Design and fabrication of 3D porous scaffolds to facilitate cell-based gene therapy

Applications of Biomaterials in 3D Cell Culture and Contributions of 3D Cell Culture to Drug Development and Basic Biomedical Research

The process of evaluating the efficacy and toxicity of drugs is important in the production of new drugs to treat diseases. Testing in humans is the most accurate method, but there are technical and ethical limitations. To overcome these limitations, various models have been developed in which responses to various external stimuli can be observed to help guide future trials. In particular, three-dimensional (3D) cell culture has a great advantage in simulating the physical and biological functions of tissues in the human body. This article reviews the biomaterials currently used to improve cellular functions in 3D culture and the contributions of 3D culture to cancer research, stem cell culture and drug and toxicity screening.

3D Printed Bioconstructs: Regenerative Modulation for Genetic Expression

Layer-by-layer deposition of cells, tissues and similar molecules provided by additive manufacturing techniques such as 3D bioprinting offers safe, biocompatible, effective and inert methods for the production of biological structures and biomimetic scaffolds. 3D bioprinting assisted through computer programmes and software develops mutli-modal nano- or micro-particulate systems such as biosensors, dosage forms or delivery systems and other biological scaffolds like pharmaceutical implants, prosthetics, etc. This review article focuses on the implementation of 3D bioprinting techniques in the gene expression, in gene editing or therapy and in delivery of genes. The applications of 3D printing are extensive and include gene therapy, modulation and expression in cancers, tissue engineering, osteogenesis, skin and vascular regeneration. Inclusion of nanotechnology with genomic bioprinting parameters such as gene conjugated or gene encapsulated 3D printed nanostructures may offer new avenues in the future for efficient and controlled treatment and help in overcoming the limitations faced in conventional methods. Moreover, expansion of the benefits from such techniques is advantageous in real-time delivery or in-situ production of nucleic acids into the host cells.

Three-dimensional bio-printing equipment technologies for tissue engineering and regenerative medicine

Three-Dimensional (3D) printing technologies have been widely used in the medical sector for the production of medical assistance equipment and surgical guides, particularly 3D bio-printing that combines 3D printing technology with biocompatible materials and cells in field of tissue engineering and regenerative medicine. These additive manufacturing technologies can make patient-made production from medical image data. Thus, the application of 3D bio-printers with biocompatible materials has been increasing. Currently, 3D bio-printing technology is in the early stages of research and development but it has great potential in the fields of tissue and organ regeneration. The present paper discusses the history and types of 3D printers, the classification of 3D bio-printers, and the technology used to manufacture artificial tissues and organs.

Strategic design and fabrication of engineered scaffolds for articular cartilage repair

Damage to articular cartilage can eventually lead to osteoarthritis (OA), a debilitating, degenerative joint disease that affects millions of people around the world. The limited natural healing ability of cartilage and the limitations of currently available therapies make treatment of cartilage defects a challenging clinical issue. Hopes have been raised for the repair of articular cartilage with the help of supportive structures, called scaffolds, created through tissue engineering (TE). Over the past two decades, different designs and fabrication techniques have been investigated for developing TE scaffolds suitable for the construction of transplantable artificial cartilage tissue substitutes. Advances in fabrication technologies now enable the strategic design of scaffolds with complex, biomimetic structures and properties. In particular, scaffolds with hybrid and/or biomimetic zonal designs have recently been developed for cartilage tissue engineering applications. This paper reviews critical aspects of the design of engineered scaffolds for articular cartilage repair as well as the available advanced fabrication techniques. In addition, recent studies on the design of hybrid and zonal scaffolds for use in cartilage tissue repair are highlighted.

