Tailoring nanocarriers for intracellular protein delivery

Nanostraw-electroporation system for highly efficient intracellular delivery and transfection

Nondestructive introduction of genes, proteins, and small molecules into mammalian cells with high efficiency is a challenging, yet critical, process. Here we demonstrate a simple nanoelectroporation platform to achieve highly efficient molecular delivery and high transfection yields with excellent uniformity and cell viability. The system is built on alumina nanostraws extending from a track-etched membrane, forming an array of hollow nanowires connected to an underlying microfluidic channel. Cellular engulfment of the nanostraws provides an intimate contact, significantly reducing the necessary electroporation voltage and increasing homogeneity over a large area. Biomolecule delivery is achieved by diffusion through the nanostraws and enhanced by electrophoresis during pulsing. The system was demonstrated to offer excellent spatial, temporal, and dose control for delivery, as well as providing high-yield cotransfection and sequential transfection.

Layer-by-layer assembled polyaspartamide nanocapsules for pH-responsive protein delivery

Biodegradable shell cross-linked nanocapsules were prepared via layer-by-layer assembly of PADH (tertiary amine and hydrazide grafted polyaspartamide) and PACA (carboxyl and aldehyde grafted polyaspartamide) on silica spheres. Both of the polyaspartamide derivatives are water-soluble and biodegradable polymers with a protein-like structure, and obtained by aminolysis reaction of polysuccinimide. The latter is prepared by thermal polycondensation of aspartic acid. Dynamic light scattering and zeta potential measurements were used to analyze the layer-by-layer assembly process. Bovine serum albumin (BSA), as a model protein, was entrapped in the nanocapsules via electrostatic adsorption. Nanocapsules encapsulating BSA were prepared via layer-by-layer assembly on protein-entrapping amino-functionalized silica spheres, hydrazone cross-linking and silica core removal. The BSA release profiles exhibited a pH-dependent behavior. BSA release rate increased significantly as the ambient pH dropped from the physiological pH to acidic. Cell viability study suggests that the obtained polymeric nanocapsules have good biocompatibility. These kinds of novel composite nanocapsules may offer a promising delivery system for proteins.

Reversibly crosslinked nanocarriers for on-demand drug delivery in cancer treatment

Polymer micelles have proven to be one of the most versatile nanocarriers for anticancer drug delivery. However, the in vitro and in vivo stability of micelles remains a challenge due to the dynamic nature of these self-assembled systems, which leads to premature drug release and nonspecific biodistribution in vivo. Recently, reversibly crosslinked micelles have been developed to provide solutions to stabilize nanocarriers in blood circulation. Increased stability allows nanoparticles to accumulate at tumor sites efficiently via passive and/or active tumor targeting, while cleavage of the micelle crosslinkages, through internal or external stimuli, facilitates on-demand drug release. In this review, various crosslinking chemistries as well as the choices for reversible linkages in these nanocarriers will be introduced. Then, the development of reversibly crosslinked micelles for on-demand drug release in response to single or dual stimuli in the tumor microenvironment is discussed, for example, acidic pH, reducing microenvironment, enzymatic microenvironment, photoirradiation and the administration of competitive reagents postmicelle delivery.

Preparation of bioactive interferon alpha-loaded polysaccharide nanoparticles using a new approach of temperature-induced water phase/water-phase emulsion

The aim of this study was to develop a temperature-induced polyethylene glycol (PEG) water phase/polysaccharide water-phase emulsion approach for preparing interferon alpha-2b (IFNα-2b)-loaded polysaccharide nanoparticles. IFNα-2b was first added to a mixture of an aqueous solution of PEG and polysaccharide. The mixture solution was stirred in a magnetic stirrer at a rate of 2000 rpm for 45 seconds at 0°C ± 0.5°C. The solution was then prefrozen at different temperatures. The polysaccharide and IFNα-2b partitioned in the polysaccharide phase were preferentially separated out as the dispersed phase from the mixture solution during the prefreezing process. Then the prefrozen sample was freeze-dried to powder form. In order to remove the PEG, the powder was washed with dichloromethane. Once IFNα-2b was loaded into the polysaccharide nanoparticles, these nanoparticles could gain resistance to vapor–water and water–oil interfaces to protect IFNα-2b. The antiviral activity of the polysaccharide nanoparticles in vitro was highly preserved (above 97%), while the antiviral activity of IFNα-2b–loaded polysaccharide nanoparticles using the control water-in-oil-in-water method was only 71%. The antiviral activity of the IFNα-2b from blood samples was also determined on the basis of the activity to inhibit the cytopathic effects of the Sindbis virus on Follicular Lymphoma cells (FL). The antiviral activity in vivo was also highly preserved (above 97%). These polysaccharide nanoparticles could be processed to different formulations according to clinical requirements.

Magnetic response of mitochondria-targeted cancer cells with bacterial magnetic nanoparticles

We first demonstrate the effects of magnetic trapping of mitochondria using aptamer conjugated to bacterial magnetic nanoparticles that allowed targeting of the mitochondrial cytochrome c in the treatment of cancer cells. Our findings offer a new approach for targeted cell therapy, with the advantage of remote control over subcellular elements.

Multifunctional nanoparticle-loaded spherical and wormlike micelles formed by interfacial instabilities

Hybrid spherical and wormlike amphiphilic block copolymer micelles are formed through evaporation-induced interfacial instabilities of emulsion droplets, allowing the incorporation of pre-synthesized hydrophobic inorganic nanoparticles within the micelle cores, as well as co-encapsulation of different nanoparticles. This encapsulation behavior is largely insensitive to particle surface chemistry, shape, and size, thus providing a versatile route to fabricate multifunctional micelles.

