Substrate-mediated nucleic acid delivery from self-assembled monolayers

Supramolecular Nanosubstrate-Mediated Delivery for CRISPR/Cas9 Gene Disruption and Deletion

The clustered regularly interspaced short palindromic repeats (CRISPR)-associated protein 9 (CRISPR/Cas9) is an efficient and precise gene-editing technology that offers a versatile solution for establishing treatments directed at genetic diseases. Currently, CRISPR/Cas9 delivery into cells relies primarily on viral vectors, which suffer from limitations in packaging capacity and safety concerns. These issues with a nonviral delivery strategy are addressed, where Cas9•sgRNA ribonucleoprotein (RNP) complexes can be encapsulated into supramolecular nanoparticles (SMNP) to form RNP⊂SMNPs, which can then be delivered into targeted cells via supramolecular nanosubstrate-mediated delivery. Utilizing the U87 glioblastoma cell line as a model system, a variety of parameters for cellular-uptake of the RNP-laden nanoparticles are examined. Dose- and time-dependent CRISPR/Cas9-mediated gene disruption is further examined in a green fluorescent protein (GFP)-expressing U87 cell line (GFP-U87). The utility of an optimized SMNP formulation in co-delivering Cas9 protein and two sgRNAs that target deletion of exons 45-55 (708 kb) of the dystrophin gene is demonstrated. Mutations in this region lead to Duchenne muscular dystrophy, a severe genetic muscle wasting disease. Efficient delivery of these gene deletion cargoes is observed in a human cardiomyocyte cell line (AC16), induced pluripotent stem cells, and mesenchymal stem cells.

Polymeric Delivery of Therapeutic Nucleic Acids

The advent of genome editing has transformed the therapeutic landscape for several debilitating diseases, and the clinical outlook for gene therapeutics has never been more promising. The therapeutic potential of nucleic acids has been limited by a reliance on engineered viral vectors for delivery. Chemically defined polymers can remediate technological, regulatory, and clinical challenges associated with viral modes of gene delivery. Because of their scalability, versatility, and exquisite tunability, polymers are ideal biomaterial platforms for delivering nucleic acid payloads efficiently while minimizing immune response and cellular toxicity. While polymeric gene delivery has progressed significantly in the past four decades, clinical translation of polymeric vehicles faces several formidable challenges. The aim of our Account is to illustrate diverse concepts in designing polymeric vectors towards meeting therapeutic goals of in vivo and ex vivo gene therapy. Here, we highlight several classes of polymers employed in gene delivery and summarize the recent work on understanding the contributions of chemical and architectural design parameters. We touch upon characterization methods used to visualize and understand events transpiring at the interfaces between polymer, nucleic acids, and the physiological environment. We conclude that interdisciplinary approaches and methodologies motivated by fundamental questions are key to designing high-performing polymeric vehicles for gene therapy.

Surface-Mediated Intracellular Delivery by Physical Membrane Disruption

Effective and nondestructive intracellular delivery of exogenous molecules and other functional materials into living cells is of importance for diverse biological fundamental research and therapeutic applications, such as gene editing and cell-based therapies. However, for most exogenous molecules, the cell plasma membrane is effectively impermeable and thus remains the greatest barrier to intracellular delivery. In recent years, methods based on surface-mediated physical membrane disruption have attracted considerable attention. These methods exploit the physical properties of the surface to transiently increase the membrane permeability of cells come in contact thereto, thereby facilitating the efficient intracellular delivery of molecules regardless of molecule or target cell type. In this Review, we focus on recent progress, particularly over the past decade, on these surface-mediated membrane disruption-based delivery systems. According to the membrane disruption mechanism, three categories can be recognized: (i) mechanical penetration, (ii) electroporation, and (iii) photothermal poration. Each of these is discussed in turn and a brief perspective on future developments in this promising area is presented.

Mechanical Effect on Gene Transfection Based on Dielectric Elastomer Actuator

Gene transfection has been widely applied in genome function and gene therapy. Although many efforts have been focused on designing carrier materials and transfection methods, the influence of mechanical stimulation on gene transfection efficiency has rarely been studied. Herein, dielectric elastomer actuator (DEA)-based stimulation bioreactors are designed to generate tensile and contractile stress on cells simultaneously. With the example of the EGFP transfection, cells with high membrane tension in the stretching stimulation regions had lower transfection efficiency, while the transfection efficiency of cells in the compressing regions tended to increase. Besides, the duty cycle and loading frequency of the applied stress on cells were also important factors that affect gene transfection efficiency. Furthermore, the pathways of cell endocytosis with the effect of mechanical stimulation were explored on the mechanism for the change of EGFP transfection efficiency. This design of the DEA-based bioreactor, as a strategy to study gene transfection efficiency, could be helpful for developing efficient transfection methods.