Multimodal imaging of sustained drug release from 3-D poly(propylene fumarate) (PPF) scaffolds

The potential of poly(propylene fumarate) (PPF) scaffolds as drug carriers was investigated and the kinetics of the drug release quantified using magnetic resonance imaging (MRI) and optical imaging. Three different MR contrast agents were used for coating PPF scaffolds. Initially, iron oxide (IONP) or manganese oxide nanoparticles (MONP) carrying the anti-cancer drug doxorubicin were absorbed or mixed with the scaffold and their release into solution at physiological conditions was measured with MRI and optical imaging. A slow (hours to days) and functional release of the drug molecules into the surrounding solution was observed. In order to examine the release properties of proteins and polypeptides, protamine sulfate, a chemical exchange saturation transfer (CEST) MR contrast agent, was attached to the scaffold. Protamine sulfate showed a steady release rate for the first 24h. Due to its biocompatibility, versatile drug-loading capability and constant release rate, the porous PPF scaffold has potential in various biomedical applications, including MR-guided implantation of drug-dispensing materials, development of drug carrying vehicles, and drug delivery for tumor treatment.

Ovalbumin-based porous scaffolds for bone tissue regeneration

Cell differentiation on glutaraldehyde cross-linked ovalbumin scaffolds was the main focus of this research. Salt leaching and freeze drying were used to create a three-dimensional porous structure. Average pore size was 147.84 ± 40.36 μm and 111.79 ± 30.71 μm for surface and cross sectional area, respectively. Wet compressive strength and elastic modulus were 6.8 ± 3.6 kPa. Average glass transition temperature was 320.1 ± 1.4°C. Scaffolds were sterilized with ethylene oxide prior to seeding MC3T3-E1 cells. Cells were stained with DAPI and Texas red to determine morphology and proliferation. Average cell numbers increased between 4-hour- and 96-hour-cultured scaffolds. Alkaline phosphatase and osteocalcin levels were measured at 3, 7, 14, and 21 days. Differentiation studies showed an increase in osteocalcin at 21 days and alkaline phosphatase levels at 14 days, both indicating differentiation occurred. This work demonstrated the use of ovalbumin scaffolds for a bone tissue engineering application.

Gene delivery by surface immobilization of plasmid to tissue-engineering scaffolds

Biomaterial scaffolds that serve as vehicles for gene delivery to promote expression of inductive factors have numerous regenerative medicine applications. In this report, we investigate plasmid delivery from biomaterial scaffolds using a surface immobilization strategy. Porous scaffolds were fabricated from poly(D,L-lactide-co-glycolide) (PLG), and plasmids were immobilized by drying. In vitro plasmid release indicated that the majority (>70%) of adsorbed plasmids were released within 24 h and >98% within 3 days; however, in vivo implantation of the scaffolds at the subcutaneous site yielded transgene expression that persisted for at least 28 weeks and was localized to the site of implantation. Histological analysis of DNA-adsorbed scaffolds indicated that macrophages at the scaffold were transfected in the first 2 weeks after implantation, whereas muscle cells adjacent to the implant primarily expressed the transgene at 4 weeks. In addition to localized gene expression, a secreted protein (human factor IX) was retained at the implant site and not available systemically after 3 days, indicating minimal off-target effects. These findings show that surface immobilization of plasmid onto microporous PLG scaffolds can produce localized and long-term gene expression in vivo, which may be used to enhance the bioactivity of scaffolds used for regenerative medicine.

Mesenchymal stromal cells engineered to express erythropoietin induce anti-erythropoietin antibodies and anemia in allorecipients

Autologous bone marrow mesenchymal stromal cells (MSCs) have been successfully used for the delivery of erythropoietin (EPO) in murine models of anemia and myocardial infarction. For clinical applications where a transient effect would be adequate, such as myocardial infarction, the use of EPO-engineered universal donor allogeneic MSCs would be a substantial convenience. We thus investigated whether MSCs from C57BL/6 mice would permit robust transient EPO delivery in normal BALB/c allorecipients. Implantation of MSCs overexpressing murine EPO led to increases in hematocrit in syngeneic and allogeneic mice, but the latter eventually developed severe anemia due to acquired neutralizing anti-EPO antibodies. As MSCs constitutively produce the CCL2 chemokine which may behave as an adjuvant to the anti-EPO immune response, experiments were performed using EPO-engineered MSCs derived from CCL2(-/-) mice and similar results were obtained. In conclusion, MHC-mismatched MSCs can break the tolerance to autoantigens and lead to the development of pathogenic autoantibodies.