A novel double-coating carrier produced by solid-in-oil and solid-in-water nanodispersion technology for delivery of genes and proteins into cells

A novel intracellular delivery method both for genes and proteins is one of the most coveted systems in the drug delivery field. In the present study, we developed a double-coating carrier loaded with gene and protein produced by solid-in-oil and solid-in-water nanodispersion technology. The double-coating carriers did not require electrostatic interactions during the preparation so were able to encapsulate plasmid DNA, ovalbumin (pI 4.5), horseradish peroxidase (pI 7.2), and cytochrome-c (pI 10.5) in a consistent manner. The carriers had practical encapsulation efficiencies and release profiles for genes and proteins. Furthermore, effective gene expression and cellular uptakes of both anionic and cationic proteins were achieved by modification of carriers with functional molecules. These findings indicate that the double-coating carrier has high potential for cellular delivery of various drugs and is a novel, superior method for both gene and protein delivery into cells.

Tissue engineering tools for modulation of the immune response

Tissue engineering scaffolds have emerged as a powerful tool within regenerative medicine. These materials are being designed to create environments that promote regeneration through a combination of: (i) scaffold architecture, (ii) the use of scaffolds as vehicles for transplanting progenitor cells, and/or (iii) localized delivery of inductive factors or genes encoding for these inductive factors. This review describes the techniques associated with each of these components. Additionally, the immune response is increasingly recognized as a factor influencing regeneration. The immune reaction to an implant begins with an acute response to the injury and innate recognition of foreign materials, with the subsequent chronic immune response involving specific recognition of antigens (e.g., transplanted cells) by the adaptive immune response, which can eventually lead to rejection of the implant. Thus, we also describe the impact of each component on the immune response, and strategies (e.g., material design, anti-inflammatory cytokine delivery, and immune cell recruitment/transplantation) to modulate, yet not eliminate, the local immune response in order to promote regeneration, which represents another important tool for regenerative medicine.

pH and reduction dual-bioresponsive polymersomes for efficient intracellular protein delivery

pH and reduction dual-bioresponsive nanosized polymersomes based on poly(ethylene glycol)-SS-poly(2-(diethyl amino)ethyl methacrylate) (PEG-SS-PDEA) diblock copolymers were developed for efficient encapsulation and triggered intracellular release of proteins. PEG-SS-PDEA copolymers with PDEA-block molecular weights ranging from 4.7, 6.8, to 9.2 kg/mol were synthesized in a controlled manner via reversible addition-fragmentation chain transfer (RAFT) polymerization of 2-(diethyl amino)ethyl methacrylate (DEAEMA) using PEG-SS-CPADN (CPADN = 4-cyanopentanoic acid dithionaphthalenoate; M(n) PEG = 1.9 kg/mol) as a macro-RAFT agent. These copolymers existed as unimers in water at mildly acidic pH (<7.2) conditions, but readily formed monodisperse nanosized polymersomes (54.5-66.8 nm) when adjusting solution pH to 7.4. These polymersomes were highly sensitive to intracellular pH and reductive environments, which resulted in fast dissociation and aggregation of polymersomes, respectively. Notably, both fluorescein isothiocyanate (FITC)-labeled bovine serum albumin (FITC-BSA) and cytochrome C (FITC-CC) proteins could facilely be encapsulated into polymersomes with excellent protein-loading efficiencies, likely as a result of electrostatic interactions between proteins and PDEA. The in vitro release studies showed that protein release was minimal (<20% in 8 h) at pH 7.4 and 37 °C. The release of proteins was significantly enhanced at pH 6.0 due to collapse of polymersomes. Notably, the fastest protein release was observed under intracellular-mimicking reductive environments (10 mM dithiothreitol, pH 7.4). MTT assays in RAW 264.7 and MCF-7 cells indicated that PEG-SS-PDEA (9.2 k) polymersomes had low cytotoxicity up to a polymer concentration of 300 μg/mL. Confocal laser scanning microscope (CLSM) observations revealed that FITC-CC-loaded PEG-SS-PDEA (9.2 k) polymersomes efficiently delivered and released proteins into MCF-7 cells following 6 h of incubation. Importantly, flow cytometry assays showed that CC-loaded PEG-SS-PDEA (9.2 k) polymersomes induced markedly enhanced apoptosis of MCF-7 cells as compared to free CC and CC-loaded PEG-PDEA (8.9 k) polymersomes (reduction-insensitive control). These dual-bioresponsive polymersomes have appeared to be highly promising for intracellular delivery of protein drugs.

Evaluation of a symmetry-based strategy for assembling protein complexes

We evaluate a strategy for assembling proteins into large cage-like structures, based on the symmetry associated with the native protein's quaternary structure. Using a trimeric protein, KDPG aldolase, as a building block, two fusion proteins were designed that could assemble together upon mixing. The fusion proteins, designated A-(+) and A-(-), comprise the aldolase domain, a short, flexible spacer sequence, and a sequence designed to form a heterodimeric antiparallel coiled-coil between A-(+) and A-(-). The flexible spacer is included to minimize constraints on the ability of the fusion proteins to assemble into larger structures. On incubating together, A-(+) and A-(-) assembled into a mixture of complexes that were analyzed by size exclusion chromatography coupled to multi-angle laser light scattering, analytical ultracentrifugation, transmission electron microscopy and atomic force microscopy. Our analysis indicates that, despite the inherent flexibility of the assembly strategy, the proteins assemble into a limited number of globular structures. Dimeric and tetrameric complexes of A-(+) and A-(-) predominate, with some evidence for the formation of larger assemblies; e.g. octameric A-(+): A-(-) complexes.