Surface-mediated gene transfer from nanocomposites of controlled texture

The enhancing effects of heparin on the biological activity of FGF-2 in heparin-FGF-2-calcium phosphate composite layers

Orthopedic and dental implants coated with fibroblast growth factor-2 (FGF-2)-calcium phosphate composite layers promote dermis formation, bone formation, and angiogenesis because of the biological activity of FGF-2. Enhancing the biological activity of FGF-2 in the composite layers is important for its wider application in orthopedics and dentistry. This study incorporated low-molecular-weight heparin (LMWH) into the FGF-2-calcium phosphate composite layers and clarified the enhancing effects of LMWH on the biological activity of FGF-2 in the composite layers in vitro. LMWH-FGF-2-calcium phosphate composite layers were successfully formed on zirconia in supersaturated calcium phosphate solutions. The composite layers comprised continuous and macroscopically homogeneous layers and particles smaller than 500 nm in size composed of amorphous calcium phosphate. The amounts of Ca and P deposited on zirconia remained almost unchanged with the addition of LMWH under the presence of FGF-2 in the supersaturated calcium phosphate solution. The LMWH in the supersaturated calcium phosphate solution increased the stability of FGF-2 in the solution and the amount of FGF-2 in the composite layers. The LMWH in the composite layers increased the mitogenic and endothelial tube-forming activities of FGF-2, and FGF-2 activity of inducing osteogenic differentiation gene expression pattern in the composite layers. Our results indicate that the enhanced biological activity of FGF-2 in the LMWH-FGF-2-calcium phosphate composite layers is attributed to an LMWH-mediated increase in the amount of FGF-2, which maintains its biological activity in the supersaturated calcium phosphate solution and the composite layers. The LMWH-FGF-2-calcium phosphate composite layer is a promising coating for orthopedic and dental implants. STATEMENT OF SIGNIFICANCE: Orthopedic and dental implants coated with fibroblast growth factor-2 (FGF-2)-calcium phosphate composite layers promote dermis formation, bone formation, and angiogenesis because of the biological activity of FGF-2. Enhancing the biological activity of FGF-2 in the layers is important for wider its application in orthopedics and dentistry. This study demonstrates the enhancing effects of low-molecular-weight heparin (LMWH) contained within LMWH-FGF-2-calcium phosphate composite layers on the biological activity of FGF-2 in vitro. Our results indicate that the enhanced biological activity of FGF-2 within the composite layers arises from an LMWH-mediated increase in the amount of FGF-2, which maintains its biological activity in the LMWH-FGF-2-calcium phosphate composite layers and supersaturated calcium phosphate solutions used for coating the composite layers.

Mineralized vectors for gene therapy

There is an intense interest in developing materials for safe and effective delivery of polynucleotides using non-viral vectors. Mineralization of organic templates has long been used to produce complex materials with outstanding biocompatibility. However, a lack of control over mineral growth has limited the applicability of mineralized materials to a few in vitro applications. With better control over mineral growth and surface functionalization, mineralized vectors have advanced significantly in recent years. Here, we review the recent progress in chemical synthesis, physicochemical properties, and applications of mineralized materials in gene therapy, focusing on structure-function relationships. We contrast the classical understanding of the mineralization mechanism with recent ideas of mineralization. A brief introduction to gene delivery is summarized, followed by a detailed survey of current mineralized vectors. The vectors derived from calcium phosphate are articulated and compared to other minerals with unique features. Advanced mineral vectors derived from templated mineralization and specialty coatings are critically analyzed. Mineral systems beyond the co-precipitation are explored as more complex multicomponent systems. Finally, we conclude with a perspective on the future of mineralized vectors by carefully demarcating the boundaries of our knowledge and highlighting ambiguous areas in mineralized vectors. STATEMENT OF SIGNIFICANCE: Therapy by gene-based medicines is increasingly utilized to cure diseases that are not alleviated by conventional drug therapy. Gene medicines, however, rely on macromolecular nucleic acids that are too large and too hydrophilic for cellular uptake. Without tailored materials, they are not functional for therapy. One emerging class of nucleic acid delivery system is mineral-based materials. The fact that they can undergo controlled dissolution with minimal footprint in biological systems are making them attractive for clinical use, where safety is utmost importance. In this submission, we will review the emerging synthesis technology and the range of new generation minerals for use in gene medicines.

A Self-Biomineralized Novel Adenovirus Vectored COVID-19 Vaccine for Boosting Immunization of Mice

SARS-CoV-2 has caused more than 3.8 million deaths worldwide, and several types of COVID-19 vaccines are urgently approved for use, including adenovirus vectored vaccines. However, the thermal instability and pre-existing immunity have limited its wide applications. To circumvent these obstacles, we constructed a self-biomineralized adenovirus vectored COVID-19 vaccine (Sad23L-nCoV-S-CaP) by generating a calcium phosphate mineral exterior (CaP) based on Sad23L vector carrying the full-length gene of SARS-CoV-2 spike protein (S) under physiological condition. This Sad23L-nCoV-S-CaP vaccine was examined for its characteristics of structure, thermostability, immunogenicity and avoiding the problem of preexisting immunity. In thermostability test, Sad23L-nCoV-S-CaP could be stored at 4 °C for over 45 days, 26 °C for more than 8 days and 37 °C for approximately 2 days. Furthermore, Sad23L-nCoV-S-CaP induced higher level of S-specific antibody and T cell responses, and was not affected by the pre-existing anti-Sad23L immunity, suggesting it could be used as boosting immunization on Sad23L-nCoV-S priming vaccination. The boosting with Sad23L-nCoV-S-CaP vaccine induced high titers of 10^5.01 anti-S1, 10^4.77 anti-S2 binding antibody, 10^3.04 pseudovirus neutralizing antibody (IC₅₀), and robust T-cell response of IFN-γ (1466.16 SFCs/10⁶ cells) to S peptides, respectively. In summary, the self-biomineralization of the COVID-19 vaccine Sad23L-nCoV-S-CaP improved vaccine efficacy, which could be used in prime-boost regimen for prevention of SARS-CoV-2 infection in humans.

