Conductive Hydrogel Restores Electrical Conduction to Promote Neurological Recovery in a Rat Model

Spinal cord injury (SCI), caused by significant physical trauma, as well as other pathological conditions, results in electrical signaling disruption and loss of bodily functional control below the injury site. Conductive biomaterials have been considered a promising approach for treating SCI, owing to their ability to restore electrical connections between intact spinal cord portions across the injury site. In this study, we evaluated the ability of a conductive hydrogel, poly-3-amino-4-methoxybenzoic acid-gelatin (PAMB-G), to restore electrical signaling and improve neuronal regeneration in a rat SCI model generated using the compression clip method. Gelatin or PAMB-G was injected at the SCI site, yielding three groups: Control (saline), Gelatin, and PAMB-G. During the 8-week study, PAMB-G, compared to Control, had significantly lower proinflammatory factor expression, such as for tumor necrosis factor -α (0.388 ± 0.276 for PAMB-G vs. 1.027 ± 0.431 for Control) and monocyte chemoattractant protein (MCP)-1 (0.443 ± 0.201 for PAMB-G vs. 1.662 ± 0.912 for Control). In addition, PAMB-G had lower astrocyte and microglia numbers (35.75 ± 4.349 and 40.75 ± 7.890, respectively) compared to Control (50.75 ± 6.5 and 64.75 ± 10.72) and Gelatin (48.75 ± 4.787 and 71.75 ± 7.411). PAMB-G-treated rats also had significantly greater preservation and regeneration of remaining intact neuronal tissue (0.523 ± 0.059% mean white matter in PAMB-G vs 0.377 ± 0.044% in Control and 0.385 ± 0.051% in Gelatin) caused by reduced apoptosis and increased neuronal growth-associated gene expression. All these processes stemmed from PAMB-G facilitating increased electrical signaling conduction, leading to locomotive functional improvements, in the form of increased Basso-Beattie-Bresnahan scores and steeper angles in the slope test (76.667 ± 5.164 for PAMB-G, vs. 59.167 ± 4.916 for Control and 58.333 ± 4.082 for Gelatin), as well as reduced gastrocnemius muscle atrophy (0.345 ± 0.085 for PAMB-G, vs. 0.244 ± 0.021 for Control and 0.210 ± 0.058 for Gelatin). In conclusion, PAMB-G injection post-SCI resulted in improved electrical signaling conduction, which contributed to lowered inflammation and apoptosis, increased neuronal growth, and greater bodily functional control, suggesting its potential as a viable treatment for SCI.

Orally Ingested Self-Powered Stimulators for Targeted Gut-Brain Axis Electrostimulation to Treat Obesity and Metabolic Disorders

Obesity is a significant health concern that often leads to metabolic dysfunction and chronic diseases. This study introduces a novel approach to combat obesity using orally ingested self-powered electrostimulators. These electrostimulators consist of piezoelectric BaTiO3 (BTO) particles conjugated with capsaicin (Cap) and aim to activate the vagus nerve. Upon ingestion by diet-induced obese (DIO) mice, the BTO@Cap particles specifically target and bind to Cap-sensitive sensory nerve endings in the gastric mucosa. In response to stomach peristalsis, these particles generate electrical signals. The signals travel via the gut-brain axis, ultimately influencing the hypothalamus. By enhancing satiety signals in the brain, this neuromodulatory intervention reduces food intake, promotes energy metabolism, and demonstrates minimal toxicity. Over a 3-week period of daily treatments, DIO mice treated with BTO@Cap particles show a significant reduction in body weight compared to control mice, while maintaining their general locomotor activity. Furthermore, this BTO@Cap particle-based treatment mitigates various metabolic alterations associated with obesity. Importantly, this noninvasive and easy-to-administer intervention holds potential for addressing other intracerebral neurological diseases.

