DNA/Calcium phosphate precipitates mixed with medium are stable and maintain high transfection efficiency

Anhydrous calcium phosphate crystals stabilize DNA for dry storage

The resilience of ancient DNA (aDNA) in bone gives rise to the preservation of synthetic DNA with bioinorganic materials such as calcium phosphate (CaP). Accelerated aging experiments at elevated temperature and humidity displayed a positive effect of co-precipitated, crystalline dicalcium phosphate on the stability of synthetic DNA in contrast to amorphous CaP. Quantitative PXRD in combination with SEM and EDX measurements revealed distinct CaP phase transformations of calcium phosphate dihydrate (brushite) to anhydrous dicalcium phosphate (monetite) influencing DNA stability.

High Glycolytic Activity Enhances Stem Cell Reprogramming of Fahd1-KO Mouse Embryonic Fibroblasts

Mitochondria play a key role in metabolic transitions involved in the reprogramming of somatic cells into induced pluripotent stem cells (iPSCs), but the underlying molecular mechanisms remain largely unexplored. To obtain new insight into the mechanisms of cellular reprogramming, we studied the role of FAH domain-containing protein 1 (FAHD1) in the reprogramming of murine embryonic fibroblasts (MEFs) into iPSCs and their subsequent differentiation into neuronal cells. MEFs from wild type (WT) and Fahd1-knock-out (KO) mice were reprogrammed into iPSCs and characterized for alterations in metabolic parameters and the expression of marker genes indicating mitochondrial biogenesis. Fahd1-KO MEFs showed a higher reprogramming efficiency accompanied by a significant increase in glycolytic activity as compared to WT. We also observed a strong increase of mitochondrial DNA copy number and expression of biogenesis marker genes in Fahd1-KO iPSCs relative to WT. Neuronal differentiation of iPSCs was accompanied by increased expression of mitochondrial biogenesis genes in both WT and Fahd1-KO neurons with higher expression in Fahd1-KO neurons. Together these observations establish a role of FAHD1 as a potential negative regulator of reprogramming and add additional insight into mechanisms by which FAHD1 modulates mitochondrial functions.

Close contacts at the interface: Experimental-computational synergies for solving complexity problems

The study of material science has been long devoted to the disentanglement of bulk structures which mainly entails finding the inner structure of materials. That structure is accountable for a major portion of materials’ properties. Yet, as our knowledge of these “backbones” enlarged so did the interest for the materials’ boundaries properties which means the properties at the frontier with the surrounding environment that is called interface. The interface is thus to be understood as the sum of the material’s surface plus the surrounding environment be it in solid, liquid or gas phase. The study of phenomena at this interface requires both the use of experimental and theoretical techniques and, above all, a wise combination of them in order to shed light over the most intimate details at atomic, molecular and mesostructure levels. Here, we report several cases to be used as proof of concept of the results achieved when studying interface phenomena by combining a myriad of experimental and theoretical tools to overcome the usual limitation regardind  atomic detail, size and time scales and systems of complex composition. Real world examples of the combined experimental-theoretical work and new tools, software, is offered to the readers.

Autophagy and mTORC1 regulate the stochastic phase of somatic cell reprogramming

We describe robust induction of autophagy during the reprogramming of mouse fibroblasts to induced pluripotent stem cells by four reprogramming factors (Sox2, Oct4, Klf4 and c-Myc), henceforth 4F. This process occurs independently of p53 activation, and is mediated by the synergistic downregulation of mechanistic target of rapamycin complex 1 (mTORC1) and the induction of autophagy-related genes. The 4F coordinately repress mTORC1, but bifurcate in their regulation of autophagy-related genes, with Klf4 and c-Myc inducing them but Sox2 and Oct4 inhibiting them. On one hand, inhibition of mTORC1 facilitates reprogramming by promoting cell reshaping (mitochondrial remodelling and cell size reduction). On the other hand, mTORC1 paradoxically impairs reprogramming by triggering autophagy. Autophagy does not participate in cell reshaping in reprogramming but instead degrades p62, whose accumulation in autophagy-deficient cells facilitates reprogramming. Our results thus reveal a complex signalling network involving mTORC1 inhibition and autophagy induction in the early phase of reprogramming, whose delicate balance ultimately determines reprogramming efficiency.

