Sirolimus-Embedded Silk Microneedle Wrap to Prevent Neointimal Hyperplasia in Vein Graft Model.

We investigated the role of a sirolimus-embedded silk microneedle (MN) wrap as an external vascular device for drug delivery efficacy, inhibition of neointimal hyperplasia, and vascular remodeling. Using dogs, a vein graft model was developed to interpose the carotid or femoral artery with the jugular or femoral vein. The control group contained four dogs with only interposed grafts; the intervention group contained four dogs with vein grafts in which sirolimus-embedded silk-MN wraps were applied. After 12-weeks post-implantation, 15 vein grafts in each group were explanted and analyzed. Vein grafts applied with the rhodamine B-embedded silk-MN wrap showed far higher fluorescent signals than those without the wrap. The diameter of vein grafts in the intervention group decreased or remained stable without dilatation; however, it increased in the control group. The intervention group had femoral vein grafts with a significantly lower mean neointima-to-media ratio, and had vein grafts with an intima layer showing a significantly lower collagen density ratio than the control group. In conclusion, sirolimus-embedded silk-MN wrap in a vein graft model successfully delivered the drug to the intimal layer of the vein grafts. It prevented vein graft dilatation, avoiding shear stress and decreasing wall tension, and it inhibited neointimal hyperplasia.

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.

Insertion of Vertically Aligned Nanowires into Living Cells by Inkjet Printing of Cells.

Effective insertion of vertically aligned nanowires (NWs) into cells is critical for bioelectrical and biochemical devices, biological delivery systems, and photosynthetic bioenergy harvesting. However, accurate insertion of NWs into living cells using scalable processes has not yet been achieved. Here, NWs are inserted into living Chlamydomonas reinhardtii cells (Chlamy cells) via inkjet printing of the Chlamy cells, representing a low-cost and large-scale method for inserting NWs into living cells. Jetting conditions and printable bioink composed of living Chlamy cells are optimized to achieve stable jetting and precise ink deposition of bioink for indentation of NWs into Chlamy cells. Fluorescence confocal microscopy is used to verify the viability of Chlamy cells after inkjet printing. Simple mechanical considerations of the cell membrane and droplet kinetics are developed to control the jetting force to allow penetration of the NWs into cells. The results suggest that inkjet printing is an effective, controllable tool for stable insertion of NWs into cells with economic and scale-related advantages.

Prolonged hydrogen production by engineered green algae photovoltaic power stations.

Interest in securing energy production channels from renewable sources is higher than ever due to the daily observation of the impacts of climate change. A key renewable energy harvesting strategy achieving carbon neutral cycles is artificial photosynthesis. Solar-to-fuel routes thus far relied on elaborately crafted semiconductors, undermining the cost-efficiency of the system. Furthermore, fuels produced required separation prior to utilization. As an artificial photosynthesis design, here we demonstrate the conversion of swimming green algae into photovoltaic power stations. The engineered algae exhibit bioelectrogenesis, en route to energy storage in hydrogen. Notably, fuel formation requires no additives or external bias other than CO2 and sunlight. The cellular power stations autoregulate the oxygen level during artificial photosynthesis, granting immediate utility of the photosynthetic hydrogen without separation. The fuel production scales linearly with the reactor volume, which is a necessary trait for contributing to the large-scale renewable energy portfolio.

Highly-sensitive single-step sensing of levodopa by swellable microneedle-mounted nanogap sensors.

Microneedle (MN) sensing of biomarkers in interstitial fluid (ISF) can overcome the challenges of self-diagnosis of diseases by a patient, such as blood sampling, handling, and measurement analysis. However, the MN sensing technologies still suffer from poor measurement accuracy due to the small amount of target molecules present in ISF, and require multiple steps of ISF extraction, ISF isolation from MN, and measurement with additional equipment. Here, we present a swellable MN-mounted nanogap sensor that can be inserted into the skin tissue, absorb ISF rapidly, and measure biomarkers in situ by amplifying the measurement signals by redox cycling in nanogap electrodes. We demonstrate that the MN-nanogap sensor measures levodopa (LDA), medication for Parkinson disease, down to 100 nM in an aqueous solution, and 1 µM in both the skin-mimicked gelatin phantom and porcine skin.

Balloon Catheter-Integrated Piezoelectric Micropyramid Arrays for Measuring Vascular Stiffness.