Harnessing HfO2 Nanoparticles for Wearable Tumor Monitoring and Sonodynamic Therapy in Advancing Cancer Care

Addressing the critical requirement for real-time monitoring of tumor progression in cancer care, this study introduces an innovative wearable platform. This platform employs a thermoplastic polyurethane (TPU) film embedded with hafnium oxide nanoparticles (HfO2 NPs) to facilitate dynamic tracking of tumor growth and regression in real time. Significantly, the synthesized HfO2 NPs exhibit promising characteristics as effective sonosensitizers, holding the potential to efficiently eliminate cancer cells through ultrasound irradiation. The TPU-HfO2 film, acting as a dielectric elastomer (DE) strain sensor, undergoes proportional deformation in response to changes in the tumor volume, thereby influencing its electrical impedance. This distinctive behavior empowers the DE strain sensor to continuously and accurately monitor alterations in tumor volume, determining the optimal timing for initiating HfO2 NP treatment, optimizing dosages, and assessing treatment effectiveness. Seamless integration with a wireless system allows instant transmission of detected electrical impedances to a smartphone for real-time data processing and visualization, enabling immediate patient monitoring and timely intervention by remote medical staff. By combining the dynamic tumor monitoring capabilities of the TPU-HfO2 film with the sonosensitizer potential of HfO2 NPs, this approach propels cancer care into the realm of telemedicine, representing a significant advancement in patient treatment.

Macrophage-Hitchhiked Orally Administered β-Glucans-Functionalized Nanoparticles as "Precision-Guided Stealth Missiles" for Targeted Pancreatic Cancer Therapy

The prognosis in cases of pancreatic ductal adenocarcinoma (PDAC) with current treatment modalities is poor owing to the highly desmoplastic tumor microenvironment (TME). Herein, a β-glucans-functionalized zinc-doxorubicin nanoparticle system (βGlus-ZnD NPs) that can be orally administered, is developed for targeted PDAC therapy. Following oral administration in PDAC-bearing mice, βGlus-ZnD NPs actively target/transpass microfold cells, overcome the intestinal epithelial barrier, and then undergo subsequent phagocytosis by endogenous macrophages (βGlus-ZnD@Mϕ). As hitchhiking cellular vehicles, βGlus-ZnD@Mϕ transits through the intestinal lymphatic system and enters systemic circulation, ultimately accumulating in the tumor tissue as a result of the tumor-homing and "stealth" properties that are conferred by endogenous Mϕ. Meanwhile, the Mϕ that hitchhikes βGlus-ZnD NPs is activated to produce matrix metalloproteinases, destroying the desmoplastic stromal barrier, and differentiates toward the M1 -like phenotype, modulating the TME and recruiting effector T cells, ultimately inducing apoptosis of the tumor cells. The combination of βGlus-ZnD@Mϕ and immune checkpoint blockade effectively inhibits the growth of the primary tumor and suppresses the development of metastasis. It thus represents an appealing approach to targeted PDAC therapy.

A low-energy emulsification platform based on a Diet Coke-Mentos reaction-derived bubbly flow for formulating various emulsions as drug carriers

The formulation of a drug using high-energy emulsification commonly causes drug deterioration. Exploiting the well-known Diet Coke-Mentos reaction (DCMR), a U-shaped tube reactor that can generate an eruption of bubbly flow that can serve as a low-energy emulsification platform, is proposed. The liquid in the U-tube reactor is a supersaturated solution of aqueous CO2, which mimics Diet Coke. When glass beads with rough surfaces, mimicking Mentos, are dropped into the carbonated water, an eruptive bubbly flow is spontaneously created, mediating effective emulsification at a compound water-oil interface. Experimental results demonstrate that DCMR-mediated bubbly flow may provide a versatile platform for the production of "oil-in-water" or "water-in-oil" droplets and Pickering emulsion composite particles as drug carriers. The DCMR-derived bubbly flow is generated without significant temperature elevation, so the activity of the drug to be emulsified is unaffected. In vivo results reveal the feasibility of using this low-energy emulsification platform to formulate an emulsion system that contains catalase, a temperature-sensitive oxidoreductase, to mitigate an experimentally formed paw inflammation in mice. The as-proposed emulsification platform is attractive for formulating numerous drug delivery systems on a small-scale in a customized manner to meet the needs of each individual for personalized medicine.