Characterization and evaluation of the efficacy of cationic complex mediated plasmid DNA delivery in human embryonic palatal mesenchyme cells

The purpose of this study was to develop and test a non-viral gene delivery system that can be employed to deliver genes of interest into a pre-osteoblastic cell line. Human embryonic palatal mesenchymal (HEPM 1486) cells were transfected with vector-plasmid DNA (pDNA) complexes. We explored calcium phosphate and polyethylenimine (PEI) as non-viral vectors and compared their respective in vitro transfection efficacies. Plasmid DNA encoding luciferase protein (LUC) was complexed with PEI (with differing N:P ratios) and calcium phosphate (with differing Ca:P ratios), using established protocols. The complexes prepared were then characterized for size and surface charge, using a Malvern Zetasizer Nano-ZS. The transfection efficiency and cytotoxicity of the prepared complexes were evaluated in HEPM cells. The PEI-pDNA complexes over the whole range of N:P ratios were found to be < 160 nm in size, while the calcium phosphate-pDNA complexes were relatively bigger. The PEI-pDNA complexes prepared at a N:P ratio of 10 were found to have maximum transfection efficiency at 4 h of treatment, with minimal cytotoxicity. The highest transfection efficiency obtained with calcium phosphate-pDNA complexes (Ca:P 200) was nearly 12-fold lower than that obtained with PEI-pDNA complexes (N:P 10). Following this, transgene expression in the HEPM cells treated with complexes prepared at a N:P ratio of 10 was further examined, using pDNA coding for enhanced green fluorescent protein (EGFP-N1) or therapeutically relevant platelet-derived growth factor B (PDGF-B). In conclusion, PEI was a more effective vector for delivering genes of interest to pre-osteoblasts than calcium phosphate. Copyright © 2014 John Wiley & Sons, Ltd.

Modeling biominerals formed by apatites and DNA

Different aspects of biominerals formed by apatite and DNA have been investigated using computer modeling tools. Firstly, the structure and stability of biominerals in which DNA molecules are embedded into hydroxyapatite and fluoroapatite nanopores have been examined by combining different molecular mechanics methods. After this, the early processes in the nucleation of hydroxyapatite at a DNA template have been investigated using molecular dynamics simulations. Results indicate that duplexes of DNA adopting a B double helix can be encapsulated inside nanopores of hydroxyapatite without undergoing significant distortions in the inter-strand hydrogen bonds and the intra-strand stacking. This ability of hydroxyapatite is practically independent of the DNA sequence, which has been attributed to the stabilizing role of the interactions between the calcium atoms of the mineral and the phosphate groups of the biomolecule. In contrast, the fluorine atoms of fluoroapatite induce pronounced structural distortions in the double helix when embedded in a pore of the same dimensions, resulting in the loss of its most relevant characteristics. On the other hand, molecular dynamics simulations have allowed us to observe the formation of calcium phosphate clusters at the surface of the B-DNA template. Electrostatic interactions between the phosphate groups of DNA and Ca(2+) have been found to essential for the formation of stable ion complexes, which were the starting point of calcium phosphate clusters by incorporating PO3(4) from the solution.

Calcium phosphate composite layers for surface-mediated gene transfer

In this review, the surface-mediated gene transfer system using calcium phosphate composite layers is described. Calcium phosphate ceramics are osteoconductive bioceramics used typically in orthopedic and dental applications. Additionally, calcium phosphate particles precipitated by a liquid-phase process have long been used as a safe and biocompatible transfection reagent in molecular biology. Recently, calcium phosphate composite layers immobilizing DNA were fabricated on the surfaces of base materials through a biomimetic process using supersaturated solutions. These composite layers possess useful characteristics of both osteoconductive bioceramics and transfection reagents; they thus provide a biocompatible surface to support cell adhesion and growth, and can stimulate the cell effectively via surface-mediated gene transfer. By modifying the fabrication conditions, physicochemical and biological properties of the composite layers can be varied. With such an approach, these composite layers can be designed to have improved affinity for cells and to exhibit increased gene transfer efficiency over that of conventional lipid transfection reagents. The composite layers with the increased gene transfer efficiency induced specific cell differentiation and tissue regeneration in vivo. These composite layers, given their good biocompatibility and the potential to control cell behavior on their surfaces, have great potential in tissue engineering applications.

