Electrospun fiber-mediated delivery of neurotrophin-3 mRNA for neural tissue engineering applications

Aligned electrospun fibers provide topographical cues and local therapeutic delivery to facilitate robust peripheral nerve regeneration. mRNA delivery enables transient expression of desired proteins that promote axonal regeneration. However, no prior work delivers mRNA from electrospun fibers for peripheral nerve regeneration applications. Here, we developed the first aligned electrospun fibers to deliver pseudouridine-modified (Ψ) neurotrophin-3 (NT-3) mRNA (ΨNT-3mRNA) to primary Schwann cells and assessed NT-3 secretion and bioactivity. We first electrospun aligned poly(L-lactic acid) (PLLA) fibers and coated them with the anionic substrates dextran sulfate sodium salt (DSS) or poly(3,4-dihydroxy-L-phenylalanine) (pDOPA). Cationic lipoplexes containing ΨNT-3mRNA complexed to JetMESSENGER® were then immobilized to the fibers, resulting in detectable ΨNT-3mRNA release for 28 days from all fiber groups investigated (PLLA+mRNA, 0.5DSS4h+mRNA, and 2pDOPA4h+mRNA). The 2pDOPA4h+mRNA group significantly increased Schwann cell secretion of NT-3 for 21 days compared to control PLLA fibers (p < 0.001-0.05) and, on average, increased Schwann cell secretion of NT-3 by ≥ 2-fold compared to bolus mRNA delivery from the 1µgBolus+mRNA and 3µgBolus+mRNA groups. The 2pDOPA4h+mRNA fibers supported Schwann cell secretion of NT-3 at levels that significantly increased dorsal root ganglia (DRG) neurite extension by 44% (p < 0.0001) and neurite area by 64% (p < 0.001) compared to control PLLA fibers. The data show that the 2pDOPA4h+mRNA fibers enhance the ability of Schwann cells to promote neurite growth from DRG, demonstrating this platform's potential capability to improve peripheral nerve regeneration. STATEMENT OF SIGNIFICANCE: Aligned electrospun fibers enhance axonal regeneration by providing structural support and guidance cues, but further therapeutic stimulation is necessary to improve functional outcomes. mRNA delivery enables the transient expression of therapeutic proteins, yet achieving local, sustained delivery remains challenging. Previous work shows that genetic material delivery from electrospun fibers improves regeneration; however, mRNA delivery has not been explored. Here, we examine mRNA delivery from aligned electrospun fibers to enhance neurite outgrowth. We show that immobilization of NT-3mRNA/JetMESSENGER® lipoplexes to aligned electrospun fibers functionalized with pDOPA enables local, sustained NT-3mRNA delivery to Schwann cells, increasing Schwann cell secretion of NT-3 and enhancing DRG neurite outgrowth. This study displays the potential benefits of electrospun fiber-mediated mRNA delivery platforms for neural tissue engineering.

Poly(amino ester)-Based Polymers for Gene and Drug Delivery Systems and Further Application toward Cell Culture System

Various synthetic polymers based on poly(amino ester) (PAE) are suggested as candidates for gene and drug delivery owing to their pH-responsiveness, which contributes to efficient delivery performance. PAE-based pH-responsive polymers are more biodegradable and hydrophilic than other types of pH-responsive polymers. The functionality of PAE-based polymers can be reinforced by using different chemical modifications to improve the efficiency of gene and drug delivery. Additionally, PAE-based polymers are used in many ways in the biomedical field, such as in transdermal delivery and stem cell culture systems. Here, the recent novel PAE-based polymers designed for gene and drug delivery systems along with their further applications toward adult stem cell culture systems are reviewed. The synthetic tactics are contemplated and pros and cons of each type of polymer are analyzed, and detailed examples of the different types are analyzed.

Tannic acid-based nanogel as an efficient anti-inflammatory agent

Biologically produced reactive oxygen species (ROS) are important signaling molecules in the human body. Despite their importance under normal conditions, abnormal overproduction of ROS under unbalanced or irregular homeostasis can cause severe inflammatory diseases. Various antioxidants have been developed in the biomedical field to resolve high levels of ROS; however, high doses of natural antioxidants such as polyphenol can induce side effects on health. Further, synthetic antioxidants are still controversial in regards to their safety and their complicated synthesis. Inspired from our previous work, a nitric oxide-scavenging nanogel designed for treating rheumatoid arthritis, we report herein a biocompatible tannic acid (TA)-based nanogel as an effective ROS scavenger. A polymeric phenylboronic acid-tannic acid nanogel (PTNG) was prepared by simply mixing through to the formation of phenylboronic ester bonds between polymeric phenylboronate and TA. We focused on the reaction of phenylboronic ester with H₂O₂, which readily consumes H₂O₂ molecules, and applied it as an antioxidant. In addition, TA is a well-known antioxidant, specifically a free radical scavenger; thus, we expected combinatory ROS scavenging effects for PTNG. Various ROS scavenging assays revealed the significant antioxidant effects of PTNG. Under an induced inflammation model in vitro, our PTNG showed high biocompatibility as well as strong anti-inflammatory effects. Furthermore, in the zymosan-induced peritonitis mouse model, a representative acute inflammation model in vivo, PTNG reduced significant neutrophil recruitment and pro-inflammatory cytokines, indicating successful alleviation of inflammation. On the basis of these results, we suggest that PTNG has great potential as an antioxidant and should find application in the treatment of further ROS-overproducing inflammatory diseases.

