SciCombinator

Discover the most talked about and latest scientific content & concepts.

Journal: Biomaterials

677

Despite significant advances in the fabrication of bioengineered scaffolds for tissue engineering, delivery of nutrients in complex engineered human tissues remains a challenge. By taking advantage of the similarities in the vascular structure of plant and animal tissues, we developed decellularized plant tissue as a prevascularized scaffold for tissue engineering applications. Perfusion-based decellularization was modified for different plant species, providing different geometries of scaffolding. After decellularization, plant scaffolds remained patent and able to transport microparticles. Plant scaffolds were recellularized with human endothelial cells that colonized the inner surfaces of plant vasculature. Human mesenchymal stem cells and human pluripotent stem cell derived cardiomyocytes adhered to the outer surfaces of plant scaffolds. Cardiomyocytes demonstrated contractile function and calcium handling capabilities over the course of 21 days. These data demonstrate the potential of decellularized plants as scaffolds for tissue engineering, which could ultimately provide a cost-efficient, “green” technology for regenerating large volume vascularized tissue mass.

Concepts: Stem cell, Plant, Mesenchymal stem cell, Bone marrow, Stem cells, Cell biology, Induced pluripotent stem cell, Pluripotency

178

The E4 isoform of apolipoprotein (apoE4) is known to be a major risk factor for Alzheimer’s Disease (AD). Previous in vitro studies have shown apoE4 to have a negative effect on neuronal outgrowth when incubated with lipids. The effect of apoE4 itself on the development of neurons from the central nervous system (CNS), however, has not been well characterized. Consequently, apoE4 alone has not been pursued as a substrate for neuronal cultures. In this study, the effect of surface-bound apoE4 on developmental features of rat hippocampal neurons was examined. We show that apoE4 substrates elicit significantly enhanced values in all developmental features at day 2 of culture when compared to laminin (LN) substrates, which is the current substrate-of-choice for neuronal cultures. Interestingly, the adhesion of hippocampal neurons was found to be significantly lower on LN substrates than on glass substrates, but the axon lengths on both substrates were similar. In addition, this study demonstrates that the adhesion- and growth-enhancing effects of apoE4 substrates are not mediated by heparan sulfate proteoglycans (HSPGs), proteins that have been indicated to function as receptors or co-receptors for apoE4. In the absence of lipids, apoE4 appears to use an unknown pathway for up-regulating neuronal adhesion and neurite outgrowth. Our results indicate that apoE4 is better than LN as a substrate for primary cultures of CNS neurons and should be considered in the design of tissue engineered CNS.

Concepts: Alzheimer's disease, Central nervous system, Nervous system, Neuron, Brain, Axon, Synapse, Heparan sulfate

169

Articular cartilage maturation is the postnatal development process that adapts joint surfaces to their site-specific biomechanical demands. Maturation involves gross morphological changes that occur through a process of synchronised growth and resorption of cartilage and generally ends at sexual maturity. The inability to induce maturation in biomaterial constructs designed for cartilage repair has been cited as a major cause for their failure in producing persistent cell-based repair of joint lesions. The combination of growth factors FGF2 and TGFβ1 induces accelerated articular cartilage maturation in vitro such that many molecular and morphological characteristics of tissue maturation are observable. We hypothesised that experimental growth factor-induced maturation of immature cartilage would result in a biophysical and biochemical composition consistent with a mature phenotype. Using native immature and mature cartilage as reference, we observed that growth factor-treated immature cartilages displayed increased nano-compressive stiffness, decreased surface adhesion, decreased water content, increased collagen content and smoother surfaces, correlating with a convergence to the mature cartilage phenotype. Furthermore, increased gene expression of surface structural protein collagen type I in growth factor-treated explants compared to reference cartilages demonstrates that they are still in the dynamic phase of the postnatal developmental transition. These data provide a basis for understanding the regulation of postnatal maturation of articular cartilage and the application of growth factor-induced maturation in vitro and in vivo in order to repair and regenerate cartilage defects.