Quantitative determination of the composition of multi-shell calcium phosphate-oligonucleotide nanoparticles and their application for the activation of dendritic cells

Biodegradable calcium phosphate nanoparticles as carriers for the immunoactive toll-like receptor ligands CpG and polyinosinic-polycytidylic acid for the activation of dendritic cells (DC) combined with the viral antigen hemagglutinin (HA) were prepared. A purification method based on ultracentrifugation and ultrasonication was developed to separate the nanoparticles from dissolved biomolecules. The number of biomolecules, i.e., oligonucleotides and peptide, incorporated into the nanoparticles was quantitatively determined by UV-spectroscopy, using fluorescent derivatives of the biomolecules. The immunostimulatory effects of purified calcium phosphate nanoparticles on DC were studied, i.e., cytokine production and activation of the cells in terms of the upregulation of surface molecules. Purified calcium phosphate nanoparticles, i.e., without dissolved biomolecules, are capable of inducing adaptive immunity by activation of DC. Immunostimulatory effects of purified calcium phosphate nanoparticles on DC were demonstrated by increased expression of co-stimulatory molecules and MHC II and by cytokine secretion. In addition, DC treated with purified functionalized calcium phosphate nanoparticles induced an antigen-specific T-cell response in vitro.

An efficient calcium phosphate nanoparticle-based nonviral vector for gene delivery

Background:

Smaller nanoparticles facilitate the delivery of DNA into cells through endocytosis and improve transfection efficiency. The aim of this study was to determine whether protamine sulfate-coated calcium phosphate (PS-CaP) could stabilize particle size and enhance transfection efficiency.

Methods:

pEGFP-C1 green fluorescence protein was employed as an indicator of transfection efficiency. Atomic force microscopy was used to evaluate the morphology and the size of the particles, and an MTT assay was introduced to detect cell viability and inhibition. The classical calcium phosphate method was used as the control.

Results:

Atomic force microscopy images showed that the PS-CaP were much smaller than classical calcium phosphate particles. In 293 FT, HEK 293, and NIH 3T3 cells, the transfection efficiency of PS-CaP was higher than for the classical calcium phosphate particles. The difference in efficiencies implies that the smaller nanoparticles may promote the delivery of DNA into cells through endocytosis and could improve transfection efficiency. In addition, PS-CaP could be used to transfect HEK 293 cells after one week of storage at 4°C with a lesser extent of efficiency loss compared with classical calcium phosphate, indicating that protamine sulfate may increase the stability of calcium phosphate nanoparticles. The cell viability inhibition assay indicated that both nanoparticles show similar low cell toxicity.

Conclusion:

PS-CaP can be used as a better nonviral transfection vector compared with classical calcium phosphate.

The intracellular localization and function of the ATP-sensitive K+ channel subunit Kir6.1

Our aim was to determine the subcellular localization and functional roles of the K(ATP) channel subunit Kir6.1 in intracellular membranes. Specifically, we focused on the potential role of Kir6.1 as a subunit of the mitochondrial ATP-sensitive K+ channel. Cell imaging showed that a major proportion of heterologously expressed Kir6.1-GFP and endogenously expressed Kir6.1 was distributed in the endoplasmic reticulum with little in the mitochondria or plasma membrane. We used pharmacological and molecular tools to investigate the functional significance of this distribution. The K(ATP) channel opener diazoxide increased reactive oxygen species production, and glibenclamide abolished this effect. However, in cells lacking Kir6.1 or expressing siRNA or dominant negative constructs of Kir6.1, the same effect was seen. Ca2+ handling was examined in the muscle cell line C2C12. Transfection of the dominant negative constructs of Kir6.1 significantly reduced the amplitude and rate of rise of [Ca2+]( c ) transients elicited by ATP. This study suggests that Kir6.1 is located in the endoplasmic reticulum and plays a role in modifying Ca2+ release from intracellular stores.

Mechanisms of disease pathogenesis in long QT syndrome type 5

KCNE1 associates with the pore-forming alpha-subunit KCNQ1 to generate the slow (I(Ks)) current in cardiac myocytes. Mutations in either KCNQ1 or KCNE1 can alter the biophysical properties of I(Ks) and mutations in KCNE1 underlie cases of long QT syndrome type 5 (LQT5). We previously investigated a mutation in KCNE1, T58P/L59P, which causes severe attenuation of I(Ks). However, how T58P/L59P acts to disrupt I(Ks) has not been determined. In this study, we investigate and compare the effects of T58P/L59P with three other LQT5 mutations (G52R, S74L, and R98W) on the biophysical properties of the current, trafficking of KCNQ1, and assembly of the I(Ks) channel. G52R and T58P/L59P produce currents that lack the kinetic behavior of I(Ks). In contrast, S74L and R98W both produce I(Ks)-like currents but with rightward shifted voltage dependence of activation. All of the LQT5 mutants express protein robustly, and T58P/L59P and R98W cause modest, but significant, defects in the trafficking of KCNQ1. Despite defects in trafficking, in the presence of KCNQ1, T58P/L59P and the other LQT5 mutants are present at the plasma membrane. Interestingly, in comparison to KCNE1 and the other LQT5 mutants, T58P/L59P associates only weakly with KCNQ1. In conclusion, we identify the disease mechanisms for each mutation and reveal that T58P/L59P causes disease through a novel mechanism that involves defective I(Ks) complex assembly.