Calcium phosphate engineered photosynthetic microalgae to combat hypoxic-tumor by in-situ modulating hypoxia and cascade radio-phototherapy

Rationale: Hypoxia is one of the crucial restrictions in cancer radiotherapy (RT), which leads to the hypoxia-associated radioresistance of tumor cells and may result in the sharp decline in therapeutic efficacy. Methods: Herein, living photosynthetic microalgae (Chlorella vulgaris, C. vulgaris), were used as oxygenators, for in situ oxygen generation to relieve tumor hypoxia. We engineered the surface of C. vulgaris (CV) cells with calcium phosphate (CaP) shell by biomineralization, to form a biomimetic system (CV@CaP) for efficient tumor delivery and in-situ active photosynthetic oxygenation reaction in tumor. Results: After intravenous injection into tumor-bearing mice, CV@CaP could remarkably alleviate tumor hypoxia by continuous oxygen generation, thereby achieving enhanced radiotherapeutic effect. Furthermore, a cascade phototherapy could be fulfilled by the chlorophyll released from photosynthetic microalgae combined thermal effects under 650 nm laser irradiation. The feasibility of CV@CaP-mediated combinational treatment was finally validated in an orthotropic breast cancer mouse model, revealing its prominent anti-tumor and anti-metastasis efficacy in hypoxic-tumor management. More importantly, the engineered photosynthetic microalgae exhibited excellent fluorescence and photoacoustic imaging properties, allowing the self-monitoring of tumor therapy and tumor microenvironment. Conclusions: Our studies of this photosynthetic microsystem open up a new dimension for solving the radioresistance issue of hypoxic tumors.

Biomimetic vs. Direct Approach to Deposit Hydroxyapatite on the Surface of Low Melting Point Polymers for Tissue Engineering

Polymers are widely used in many applications in the field of biomedical engineering. Among eclectic selections of polymers, those with low melting temperature (T_m < 200 °C), such as poly(methyl methacrylate), poly(lactic-co-glycolic acid), or polyethylene, are often used in bone, dental, maxillofacial, and corneal tissue engineering as substrates or scaffolds. These polymers, however, are bioinert, have a lack of reactive surface functional groups, and have poor wettability, affecting their ability to promote cellular functions and biointegration with the surrounding tissue. Improving the biointegration can be achieved by depositing hydroxyapatite (HAp) on the polymeric substrates. Conventional thermal spray and vapor phase coating, including the Food and Drug Administration (FDA)-approved plasma spray technique, is not suitable for application on the low T_m polymers due to the high processing temperature, reaching more than 1000 °C. Two non-thermal HAp coating approaches have been described in the literature, namely, the biomimetic deposition and direct nanoparticle immobilization techniques. In the current review, we elaborate on the unique features of each technique, followed by discussing the advantages and disadvantages of each technique to help readers decide on which method is more suitable for their intended applications. Finally, the future perspectives of the non-thermal HAp coating are given in the conclusion.

The CpG molecular structure controls the mineralization of calcium phosphate nanoparticles and their immunostimulation efficacy as vaccine adjuvants

The co-precipitation of calcium phosphate nanoparticles (CaPs) in the presence of nucleotide chains such as polynucleotides (i.e., plasmid DNA and siRNA) and oligonucleotides has been extensively used for pre-clinical gene or drug delivery and immunotherapy studies. However, the exact role of these molecules in mineralization and tuning the physicochemical characteristics of the synthesized CaPs is still not entirely clear. In this study, we evaluated the effects of three different CpG oligodeoxynucleotides (ODN) and two representative nucleic acids (siRNA and DNA), when used as templates for the formation of CaPs. We examined the influence of CpGs with naturally-occurring phosphodiester or modified phosphorothioate backbones on the homogeneous formation of CaPs from a modified simulated body fluid solution. The hydrodynamic size, size polydispersity, morphology and surface charge of the CaPs were used as the most critical checkpoints to unravel the involved mechanisms. Our results show that the characteristics of CaPs are highly dependent on the composition, backbone, sequence and concentrations of the CpGs. The CpG type and concentration control the size distribution of the mineralized CaPs and their immunostimulation performance as verified by the activation of dendritic cells and secretion of the pro-inflammatory interleukin-6 (IL-6) cytokine, type I interferon-α (IFN-α) and co-stimulatory CD80, CD86 and CD40 markers. This study paves the way for better design of more efficient CaPs loaded with different types of CpGs for immunostimulation applications as vaccine adjuvants.

Biodegradable calcium phosphate nanoparticles for cancer therapy

Calcium phosphate is the inorganic mineral of hard tissues such as bone and teeth. Due to their similarities to the natural bone, calcium phosphates are highly biocompatible and biodegradable materials that have found numerous applications in dental and orthopedic implants and bone tissue engineering. In the form of nanoparticles, calcium phosphate nanoparticles (CaP's) can also be used as effective delivery vehicles to transfer therapeutic agents such as nucleic acids, drugs, proteins and enzymes into tumor cells. In addition, facile preparation and functionalization of CaP's, together with their inherent properties such as pH-dependent solubility provide advantages in delivery and release of these bioactive agents using CaP's as nanocarriers. In this review, the challenges and achievements in the intracellular delivery of these agents to tumor cells are discussed. Also, the most important issues in the design and potential applications of CaP-based biominerals are addressed with more focus on their biodegradability in tumor microenvironment.