Atherosclerosis is one of the severe cardiovascular diseases in which blood vessels lose elasticity and the lumen narrows. If atherosclerosis worsens, it commonly leads to acute coronary syndrome (ACS) due to the rupture of vulnerable plaque or aortic aneurysm. As the mechanical properties of vascular tissues vary from their conditions, measuring the vascular stiffness of an inner blood vessel wall may be applied to the accurate diagnosis of atherosclerotic symptoms. Therefore, early mechanical detection of vascular stiffness is highly needed for immediate medical attention for ACS. Even with conventional examination methods such as intravascular ultrasonography and optical coherence tomography, several limitations still remain that make it difficult to directly determine the mechanical properties of the vascular tissue. As piezoelectric materials convert mechanical energy to electricity without an external power source, a piezoelectric nanocomposite could be utilized as a balloon catheter-integrated mechanical sensor on its surface. Here, we present piezoelectric nanocomposite micropyramid balloon catheter (p-MPB) arrays for measuring vascular stiffness. We study the structural characterization and feasibility of p-MPB as endovascular sensors by conducting finite element method analyses. Also, multifaceted piezoelectric voltages are measured by compression/release tests, in vitro vascular phantom tests, and ex vivo porcine heart tests to confirm that the p-MPB sensor properly operates in blood vessels.

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.

Controlled release of bupivacaine HCl through microchannels of biodegradable drug delivery device.

Local and prolonged delivery of local analgesics is much desired for post-operative pain management. For delivery of local analgesics at a constant rate over couple of days, a microfluidic device comprised of a drug reservoir and microchannels for drug release was developed using a biodegradable polymer, 85/15 poly(lactic-co-glycolic acid). Unlike conventional methods relying on material property, this device enables convenient modulation of the release speed of drugs by a simple change of the channel geometry such as the length and cross-sectional area. Bupivacaine was selected as our model local analgesic drug and its diffusional transport through microchannels was studied using the microfluidic devices. However, since the salt form of bupivacaine, bupivacaine hydrochloride, has pH-dependent solubility, its precipitation in microchannels had an adverse impact on the release performance of the microfluidic drug delivery devices. Thus, in this investigation, the diffusional transport and precipitation of bupivacaine hydrochloride in microfluidic channels were studied using in vitro release experiments and optical analysis. Furthermore, a concept of co-delivery of bupivacaine hydrochloride together with acidic additives was demonstrated to achieve a zero-order delivery of bupivacaine hydrochloride without the clogging of microchannels by its precipitation.

Research progress on detachable microneedles for advanced applications.

INTRODUCTION: Microneedles (MNs) have undergone great advances in transdermal drug delivery, and commercialized MN applications are currently available in vaccination and cosmetic products. Despite the development of MN technologies, common limitations of MN products still exist. Typical MN patches are applied to target tissues, where the substrate of an MN patch must remain until the drug is delivered, which reduces patients' compliance and hinders the applicability of the MN technique to many diseases in various tissues. MN research is ongoing to solve this issue. AREAS COVERED: Most recent MNs developed by combining various biomaterials with appropriate fabrication processes are detachable MNs (DeMNs). Because of advances in biomaterials and fabrication techniques, various DeMNs have been rapidly developed. In this review, we discuss four types of DeMN: substrate-separable, multi-layered, crack-inducing, and shell DeMN. These DeMNs deliver various therapeutic agents ranging from small- and large-molecular-weight drugs to proteins and even stem cells for regeneration therapy. Furthermore, DeMNs are applied to skin as well as non-transdermal tissues. EXPERT OPINION: It has become increasingly evident that novel MN technologies can be expected in terms of designs, fabrication methods, materials, and even possible application sites given the recent advances in DeMNs.

A laser-driven optical atomizer: photothermal generation and transport of zeptoliter-droplets along a carbon nanotube deposited hollow optical fiber.

From mechanical syringes to electric field-assisted injection devices, precise control of liquid droplet generation has been sought after, and the present state-of-the-art technologies have provided droplets ranging from nanoliter to subpicoliter volume sizes. In this study, we present a new laser-driven method to generate liquid droplets with a zeptoliter volume, breaking the fundamental limits of previous studies. We guided an infrared laser beam through a hollow optical fiber (HOF) with a ring core whose end facet was coated with single-walled carbon nanotubes. The laser light was absorbed by this nanotube film and efficiently generated a highly localized microring heat source. This evaporated the liquid inside the HOF, which rapidly recondensed into zeptoliter droplets in the surrounding air at room temperature. We spectroscopically confirmed the chemical structures of the liquid precursor maintained in the droplets by atomizing dye-dissolved glycerol. Moreover, we explain the fundamental physical principles as well as functionalities of the optical atomizer and perform a detailed characterization of the droplets. Our approach has strong prospects for nanoscale delivery of biochemical substances in minuscule zeptoliter volumes.

Self-Plugging Microneedle (SPM) for Intravitreal Drug Delivery.