Concepts: Bone, Gene, Molecular biology, Collagen, Cartilage, Knee, Biochemistry, Articular cartilage repair

167

To date, gold nanoparticles (AuNPs) have been investigated for diverse bioapplications. Generally, AuNPs are engineered to possess surface coating with organic/inorganic shells to increase colloidal stability in biological solutions and to facilitate chemical conjugation. In the present study, we developed a strategy to prepare dextran-coated AuNPs with control over its size by simply boiling an aqueous solution of Au salt and dextran, in which dextran serves as both reducing agent for AuNP (Au(0)) formation from Au(III) and AuNP surface coating material. The prepared dextran-coated AuNPs (dAuNPs) maintained its colloidal stability under high temperature, high salt concentration, and extreme pH. Importantly, the dAuNP remarkably improved efficacy of an anti-cancer agent, doxorubicin (Dox), when harnessed as a Dox delivery carrier. The half-maximal inhibitory concentration (EC50) of Dox-conjugated dAuNP with diameter of 170 nm was ∼9 pM in HeLa cells, which was 1.1 × 10(5) times lower than that of free Dox and lower than any previously reported values of Dox-nanoparticle complex. Interestingly, smaller AuNPs with 30 and 70 nm showed about 10 times higher EC50 than 170 nm AuNPs when treated to HeLa cells after conjugation with Dox. To achieve high cytotoxicity as cancer therapeutics, Dox should be delivered into nucleus to intercalate with DNA double helix. We show here that Dox-AuNPs was far more efficient as an anti-cancer drug than free Dox by releasing from AuNPs through spontaneous degradation of dextran, allowing free diffusion and nuclear uptake of Dox. We also revealed that larger AuNPs with lower degree of dextran crosslinking promoted faster degradation of dextran shells.

Concepts: DNA, Cell nucleus, Nanoparticle, Chemotherapy, Concentration, Chemistry, Gold, Doxorubicin

167

Mesoporous silica-encapsulated gold nanorods (GNRs@mSiO(2)) have great potential both in photothermal therapy and drug delivery. In this paper, we firstly developed GNRs@mSiO(2) as a synergistic therapy tool for delivery heat and drug to the tumorigenic region. We studied the ablation of tumor both in vitro and in vivo by the combination of photothermal therapy and chemotherapy using doxorubicin (DOX)-loaded GNRs@mSiO(2). Significantly greater cell killing was observed when A549 cells incubated with DOX-loaded GNRs@mSiO(2) were irradiated with near-infrared (NIR) illumination, attributable to both GNRs@mSiO(2)-mediated photothermal ablation and cytotoxicity of light-triggered DOX release. We then performed in vivo therapy studies and observed a promising tumor treatment. Compared with chemotherapy or photothermal treatment alone, the combined treatment showed a synergistic effect, resulting in higher therapeutic efficacy. Furthermore, the lower systematic toxicity of GNRs@mSiO(2) has been validated.

Concepts: DNA, Cancer, Oncology, Chemotherapy, Therapy, Efficacy, Doxorubicin, Photothermal Therapy

161

Protein drugs (PD) are minimally utilized in dental medicine due to high cost and invasive surgical delivery. There is limited clinical advancement in disrupting virulent oral biofilms, despite their high prevalence in causing dental caries. Poor efficacy of antimicrobials following topical treatments or to penetrate and disrupt formed biofilms is a major challenge. We report an exciting low-cost approach using plant-made antimicrobial peptides (PMAMPs) retrocyclin or protegrin with complex secondary structures (cyclic/hairpin) for topical use to control biofilms. The PMAMPs rapidly killed the pathogen Streptococcus mutans and impaired biofilm formation following a single topical application of tooth-mimetic surface. Furthermore, we developed a synergistic approach using PMAMPs combined with matrix-degrading enzymes to facilitate their access into biofilms and kill the embedded bacteria. In addition, we identified a novel role for PMAMPs in delivering drugs to periodontal and gingival cells, 13-48 folds more efficiently than any other tested cell penetrating peptides. Therefore, PDs fused with protegrin expressed in plant cells could potentially play a dual role in delivering therapeutic proteins to gum tissues while killing pathogenic bacteria when delivered as topical oral formulations or in chewing gums. Recent FDA approval of plant-produced PDs augurs well for clinical advancement of this novel concept.

Concepts: Protein, Bacteria, Microbiology, Biofilm, Dental caries, Dental plaque, Oral hygiene, Streptococcus mutans

131

Oral lichen planus (OLP) and recurrent aphthous stomatitis (RAS) are chronic inflammatory conditions often characterised by erosive and/or painful oral lesions that have a considerable impact on quality of life. Current treatment often necessitates the use of steroids in the form of mouthwashes, creams or ointments, but these are often ineffective due to inadequate drug contact times with the lesion. Here we evaluate the performance of novel mucoadhesive patches for targeted drug delivery. Electrospun polymeric mucoadhesive patches were produced and characterised for their physical properties and cytotoxicity before evaluation of residence time and acceptability in a human feasibility study. Clobetasol-17-propionate incorporated into the patches was released in a sustained manner in both tissue-engineered oral mucosa and ex vivo porcine mucosa. Clobetasol-17 propionate-loaded patches were further evaluated for residence time and drug release in an in vivo animal model and demonstrated prolonged adhesion and drug release at therapeutic-relevant doses and time points. These data show that electrospun patches are adherent to mucosal tissue without causing tissue damage, and can be successfully loaded with and release clinically active drugs. These patches hold great promise for the treatment of oral conditions such as OLP and RAS, and potentially many other oral lesions.

