Controlled Tyrosine Kinase Inhibitor Delivery to Liver Cancer Cells by Gate-Capped Mesoporous Silica Nanoparticles

Hepatocellular carcinoma is the most common type of primary malignancy in the liver and one of the most common types of cancer worldwide. Its readily increasing mortality rate highlights the urgent need for the development of efficient therapeutic strategies. Tyrosine kinase inhibitors (TKIs) such as sorafenib and sunitinib are used as efficient angiogenesis inhibitors for this purpose. However, despite their pharmacological effects, their transfer into clinical practice is characterized by their poor aqueous solubility and accumulation in off-target tissues, resulting in unfavorable side effects. Here, we report a nanocomposite made of amine-functionalized mesoporous silica nanocomposites (MSNs) that are surface-coated with cerium oxide nanoparticles (CNPs) for the controlled delivery and release of TKIs. Amine-functionalized MSNs were prepared using a sol-gel method and loaded with TKIs. To trap drug molecules into the mesoporous structure, CNPs were covalently conjugated to the surface of MSNs. The synthesis and functionalization steps were controlled using different characterization methods, confirming the desired morphology and structure, the identity of functional groups on the surface, successful coating, and appropriate loading efficiency. Under physiological conditions, CNP-capped MSNs demonstrated a sustained drug release over time as a result of CNPs' gatekeeping effect on the payloads. Strong cellular interactions with different liver cancer cells and enhanced cellular uptake were also observed in vitro for the gate-capped MSNs. Internalization of nanocomposites induced cell death via the production of reactive oxygen species, and subsequent activation of apoptosis pathways. This study demonstrates that gate-capped MSNs are promising chemotherapeutic vehicles characterized by a sustained drug release profile and high cellular internalization.

Targeting Somatostatin Receptors By Functionalized Mesoporous Silica Nanoparticles - Are We Striking Home?

The concept of delivering nanoformulations to desired tissues by means of targeting membrane receptors of high local abundance by ligands anchored to the nanocarrier has gained a lot of attention over the last decade. Currently, there is no unanimous opinion on whether surface functionalization of nanocarriers by targeting ligands translates into any real benefit in terms of pharmacokinetics or treatment outcomes. Having examined the published nanocarriers designed to engage with somatostatin receptors, we realized that in the majority of cases targetability claims were not supported by solid evidence of targeting ligand-targeted receptor coupling, which is the very crux of a targetability concept. Here, we present an approach to characterize targetability of mesoporous silica-based nanocarriers functionalized with ligands of somatostatin receptors. The targetability proof in our case comes from a functional assay based on a genetically-encoded cAMP probe, which allows for real-time capture of receptor activation in living cells, triggered by targeting ligands on nanoparticles. We elaborate on the development and validation of the assay, highlighting the power of proper functional tests in the characterization pipeline of targeted nanoformulations.

Mesoporous silica materials: From physico-chemical properties to enhanced dissolution of poorly water-soluble drugs

New approaches in pharmaceutical chemistry have resulted in more complex drug molecules in the quest to achieve higher affinity to their targets. However, these 'highly active' drugs can also suffer from poor water solubility. Hence, poorly water soluble drugs became a major challenge in drug formulation, and this problem is increasing, as currently about 40 of the marketed drugs and 90% of drug candidates are classified as poorly water soluble. Various approaches exist to circumvent poor water solubility and poor dissolution rate in aqueous environment, however, each having disadvantages and certain limitations. Recently, mesoporous silica materials (MSMs) have been proposed to be used as matrices for enhancing the apparent solubility and dissolution rate of different drug molecules. MSMs are ideal candidates for this purpose, as silica is a "generally regarded as safe" (GRAS) material, is biodegradable, and can be readily surface-modified in order to optimize drug loading and subsequent release in the human body. The major advantage of mesoporous silica as drug delivery systems (DDSs) for poorly water soluble drugs lies in their pore size, pore morphology, and versatility in alteration of the surface groups, which can result in optimized interactions between a drug candidate and MSM carrier by modifying the pore surfaces. Furthermore, the drug of interest can be loaded into these pores in a preferably amorphous state, which can increase the drug dissolution properties dramatically. The highlights of this review include a critical discussion about the modification of the physico-chemical properties of MSMs and how these physico-chemical modifications influence the drug loading and the subsequent dissolution of poorly water soluble drugs. It aims to further promote the use of MSMs as alternative strategy to common methods like solubility enhancement by cyclodextrins, micronization, or microemulsion techniques. This review can provide guidance on how to tailor MSMs to achieve optimized drug loading and drug dissolution.

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.

Engineered nanomaterial uptake and tissue distribution: from cell to organism

Improved understanding of interactions between nanoparticles and biological systems is needed to develop safety standards and to design new generations of nanomaterials. This article reviews the molecular mechanisms of cellular uptake of engineered nanoparticles, their intracellular fate, and their distribution within an organism. We have reviewed the available literature on the uptake and disposition of engineered nanoparticles. Special emphasis was placed on the analysis of experimental systems and their limitations with respect to their usefulness to predict the in vivo situation. The available literature confirms the need to study particle characteristics in an environment that simulates the situation encountered in biological systems. Phenomena such as protein binding and opsonization are of prime importance since they may have a strong impact on cellular internalization, biodistribution, and immunogenicity of nanoparticles in vitro and in vivo. Extrapolation from in vitro results to the in vivo situation in the whole organism remains a challenge. However, improved understanding of physicochemical properties of engineered nanoparticles and their influence on biological systems facilitates the design of nanomaterials that are safe, well tolerated, and suitable for diagnostic or therapeutic use in humans.