Effect of sequential release of sirolimus and rosuvastatin using silk fibroin microneedle to prevent intimal hyperplasia.

Intimal hyperplasia (IH) is a major cause of vascular restenosis after bypass surgery, which progresses as a series of processes from the acute to chronic stage in response to endothelial damage during bypass grafting. A strategic localized drug delivery system that reflects the pathophysiology of IH and minimizes systemic side effects is necessary. In this study, the sequential release of sirolimus, a mechanistic target of rapamycin (mTOR) inhibitor, and statin, an HMG-COA inhibitor, was realized as a silk fibroin-based microneedle device in vivo. The released sirolimus in the acute stage reduced neointima (NI) and vascular fibrosis through mTOR inhibition. Furthermore, rosuvastatin, which was continuously released from the acute to chronic stage, reduced vascular stiffness and apoptosis through the inactivation of Yes-associated protein (YAP). The sequential release of sirolimus and rosuvastatin confirmed the synergistic treatment effects on vascular inflammation, VSMC proliferation, and ECM degradation remodeling through the inhibition of transforming growth factor (TGF)-beta/NF-κB pathway. These results demonstrate the therapeutic effect on preventing restenosis with sufficient vascular elasticity and significantly reduced IH in response to endothelial damage. Therefore, this study suggests a promising strategy for treating coronary artery disease through localized drug delivery of customized drug combinations.

Co-Electrospun Silk Fibroin and Gelatin Methacryloyl Sheet Seeded with Mesenchymal Stem Cells for Tendon Regeneration.

Silk fibroin (SF) is a promising biomaterial for tendon repair, but its relatively rigid mechanical properties and low cell affinity have limited its application in regenerative medicine. Meanwhile, gelatin-based polymers have advantages in cell attachment and tissue remodeling but have insufficient mechanical strength to regenerate tough tissue such as tendons. Taking these aspects into account, in this study, gelatin methacryloyl (GelMA) is combined with SF to create a mechanically strong and bioactive nanofibrous scaffold (SG). The mechanical properties of SG nanofibers can be flexibly modulated by varying the ratio of SF and GelMA. Compared to SF nanofibers, mesenchymal stem cells (MSCs) seeded on SG fibers with optimal composition (SG7) exhibit enhanced growth, proliferation, vascular endothelial growth factor production, and tenogenic gene expression behavior. Conditioned media from MSCs cultured on SG7 scaffolds can greatly promote the migration and proliferation of tenocytes. Histological analysis and tenogenesis-related immunofluorescence staining indicate SG7 scaffolds demonstrate enhanced in vivo tendon tissue regeneration compared to other groups. Therefore, rational combinations of SF and GelMA hybrid nanofibers may help to improve therapeutic outcomes and address the challenges of tissue-engineered scaffolds for tendon regeneration.

Combination of Irreversible Electroporation and STING Agonist for Effective Cancer Immunotherapy.

Recently, cancer immunotherapy has received attention as a viable solution for the treatment of refractory tumors. However, it still has clinical limitations in its treatment efficacy due to inter-patient tumor heterogeneity and immunosuppressive tumor microenvironment (TME). In this study, we demonstrated the triggering of anti-cancer immune responses by a combination of irreversible electroporation (IRE) and a stimulator of interferon genes (STING) agonist. Optimal electrical conditions inducing damage-associated molecular patterns (DAMPs) by immunogenic cell death (ICD) were determined through in vitro 2D and 3D cell experiments. In the in vivo syngeneic lung cancer model, the combination of IRE and STING agonists demonstrated significant tumor growth inhibition. We believe that the combination strategy of IRE and STING agonists has potential for effective cancer immunotherapy.

A 0.9m Long 0.5gf Resolution Catheter-based Force Sensor for Real-Time Force Monitoring of Cardiovascular Surgery.

This paper presents a 0.9m long capacitive force sensor for a catheter integration, which measures a contact force to inner vessel wall or organs with a resolution of 0.5gf. The force sensor is implemented with a thin flexible printed circuit board (FPCB) encapsulated by a force sensitive medium, multilayer polydimethylsiloxane (PDMS). The parasitic capacitance $( \mathrm {C}_{P})$ inherent in long catheters significantly degrades the sensing accuracy of capacitive force sensors. To account for this, this work proposes a sensor interface with $\mathrm {C}_{P}$ canceller. By removing the 348pF (91.5%) of $\mathrm {C}_{\mathrm{P}}$with the $\mathrm {C}_{\mathrm{P}}$ canceller, the capacitive force sensor achieves a capacitance resolution of 16aF equivalent to a force error of 0.5gf, which is a $10 \times $ improvement compared to the conventional sensor interface. The proposed force sensor offers great potential for real-time force monitoring of cardiovascular surgery.

Electrospun Silk Fibroin Nanofibrous Scaffolds with Two-Stage Hydroxyapatite Functionalization for Enhancing the Osteogenic Differentiation of Human Adipose-Derived Mesenchymal Stem Cells.