Ultrasound-Activated, Tumor-Specific In Situ Synthesis of a Chemotherapeutic Agent Using ZIF-8 Nanoreactors for Precision Cancer Therapy

The in situ transformation of low-toxicity precursors into a chemotherapeutic agent at a tumor site to enhance the efficacy of its treatment has long been an elusive goal. In this work, a zinc-based zeolitic imidazolate framework that incorporates pharmaceutically acceptable precursors is prepared as a nanoreactor (NR) system for the localized synthesis of an antitumor drug. The as-prepared NRs are administered intratumorally in a tumor-bearing mouse model and then irradiated with ultrasound (US) to activate the chemical synthesis. The US promotes the penetration of the administered NRs into the tumor tissue to cover the lesion entirely, although some NRs leak into the surrounding normal tissue. Nevertheless, only the tumor tissue, where the H₂O₂ concentration is high, is adequately exposed to the as-synthesized antitumor drug, which markedly impedes development of the tumor. No significant chemical synthesis is detected in the surrounding normal tissue, where the local H₂O₂ concentration is negligible and the US irradiation is not directly applied. The as-proposed tumor-specific in situ synthesis of therapeutic molecules induces hardly any significant in vivo toxicity and, thus, is potentially a potent biocompatible approach to precision chemotherapy.

Engineering Nano- and Microparticles as Oral Delivery Vehicles to Promote Intestinal Lymphatic Drug Transport

Targeted oral delivery of a drug via the intestinal lymphatic system (ILS) has the advantages of protecting against hepatic first-pass metabolism of the drug and improving its pharmacokinetic performance. It is also a promising route for the oral delivery of vaccines and therapeutic agents to induce mucosal immune responses and treat lymphatic diseases, respectively. This article describes the anatomical structures and physiological characteristics of the ILS, with an emphasis on enterocytes and microfold (M) cells, which are the main gateways for the transport of particulate delivery vehicles across the intestinal epithelium into the lymphatics. A comprehensive overview of recent advances in the rational engineering of particulate vehicles, along with the challenges and opportunities that they present for improving ILS drug delivery, is provided, and the mechanisms by which such vehicles target and transport through enterocytes or M cells are discussed. The use of naturally sourced materials, such as yeast microcapsules and their derived polymeric β-glucans, as novel ILS-targeting delivery vehicles is also reviewed. Such use is the focus of an emerging field of research. Their potential use in the oral delivery of nucleic acids, such as mRNA vaccines, is proposed.

A Noninvasive Gut-to-Brain Oral Drug Delivery System for Treating Brain Tumors

Most orally administered drugs fail to reach the intracerebral regions because of the intestinal epithelial barrier (IEB) and the blood-brain barrier (BBB), which are located between the gut and the brain. Herein, an oral prodrug delivery system that can overcome both the IEB and the BBB noninvasively is developed for treating gliomas. The prodrug is prepared by conjugating an anticancer drug on β-glucans using a disulfide-containing linker. Following oral administration in glioma-bearing mice, the as-prepared prodrug can specifically target intestinal M cells, transpass the IEB, and be phagocytosed/hitchhiked by local macrophages (Mϕ). The Mϕ-hitchhiked prodrug is transported to the circulatory system via the lymphatic system, crossing the BBB. The tumor-overexpressed glutathione then cleaves the disulfide bond within the prodrug, releasing the active drug, improving its therapeutic efficacy. These findings reveal that the developed prodrug may serve as a gut-to-brain oral drug delivery platform for the well-targeted treatment of gliomas.