The Application of Nanomaterials in Cell Autophagy

Autophagy is defined as separation and degradation of cytoplasmic components through autophagosomes, which plays an essential part in physiological and pathological events. Hence it is also essential for cellular homeostasis. Autophagy disorder may bring about the failure of stem cells to maintain the fundamental transformation and metabolism of cell components. However, for cancer cells, the disorder of autophagy is a feasible antitumor idea. Nanoparticles, referring to particles of the size range 1-100 nanometers, are appearing as a category of autophagy regulators. These nanoparticles may revolutionize and broaden the therapeutic strategies of many diseases, including neurodegenerative diseases, tumors, muscle disease, and so on. Researches of autophagy-induced nanomaterials mainly focus on silver particles, gold particles, silicon particles, and rare earth oxides. But in recent years, more and more materials have been found to regulate autophagy, such as nano-nucleic acid materials, nanofiber scaffolds, quantum dots, and so on. The review highlights that various kinds of nanoparticles have the power to regulate autophagy intensity in stem cells of interest and further control biological behaviors, which may become a reliable treatment choice for disease therapy.

Langmuir Analysis of the Binding Affinity and Kinetics for Surface Tethered Duplex DNA and a Ligand-Apoprotein Complex

In this work, the hybridization and dehybridization of ssDNA with 20 bases at gold coated sensor surfaces modified with complementary 20 bases capture probe ssDNA was investigated at 18 °C by quartz crystal microbalance measurements with dissipation monitoring (QCM-D). A sequence of 20 base pairs with a melting temperature of about 64 °C was chosen, since in many biosensor studies the target molecules are DNA or RNA oligomers of similar length. It turned out that at the applied experimental conditions the DNA hybridization was irreversible, and therefore the hybridization and dehybridization process could not be described by the Langmuir model of adsorption. Nevertheless, quantitative dehybridization could be achieved by rinsing the sensor surface thoroughly with pure water. When in contrast the hybridization of a target with only 10 bases complementary to the outermost 10 bases of the 20 bases capture probe was studied, binding and unbinding were reversible, and the hybridization/dehybridization process could be satisfactorily described by the Langmuir model. For the 10 base pair sequence, the melting temperature was about 36 °C. Apparently, for Langmuir behavior, it is important that the experiments are applied at a temperature sufficiently close to the melting temperature of the sequence under investigation to ensure that at least traces of the target molecules are unhybridized (i.e., there needs to be an equilibrium between hybridized and dehybridized target molecules). To validate the reliability of our experimental approach we also studied the reconstitution and disassembly of the flavoprotein dodecin at flavin-terminated DNA monolayers, as according to previous studies it is assumed that the apododecin-flavin system can be well described by the Langmuir model. As a result, this assumption could be verified. Using three different approaches, K_D values were obtained that differ not more than by a factor of 4.

Exploring Molecular-Biomembrane Interactions with Surface Plasmon Resonance and Dual Polarization Interferometry Technology: Expanding the Spotlight onto Biomembrane Structure

The molecular analysis of biomolecular-membrane interactions is central to understanding most cellular systems but has emerged as a complex technical challenge given the complexities of membrane structure and composition across all living cells. We present a review of the application of surface plasmon resonance and dual polarization interferometry-based biosensors to the study of biomembrane-based systems using both planar mono- or bilayers or liposomes. We first describe the optical principals and instrumentation of surface plasmon resonance, including both linear and extraordinary transmission modes and dual polarization interferometry. We then describe the wide range of model membrane systems that have been developed for deposition on the chips surfaces that include planar, polymer cushioned, tethered bilayers, and liposomes. This is followed by a description of the different chemical immobilization or physisorption techniques. The application of this broad range of engineered membrane surfaces to biomolecular-membrane interactions is then overviewed and how the information obtained using these techniques enhance our molecular understanding of membrane-mediated peptide and protein function. We first discuss experiments where SPR alone has been used to characterize membrane binding and describe how these studies yielded novel insight into the molecular events associated with membrane interactions and how they provided a significant impetus to more recent studies that focus on coincident membrane structure changes during binding of peptides and proteins. We then discuss the emerging limitations of not monitoring the effects on membrane structure and how SPR data can be combined with DPI to provide significant new information on how a membrane responds to the binding of peptides and proteins.