Scaffold-mediated non-viral delivery platform for CRISPR/Cas9-based genome editing

Genome editing, especially via the simple and versatile type II CRISPR/Cas9 system, offers an effective avenue to precisely control cell fate, an important aspect of tissue regeneration. Unfortunately, most CRISPR/Cas9 non-viral delivery strategies only utilise micro-/nano-particle delivery methods. While these approaches provide reasonable genomic editing efficiencies, their systemic delivery may lead to undesirable off-target effects. For in vivo applications, a more localized and sustained delivery approach may be useful, particularly in the context of tissue regeneration. Here, we developed a scaffold that delivers the CRISPR/Cas9 components (i.e. single guide RNA (sgRNA) and Cas9 protein complexes) in a localized and non-viral manner. Specifically, using mussel-inspired bioadhesive coating, polyDOPA-melanin (pDOPA), we adsorbed Cas9:sgRNA lipofectamine complexes onto bio-mimicking fiber scaffolds. To evaluate the genome-editing efficiency of this platform, U2OS.EGFP cells were used as the model cell type. pDOPA coating was essential in allowing Cas9:sgRNA lipofectamine complexes to adhere onto the scaffolds with a higher loading efficiency, while laminin coating was necessary for maintaining cell viability and proliferation on the pDOPA-coated fibers for effective gene editing (21.5% editing efficiency, p < 0.001). Importantly, U2OS.EGFP cells took up Cas9:sgRNA lipofectamine complexes directly from the scaffolds via reverse transfection. Overall, we demonstrate the efficacy of such fiber scaffolds in providing localized, sustained and non-viral delivery of Cas9:sgRNA complexes. Such genome editing scaffolds may find useful applications in tissue regeneration. STATEMENT OF SIGNIFICANCE: Currently, there is a lack of effective non-viral means to deliver CRISPR/Cas9 components for genome editing. Most existing approaches only utilize micro-/nano-particles by injection or systemic delivery, which may lead to undesirable off-target effects. Here, we report a platform that delivers the CRISPR/Cas9 components (i.e. single guide RNA (sgRNA) and Cas9 protein complexes) in a localized and sustained manner. We used mussel-inspired bioadhesive coating to functionalize the bio-mimicking fiber scaffolds with Cas9:sgRNA lipofectamine complexes, to allow effective gene editing for the cells seeded on the scaffolds. Importantly, the cells took up Cas9:sgRNA lipofectamine complexes directly from the scaffolds. Such genome editing scaffolds may find useful applications in tissue regeneration.

Sphingosine-1-Phosphate Immobilized on Nanotopographical Scaffolds Improve Myogenic Differentiation

The skeletal muscle consists of highly aligned dense cables of collagen fibers with nanometer feature size to support muscle fibers. The skeletal myocyte can be greatly affected to differentiate by their surrounding topographical structure. To improve myogenic differentiation, we fabricated cell culture platform that sphingosine-1-phosphate (S1P) which regulated myocyte behavior is immobilized on a biomimetic nanopatterned polyurethaneacrylate (PUA) substrate using 3,4-dihydroxyphenylalanine (L-DOPA) for providing topographical and biological cues synergistically. In the present study, we hypothesized that cultured C2C12 cells can be induced to synergistically promote myogenic differenntiation on nanopatterned PUA-L-DOPA-S1P. We confirmed that nanopatterned PUA-L-DOPA-S1P has high hydrophilicity with a suitable range of water contact angle and small intensity of phosphate peak (P2p) by analyses of water contact analyzer and X-ray photoelectron spectroscopy. In addition, C2C12 cells culured on nanopatterned PUA-L-DOPA-S1P has well-oriented and organized myodubes formed with greater expression of myogenic regulatory factors such as MyoD and MyoG comapred to flat PUA groups. This functional platform which is not only provided topographical and biological cues has a suitable potential function to apply muscle cell niche as similar structure of muscle fiber but also utilized cell behavior within tissue engineered scaffolds and cellular microenvironment.

3,4-Dihydroxy-L-Phenylalanine as a Novel Covalent Linker of Extracellular Matrix Proteins to Polyacrylamide Hydrogels with a Tunable Stiffness

Cells acquire mechanical information from their surrounding and convert this into biochemical activity. The concept and mechanism behind this cellular mechanosensing and mechanotransduction are often studied by means of two-dimensional hydrogels. Polyacrylamide hydrogels (PAAMs) offer chemical, mechanical, and optical advantages but due to their inert surface do not allow protein and cell adherence. Several cross-linkers have been used to functionalize the surface of PAAMs with extracellular matrix (ECM) proteins to enable cell culture. However, the most commonly used cross-linkers are either unstable, expensive, or laborious and often show heterogeneous coating or require PAAM modification. Here, we introduce 3,4-dihydroxy-l-phenylalanine (L-DOPA) as a novel cross-linker that can functionalize PAAMs with ECM without the above-mentioned disadvantages. A homogenous collagen type I and fibronectin coating was observed after L-DOPA functionalization. Fibroblasts responded to differences in PAAMs' stiffness; morphology, cell area, and protein localization were all affected as expected, in accordance with literature where other cross-linkers were used. In conclusion, L-DOPA can be used as a cross-linker between PAAMs and ECM and represents a novel, straightforward, nonlaborious, and robust method to functionalize PAAMs for cell culture to study cell mechanosensing.