Intravitreal injection (IVI) is a common technology which is used to treat ophthalmic diseases inside eyeballs by delivering various drugs into the vitreous cavity using hypodermic needles. However, in some cases, there are possible side effects such as ocular tissue damage due to repeated injection or eyeball infection through the hole created during the needle retraction process. The best scenario of IVI is a one-time injection of drugs without needle retraction, keeping the system of the eyeball closed. Microneedles (MNs) have been applied to ocular tissues over 10 years, and no serious side effects on ocular tissue due to MN injection have been reported. Therefore, a self-plugging MN (SPM) is developed to perform intraocular drug delivery and to seal the scleral puncture simultaneously. The SPMs are fabricated by a thermal drawing process and then coated with a polymeric carrier of drugs and a hydrogel-based scleral plugging component. Each coated functional layer is characterized and demonstrated by in vitro and ex vivo experiments. Finally, in vivo tests using a porcine model confirms prompt sealing of SPM and sustained intraocular drug delivery.

In vivo O2 measurement inside single photosynthetic cells.

The oxygen evolution of single cells was investigated using a nano-probe with an ultra-micro electrode (UME) in a submicron sized system in combination with a micro-fluidic system. A single cell was immobilized in the micro-fluidic system and a nano-probe was inserted into the cytosolic space of the single cell. Then, the UME was used for an in vivo amperometric experiment at a fixed potential and electrochemical impedance spectroscopy to detect oxygen evolution of the single cell under various light intensities.

Direct extraction of photosynthetic electrons from single algal cells by nanoprobing system.

There are numerous sources of bioenergy that are generated by photosynthetic processes, for example, lipids, alcohols, hydrogen, and polysaccharides. However, generally only a small fraction of solar energy absorbed by photosynthetic organisms is converted to a form of energy that can be readily exploited. To more efficiently use the solar energy harvested by photosynthetic organisms, we evaluated the feasibility of generating bioelectricity by directly extracting electrons from the photosynthetic electron transport chain before they are used to fix CO(2) into sugars and polysaccharides. From a living algal cell, Chlamydomonas reinhardtii, photosynthetic electrons (1.2 pA at 6000 mA/m(2)) were directly extracted without a mediator electron carrier by inserting a nanoelectrode into the algal chloroplast and applying an overvoltage. This result may represent an initial step in generating "high efficiency" bioelectricity by directly harvesting high energy photosynthetic electrons.

Photosynthetic Nanomaterial Hybrids for Bioelectricity and Renewable Energy Systems.

Harvesting solar energy in the form of electricity from the photosynthesis of plants, algal cells, and bacteria has been researched as the most environment-friendly renewable energy technology in the last decade. The primary challenge has been the engineering of electrochemical interfacing with photosynthetic apparatuses, organelles, or whole cells. However, with the aid of low-dimensional nanomaterials, there have been many advances, including enhanced photon absorption, increased generation of photosynthetic electrons (PEs), and more efficient transfer of PEs to electrodes. These advances have demonstrated the possibility for the technology to advance to a new level. In this article, the fundamentals of photosynthesis are introduced. How PE harvesting systems have improved concerning solar energy absorption, PE production, and PE collection by electrodes is discussed. The review focuses on how different kinds of nanomaterials are applied and function in interfacing with photosynthetic materials for enhanced PE harvesting. Finally, the review analyzes how the performance of PE harvesting and stand-alone systems have evolved so far and its future prospects.

Single Administration of a Biodegradable, Separable Microneedle Can Substitute for Repeated Application of Eyedrops in the Treatment of Infectious Keratitis.

Infectious keratitis is mainly treated with topical antibiotics. To achieve and maintain the required therapeutic concentration in the cornea where the tear fluid continuously rinses the surface, the antibiotics must be frequently applied, even while the patient is sleeping, and oral medication is sometimes required. However, the inevitably poor compliance and avascular nature of the cornea decrease drug bioavailability. In this study, a single microneedle (MN) is injected into the cornea to substitute for the repeated application of eyedrops in the treatment of infectious keratitis. After comparing the mechanical integrity and drug release profiles of three different drug-tips, the drug-tip with the "high" drug concentration that releases 12.5 ng drug within 3 days is applied to a cornea to evaluate the transferability and in vivo drug release. In the treatment of infectious keratitis with repeated application of eyedrops for six consecutive days, a single MN injection is substituted for the initial 3 days of eyedrop applications. The progression remains similarly attenuated after 3 days without eyedrops, and comparable efficacy is achieved on day 6 when combined with delayed eyedrop treatment from day 3. Thus, the single administration of a biodegradable MN can substitute for the repeated application of eyedrops in the treatment of infectious keratitis.

Highly flexible and porous silk fibroin microneedle wraps for perivascular drug delivery.