A Valid Bisphosphonate Modified Calcium Phosphate-Based Gene Delivery System: Increased Stability and Enhanced Transfection Efficiency In Vitro and In Vivo

Calcium phosphate (CaP) nanoparticles, as a promising vehicle for gene delivery, have been widely used owing to their biocompatibility, biodegradability and adsorptive capacity for nucleic acids. Unfortunately, their utility in vivo has been profoundly restricted due to numerous technical barriers such as the lack of tissue specificity and limited transfection efficiency, as well as uncontrollable aggregation over time. To address these issues, an effective conjugate folate-polyethylene glycol-pamidronate (shortened as FA-PEG-Pam) was designed and coated on the surface of CaP/NLS/pDNA (CaP/NDs), forming a versatile gene carrier FA-PEG-Pam/CaP/NDs. Inclusion of FA-PEG-Pam significantly reduced the size of CaP nanoparticles, thus inhibiting the aggregation of CaP nanoparticles. FA-PEG-Pam/CaP/NDs showed better cellular uptake than mPEG-Pam/CaP/NDs, which could be attributed to the high-affinity interactions between FA and highly expressed FR. Meanwhile, FA-PEG-Pam/CaP/NDs had low cytotoxicity and desired effect on inducing apoptosis (71.1%). Furthermore, FA-PEG-Pam/CaP/NDs showed admirable transfection efficiency (63.5%) due to the presence of NLS peptides. What’s more, in vivo studies revealed that the hybrid nanoparticles had supreme antitumor activity (IR% = 58.7%) among the whole preparations. Altogether, FA-PEG-Pam/CaP/NDs was expected to be a hopeful strategy for gene delivery.

Plasmid DNA Delivery: Nanotopography Matters

Plasmid DNA molecules with unique loop structures have widespread bioapplications, in many cases relying heavily on delivery vehicles to introduce them into cells and achieve their functions. Herein, we demonstrate that control over delicate nanotopography of silica nanoparticles as plasmid DNA vectors has significant impact on the transfection efficacy. For silica nanoparticles with rambutan-, raspberry-, and flower-like morphologies composed of spike-, hemisphere-, and bowl-type subunit nanotopographies, respectively, the rambutan-like nanoparticles with spiky surfaces demonstrate the highest plasmid DNA binding capability and transfection efficacy of 88%, higher than those reported for silica-based nanovectors. Moreover, it is shown that the surface spikes of rambutan nanoparticles provide a continuous open space to bind DNA chains via multivalent interactions and protect the gene molecules sheltered in the spiky layer against nuclease degradation, exhibiting no significant transfection decay. This unique protection feature is in great contrast to a commercial transfection agent with similar transfection performance but poor protection capability against enzymatic cleavage. Our study provides new understandings in the rational design of nonviral vectors for efficient gene delivery.

Functionalization of microparticles with mineral coatings enhances non-viral transfection of primary human cells

Gene delivery to primary human cells is a technology of critical interest to both life science research and therapeutic applications. However, poor efficiencies in gene transfer and undesirable safety profiles remain key limitations in advancing this technology. Here, we describe a materials-based approach whereby application of a bioresorbable mineral coating improves microparticle-based transfection of plasmid DNA lipoplexes in several primary human cell types. In the presence of these mineral-coated microparticles (MCMs), we observed up to 4-fold increases in transfection efficiency with simultaneous reductions in cytotoxicity. We identified mechanisms by which MCMs improve transfection, as well as coating compositions that improve transfection in three-dimensional cell constructs. The approach afforded efficient transfection in primary human fibroblasts as well as mesenchymal and embryonic stem cells for both two- and three-dimensional transfection strategies. This MCM-based transfection is an advancement in gene delivery technology, as it represents a non-viral approach that enables highly efficient, localized transfection and allows for transfection of three-dimensional cell constructs.

Biomimetic Mineralization of Biomaterials Using Simulated Body Fluids for Bone Tissue Engineering and Regenerative Medicine<sup/>

Development of synthetic biomaterials imbued with inorganic and organic characteristics of natural bone that are capable of promoting effective bone tissue regeneration is an ongoing goal of regenerative medicine. Calcium phosphate (CaP) has been predominantly utilized to mimic the inorganic components of bone, such as calcium hydroxyapatite, due to its intrinsic bioactivity and osteoconductivity. CaP-based materials can be further engineered to promote osteoinductivity through the incorporation of osteogenic biomolecules. In this study, we briefly describe the microstructure and the process of natural bone mineralization and introduce various methods for coating CaP onto biomaterial surfaces. In particular, we summarize the advantages and current progress of biomimetic surface-mineralizing processes using simulated body fluids for coating bone-like carbonated apatite onto various material surfaces such as metals, ceramics, and polymers. The osteoinductive effects of integrating biomolecules such as proteins, growth factors, and genes into the mineral coatings are also discussed.

Calcium phosphate nanoparticles prepared from infusion fluids for stem cell transfection: process optimization and cytotoxicity analysis

The preparation of calcium phosphate nanoparticles from infusion fluids for gene delivery to stem cells and CHO-K1 cells is reported.