The importance of particle size and DNA condensation salt for calcium phosphate nanoparticle transfection

Calcium phosphate has been used for over 30 years to deliver genetic material to mammalian cells. This vector has proven advantages over other transfection species such as viruses and dendrimers in terms of superior biocompatibility and reduced immune response. However, clinical application of calcium phosphate based transfection techniques is hampered by poor understanding of the key factors underlying its action. Despite widespread in vitro use, little attention has been given to the physico-chemical characteristics of the calcium phosphate particles mediating transfection. In this study parameters were optimised to produce calcium phosphate nanoparticles onto which plasmid DNA (pDNA) was adsorbed that were more effective than a commercial dendrimer vector in delivering pDNA to an osteoblastic cell line and compared favourably in a fibroblastic cell line without the need for special culture conditions such as cell cycle synchronization or glycerol shock treatment. Addition of the pDNA after nanoparticle synthesis allowed for characterisation of particle morphology, size, surface charge and composition. We found that the key parameters for effective calcium phosphate nanoparticle transfection were an optimal concentration of calcium and chloride ions and a nanosized non-agglomerated precipitate.

Importance of divalent cations in nanolipoplex gene delivery

Gene therapy is a promising therapeutic strategy to combat genetic or acquired diseases at their root cause rather than just treating symptoms. It is well recognised that there is an urgent need for non-toxic and efficient gene delivery vectors to fully exploit the current potential of gene therapy in molecular medicine. Cell-specific targeting of bioactive nucleotides is a prerequisite to attain the concentration of nucleic acids required for therapeutic efficacy in the target tissue. Many metal ions such as Mg2+, Mn2+, Ba2+ and, most importantly, Ca2+ have been demonstrated to have significant roles in gene delivery. These inorganic cations show low toxicity, good biocompatibility and promise for controlled delivery properties, thus presenting a new alternative to toxic and immunogenic carriers. Recently, inorganic nanoparticles alone, or in combination with a colloidal particulate system such as nanoliposome, an advanced approach to gene delivery, were found to exert a positive effect on gene transfer. In this report, the role of the divalent cations in nucleic acid delivery, particularly with respect to the potential improvement of transfection efficiency of nanolipoplexes, is reviewed.

Effective transfection of cells with multi-shell calcium phosphate-DNA nanoparticles

Coated calcium phosphate nanoparticles were prepared for cell transfection. A calcium phosphate nanoparticle served as core which was then coated with DNA for colloidal stabilisation. The efficiency of transfection could be considerably increased by adding another layer of calcium phosphate on the surface, thereby incorporating DNA into the particle and preventing its degradation within the cell by lysosomes. A subsequent outermost layer of DNA on the calcium phosphate gave a colloidal stabilisation. The efficiency of such multi-shell particles was significantly higher than that of simple DNA-coated calcium phosphate nanoparticles. The transfection efficiency of EGFP-encoding DNA was tested with different cell lines (T-HUVEC, HeLa, and LTK). The dispersions were stable and could be used for transfection after 2 weeks of storage at 4 degrees C without loss of efficiency.

pH-sensing nano-crystals of carbonate apatite: effects on intracellular delivery and release of DNA for efficient expression into mammalian cells

Two unique and fascinating properties of carbonate apatite which are well-known in hard tissue engineering, have been unveiled, for the first time, for the development of the simplest, but most efficient non-viral gene delivery device - ability of preventing the growth of crystals needed for high frequency DNA transfer across a plasma membrane and a fast dissolution rate for effective release of DNA during endosomal acidification, leading to a remarkably high transgene expression (5 to 100-fold) in mammalian cells compared to the widely used transfecting agents. Moreover, by modulating the crystal dissolution rate of carbonate apatite through incorporation of fluoride or strontium into it, transfection activity could be dramatically controlled, thus shedding light on a new barrier in the non-viral route, which was overlooked so far. Thus we have developed an innovative technology with significant insights, that would come as a promising tool for both basic research laboratories and clinical settings.