58

Covalently cross-linked gels are utilized in a broad range of biomedical applications though their synthesis often compromises easy implementation. Cross-linking reactions commonly utilize catalysts or conditions that can damage biologics and sensitive compounds, producing materials that require extensive post processing to achieve acceptable biocompatibility. As an alternative, we report a batch synthesis platform to produce covalently cross-linked materials appropriate for direct biomedical application enabled by green chemistry and commonly available food grade ingredients. Using caffeine, a mild base, to catalyze anhydrous carboxylate ring-opening of diglycidyl-ether functionalized monomers with citric acid as a tri-functional crosslinking agent we introduce a novel poly(ester-ether) gel synthesis platform. We demonstrate that biocompatible Caffeine Catalyzed Gels (CCGs) exhibit dynamic physical, chemical, and mechanical properties, which can be tailored in shape, surface texture, solvent response, cargo release, shear and tensile strength, among other potential attributes. The demonstrated versatility, low cost and facile synthesis of these CCGs renders them appropriate for a broad range of customized engineering applications including drug delivery constructs, tissue engineering scaffolds, and medical devices.

Concepts: Chemical reaction, Polymer chemistry, Cross-link, Cross-linked polyethylene

46

Hair follicle morphogenesis is triggered by reciprocal interactions between hair follicle germ (HFG) epithelial and mesenchymal layers. Here, we developed a method for large-scale preparation of HFGs in vitro via self-organization of cells. We mixed mouse epidermal and mouse/human mesenchymal cells in suspension and seeded them in microwells of a custom-designed array plate. Over a 3-day culture period, cells initially formed a randomly distributed single cell aggregate and then spatially separated from each other, exhibiting typical HFG morphological features. These self-sorted hair follicle germs (ssHFGs) were shown to be capable of efficient hair-follicle and shaft generation upon intracutaneous transplantation into the backs of nude mice. This finding facilitated the large-scale preparation of approximately 5000 ssHFGs in a microwell-array chip made of oxygen-permeable silicone. We demonstrated that the integrity of the oxygen supply through the bottom of the silicone chip was crucial to enabling both ssHFG formation and subsequent hair shaft generation. Finally, spatially aligned ssHFGs on the chip were encapsulated into a hydrogel and simultaneously transplanted into the back skin of nude mice to preserve their intervening spaces, resulting in spatially aligned hair follicle generation. This simple ssHFG preparation approach is a promising strategy for improving current hair-regenerative medicine techniques.

Concepts: Protein, Gene, Stem cell, Mesenchymal stem cell, Skin, Mouse, Hair, Hair follicle

33

Antibodies (inhibitors) developed by hemophilia B patients against coagulation factor IX (FIX) are challenging to eliminate because of anaphylaxis or nephrotic syndrome after continued infusion. To address this urgent unmet medical need, FIX fused with a transmucosal carrier (CTB) was produced in a commercial lettuce (Simpson Elite) cultivar using species specific chloroplast vectors regulated by endogenous psbA sequences. CTB-FIX (∼1 mg/g) in lyophilized cells was stable with proper folding, disulfide bonds and pentamer assembly when stored ∼2 years at ambient temperature. Feeding lettuce cells to hemophilia B mice delivered CTB-FIX efficiently to the gut immune system, induced LAP(+) regulatory T cells and suppressed inhibitor/IgE formation and anaphylaxis against FIX. Lyophilized cells enabled 10-fold dose escalation studies and successful induction of oral tolerance was observed in all tested doses. Induction of tolerance in such a broad dose range should enable oral delivery to patients of different age groups and diverse genetic background. Using Fraunhofer cGMP hydroponic system, ∼870 kg fresh or 43.5 kg dry weight can be harvested per 1000 ft(2) per annum yielding 24,000-36,000 doses for 20-kg pediatric patients, enabling first commercial development of an oral drug, addressing prohibitively expensive purification, cold storage/transportation and short shelf life of current protein drugs.

Concepts: Blood, Coagulation, Haemophilia A, Haemophilia B, Factor X, Factor XI, Factor VII, Factor IX