Enhanced cryopreservation of MSCs in microfluidic bioreactor by regulated shear flow

Cell-matrix systems can be stored for longer period of time by means of cryopreservation. Cell-matrix and cell-cell interaction has been found to be critical in a number of basic biological processes. Tissue structure maintenance, cell secretary activity, cellular migration, and cell-cell communication all exist because of the presence of cell interactions. This complex and co-ordinated interaction between cellular constituents, extracellular matrix and adjacent cells has been identified as a significant contributor in the overall co-ordination of tissue. The prime objective of this investigation is to evaluate the effects of shear-stress and cell-substrate interaction in successful recovery of adherent human mesenchymal-stem-cells (hMSCs). A customized microfluidic bioreactor has been used for the purpose. We have measured the changes in focal-point-adhesion (FPAs) by changing induced shear stress inside the bioreactor. The findings indicate that with increase in shear stress, FPAs increases between substrate and MSCs. Further, experimental results show that increased FPAs (4e-3 μbar) enhances the cellular survivability of adherent MSCs. Probably, for the first time involvement of focal point interaction in the outcome of cryopreservation of MSCs has been clarified, and it proved a potentially new approach for modification of cryopreservation protocol by up-regulating focal point of cells to improve its clinical application.

Communication between nitric oxide synthase and positively-charged surface and bone formation promotion

Despite the effects on physiology of bone marrow mesenchymal stem cells (BMSCs) and bone tissue, biological signal communication between bone implants and them is seldom employed as a guidance to create an osteo-inductive interface. Herein, the positively-charged surface is constructed on bone implant from the perspective of mediation of nitric oxide synthase (NOS) expression to signal BMSCs osteo-differentiation. In vitro and in vivo results indicate that the proper surface potential on the positively-charged surface affects NOS to express a high level of inducible nitric oxide synthase (iNOS) in three NOS isoforms of the contacted BMSCs, upregulates their osteogenetic expression, and ultimately foster new bone growth. However, an excessively high surface potential produces substantial immunomodulatory effects thereby offsetting the aforementioned advantages. This study demonstrates that fine-tuning of the positively-charged surface and proper utilization of the communication between NOS and bone implants promote bone formation.

Mesenchymal Stem Cells on Plasma-Deposited Acrylic Acid Coatings: An In Vitro Investigation to Improve Biomaterial Performance in Bone Reconstruction

In this in vitro investigation of a heterogeneous range of bio-functional and modulatory performances of mesenchymal stem cells (MSCs) grown on two plasma-deposited acrylic acid (pdAA) coatings, which differed in chemical characteristics, a view of their potential utility as hybrid scaffolds for bone tissue engineering was obtained. The in vitro behavior of MSCs was compared to that of MG-63 cells, an osteoblast-like cell line that is commonly used to test biocompatibility of materials intended for bone-tissue interface. The coatings exerted a greater stimulus on MSCs and on MG-63 cells in comparison with control cultures. Both studied coatings exhibited satisfactory compatibility and modulatory effects on MSCs, thus they may be suitable for use in 2D or 3D scaffolds for bone tissue reconstruction.

Vaccine Engineering with Dual-Functional Mineral Shell: A Promising Strategy to Overcome Preexisting Immunity

Dual-functional biomineral-vaccine core-shell nanohybrids are obtained using recombinant adenovirus serotype 5 (rAd5) as templates, which efficiently masks the neutralizing epitope of vaccines and preserve their original immunogenicity. The versatile vaccine hybrid can evade the preexisting anti-Ad5 immunity, leading to boosted multifunctional antigen-specific cytokine-secreting T cell responses and presenting promising applications of vaccine-material hybrid for the rational design of vaccines.

Live Imaging of Cellular Internalization of Single Colloidal Particle by Combined Label-Free and Fluorescence Total Internal Reflection Microscopy

In this work we utilize the combination of label-free total internal reflection microscopy and total internal reflectance fluorescence (TIRM/TIRF) microscopy to achieve a simultaneous, live imaging of single, label-free colloidal particle endocytosis by individual cells. The TIRM arm of the microscope enables label free imaging of the colloid and cell membrane features, while the TIRF arm images the dynamics of fluorescent-labeled clathrin (protein involved in endocytosis via clathrin pathway), expressed in transfected 3T3 fibroblasts cells. Using a model polymeric colloid and cells with a fluorescently tagged clathrin endocytosis pathway, we demonstrate that wide field TIRM/TIRF coimaging enables live visualization of the process of colloidal particle interaction with the labeled cell structure, which is valuable for discerning the membrane events and route of colloid internalization by the cell. We further show that 500 nm in diameter model polystyrene colloid associates with clathrin, prior to and during its cellular internalization. This association is not apparent with larger, 1 μm in diameter colloids, indicating an upper particle size limit for clathrin-mediated endocytosis.

