Ting Yi Wang

In vivo assessment of grafted cortical neural progenitor cells and host response to functionalized self-assembling peptide hydrogels and the implications for tissue repair

Tissue specific scaffolds formed from minimalist N-fluorenylmethyloxycarbonyl self-assembling peptides (Fmoc-SAPs) have emerged as promising biomaterials due to their ease of synthesis and capacity to self-assemble via simple, non-covalent interactions into complex nanofibrous hydrogels. However, concerns remain over their biocompatibility and cytotoxicity for in vivo applications. Here, we demonstrate that these Fmoc-SAPs are biocompatible in vivo and well suited as a delivery vehicle for cell transplantation. In order to determine the effect of tissue specific parameters, we designed three Fmoc-SAPs containing varying bioactive peptide sequences derived from extracellular matrix proteins, laminin and fibronectin. Fmoc-SAPs delivering cortical neural progenitor cells into the mouse brain display a limited foreign body response, effective functionalization and low cytotoxicity for at least 28 days. These results highlight the suitability of Fmoc-SAPs for improved neural tissue repair through the support of grafted cells and adjacent host parenchyma. Overall, we illustrate that Fmoc-SAPs are easily engineered materials for use as a tool in cell transplantation, where biocompatibility is key to promoting cell survival, enhancing the graft-host interface and attenuation of the inflammatory response for improved tissue repair outcomes.

Biofunctionalisation of polymeric scaffolds for neural tissue engineering

Patients who experience injury to the central or peripheral nervous systems invariably suffer from a range of dysfunctions due to the limited ability for repair and reconstruction of damaged neural tissue. Whilst some treatment strategies can provide symptomatic improvement of motor and cognitive function, they fail to repair the injured circuits and rarely offer long-term disease modification. To this end, the biological molecules, used in combination with neural tissue engineering scaffolds, may provide feasible means to repair damaged neural pathways. This review will focus on three promising classes of neural tissue engineering scaffolds, namely hydrogels, electrospun nanofibres and self-assembling peptides. Additionally, the importance and methods for presenting biologically relevant molecules such as, neurotrophins, extracellular matrix proteins and protein-derived sequences that promote neuronal survival, proliferation and neurite outgrowth into the lesion will be discussed.

Characterization of the Stability and Bio-functionality of Tethered Proteins on Bioengineered Scaffolds: Implications for stem cell biology and tissue repair

Background: Tethering proteins onto bioengineered scaffolds enables longterm delivery, however protein stability, release kinetics, and functionality over time remains unknown. Results: Tethered proteins remain stable and functional for several months, capable of activating intracellular signaling pathways and influencing cell fate. Conclusion: Tethered proteins are stable and functional long-term. Significance: Such knowledge may have implications for promoting tissue repair. Various engineering applications have been utilized to deliver molecules and compounds in both innate and biological settings. In the context of biological applications, the timely delivery of molecules can be critical for cellular and organ function. As such, previous studies have demonstrated the superiority of long-term protein delivery, by way of protein tethering onto bioengineered scaffolds, compared with conventional delivery of soluble protein in vitro and in vivo. Despite such benefits little knowledge exists regarding the stability, release kinetics, longevity, activation of intracellular pathway, and functionality of these proteins over time. By way of example, here we examined the stability, degradation and functionality of a protein, glial-derived neurotrophic factor (GDNF), which is known to influence neuronal survival, differentiation, and neurite morphogenesis. Enzyme-linked immunosorbent assays (ELISA) revealed that GDNF, covalently tethered onto polycaprolactone (PCL) electrospun nanofibrous scaffolds, remained present on the scaffold surface for 120 days, with no evidence of protein leaching or degradation. The tethered GDNF protein remained functional and capable of activating downstream signaling cascades, as revealed by its capacity to phosphorylate intracellular Erk in a neural cell line. Furthermore, immobilization of GDNF protein promoted cell survival and differentiation in culture at both 3 and 7 days, further validating prolonged functionality of the protein, well beyond the minutes to hours timeframe observed for soluble proteins under the same culture conditions. This study provides important evidence of the stability and functionality kinetics of tethered molecules.

