorate modestly the quality of life of these patients. Here, an engineered nanocarrier is reported for targeted drug delivery into the endocardial layer of the left ventricle for cardiac repair. Biodegradable porous silicon (PSi) nanoparticles are functionalized with atrial natriuretic peptide (ANP), which is known to be expressed predominantly in the endocardium of the failing heart. The ANP-PSi nanoparticles exhibit improved colloidal stability and enhanced cellular interactions with cardiomyocytes and non-myocytes with minimal toxicity. After confirmation of good retention of the radioisotope 111-Indium in relevant physiological buffers over 4 h, in vivo single-photon emission computed tomography (SPECT/CT) imaging and autoradiography demonstrate increased accumulation of ANP-PSi nanoparticles in the ischemic heart, particularly in the endocardial layer of the left ventricle. Moreover, ANP-PSi nanoparticles loaded with a novel cardioprotective small molecule attenuate hypertrophic signaling in the endocardium, demonstrating cardioprotective potential. These results provide unique insights into the development of nanotherapies targeted to the injured region of the myocardium.

Biomimetic Engineering Using Cancer Cell Membranes for Designing Compartmentalized Nanoreactors with Organelle‐Like Functions

A new biomimetic nanoreactor design is presented based on cancer cell membrane material in combination with porous silicon nanoparticles. This cellular nanoreactor features a biocompartment enclosed by a cell membrane and readily integrated with cells and supplementing the cellular functions under oxidative stress. The study demonstrates the impact of the nanoreactors on improving cellular functions with a potential to serve as artificial organelles.

Quercetin-Based Modified Porous Silicon Nanoparticles for Enhanced Inhibition of Doxorubicin-Resistant Cancer Cells

One of the most challenging obstacles in nanoparticles surface modification is to achieve the concept that one ligand can accomplish multiple purposes. Upon such consideration, 3-aminopropoxy-linked quercetin (AmQu), a derivative of a natural flavonoid inspired by the structure of dopamine, is designed and subsequently used to modify the surface of thermally hydrocarbonized porous silicon (PSi) nanoparticles. This nanosystem inherits several advanced properties in a single carrier, including promoted anticancer efficiency, multiple drug resistance (MDR) reversing, stimuli-responsive drug release, drug release monitoring, and enhanced particle-cell interactions. The anticancer drug doxorubicin (DOX) is efficiently loaded into this nanosystem and released in a pH-dependent manner. AmQu also effectively quenches the fluorescence of the loaded DOX, thereby allowing the use of the nanosystem for monitoring the intracellular drug release. Furthermore, a synergistic effect with the presence of AmQu is observed in both normal MCF-7 and DOX-resistant MCF-7 breast cancer cells. Due to the similar structure as dopamine, AmQu may facilitate both the interaction and internalization of PSi into the cells. Overall, this PSi-based platform exhibits remarkable superiority in both multifunctionality and anticancer efficiency, making this nanovector a promising system for anti-MDR cancer treatment.