Pollen-Mimetic Metal-Organic Frameworks with Tunable Spike-Like Nanostructures That Promote Cell Interactions to Improve Antigen-Specific Humoral Immunity

The exine capsules of pollen particles exhibit a variety of characteristic surface morphologies that promote their cell interactions; their use as antigen carriers for vaccination has been proposed. However, the allergy-causing substances in pollen particles may not all be removed, even by vigorous chemical treatments. To resolve this issue, this work develops systemic approaches for synthesizing pollen-mimetic metal-organic frameworks (MOFs), which comprise aluminum (Al) ions and an organic linker (2-aminoterephthalic acid), with tunable spike-like nanostructures on their surfaces. The as-synthesized MOFs act not only as a delivery vehicle that carries a model antigen (ovalbumin, OVA) but also as an adjuvant (Al). Scanning and transmission electron microscopies images reveal that the aspect ratio of the nanospikes that are grown on the MOFs can be controlled. A higher aspect ratio of the nanospikes on the MOFs is associated with greater cell attachment and faster and more efficient phagocytosis in cells, which results in greater expressions of pro-inflammatory cytokines. Consequently, a more robust immune response against the antigen of interest is elicited. These findings have broad implications for the rational design of the future antigen/adjuvant-presenting particles for vaccination.

A fast and facile platform for fabricating phase-change materials-based drug carriers powered by chemical Marangoni effect

Emulsions of oil droplets as drug carriers are typically formulated by emulsification, which is complex and time-consuming and requires high energy input. To address these concerns, a fast and facile method for fabricating lipid-based oil droplets, using propulsive forces that arise from the chemical Marangoni effect, is developed for the oral delivery of lipophilic drugs, such as vitamin D. The oil droplets are prepared by solubilizing vitamin D in a phase-changeable fatty acid with the addition of ethanol as an oil phase, which is then deposited on a water bath. As a result of the differing surface tensions of water and ethanol (chemical energy), propulsive Marangoni forces are generated (kinetic energy), rapidly spreading the oil phase into many tiny oil droplets. To prevent their coalescence, the generated oil droplets are solidified by reducing their environmental temperature. Following oral administration, the fluidity of the solidified droplets increases at body temperature; they can be further emulsified into the vitamin D-containing micelles by intestinal bile salts. The micelles are then taken up by the intestinal epithelial cells, enabling their contained vitamin D to be absorbed into systemic circulation, improving its oral bioavailability.

Injectable conductive hydrogel can reduce pacing threshold and enhance efficacy of cardiac pacemaker

Background: Pacemaker implantation is currently used in patients with symptomatic bradycardia. Since a pacemaker is a lifetime therapeutic device, its energy consumption contributes to battery exhaustion, along with its voltage stimulation resulting in local fibrosis and greater resistance, which are all detrimental to patients. The possible resolution for those clinical issues is an injection of a conductive hydrogel, poly-3-amino-4-methoxybenzoic acid-gelatin (PAMB-G), to reduce the myocardial threshold voltage for pacemaker stimulation. Methods: PAMB-G is synthesized by covalently linking PAMB to gelatin, and its conductivity is measured using two-point resistivity. Rat hearts are injected with gelatin or PAMB-G, and pacing threshold is evaluated using electrocardiogram and cardiac optical mapping. Results: PAMB-G conductivity is 13 times greater than in gelatin. The ex vivo model shows that PAMB-G significantly enhances cardiac tissue stimulation. Injection of PAMB-G into the stimulating electrode location at the myocardium has a 4 times greater reduction of pacing threshold voltage, compared with electrode-only or gelatin-injected tissues. Multi-electrode array mapping reveals that the cardiac conduction velocity of PAMB-G group is significantly faster than the non- or gelatin-injection groups. PAMB-G also reduces pacing threshold voltage in an adenosine-induced atrial-ventricular block rat model. Conclusion: PAMB-G hydrogel reduces cardiac pacing threshold voltage, which is able to enhance pacemaker efficacy.