Tailoring minimalist self-assembling peptides for localized viral vector gene delivery

Viral vector gene delivery is a promising technique for the therapeutic administration of proteins to damaged tissue for the improvement of regeneration outcomes in various disease settings including brain and spinal cord injury, as well as autoimmune diseases. Though promising results have been demonstrated, limitations of viral vectors, including spread of the virus to distant sites, neutralization by the host immune system, and low transduction efficiencies have stimulated the investigation of biomaterials as gene delivery vehicles for improved protein expression at an injury site. Here, we show how Nfluorenylmethyloxycarbonyl (Fmoc) self-assembling peptide (SAP) hydrogels, designed for tissue-specific central nervous system (CNS) applications via incorporation of the laminin peptide sequence isoleucine–lysine–valine–alanine–valine (IKVAV), are effective as biocompatible, localized viral vector gene delivery vehicles in vivo. Through the addition of a C-terminal lysine (K) residue, we show that increased electrostatic interactions, provided by the additional amine side chain, allow effective immobilization of lentiviral vector particles, thereby limiting their activity exclusively to the site of injection and enabling focal gene delivery in vivo in a tissue-specific manner. When the C-terminal lysine was absent, no difference was observed between the number of transfected cells, the volume of tissue transfected, or the transfection efficiency with and without the Fmoc-SAP. Importantly, immobilization of the virus only affected transfection cell number and volume, with no impact observed on transfection efficiency. This hydrogel allows the sustained and targeted delivery of growth factors post injury. We have established Fmoc-SAPs as a versatile platform for enhanced biomaterial design for a range of tissue engineering applications.

Locomotor hyperactivity in 14-3-3ζ KO mice is associated with dopamine transporter dysfunction

Dopamine (DA) neurotransmission requires a complex series of enzymatic reactions that are tightly linked to catecholamine exocytosis and receptor interactions on pre- and postsynaptic neurons. Regulation of dopaminergic signalling is primarily achieved through reuptake of extracellular DA by the DA transporter (DAT) on presynaptic neurons. Aberrant regulation of DA signalling, and in particular hyperactivation, has been proposed as a key insult in the presentation of schizophrenia and related neuropsychiatric disorders. We recently identified 14-3-3ζ as an essential component of neurodevelopment and a central risk factor in the schizophrenia protein interaction network. Our analysis of 14-3-3ζ-deficient mice now shows that baseline hyperactivity of knockout (KO) mice is rescued by the antipsychotic drug clozapine. 14-3-3ζ KO mice displayed enhanced locomotor hyperactivity induced by the DA releaser amphetamine. Consistent with 14-3-3ζ having a role in DA signalling, we found increased levels of DA in the striatum of 14-3-3ζ KO mice. Although 14-3-3ζ is proposed to modulate activity of the rate-limiting DA biosynthesis enzyme, tyrosine hydroxylase (TH), we were unable to identify any differences in total TH levels, TH localization or TH activation in 14-3-3ζ KO mice. Rather, our analysis identified significantly reduced levels of DAT in the absence of notable differences in RNA or protein levels of DA receptors D1–D5. Providing insight into the mechanisms by which 14-3-3ζ controls DAT stability, we found a physical association between 14-3-3ζ and DAT by co-immunoprecipitation. Taken together, our results identify a novel role for 14-3-3ζ in DA neurotransmission and provide support to the hyperdopaminergic basis of pathologies associated with schizophrenia and related disorders.

Self-Assembled Nanoparticles from Phenolic Derivatives for Cancer Therapy

Therapeutic nanoparticles hold clinical promise for cancer treatment by avoiding limitations of conventional pharmaceuticals. Herein, a facile and rapid method is introduced to assemble poly(ethylene glycol) (PEG)-modified Pt prodrug nanocomplexes through metal-polyphenol complexation and combined with emulsification, which results in ≈100 nm diameter nanoparticles (PtP NPs) that exhibit high drug loading (0.15 fg Pt per nanoparticle) and low fouling properties. The PtP NPs are characterized for potential use as cancer therapeutics. Mass cytometry is used to quantify uptake of the nanoparticles and the drug concentration in individual cells in vitro. The PtP NPs have long circulation times, with an elimination half-life of ≈18 h in healthy mice. The in vivo antitumor activity of the PtP NPs is systematically investigated in a human prostate cancer xenograft mouse model. Mice treated with the PtP NPs demonstrate four times better inhibition of tumor growth than either free prodrug or cisplatin. This study presents a promising strategy to prepare therapeutic nanoparticles for biomedical applications.