Multilayered thin films from poly(amido amine)s and DNA

Dip-coated multilayered thin films of poly(amido amine)s (PAAs) and DNA have been developed to provide surfaces with cell-transfecting capabilities. Three types of PAAs, differing in side chain functional groups, were synthesized and characterized for their properties in forming multilayered structures with ultrasonicated calf thymus DNA (CTDNA) as model DNA. All three polymers display a multilayer build-up in linear profiles as demonstrated by UV spectroscopy. More highly charged side chains were found to provide the lowest deposition of DNA. Surface profiles of the obtained films were investigated by atomic force microscopy (AFM) and static water contact angle measurements to reveal complete surface coverage after at least four layer pair depositions, where alternating patterns of surface profiles were observed depending on whether the cationic polymer or the anionic DNA layer was on top. The stability of the formed surfaces was investigated in vitro under physiological and reductive conditions. Owing to the presence of disulfide bonds in the PAA main chain, the films were readily degraded in the presence of 1mM of DTT in vitro. Under non-reductive physiological conditions, two of the thicker films underwent thermodynamic rearrangement, which resulted in release of approximately half of the incorporated material within 1h, which was caused by the physiological salt concentration. Further, this unpacking phenomenon proved useful in transfecting COS-7 cells seeded on top of these multilayers containing functional plasmid DNA encoding for green fluorescence protein (GFP). Two out of the three different multilayers facilitated good COS-7 cell attachment, proliferation, and transfection in vitro within 2d ays of culture. Fluorescence staining further revealed the presence of DNA-containing released film material among cultured cells. The present work demonstrates the possibility of coating surfaces with thin films that are conveniently adjustable in thickness and amount of active agent to provide cell-transfecting functionality. In this manner transfection can be achieved by simply culturing cells on a multilayer-coated surface in their optimal culture condition (in the presence of serum) and without the need of removing the transfection agent to avoid cytotoxicity.

Area-specific cell stimulation via surface-mediated gene transfer using apatite-based composite layers

Surface-mediated gene transfer systems using biocompatible calcium phosphate (CaP)-based composite layers have attracted attention as a tool for controlling cell behaviors. In the present study we aimed to demonstrate the potential of CaP-based composite layers to mediate area-specific dual gene transfer and to stimulate cells on an area-by-area basis in the same well. For this purpose we prepared two pairs of DNA–fibronectin–apatite composite (DF-Ap) layers using a pair of reporter genes and pair of differentiation factor genes. The results of the area-specific dual gene transfer successfully demonstrated that the cells cultured on a pair of DF-Ap layers that were adjacently placed in the same well showed specific gene expression patterns depending on the gene that was immobilized in theunderlying layer. Moreover, preliminary real-time PCR results indicated that multipotential C3H10T1/2 cells may have a potential to change into different types of cells depending on the differentiation factor gene that was immobilized in the underlying layer, even in the same well. Because DF-Ap layers have a potential to mediate area-specific cell stimulation on their surfaces, they could be useful in tissue engineering applications.

Correlation of the composition of biominerals with their ability of stimulating intracellular DNA sensors and inflammatory cytokines

Biominerals (or microcalcification) deposited in soft tissues are associated with a number of pathogeneses and cancer progressions. Biominerals have also shown promise for DNA delivery and tissue engineering. Biominerals themselves may stimulate NALP3 inflammasomes, and DNA delivered by biominerals can potentially engage with intracellular DNA sensors, resulting in unwanted inflammatory responses. In this study, a library of biominerals doped with or without DNA is formed through surface-induced biomineralization. It is demonstrated that empty biominerals stimulate NALP3 inflammasomes and induce the production of IL-1β. They are also able to activate mouse embryonic fibroblasts (MEFs) and induce inflammatory cytokines, i.e. IL-6. DNA delivered by biominerals escapes the detection of TLR9, but activates DAI and inflammasomes. Furthermore, it is shown that the level of both IL-1β and IL-6 is correlated with the composition of biominerals, in particular the ratio of Mg(Sr) to Ca, and the pH sensitivity of biominerals. These results provide insights into the design of safe and effective DNA delivery systems and biocompatible implants as well as the understanding of the pathogeneses of biominerals deposited in soft tissues.

Cartilage oligomeric matrix protein gene multilayers inhibit osteogenic differentiation and promote chondrogenic differentiation of mesenchymal stem cells

There are still many challenges to acquire the optimal integration of biomedical materials with the surrounding tissues. Gene coatings on the surface of biomaterials may offer an effective approach to solve the problem. In order to investigate the gene multilayers mediated differentiation of mesenchymal stem cells (MSCs), gene functionalized films of hyaluronic acid (HA) and lipid-DNA complex (LDc) encoding cartilage oligomeric matrix protein (COMP) were constructed in this study via the layer-by-layer self-assembly technique. Characterizations of the HA/DNA multilayered films indicated the successful build-up process. Cells could be directly transfected by gene films and a higher expression could be obtained with the increasing bilayer number. The multilayered films were stable for a long period and DNA could be easily released in an enzymatic condition. Real-time polymerase chain reaction (RT-PCR) assay presented significantly higher (p < 0.01) COMP expression of MSCs cultured with HA/COMP multilayered films. Compared with control groups, the osteogenic gene expression levels of MSCs with HA/COMP multilayered films were down-regulated while the chondrogenic gene expression levels were up-regulated. Similarly, the alkaline phosphatase (ALP) staining and Alizarin red S staining of MSCs with HA/COMP films were weakened while the alcian blue staining was enhanced. These results demonstrated that HA/COMP multilayered films could inhibit osteogenic differentiation and promote chondrogenic differentiation of MSCs, which might provide new insight for physiological ligament-bone healing.

