Characterization of structure and mechanism of transfection-active peptide-DNA complexes

A Review of Brain-Targeted Nonviral Gene-Based Therapies for the Treatment of Alzheimer's Disease

Diseases of the central nervous system (CNS) are difficult to treat owing to the complexity of the brain and the presence of a natural blood-brain-barrier (BBB). Alzheimer's disease (AD) is one of the major progressive and currently incurable neurodegenerative disorders of the CNS, which accounts for 60-80% of cases of dementia. The pathophysiology of AD involves the accumulation of amyloid beta (Aβ) plaques and neurofibrillary tangles (NFTs) in the brain. Additionally, synaptic loss and imbalance of neuronal signaling molecules are characterized as important markers of AD. Existing treatments of AD help in the management of its symptoms and aim toward the maintenance of cognitive functions, behavior, and attenuation of gradual memory loss. Over the past decade, nonviral gene therapy has attracted increasing interest due to its various advantages over its viral counterparts. Moreover, advancements in nonviral gene technology have led to their increasing contributions in clinical trials. However, brain-targeted nonviral gene delivery vectors come across various extracellular and intracellular barriers, limiting their ability to transfer the therapeutic gene into the target cells. Chief barriers to nonviral gene therapy have been discussed briefly in this review. We have also highlighted the rapid advancement of several nonviral gene therapies for AD, which are broadly categorized into physical and chemical methods. These methods aim to modulate Aβ, beta-site amyloid precursor protein (APP) cleaving enzyme 1 (BACE1), apolipoprotein E, or neurotrophic factors' expression in the CNS. Overall, this review discusses challenges and recent advancements of nonviral gene therapy for AD.

Evaluating Endosomal Escape of Caspase-3-Containing Nanomaterials Using Split GFP

The ability for biologics to access intracellular targets hinges on the translocation of active, unmodified proteins. This is often achieved using nanoscale formulations, which enter cells through endocytosis. This uptake mechanism often limits the therapeutic potential of the biologics, as the propensity of the nanocarrier to escape the endosome becomes the key determinant. To appropriately evaluate and compare competing delivery systems of disparate compositions, it is therefore critical to assess endosomal escape efficiencies. Unfortunately, quantitative tools to assess endosomal escape are lacking, and standard approaches often lead to an erroneous interpretation of cytosolic localization. In this study we use a split-complementation endosomal escape (SEE) assay to evaluate levels of cytosolic caspase-3 following delivery by polymer nanogels and mesoporous silica nanoparticles. In particular, we use SEE as a means to enable the systematic investigation of the effect of polymer composition, polymer architecture (random vs block), hydrophobicity, and surface functionality. Although polymer structure had little influence on endosomal escape, nanogel functionalization with cationic and pH-sensitive peptides significantly enhanced endosomal escape levels and, further, significantly increased the amount of nanogel per endosome. This work serves as a guide for developing an optimal caspase-3 delivery system, as this caspase-3 variant can be easily substituted for a therapeutic caspase-3 cargo in any system that results in cytosolic accumulation and cargo release. In addition, these data provide a framework that can be readily applied to a wide variety of protein cargos to assess the independent contributions of both uptake and endosomal escape of a wide range of protein delivery vehicles.

Distinct effects of endosomal escape and inhibition of endosomal trafficking on gene delivery via electrotransfection

A recent theory suggests that endocytosis is involved in uptake and intracellular transport of electrotransfected plasmid DNA (pDNA). The goal of the current study was to understand if approaches used previously to improve endocytosis of gene delivery vectors could be applied to enhancing electrotransfection efficiency (eTE). Results from the study showed that photochemically induced endosomal escape, which could increase poly-L-lysine (PLL)-mediated gene delivery, decreased eTE. The decrease could not be blocked by treatment of cells with endonuclease inhibitors (aurintricarboxylic acid and zinc ion) or antioxidants (L-glutamine and ascorbic acid). Chemical treatment of cells with an endosomal trafficking inhibitor that blocks endosome progression, bafilomycin A1, resulted in a significant decrease in eTE. However, treatment of cells with lysosomotropic agents (chloroquine and ammonium chloride) had little effects on eTE. These data suggested that endosomes played important roles in protecting and intracellular trafficking of electrotransfected pDNA.