The conductive function of biopolymer corrects myocardial scar conduction blockage and resynchronizes contraction to prevent heart failure

Myocardial fibrosis, resulting from ischemic injury, increases tissue resistivity in the infarct area, which impedes heart synchronous electrical propagation. The uneven conduction between myocardium and fibrotic tissue leads to dys-synchronous contraction, which progresses towards ventricular dysfunction. We synthesized a conductive poly-pyrrole-chitosan hydrogel (PPY-CHI), and investigated its capabilities in improving electrical propagation in fibrotic tissue, as well as resynchronizing cardiac contraction to preserve cardiac function. In an in vitro fibrotic scar model, conductivity increased in proportion to the amount of PPY-CHI hydrogel added. To elucidate the mechanism of interaction between myocardial ionic changes and electrical current, an equivalent circuit model was used, which showed that PPY-CHI resistance was 10 times lower, and latency time 5 times shorter, compared to controls. Using a rat myocardial infarction (MI) model, PPY-CHI was injected into fibrotic tissue 7 days post MI. There, PPY-CHI reduced tissue resistance by 30%, improved electrical conduction across the fibrotic scar by 33%, enhanced field potential amplitudes by 2 times, and resynchronized cardiac contraction. PPY-CHI hydrogel also preserved cardiac function at 3 months, and reduced susceptibility to arrhythmia by 30% post-MI. These data demonstrated that the conductive PPY-CHI hydrogel reduced fibrotic scar resistivity, and enhanced electrical conduction, to synchronize cardiac contraction.

A bubble bursting-mediated oral drug delivery system that enables concurrent delivery of lipophilic and hydrophilic chemotherapeutics for treating pancreatic tumors in rats

The therapeutic outcome of pancreatic cancer remains unsatisfactory, despite many attempts to improve it. To address this challenge, an oral drug delivery system that spontaneously initiates an effervescent reaction to form gas-bubble carriers is proposed. These carriers concurrently deliver lipophilic paclitaxel (PTX) and hydrophilic gemcitabine (GEM) in the small intestine. The bursting of the bubbles promotes the intestinal absorption of the drugs. The antitumor efficacy of this proposed oral drug delivery system is evaluated in rats with experimentally created orthotopic pancreatic tumors. The combined administration of equivalent amounts of PTX and GEM via the intravenous (i.v.) route, which is clinically used for treating pancreatic cancer, serves as a control. Following oral administration, the lipophilic PTX is initially absorbed through the intestinal lymphatic system and then enters systemic circulation, whereas the hydrophilic GEM is directly taken up into the blood circulation, ultimately accumulating in the tumorous pancreatic tissues. A pharmacokinetic study reveals that the orally delivered formulation has none of the toxic side-effects that are associated with the i.v. injected formulation; changes the pharmacokinetic profiles of the drugs; and increases the bioavailability of PTX. The oral formulation has a greater impact than the i.v. formulation on tumor-specific stromal depletion, resulting in greater inhibition of tumor growth with no evidence of metastatic spread. As well as enhancing the therapeutic efficacy, this unique approach of oral chemotherapy has potential for use on outpatients, greatly improving their quality of life.

Biomimetic Engineering of a Scavenger-Free Nitric Oxide-Generating/Delivering System to Enhance Radiation Therapy

Nitric oxide (NO) is a potent tumor-cell radiosensitizer but it can be readily scavenged by hemoglobin (Hb) in vivo. A biomimetic incubator that can generate and deliver NO in a scavenger (Hb)-free environment to enhance its radiosensitizing effect to maximize its efficacy in radiotherapy is proposed. This NO incubator comprises a poly(lactic-co-glycolic acid) (PLGA) hollow microsphere (HM) that contains an NO donor (NONOate) and a surfactant molecule (sodium caprate, SC) in its aqueous core. In acidic tumorous environments, the PLGA shell of the HM allows the penetration of protons from the outside, activating the hydrolytic cleavage of NONOate, spontaneously generating NO bubbles, which are immediately trapped/stabilized by SC. The SC-stabilized NO bubbles in the HM are then squeezed through the spaces of its PLGA matrices by the elevated internal pressure. Upon leaving the HM, the entrapped NO molecules may passively diffuse through their SC-stabilized/protected layer gradually to the tumor site, having a long-lasting radiosensitizing effect and inhibiting tumor growth. The entire process of NO generation and delivery is conducted in a scavenger (Hb)-free environment, mimicking the development of young ovoviviparous fish inside their mothers' bodies in the absence of predators before birth.