Coprecipitation of DNA-lipid complexes with apatite and comparison with superficial adsorption for gene transfer applications

Apatite can mediate gene transfer into cells by serving as a safe and biocompatible immobilization matrix for DNA and transfection reagents. Recently, an apatite layer that immobilized DNA-lipid complexes was prepared by a coprecipitation process in a supersaturated calcium phosphate solution. This composite layer (DNA-lipid-apatite layer) showed a higher gene transfer capability than an apatite layer with superficially adsorbed DNA-lipid complexes (DNA-lipid-adsorbed apatite layer). In this study, the DNA-lipid-apatite layer and the DNA-lipid-adsorbed apatite layer were compared for their physicochemical properties and gene transfer capabilities. The higher gene transfer capability of the DNA-lipid-apatite layer compared with that of the DNA-lipid-adsorbed apatite layer was reconfirmed by a luciferase assay using epithelial-like CHO-K1 cells. Physicochemical structure analyses showed that the DNA-lipid-apatite layer possessed a larger capacity for DNA-lipid complexes than the DNA-lipid-adsorbed apatite layer. The DNA-lipid-apatite layer released DNA-lipid complexes in a slow and sustained manner, whereas the DNA-lipid-adsorbed apatite layer released them in short bursts. Consequently, the release of DNA-lipid complexes from the DNA-lipid-apatite layer was larger in amount and longer in duration than release from the DNA-lipid-adsorbed apatite layer. This difference in release profiles may be responsible for the higher gene transfer capability of the DNA-lipid-apatite layer compared with that of the DNA-lipid-adsorbed apatite layer. The coprecipitation process and the resulting DNA-lipid-apatite layer have many applications in tissue engineering.

Cooperative and competitive adsorption of amino acids with Ca²⁺ on rutile (α-TiO₂)

The interactions of biomolecules such as amino acids with mineral surfaces in the near-surface environment are an important part of the short and long-term carbon cycles. Amino acid-mineral surface interactions also play an important role in biomineralization, biomedicine, and in assembling the building blocks of life in the prebiotic era. Although the pH effects during adsorption of amino acids onto mineral surfaces have been studied, little is known about the effects of environmentally important divalent cations. In this study, we investigated the adsorption of the oppositely charged amino acids glutamate and lysine with and without the addition of divalent calcium. Without calcium, glutamate shows a maximum in adsorption at a pH of ∼4 and lysine shows a maximum in adsorption at a pH of ∼9.4. In comparison, with calcium present, glutamate showed maxima in adsorption at both low and high pH, whereas lysine showed no adsorption at all. These dramatic effects can be described as cooperative adsorption between glutamate and Ca(2+) and as competitive adsorption between lysine and Ca(2+). The origin of these effects can be attributed to electrostatic phenomena. Adsorption of Ca(2+) at high pH makes the rutile surface more positive, which attracts glutamate and repels lysine. Our results indicate that the interactions of biomolecules with mineral surfaces in the environment will be strongly affected by the major dissolved species in natural waters.

Peroxisome proliferator activated receptor gamma loaded dental implant improves osteogenesis of rat mandible

Peroxisome proliferator activated receptor gamma (PPARγ) has been known for their anti-inflammatory effects. But the application of this molecule in implant-induced inflammation has not been clearly studied yet. Here, we determined in vivo anti-inflammatory and osteogenic effects of PPARγ coated dental implant in the rat mandible. We used chitosan gold nanoparticles (Ch-GNPs) as a non viral vector to carry PPARγ plasmid DNA. Ch-GNPs were conjugated with PPARγ plasmid DNA through a coacervation process. Conjugation was cast over titanium (Ti) implants (4.5 × 0.8 mm) by dipping, and implants were installed in rat mandibles. One, 2, 3, and 6 weeks post-implantation, mandibles were examined by microcomputed tomography (µCT), immunohistochemistry, hematoxylin & eosin, and tartrate resistance acid phosphatase (TRAP) staining. In vivo Ch-GNPs/PPARγcoated implants were associated with inhibition of implant induced inflammatory molecules interleukin-1β and receptor activator of nuclear factor kappa-B ligand and enhanced expression of osteogenic molecules like bone morphogenetic protein 2 and 7 (BMP-2/-7) by up-regulating anti-oxidant molecules heme oxygenase-1. µCT demonstrated that PPARγ overexpression increased the density and volume of newly formed bone surrounding the implants compared to control (n = 4; p < 0.05). Also, PPARγ reduced the number of TRAP positive cells. These results support the view that PPARγ overexpression diminishes inflammation and enhances osteogenesis around the dental implants. Thus, implant coated with anti-inflammatory molecules could have a significant utilization for the preparation of new biomaterials and may serve as prosthetic materials in patients suffering from inflammatory bone disease.

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.

Stabilization of a hyaluronate-associated gene delivery system using calcium ions

A "DPH" ternary complex consisting of plasmid DNA (pDNA), intracellularly degradable polyethyleneimine, and hyaluronic acid (HA) is a promising non-viral gene carrier with low toxicity and good gene transfection efficiency. HA plays a key role in providing an optimal balance between DNA protection and release, but it causes aggregation due to the entanglement of HA chains of neighbouring DPH particles. Here we report that the addition of an optimal level of Ca²⁺ successfully prevents particle aggregation and maintains a relatively small size. The Ca-stabilized DPH is comparable to DPH in cytotoxicity and gene transfection efficiency. MW monitoring and conductometric titration suggest that such size stabilization effect is partly mediated by the complexation between HA and Ca²⁺, which enables intra- and intermolecular interactions of HAs.

Biomineralization of hydroxyapatite on DNA molecules in SBF: morphological features and computer simulation

The hydroxyapatite (HA) formation on the DNA molecules in SBF was examined. After immersion for four weeks in SBF at 36.5 °C, the HA crystallites of ~1-14 μm in diameter grew on the surface of DNA molecules. Various morphologies were successfully observed through scanning electron microscopy analysis. The Ca/P mol ratio (1.1-1.5) in HA was estimated by energy dispersive X-ray analysis. Original peaks of both of DNA and HA were characterized by Fourier transform infrared spectroscopy. The molecular orbital computer simulation has been used to probe the interaction of DNA with two charge-balancing ions, i.e., CaOH(+) and CaH2PO4(+). The adsorption enthalpy of the two ions on ds-DNA and/or ss-DNA having large negative value (~ -60 kcal/mol per charge-balancing ion) was the evidence for the interface in mineralization of HA in SBF.

