Nanoparticle systems as tools to improve drug delivery and therapeutic efficacy

Technical tip: high-resolution isolation of nanoparticle-protein corona complexes from physiological fluids

Nanoparticles (NPs) in contact with biological fluids are generally coated with environmental proteins, forming a stronger layer of proteins around the NP surface called the hard corona. Protein corona complexes provide the biological identity of the NPs and their isolation and characterization are essential to understand their in vitro and in vivo behaviour. Here we present a one-step methodology to recover NPs from complex biological media in a stable non-aggregated form without affecting the structure or composition of the corona. This method allows NPs to be separated from complex fluids containing biological particulates and in a form suitable for use in further experiments. The study has been performed systematically comparing the new proposed methodology to standard approaches for a wide panel of NPs. NPs were first incubated in the biological fluid and successively recovered by sucrose gradient ultracentrifugation in order to separate the NPs and their protein corona from the loosely bound proteins. The isolated NP-protein complexes were characterized by size and protein composition through Dynamic Light Scattering, Nanoparticle Tracking Analysis, SDS-PAGE and LC-MS. The protocol described is versatile and can be applied to diverse nanomaterials and complex fluids. It is shown to have higher resolution in separating the multiple protein corona complexes from a biological environment with a much lower impact on their in situ structure compared to conventional centrifugal approaches.

Nanocarriers with tunable surface properties to unblock bottlenecks in systemic drug and gene delivery

Nanocarrier-mediated drug and gene delivery systems hold great promise for providing more refined delivery (especially in cancer treatments) to maximize therapeutic efficacy while minimizing unfavorable side effects. Despite their promise, the highly effective transport of therapeutics in vivo remains a challenge. Over the last 20years, there has been a large amount of research directed toward the development of a multitude of nanocarriers for drug and gene delivery, but only a very small part has progressed into clinical trials. This suggests that the properties of current nanocarriers are not yet ideal for effective drug and gene delivery in vivo. Nanocarrier-mediated drug and gene delivery is a multi-step process, and inefficient delivery at any stage would ultimately result in an unsuccessful delivery. Unfortunately, existing nanocarriers with fixed surface properties, such as a PEGylated, cationized and bioconjugated surface, are not versatile enough to overcome the extracellular and intracellular barriers which require different surface properties. Consequently, their delivery efficacy is not optimal, leading to doubts and debates on the value of nanocarrier-based product development. To resolve the "fixed surface dilemma", the switchable surfaces of nanocarriers, which can surmount both extracellular and intracellular barriers, open up the possibility of highly efficient delivery in vivo. Here, we review and highlight the recent developments in the design of nanocarrier delivery systems with tunable surface properties in response to microenvironment triggers. Strategies including zwitterionic nanocarriers, polymer brushes, layer-by-layer nanocarriers and cleavable conjugated nanocarriers are presented. These representative examples and their respective outcomes elaborate the benefits and efficiencies of these nanocarriers at the individual stages of drug and gene delivery.

Antibiofouling polymer interfaces: poly(ethylene glycol) and other promising candidates

This review highlights antibiofouling polymer interfaces with emphasis on the latest developments using poly(ethylene glycol) and the design new polymeric structures.

TAT conjugated cationic noble metal nanoparticles for gene delivery to epidermal stem cells

Most nonviral gene delivery systems are not efficient enough to manipulate the difficult-to-transfect cell types, including non-dividing, primary, neuronal or stem cells, due to a lack of an intrinsic capacity to enter the membrane and nucleus, release its DNA payload, and activate transcription. Noble metal nanoclusters have emerged as a fascinating area of widespread interest in nanomaterials. Herein, we report the synthesis of the TAT peptide conjugated cationic noble metal nanoparticles (metal NPs@PEI-TAT) as highly efficient carriers for gene delivery to stem cells. The metal NPs@PEI-TAT integrate the advantages of metal NPs and peptides: the presence of metal NPs can effectively decrease the cytotoxicity of cationic molecules, making it possible to apply them in biological systems, while the cell penetrating peptides are essential for enhanced cellular and nucleus entry to achieve high transfection efficiency. Our studies provide strong evidence that the metal NPs@PEI-TAT can be engineered as gene delivery agents for stem cells and subsequently enhance their directed differentiation for biomedical application.

The stability of citrate-capped silver nanoparticles in isotonic glucose solution for intravenous injection

Citrate-capped silver nanoparticles (AgNP) are widely used in industry, consumer products, and medical appliances. However, information on the environmental toxicity and human health is not comprehensive. Further, the physicochemical properties of AgNP make it difficult to test toxicity, as nanosized particles, due to their size, may increase by aggregation or agglomeration in some administration vehicles. In this study, stability of AgNP was investigated in different types of isotonic solutions, which is important for in vitro testing or toxicokinetic studies using intravenous (iv) injection. Size, morphology, zeta potential, and ion formation were investigated in isotonic solutions for the physicochemical characterization of AgNP. Aggregation and precipitation of AgNP were observed in phosphate-buffered saline or 0.9% NaCl, while AgNP were stable without aggregation or precipitation in 5% glucose in isotonic solution. The average size of AgNP in 5% glucose was approximately 10 nm at different temperatures of 10, 25, or 36°C and at varying concentrations from 10 to 1000 ppm. It is noteworthy that this is almost the same size distribution as that in the water-based suspension of AgNP supplied by the manufacturer. Zeta potential ranged from -40 to -60 mV, suggesting that the repulsion forces of AgNP are not disturbed to a sufficient degree to aggregate while osmolarity is in the isotonic range of 290 ± 10 mOsm/kg in 5% glucose solution. Data suggest that AgNP in a 5% glucose solution may be used in the toxicity test via iv injection without adverse consequences in blood.