Nanostructured Lipid-based Films for Substrate Mediated Applications in Biotechnology

Amphiphilic in nature, lipids spontaneously self-assemble into a range of nanostructures in the presence of water. Among lipid self-assembled structures, liposomes and supported lipid bilayers have long held scientific interest for their main applications in drug delivery and plasma membrane models, respectively. In contrast, lipid-based multi-layered membranes on solid supports only recently begun drawing scientists' attention. New studies on lipid films show that the stacking of multiple bilayers on a solid support yields interestingly complex features to these systems. Namely, multiple layers exhibit cooperative structural and dynamic behavior. In addition, the materials enable compartmentalization, templating, and enhanced release of several molecules of interest. Importantly, supported lipid phases exhibit long-range periodic nano-scale order and orientation that is tunable in response to a changing environment. Herein, we summarize current and pertinent understanding of lipid-based film research focusing on how unique structural characteristics enable the emergence of new applications in biotechnology including label-free biosensors, macroscale drug delivery, and substrate-mediated gene delivery. Our very recent contributions to lipid-based films, focusing on the structural characterization at the meso, nano, and molecular-scale, using Small-Angle X-ray Scattering, Atomic Force Microscopy, Photothermal Induced Resonance, and Solid-State NMR will be also highlighted.

Integration of growth factor gene delivery with collagen-triggered wound repair cascades using collagen-mimetic peptides

Growth factors (GFs) play vital roles in wound repair. Many GF therapies have reached clinical trials, but success has been hindered by safety concerns and a lack of efficacy. Previously, we presented an approach to produce protein factors in wound beds through localized gene delivery mediated by biomimetic peptides. Modification of polyethylenimine (PEI) DNA polyplexes with collagen-mimetic peptides (CMPs) enabled tailoring of polyplex release/retention and improved gene transfer activity in a cell-responsive manner. In this work, CMP-mediated delivery from collagen was shown to improve expression of platelet-derived growth factor-BB (PDGF-BB) and promote a diverse range of cellular processes associated with wound healing, including proliferation, extracellular matrix production, and chemotaxis. Collagens were pre-exposed to physiologically-simulating conditions (complete media, 37°C) for days to weeks prior to cell seeding to simulate the environment within typical wound dressings. In cell proliferation studies, significant increases in cell counts were demonstrated in collagen gels containing CMP-modified polyplex versus unmodified polyplex, and these effects became most pronounced following prolonged preincubation periods of greater than a week. Collagen containing CMP-modified polyplexes also induced a twofold increase in gel contraction as well as enhanced directionality and migratory activity in response to cell-secreted PDGF-BB gradients. While these PDGF-BB-triggered behaviors were observed in collagens containing unmodified polyplexes, the responses withstood much longer preincubation periods in CMP-modified polyplex samples (10 days vs. <5 days). Furthermore, enhanced closure rates in an in vitro wound model suggested that CMP-based PDGF-BB delivery may have utility in actual wound repair and other regenerative medicine applications.

Increased cell survival of cells exposed to superparamagnetic iron oxide nanoparticles through biomaterial substrate-induced autophagy

The enhanced autophagy response by culturing cells on chitosan substrate is linked to a high cell survival rate under excessive NP endocytosis conditions.

MicroRNA delivery for regenerative medicine

MicroRNA (miRNA) directs post-transcriptional regulation of a network of genes by targeting mRNA. Although relatively recent in development, many miRNAs direct differentiation of various stem cells including induced pluripotent stem cells (iPSCs), a major player in regenerative medicine. An effective and safe delivery of miRNA holds the key to translating miRNA technologies. Both viral and nonviral delivery systems have seen success in miRNA delivery, and each approach possesses advantages and disadvantages. A number of studies have demonstrated success in augmenting osteogenesis, improving cardiogenesis, and reducing fibrosis among many other tissue engineering applications. A scaffold-based approach with the possibility of local and sustained delivery of miRNA is particularly attractive since the physical cues provided by the scaffold may synergize with the biochemical cues induced by miRNA therapy. Herein, we first briefly cover the application of miRNA to direct stem cell fate via replacement and inhibition therapies, followed by the discussion of the promising viral and nonviral delivery systems. Next we present the unique advantages of a scaffold-based delivery in achieving lineage-specific differentiation and tissue development.