Synthesis of Metal Nanoparticles in Metal‐Phenolic Networks: Catalytic and Antimicrobial Applications of Coated Textiles

The synthesis of metal nanoparticle (NP)-coated textiles (nanotextiles) is achieved by a dipping process in water without toxic chemicals or complicated synthetic procedures. By taking advantage of the unique nature of tannic acid, metal-phenolic network-coated textiles serve as reducing and stabilizing sites for the generation of metal nanoparticles of controllable size. The textiles can be decorated with various metal nanoparticles, including palladium, silver, or gold, and exhibit properties derived from the presence of the metal nanoparticles, for example, catalytic activity in water (>96% over five cycles using palladium nanoparticles) and antibacterial activity against Gram-negative bacteria (inhibition of Escherichia coli using silver nanoparticles) that outperforms a commercial bandage. The reported strategy offers opportunities for the development of hybrid nanomaterials that may have application in fields outside of catalysis and antimicrobials, such as sensing and smart clothing.

Self-Assembled Metal-Phenolic Networks on Emulsions as Low-Fouling and pH-Responsive Particles

Interfacial self-assembly is a powerful organizational force for fabricating functional nanomaterials, including nanocarriers, for imaging and drug delivery. Herein, the interfacial self-assembly of pH-responsive metal-phenolic networks (MPNs) on the liquid-liquid interface of oil-in-water emulsions is reported. Oleic acid emulsions of 100-250 nm in diameter are generated by ultrasonication, to which poly(ethylene glycol) (PEG)-based polyphenolic ligands are assembled with simultaneous crosslinking by metal ions, thus forming an interfacial MPN. PEG provides a protective barrier on the emulsion phase and renders the emulsion low fouling. The MPN-coated emulsions have a similar size and dispersity, but an enhanced stability when compared with the uncoated emulsions, and exhibit a low cell association in vitro, a blood circulation half-life of ≈50 min in vivo, and are nontoxic to healthy mice. Furthermore, a model anticancer drug, doxorubicin, can be encapsulated within the emulsion phase at a high loading capacity (≈5 fg of doxorubicin per emulsion particle). The MPN coating imparts pH-responsiveness to the drug-loaded emulsions, leading to drug release at cell internalization pH and a potent cell cytotoxicity. The results highlight a straightforward strategy for the interfacial nanofabrication of pH-responsive emulsion-MPN systems with potential use in biomedical applications.

Using minimalist self-assembling peptides as hierarchical scaffolds to stabilize growth factors and promote stem cell integration in the injured brain

Neurotrophic growth factors are effective in slowing progressive degeneration and/or promoting neural repair through the support of residual host and/or transplanted neurons. However, limitations including short half‐life and enzyme susceptibility of growth factors highlight the need for alternative strategies to prolong localised delivery at a site of injury. Here, we establish the utility of minimalist N‐fluorenylmethyloxycarbonyl (Fmoc) self‐assembling peptides (SAPs) as growth factor delivery vehicle, targeted at supporting neural transplants in an animal model of Parkinsons disease. The neural tissue‐specific SAP, Fmoc‐DIKVAV, demonstrated sustained release of glial cell line derived neurotrophic factor, up to 172 hr after gel loading. This represents a significant advance in drug delivery, because its lifetime in phosphate buffered saline was less than 1 hr. In vivo transplantation of neural progenitor cells, together with our growth factor‐loaded material, into the injured brain improved graft survival compared with cell transplants alone. We show for the first time the use of minimalist Fmoc‐SAP in an in vivo disease model for sustaining the delivery of neurotrophic growth factors, facilitating their spatial and temporal delivery in vivo, whilst also providing an enhanced niche environment for transplanted cells.

Development of chondrocyte-seeded electrosprayed nanoparticles for repair of articular cartilage defects in rabbits.

Due to limited self-healing capacity in cartilages, there is a rising demand for an innovative therapy that promotes chondrocyte proliferation while maintaining its biofunctionality for transplantation. Chondrocyte transplantation has received notable attention; however, the tendencies of cell de-differentiation and de-activation of biofunctionality have been major hurdles in its development, delaying this therapy from reaching the clinic. We believe it is due to the non-stimulative environment in the injured cartilage, which is unable to provide sustainable physical and biological supports to the newly grafted chondrocytes. Therefore, we evaluated whether providing an appropriate matrix to the transplanted chondrocytes could manipulate cell fate and recovery outcomes. Here, we proposed the development of electrosprayed nanoparticles composed of cartilage specific proteins, namely collagen type II and hyaluronic acid, for implantation with pre-seeded chondrocytes into articular cartilage defects. The fabricated nanoparticles were pre-cultured with chondrocytes before implantation into injured articular cartilage. The study revealed a significant potential for nanoparticles to support pre-seeded chondrocytes in cartilage repair, serving as a protein delivery system while improving the survival and biofunctionality of transplanted chondrocytes for prolonged period of time.