Inorganic coatings for optimized non-viral transfection of stem cells

“Biomimetic” approaches for heterogeneous growth of inorganic coatings have become particularly widespread in biomedical applications, where calcium phosphate (CaP) mineral coatings are used to improve biomedical implants. Changes in coating properties can influence the effects of mineral coatings on adjacent cells, but to date it has not been practical to systematically vary inorganic coating properties to optimize specific cell behaviors. Here, we present an approach to grow CaP mineral coatings in an enhanced throughput format to identify unprecedented capabilities in non-viral gene delivery. Subtle changes in coating properties resulted in widely variable transfection, and optimized coatings led to greater than 10-fold increases in transgene expression by multiple target cell types when compared to standard techniques. The enhanced transfection observed here is substrate-mediated, and related to the characteristics of the local environment near the surface of dissolving mineral coatings. These findings may be particularly translatable to medical device applications.

Gene delivery of c-myb increases bone formation surrounding oral implants

Bone regeneration around titanium (Ti) implants is a relatively slow process. The c-myb transcription factor has been associated with high proliferation and differentiation rates in bone. This study analyzed whether c-myb can enhance new bone surrounding the implant. In vitro overexpressed chitosan-gold nanoparticles conjugated with plasmid DNA/c-myb (Ch-GNPs/c-myb)-coated Ti surfaces were associated with enhanced expression of the osteogenic molecules osteopontin (OPN), runt-related transcription factor 2 (RUNX-2), and bone morphogenetic proteins (BMP2/7) in MC-3T3E1 osteoblast cells. Further, to determine its in vivo effect, we inserted Ch-GNPs/c-myb-coated Ti implants into rat mandibles. One and 4 wks post-implantation, mandibles were examined by microcomputed tomography, immunohistochemistry, and hematoxylin & eosin staining. The microcomputed tomography analysis demonstrated that c-myb overexpression increased the density and volume of newly formed bone surrounding the implants, compared with those in controls (p < .05). Further, c-myb increased the number of cells expressing BMP2/7 and aided in the increase of new bone (p < .05). These results support the view that c-myb overexpression accelerates new bone surrounding implants and can serve as a potent molecule in promoting tissue regeneration around dental implants. The recipient rat used in this system provides an excellent in vivo model for studies of bone regeneration.

Nonviral gene transfer strategies to promote bone regeneration

Despite the inherent ability of bone to regenerate itself, there are a number of clinical situations in which complete bone regeneration fails to occur. In view of shortcomings of conventional treatment, gene therapy may have a place in cases of critical-size bone loss that cannot be properly treated with current medical or surgical treatment. The purpose of this review is to provide an overview of gene therapy in general, nonviral techniques of gene transfer including physical and chemical methods, RNA-based therapy, therapeutic genes to be transferred for bone regeneration, route of application including ex vivo application, and direct gene therapy approaches to regenerate bone.

Anchoring of self-assembled plasmid DNA/anti-DNA antibody/cationic lipid micelles on bisphosphonate-modified stent for cardiovascular gene delivery

Purpose:

To investigate the anchoring of plasmid DNA/anti-DNA antibody/cationic lipid tri-complex (DAC micelles) onto bisphosphonate-modified 316 L coronary stents for cardiovascular site-specific gene delivery.

Methods:

Stents were first modified with polyallylamine bisphosphonate (PAA-BP), thereby enabling the retention of a PAA-BP molecular monolayer that permits the anchoring (via vector-binding molecules) of DAC micelles. DAC micelles were then chemically linked onto the PAA-BP-modified stents by using N-succinimidyl-3-(2-pyridyldithiol)-propionate (SPDP) as a crosslinker. Rhodamine-labeled DNA was used to assess the anchoring of DAC micelles, and radioactive-labeled antibody was used to evaluate binding capacity and stability. DAC micelles (encoding green fluorescent protein) were tethered onto the PAA-BP-modified stents, which were assessed in cell culture. The presence of a PAA-BP molecular monolayer on the steel surface was confirmed by X-ray photoelectron spectroscopy and atomic force microscope analysis.

Results:

The anchoring of DAC micelles was generally uniform and devoid of large-scale patches of defects. Isotopic quantification confirmed that the amount of antibody chemically linked on the stents was 17-fold higher than that of the physical adsorbed control stents and its retention time was also significantly longer. In cell culture, numerous green fluorescent protein-positive cells were found on the PAA-BP modified stents, which demonstrated high localization and efficiency of gene delivery.

Conclusion:

The DAC micelle-immobilized PAA-BP-modified stents were successful as a gene delivery system. Gene delivery using DAC micelle-tethered stent-based PAA-BP functionalization should be suitable for a wide array of single or multiple therapeutic gene strategies, and could be used on cardiovascular metallic implants for achieving efficient gene therapy.