Enhancing nucleic acid delivery by photochemical internalization

Photochemical internalization (PCI) is a method for releasing macromolecules from endosomal and lysosomal compartments. The PCI approach uses a photosensitizer that localizes to endosomal and lysosomal compartments, and a light source with appropriate light spectra for excitation of the photosensitizer. Upon photosensitizer excitation, endosomal and lysosomal membranes are destroyed, due to the formation of reactive oxygen species, followed by release of the endocytosed material. PCI has been demonstrated to enhance and control (site- and time-specific) delivery of various macromolecules such as viruses, proteins, chemotherapeutics, nucleic acid, and so on. In this Review we present past and current studies of PCI-controlled delivery of natural and artificial nucleic acids, such as peptide nucleic acids, siRNA molecules, mRNA molecules and plasmids. We also discuss critical aspects to further the possibilities for successful gene targeting in space and time.

Light-induced mRNA transfection

mRNA-based transfection is an attractive strategy for manipulation of gene expression for gain-of-function studies and therapeutic applications. As a potential therapeutic regulator, mRNA transfection has mainly been hampered by poor delivery strategies, combined with lack of specific targeting to the intended tissue(s) or cells. In this chapter, we describe a protocol for light-induced mRNA transfection into human cancer cell lines with the benefit for time- and site-specific mRNA targeting. Light-induced mRNA transfection is achieved by delivering mRNA molecules into endosomal and lysosomal vesicles. Subsequently, a photosensitizer (PS) localized in the membranes of these vesicles is used to induce damage, resulting in release of mRNA molecules into the cytosol. The main benefit of the strategy proposed is the possibility for protein production from the delivered mRNA in a way that is controllable in a time- and site-specific manner.

Improved biolistic transfection of hair cells

Transient transfection of hair cells has proven challenging. Here we describe modifications to the Bio-Rad Helios Gene Gun that, along with an optimized protocol, improve transfection of bullfrog, chick, and mouse hair cells. The increased penetrating power afforded by our method allowed us to transfect mouse hair cells from the basal side, through the basilar membrane; this configuration protects hair bundles from damage during the procedure. We characterized the efficiency of transfection of mouse hair cells with fluorescently-tagged actin fusion protein using both the optimized procedure and a published procedure; while the efficiency of the two methods was similar, the morphology of transfected hair cells was improved with the new procedure. In addition, using the improved method, we were able to transfect hair cells in the bullfrog sacculus and chick cochlea for the first time. We used fluorescent-protein fusions of harmonin b (USH1C) and PMCA2 (ATP2B2; plasma-membrane Ca²⁺-ATPase isoform 2) to examine protein distribution in hair cells. While PMCA2-EGFP localization was similar to endogenous PMCA2 detected with antibodies, high levels of harmonin-EGFP were found at stereocilia tapers in bullfrog and chick, but not mouse; by contrast, harmonin-EGFP was concentrated in stereocilia tips in mouse hair cells.

Impact of magnetite nanoparticle incorporation on optical and electrical properties of nanocomposite LbL assemblies

Optical and electrical properties of polyelectrolyte/iron oxide nanocomposite planar films on silicon substrates were investigated for different amount of iron oxide nanoparticles incorporated in the films. The nanocomposite assemblies prepared by the layer-by-layer assembly technique were characterized by ellipsometry, atomic force microscopy, and secondary ion mass-spectrometry. Absorption spectra of the films reveal a shift of the optical absorption edge to higher energy when the number of deposited layers decreases. Capacitance-voltage and current-voltage measurements were applied to study the electrical properties of metal-oxide-semiconductor structures prepared by thermal evaporation of gold electrodes on nanocomposite films. The capacitance-voltage measurements show that the dielectric constant of the film increases with the number of deposited layers and the fixed charge and the trapped charge densities have a negative sign.

Photochemically enhanced cellular delivery of cell penetrating peptide-PNA conjugates

Recent studies have shown that endosomal release is a major rate-limiting step for cellular delivery via a variety of cationic cell penetrating peptides. Thus, methods and/or protocols for effective release of endosomally entrapped drugs are highly warranted. Photochemical internalization (PCI) has previously been proposed for this purpose. Here, we demonstrate an enhancement of up to two orders of magnitude of the antisense effects (cytosolic/nuclear) of peptide nucleic acid-peptide conjugates (Tat, Arg7, KLA) in HeLa cells by a PCI approach using the photosensitizer AlPc2a. These results emphasize the importance of endosomal release for cellular activity of this type of drug delivery and also raise hope that methods like PCI which have applications for in vivo use may also enhance the bioavailability and in vivo efficacy of these types of conjugates.

Ultrastructural analysis of DNA complexes during transfection and intracellular transport

We present a simple method based on transmission electron microscopy that allows investigation of the early steps of polyplex-mediated transfection without the use of labeled DNA. The ultrastructural analysis showed internalization of 0.2-1-micro m aggregates composed of 30-50-nm subunits. In addition, new details of the internalization process were revealed, suggesting an unspecific cell entry mechanism of large DNA aggregates.