The development of functional scaffolds with improved osteogenic potential is important for successful bone formation and mineralization in bone tissue engineering. In this study, we developed a functional electrospun silk fibroin (SF) nanofibrous scaffold functionalized with two-stage hydroxyapatite (HAp) particles, using mussel adhesive-inspired polydopamine (PDA) chemistry. HAp particles were first incorporated into SF scaffolds during the electrospinning process, and then immobilized onto the electrospun SF nanofibrous scaffolds containing HAp via PDA-mediated adhesive chemistry. We obtained two-stage HAp-functionalized SF nanofibrous scaffolds with improved mechanical properties and capable of providing a bone-specific physiological microenvironment. The developed scaffolds were tested for their ability to enhance the osteogenic differentiation of human adipose-derived mesenchymal stem cells (hADMSCs) in vitro and repair bone defect in vivo. To boost their ability for bone repair, we genetically modified hADMSCs with the transcriptional coactivator with PDZ-binding motif (TAZ) via polymer nanoparticle-mediated gene delivery. TAZ is a well-known transcriptional modulator that activates the osteogenic differentiation of mesenchymal stem cells (MSCs). Two-stage HAp-functionalized SF scaffolds significantly promoted the osteogenic differentiation of TAZ-transfected hADMSCs in vitro and enhanced mineralized bone formation in a critical-sized calvarial bone defect model. Our study shows the potential utility of SF scaffolds with nanofibrous structures and enriched inorganic components in bone tissue engineering.

Impact insertion of transfer-molded microneedle for localized and minimally invasive ocular drug delivery.

It has been challenging for microneedles to deliver drugs effectively to thin tissues with little background support such as the cornea. Herein, we designed a microneedle pen system, a single microneedle with a spring-loaded microneedle applicator to provide impact insertion. To firmly attach solid microneedles with 140 µm in height at the end of macro-scale applicators, a transfer molding process was employed. The fabricated microneedle pens were then applied to mouse corneas. The microneedle pens successfully delivered rhodamine dye deep enough to reach the stromal layer of the cornea with small entry only about 1000 µm(2). When compared with syringes or 30 G needle tips, microneedle pens could achieve more localized and minimally invasive delivery without any chances of perforation. To investigate the efficacy of microneedle pens as a way of drug delivery, sunitinib malate proven to inhibit in vitro angiogenesis, was delivered to suture-induced angiogenesis model. When compared with delivery by a 30 G needle tip dipped with sunitinib malate, only delivery by microneedle pens could effectively inhibit corneal neovascularization in vivo. Microneedle pens could effectively deliver drugs to thin tissues without impairing merits of using microneedles: localized and minimally invasive delivery.

Biodegradation-tunable mesoporous silica nanorods for controlled drug delivery.

Mesoporous silica in the forms of micro- or nanoparticles showed great potentials in the field of controlled drug delivery. However, for precision control of drug release from mesoporous silica-based delivery systems, it is critical to control the rate of biodegradation. Thus, in this study, we demonstrate a simple and robust method to fabricate "biodegradation-tunable" mesoporous silica nanorods based on capillary wetting of anodic aluminum oxide (AAO) template with an aqueous alkoxide precursor solution. The porosity and nanostructure of silica nanorods were conveniently controlled by adjusting the water/alkoxide molar ratio of precursor solutions, heat-treatment temperature, and Na addition. The porosity and biodegradation kinetics of the fabricated mesoporous nanorods were analyzed using N2 adsorption/desorption isotherm, TGA, DTA, and XRD. Finally, the performance of the mesoporous silica nanorods as drug delivery carrier was demonstrated with initial burst and subsequent "zero-order" release of anti-cancer drug, doxorubicin.

Perivascular biodegradable microneedle cuff for reduction of neointima formation after vascular injury.

Restenosis often occurs at the site of vascular grafting and may become fatal for patients. Restenosis at anastomosis sites is due to neointimal hyperplasia (NH) and difficult to treat with conventional treatments. Such abnormal growth of smooth muscle cells in tunica media of vascular tissue can be reduced by delivering anti-proliferation drugs such as paclitaxel (PTX) to the inner vascular layer. Drug eluting stents (DES) or drug eluting balloon (DEB) have been developed to treat such vascular diseases. However, they are less efficient in drug delivery due to the drug loss to blood stream and inadequate to be applied to re-stenotic area in the presence of stent or anastomosis sites. Recently, we have introduced microneedle cuff (MNC) as perivascular delivery devices to achieve high delivery efficiency to tunica media. In this study, we investigated in vivo microneedle insertion and efficacy in treating NH using a rabbit balloon injury model. Microneedle shape was optimized for reliable insertion into tunica media layer. Uniform distribution of PTX in tunica media delivered by MNC devices was also confirmed. Animal study demonstrated significant NH reduction by MNC treatments and much higher delivery efficiency than flat type devices.

Biodegradable micro-osmotic pump for long-term and controlled release of basic fibroblast growth factor.

Microelectromechanical system (MEMS) technology not only provides the possibility of integration of multiple functions but also enables more precise control of dosing of therapeutic agents when the therapeutic window is very limited. Local delivery of basic fibroblast growth factor (bFGF) over a specific dose and time course is critical for mesenchymal tissue regeneration. However, bFGF is degraded quickly in vivo and difficulty of controlling the dose level impedes its effective use in angiogenesis and tissue regeneration. We constructed biodegradable micro-osmotic pumps based on MEMS technology for long-term controlled release of bFGF. The devices were constructed by micro-molding and thermal assembly of 85/15 poly(L-lactide-co-glycolide) sheets. The release of bFGF was regulated at 40 ng/day for four weeks; bioactivity was assessed by monitoring the growth of 3T3 fibroblasts. The proposed devices can be further miniaturized and used for the delivery of multiple therapeutic agents at the individual releasing schedules.