Vascular gene transfer from metallic stent surfaces using adenoviral vectors tethered through hydrolysable cross-linkers

In-stent restenosis presents a major complication of stent-based revascularization procedures widely used to re-establish blood flow through critically narrowed segments of coronary and peripheral arteries. Endovascular stents capable of tunable release of genes with anti-restenotic activity may present an alternative strategy to presently used drug-eluting stents. In order to attain clinical translation, gene-eluting stents must exhibit predictable kinetics of stent-immobilized gene vector release and site-specific transduction of vasculature, while avoiding an excessive inflammatory response typically associated with the polymer coatings used for physical entrapment of the vector. This paper describes a detailed methodology for coatless tethering of adenoviral gene vectors to stents based on a reversible binding of the adenoviral particles to polyallylamine bisphosphonate (PABT)-modified stainless steel surface via hydrolysable cross-linkers (HC). A family of bifunctional (amine- and thiol-reactive) HC with an average t1/2 of the in-chain ester hydrolysis ranging between 5 and 50 days were used to link the vector with the stent. The vector immobilization procedure is typically carried out within 9 hr and consists of several steps: 1) incubation of the metal samples in an aqueous solution of PABT (4 hr); 2) deprotection of thiol groups installed in PABT with tris(2-carboxyethyl) phosphine (20 min); 3) expansion of thiol reactive capacity of the metal surface by reacting the samples with polyethyleneimine derivatized with pyridyldithio (PDT) groups (2 hr); 4) conversion of PDT groups to thiols with dithiothreitol (10 min); 5) modification of adenoviruses with HC (1 hr); 6) purification of modified adenoviral particles by size-exclusion column chromatography (15 min) and 7) immobilization of thiol-reactive adenoviral particles on the thiolated steel surface (1 hr). This technique has wide potential applicability beyond stents, by facilitating surface engineering of bioprosthetic devices to enhance their biocompatibility through the substrate-mediated gene delivery to the cells interfacing the implanted foreign material.

Molecular recognition enables nanosubstrate-mediated delivery of gene-encapsulated nanoparticles with high efficiency

Substrate-mediated gene delivery is a promising method due to its unique ability to preconcentrate exogenous genes onto designated substrates. However, many challenges remain to enable continuous and multiround delivery of the gene using the same substrates without depositing payloads and immobilizing cells in each round of delivery. Herein we introduce a gene delivery system, nanosubstrate-mediated delivery (NSMD) platform, based on two functional components with nanoscale features, including (1) DNA⊂SNPs, supramolecular nanoparticle (SNP) vectors for gene encapsulation, and (2) Ad-SiNWS, adamantane (Ad)-grafted silicon nanowire substrates. The multivalent molecular recognition between the Ad motifs on Ad-SiNWS and the β-cyclodextrin (CD) motifs on DNA⊂SNPs leads to dynamic assembly and local enrichment of DNA⊂SNPs from the surrounding medium onto Ad-SiNWS. Subsequently, once cells settled on the substrate, DNA⊂SNPs enriched on Ad-SiNWS were introduced through the cell membranes by intimate contact with individual nanowires on Ad-SiNWS, resulting in a highly efficient delivery of exogenous genes. Most importantly, sequential delivery of multiple batches of exogenous genes on the same batch cells settled on Ad-SiNWS was realized by sequential additions of the corresponding DNA⊂SNPs with equivalent efficiency. Moreover, using the NSMD platform in vivo, cells recruited on subcutaneously transplanted Ad-SiNWS were also efficiently transfected with exogenous genes loaded into SNPs, validating the in vivo feasibility of this system. We believe that this nanosubstrate-mediated delivery platform will provide a superior system for in vitro and in vivo gene delivery and can be further used for the encapsulation and delivery of other biomolecules.

Impact of plasma pretreatment and pore size on the sealing of ultra-low-k dielectrics by self-assembled monolayers