Role of calcium in gene delivery

The treatment of genetic diseases using therapeutic gene transfer is considered to be a significant development. This development has brought with it certain limitations, and the process of overcoming these barriers has seen a drastic change in gene delivery. Many metal ions such as Mg2+, Mn2+, Ba2+ and, most importantly, Ca2+ have been demonstrated to have significant roles in gene delivery. Recently, calcium phosphate alone, or in combination with viral and nonviral vectors, was found to exert a positive effect on gene transfer when incorporated in the colloidal particulate system, which is an advancing approach to gene delivery. This review elaborates on various successful methods of using calcium in gene delivery.

A calcium phosphate-based gene delivery system

Although nonviral vectors have lower transfection efficiency than viral vectors, the excellent safety profile of nonviral vectors is appealing for gene therapy. An efficient, simple nonviral vector gene delivery system has been designed that includes plasmid DNA-calcium phosphate precipitates (pDNA-CaP) and porous collagen spheres (Cultispherestrade mark). The hypothesis for this study was the pDNA-CaP would achieve efficient plasmid DNA transfection and the porous collagen spheres would provide a suitable delivery carrier system for three-dimensional (3D) administration. To test the hypothesis, plasmid DNA including the LacZ reporter gene encoding beta-galactosidase was precipitated with CaP to form particles of compacted LacZ-CaP and delivered directly or by Cultispherestrade mark to cells in vitro. The transfection efficiency was determined by beta-galactosidase gene expression. Results indicated that pLacZ-CaP promoted 25-84% of transfection efficiency in a broad cell line spectrum and in flexible experimental conditions. Maximum transfection efficiency was achieved by having mostly nano-sized partles (50-200 nm in diameter) of pDNA-CaP precipitates. Seeding density of 0.7-4 x 10(4) cells/cm2 provided sufficient transfection efficiency, and storage of pDNA-CaP at 4 degrees C was most efficient to preserve transfection efficacy for up to 3 days. The pDNA-CaP worked well in the presence of serum and serum-free conditions and was less cytotoxic than the liposomes. Cultispherestrade mark carrying plasmid LacZ-CaP was an effective 3D system for gene delivery. The technique described here is a simple and safe procedure to deliver genes, and may have application to regenerate bone and other tissues.

High-efficiency gene delivery for expression in mammalian cells by nanoprecipitates of Ca–Mg phosphate

Transfer of desirable genetic sequences into mammalian cells is an essential tool for analysis of gene structure, functions and regulation and industry-based production of therapeutically important proteins and pivotal for gene therapy and DNA vaccination strategies. Considering some severe limitations of viral systems including immunogenicity, carcinogenicity and so on, synthetic nonviral systems are highly desirable in the above applications. However, existing nonviral techniques are extremely inefficient compared to the viral ones. Therefore, we report here on the development of a highly efficient synthetic device for gene delivery and expression into mammalian cells, based on controllable growth of nanoapatite particles. Mg2+ incorporation into the apatite particles caused significant inhibition of particle growth, resulting in retention of nanosized particles which contributed remarkably to the cellular uptake of DNA and its subsequent expression (>10-fold) compared with classical calcium phosphate coprecipitation, one of the most widely used transfection methods.

Development of a calcium phosphate co-precipitate/poly(lactide-co-glycolide) DNA delivery system: release kinetics and cellular transfection studies

One of the most common non-viral methods for the introduction of foreign deoxyribonucleic acid (DNA) into cultured cells is calcium phosphate co-precipitate transfection. This technique involves the encapsulation of DNA within a calcium phosphate co-precipitate, particulate addition to in vitro cell culture, endocytosis of the co-precipitate, and exogenous DNA expression by the transfected cell. In this study, we fabricated a novel non-viral gene transfer system by adsorbing DNA, encapsulated in calcium phosphate (DNA/Ca-P) co-precipitates, to biodegradable two- and three-dimensional poly(lactide-co-glycolide) matrices (2D-DNA/Ca-P/PLAGA, 3D-DNA/Ca-P/PLAGA). Co-precipitate release studies demonstrated an initial burst release over the first 48 h. By day 7, approximately 96% of the initially adsorbed DNA/Ca-P co-precipitate had been released. This was followed by low levels of co-precipitate release for 42 days. Polymerase chain reaction was used to demonstrate the ability of the released DNA containing co-precipitates to transfect SaOS-2 cells cultured in vitro on the 3D-DNA/Ca-P/PLAGA matrix and maintenance of the structural integrity of the exogenous DNA. In summary, a promising system for the incorporation and controlled delivery of exogenous genes encapsulated within a calcium phosphate co-precipitate from biodegradable polymeric matrices has been developed and may have applicability to the delivery of therapeutic genes and the transfection of other cell types.