Various perivascular drug delivery techniques have been demonstrated for localized post-treatment of intimal hyperplasia: a vascular inflammatory response caused by endothelial damages. Although most perivascular devices have focused on controlling the delivery duration of anti-proliferation drug, the confined and unidirectional delivery of the drug to the target tissue has become increasingly important. In addition, careful attention should also be paid to the luminal stability and the adequate exchange of vascular protein or cell between the blood vessel and extravascular tissue to avoid any side effect from the long-term application of any perivascular device. Here, a highly flexible and porous silk fibroin microneedle wrap (Silk MN wrap) is proposed to directly inject antiproliferative drug to the anastomosis sites while ensuring sufficient vascular exchanges. Drug-embedded silk MNs were transfer-molded on a highly flexible and porous silk wrap. The enhanced cell compatibility, molecular permeability, and flexibility of silk MN wrap guaranteed the structural integrity of blood vessels. Silk wrap successfully supported the silk MNs and induced multiple MN penetration to the target tissue. Over 28 days, silk MN wrap significantly inhibited intimal hyperplasia with a 62.1% reduction in neointimal formation.

Enhanced interfacial electron transfer between thylakoids and RuO2 nanosheets for photosynthetic energy harvesting.

The harvesting of photosynthetic electrons (PEs) directly from photosynthetic complexes has been demonstrated over the past decade. However, their limited efficiency and stability have hampered further practical development. For example, despite its importance, the interfacial electron transfer between the photosynthetic apparatus and the electrode has received little attention. In this study, we modified electrodes with RuO2 nanosheets to enhance the extraction of PEs from thylakoids, and the PE transfer was promoted by proton adsorption and surface polarity characteristics. The adsorbed protons maintained the potential of an electrode more positive, and the surface polarity enhanced thylakoid attachment to the electrode in addition to promoting ensemble docking between the redox species and the electrode. The RuO2 bioanode exhibited a five times larger current density and a four times larger power density than the Au bioanode. Last, the electric calculators were successfully powered by photosynthetic energy using a RuO2 bioanode.

Electrosprayed Thylakoid-Alginate Film on a Micro-Pillar Electrode for Scalable Photosynthetic Energy Harvesting.

Direct harvesting of electricity from photosynthesis is highly desired as an eco-friendly and sustainable energy harvesting technology. Photosynthetic apparatuses isolated from plants, such as thylakoid membranes (TMs), are deposited on an electrode by which photosynthetic electrons (PEs) are collected from water splitting. To enhance PE collection efficiency, it is critical to increase the electrochemical interfaces between TMs and the electrode. Considering the size of TMs to be around a few hundred nanometer, we hypothesize that an array of micropillar-shaped (MP) electrode can maximize the TM/electrode interface area. Thus, we developed MP electrodes with different heights and investigated the electrospraying of TM-alginate mixtures to fill the gaps between MPs uniformly and conformally. The uniformity of the TM-alginate film and the interaction between the TM and the MP electrode were evaluated to understand how the MP heights and film quality influenced the magnitude of the PE currents. PE currents increased up to 2.4 times for an MP electrode with an A/R of 1.8 compared to a flat electrode, indicating increased direct contact interface between TMs and the electrode. Furthermore, to demonstrate the scalability of this approach, an array of replicated SU-8 MP electrodes was prepared and PE currents of up to 3.2 µA were monitored without a mediator under 68 mW/cm2. Finally, the PE current harvesting was sustained for 14 days without decay, demonstrating the long-term stability of the TM-alginate biophotoanodes.

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.

Microneedle drug eluting balloon for enhanced drug delivery to vascular tissue.

High rates of restenosis and neointimal formation have driven increasing interest in the application of drug eluting balloons (DEB) as counteractive measures for intraluminal drug delivery. The use of DEBs eliminates the need for stents so that serious side effects including in-stent restenosis and stent thrombosis can be avoided and long-term medication of anti-platelet agent is not needed. Despite their benefits, DEBs have poor drug delivery efficiency due to short balloon inflation times (30-60 s) that limit the passive drug diffusion from the balloon surface to the luminal lesion. To increase drug delivery efficiency, a microneedle DEB (MNDEB) was developed by a conformal transfer molding process using a thin polydimethylsiloxane mold bearing a negative array of MNs of 200 µm in height. A MN array composed of UV curable resin was formed onto the surface of DEB, and drugs were coated onto the structure. The mechanical properties of the MN array were investigated and MN penetration into luminal vasculature was confirmed in vivo. An increase in drug delivery efficiency compared to a standard DEB was demonstrated in an in vivo test in a rabbit aorta. Finally, the superior therapeutic efficacy of MNDEBs was evaluated using an atherosclerosis rabbit model.