Self-assembled monolayers (SAMs) from an 11-cyanoundecyltrichlorosilane (CN-SAM) precursor were deposited on porous SiCOH low-k dielectrics with three different pore radii, namely, 1.7, 0.7, and lower than 0.5 nm. The low-k dielectrics were first pretreated with either O2 or He/H2 plasma in order to generate silanol groups on the hydrophobic pristine surface. Subsequently, the SAMs were chemically grafted to the silanol groups on the low-k surface. The SAMs distribution in the low-k films depends on the pore diameter: if the pore diameter is smaller than the size of the SAMs precursors, the SAM molecules are confined to the surface, while if the pore diameter exceeds the van der Waals radius of the SAMs precursor, the SAMs molecules reach deeper in the dielectric. In the latter case, when the pore sidewalls are made hydrophilic by the plasma treatment, the chemical grafting of the SAM precursors follows the profile of the generated silanol groups. The modification depth induced by the O2 plasma is governed by the diffusion of the oxygen radicals into the pores, which makes it the preferred choice for microporous materials. On the other hand, the vacuum ultraviolet (VUV) light plays a critical role, which makes it more suitable for hydrolyzing mesoporous materials. In addition to the density of the surface -OH groups, the nanoscale concave curvature associated with the pores also affects the molecular packing density and ordering with respect to the self-assembly behavior on flat surfaces. A simple model which correlates the low-k pore structure with the plasma hydrophilization mechanism and the SAMs distribution in the pores is presented.

Use of biotinylated chitosan for substrate-mediated gene delivery

To improve transfection efficiency of nonviral vectors, biotinylated chitosan was applied to complex with DNA in different N/P ratios. The morphologies and the sizes of formed nanoparticles were suitable for cell uptake. The biotinylation decreased the surface charges of nanoparticles and hence reduced the cytotoxicity. The loading capacities of chitosan were slightly decreased with the increase of biotinylation, but most of the DNA molecules were still complexed. Using different avidin-coated surfaces, the interaction between biotinylated nanoparticles to the substrate may be manipulated. The in vitro transfection results demonstrated that biotinylated nanoparticles may be bound to avidin coated surfaces, and the transfection efficiencies were thus increased. Through regulating the N/P ratio, biotinylation levels, and surface avidin, the gene delivery can be optimized. Compared to the nonmodified chitosan, biotinylated nanoparticles on biomaterial surfaces can increase their chances to contact adhered cells. This spatially controlled gene delivery improved the gene transfer efficiency of nonviral vectors and could be broadly applied to different biomaterial scaffolds for tissue engineering applications.

Efficient cell reprogramming using bioengineered surfaces

A novel method for cell reprogramming is been developed by immobilizing nucleic acid transfer vectors containing free amino groups, like lentiviral particles, onto pentafluorophenyl methacrylate (PFM)-modified surfaces obtained by PFM grafting affter Ar plasma treatment. This technique is able to reprogram murine somatic cells into pluripotent cells at high efficiencies. We call these modified surfaces cell reprogramming surfaces, or CRS.

Nanoparticle uptake and gene transfer efficiency for MSCs on chitosan and chitosan-hyaluronan substrates

Nanoparticles (NPs) are usually surface modified to increase endocytosis for applications in cellular imaging and gene delivery. The influence of cell culture substrates on endocytosis remains relatively unexplored. This study investigated the substrate-mediated effects on the uptake of NPs by mesenchymal stem cells (MSCs). Two types of NPs were employed, negatively charged paramagnetic iron oxide (Fe(3)O(4)) NPs (~5 nm) and bare plasmid DNA pTRE-Tight-DsRED2 (3.3 kb, ~5 nm), each of which were poorly endocytosed by the adipose-derived MSCs grown on tissue culture polystyrene (TCPS). When cells were cultured on chitosan or hyaluronan-modified chitosan (chitosan-HA) membranes, significant increases (>5-fold) in the intracellular uptake of Fe(3)O(4) NPs as well as transfectability of plasmid DNA were demonstrated. The enhancement in transgene expression was more pronounced than that using the transfection agent. The beneficial effects were not caused by elevated proliferation or a change in the differentiation state of interacting MSCs. On chitosan and chitosan-HA, cells moved fast and formed spheroids. The cytoskeletal arrangement associated with the up-regulated RhoA activity during spheroid formation may have accounted for the increased endocytosis. Using different inhibitors, the endocytosis pathways were further clarified. Both Fe(3)O(4) NPs and plasmid DNA were taken up primarily by clathrin-mediated endocytosis on chitosan (~50%). The caveolae-mediated endocytosis on chitosan-HA was more evident (~30-40%) than that on chitosan (<25%). For plasmid DNA but not Fe(3)O(4) NPs, macropinocytosis also occurred on both substrates. Chitosan and chitosan-HA as cell culture substrates may activate different endocytic pathways of MSCs to increase NP internalization or plasmid transfection. The substrate-mediated endocytosis described here may represent a new and potentially attractive approach to facilitate stem cell labeling or to improve gene delivery efficiency without altering cell viability and differentiation.