Nanofibrous scaffold-mediated REST knockdown to enhance neuronal differentiation of stem cells

At present, the recovery prospect for patients with chronic neurodegenerative diseases or acute trauma in the central nervous system is sub-optimal. The controlled differentiation of neural stem/progenitor cells (NPCs) to functional neurons is a possible treatment strategy. In contrast to the classical approach of biochemicals supplementation for guided stem cell commitment, this study explores the feasibility of directing neuronal differentiation through synergistic integration of three-dimensional nanofibrous topographical cues and scaffold-mediated knockdown of RE-1 silencing transcription factor (REST) in mouse NPCs. Taking advantage of the strong adhesive property and latent reactivity of mussel-inspired polydopamine (PD) coating, electrospun polycaprolactone (PCL) nanofibers were successfully functionalized with REST siRNAs (denoted as siREST PD-fiber). Sustained REST knockdown in NPCs was achieved for up to five days in vitro and the silencing efficiency was significantly higher than that mediated through siRNA adsorption onto non-PD coated sample controls. The silencing of REST, together with nanofiber topographical effect, significantly enhanced NPC neuronal commitment (57.5% Map2(+) cells in siREST PD-fiber vs. 43.5% in siREST PD-film vs. 50% in PD-fiber controls, p < 0.05) while reducing astrocytic and oligodendrocytic differentiation (10.7% O4(+) cells vs. ∼30% in siREST PD-film, p < 0.01). Taken together, the synergistic effects of scaffold-mediated REST knockdown and topographical cues from PD-modified nanofibers may be a useful strategy for generating functional neurons for therapeutic purposes.

Fabrication of DNA-antibody-apatite composite layers for cell-targeted gene transfer

Surface-mediated gene transfer systems using apatite (Ap)-based composite layers have received increased attention in tissue engineering applications owing to their safety, biocompatibility and relatively high efficiency. In this study, DNA-antibody-apatite composite layers (DA-Ap layers), in which DNA and antibody molecules are immobilized within a matrix of apatite nanocrystals, were fabricated using a biomimetic coating process. They were then assayed for their gene transfer capability for application in a specific cell-targeted gene transfer. A DA-Ap layer that was fabricated with an anti-CD49f antibody showed a higher gene transfer capability to the CD49f-positive CHO-K1 cells than a DNA-apatite composite layer (D-Ap layer). The antibody facilitated the gene transfer capability of the DA-Ap layer only to the specific cells that were expressing corresponding antigens. When the DA-Ap layer was fabricated with an anti-N-cadherin antibody, a higher gene transfer capability compared with the D-Ap layer was found in the N-cadherin-positive P19CL6 cells, but not in the N-cadherin-negative UV♀2 cells or in the P19CL6 cells that were pre-blocked with anti-N-cadherin. Therefore, the antigen-antibody binding that takes place at the cell-layer interface should be responsible for the higher gene transfer capability of the DA-Ap than D-Ap layer. These results suggest that the DA-Ap layer works as a mediator in a specific cell-targeted gene transfer system.

Combining topographical and genetic cues to promote neuronal fate specification in stem cells

There is little remedy for the devastating effects resulting from neuronal loss caused by neural injury or neurodegenerative disease. Reconstruction of damaged neural circuitry with stem cell-derived neurons is a promising approach to repair these defects, but controlling differentiation and guiding synaptic integration with existing neurons remain significant unmet challenges. Biomaterial surfaces can present nanoscale topographical cues that influence neuronal differentiation and process outgrowth. By combining these scaffolds with additional molecular biology strategies, synergistic control over cell fate can be achieved. Here, we review recent progress in promoting neuronal fate using techniques at the interface of biomaterial science and genetic engineering. New data demonstrates that combining nanofiber topography with an induced genetic program enhances neuritogenesis in a synergistic fashion. We propose combining patterned biomaterial surface cues with prescribed genetic programs to achieve neuronal cell fates with the desired sublineage specification, neurochemical profile, targeted integration, and electrophysiological properties.

Coprecipitation of DNA and Calcium Phosphate Using an Infusion Fluid Mixture

A surface-mediated gene transfer system using DNA-calcium phosphate (CaP) composite layers (D-CaP layers) would be useful in tissue engineeing. In previous studies, D-CaP layers were fabricated in supersaturated CaP solutions prepared using chemical reagents. In this study, a so-called RKM solution prepared using clinically approved infusion fluids was employed as a supersaturated CaP solution. A D-CaP layer consisting of submicron spherical particles was successfully fabricated on a polystyrene substrate by immersing the substrate in the RKM solution for 24 h. When the immersion period was prolonged from 24 to 72 h, amount of CaP and DNA on the substrate increased. However, the gene transfer capability of the D-CaP layer for the CHO-K1 cells was kept unchanged irrespective of the immersion period. In the RKM solution process, immersion period of 24 h was found to be long enough for gene transfer application of the D-CaP layer. More importantly, the D-CaP layer fabricated by the RKM solution process exhibited a significantly higher gene transfer capability than our previous D-CaP layer fabricated in the conventional CaP solution with the same DNA concentration. The RKM solution process for the fabrication of D-CaP layers was found to be advantageous to the previous process in terms of not only safety but the layers gene transfer capability.

Advances in polymeric and inorganic vectors for nonviral nucleic acid delivery

Nonviral systems for nucleic acid delivery offer a host of potential advantages compared with viruses, including reduced toxicity and immunogenicity, increased ease of production and less stringent vector size limitations, but remain far less efficient than their viral counterparts. In this article we review recent advances in the delivery of nucleic acids using polymeric and inorganic vectors. We discuss the wide range of materials being designed and evaluated for these purposes while considering the physical requirements and barriers to entry that these agents face and reviewing recent novel approaches towards improving delivery with respect to each of these barriers. Furthermore, we provide a brief overview of past and ongoing nonviral gene therapy clinical trials. We conclude with a discussion of multifunctional nucleic acid carriers and future directions.

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.