Photosynthesis-inspired H2 generation using a chlorophyll-loaded liposomal nanoplatform to detect and scavenge excess ROS

A disturbance of reactive oxygen species (ROS) homeostasis may cause the pathogenesis of many diseases. Inspired by natural photosynthesis, this work proposes a photo-driven H2-evolving liposomal nanoplatform (Lip NP) that comprises an upconversion nanoparticle (UCNP) that is conjugated with gold nanoparticles (AuNPs) via a ROS-responsive linker, which is encapsulated inside the liposomal system in which the lipid bilayer embeds chlorophyll a (Chla). The UCNP functions as a transducer, converting NIR light into upconversion luminescence for simultaneous imaging and therapy in situ. Functioning as light-harvesting antennas, AuNPs are used to detect the local concentration of ROS for FRET biosensing, while the Chla activates the photosynthesis of H2 gas to scavenge local excess ROS. The results thus obtained indicate the potential of using the Lip NPs in the analysis of biological tissues, restoring their ROS homeostasis, possibly preventing the initiation and progression of diseases.

Strategies for improving diabetic therapy via alternative administration routes that involve stimuli-responsive insulin-delivering systems

The encapsulation of insulin in micro- or nanodelivery systems may eliminate the need for frequent subcutaneous injections, improving the quality of life of diabetic patients. Formulations for oral, intranasal, pulmonary, subcutaneous, and transdermal administration have been developed. The use of stimuli-responsive polymeric carriers that can release the encapsulated drug in response to changes of the environmental stimuli or external activation enables the design of less invasive or non-invasive systems for smart insulin delivery from depots in the body. This article will look at strategies for the development of responsive delivery systems and the future meeting of the demands of new modes of insulin delivery.

In situ self-spray coating system that can uniformly disperse a poorly water-soluble H2S donor on the colorectal surface to treat inflammatory bowel diseases

Inflammatory bowel disease (IBD) is an intestinal inflammatory disorder. Exogenous hydrogen sulfide (H₂S) donors such as diallyl trisulfide (DATS) have been used as anti-inflammatory mediators. However, an ideal method of administering DATS has yet to be established owing to its poor water solubility. Herein, a self-spray coating system that is derived from a DATS-loaded capsule with foaming capability (CAP-w-FC) is proposed for treating colitis. Following the rectal administration of CAP-w-FC into rats bearing colitis and its subsequent dissolution in the intestinal fluid, a spray coating system is self-assembled in situ. This system greatly promotes the dissolution of the poorly water-soluble DATS by producing nano-scaled micellar particles that are sprayed onto the large luminal surface of the colorectal tract. Following the internalization of the micellar particles by colon epithelial cells, their loaded DATS reacts with intracellular glutathione to yield H₂S. This exogenous H₂S then diffuses through plasma membranes to carry out its biological functions, including suppressing the overproduction of pro-inflammatory cytokines, inhibiting the adhesion of macrophages on the vascular endothelium, and repairing colonic inflamed tissues. Analytical results demonstrate that this self-spray coating system may be used as a unique drug delivery technique for covering the large colorectal surface to treat IBD.

An Intestinal "Transformers"-like Nanocarrier System for Enhancing the Oral Bioavailability of Poorly Water-Soluble Drugs

Increasing the intestinal dissolution of orally administered poorly water-soluble drugs that have poor oral bioavailability to a therapeutically effective level has long been an elusive goal. In this work, an approach that can greatly enhance the oral bioavailability of a poorly water-soluble drug such as curcumin (CUR) is developed, using a "Transformers"-like nanocarrier system (TLNS) that can self-emulsify the drug molecules in the intestinal lumen to form nanoemulsions. Owing to its known anti-inflammation activity, the use of CUR in treating pancreatitis is evaluated herein. Structural changes of the TLNS in the intestinal environment to form the CUR-laden nanoemulsions are confirmed in vitro. The therapeutic efficacy of this TLNS is evaluated in rats with experimentally induced acute pancreatitis (AP). Notably, the CUR-laden nanoemulsions that are obtained using the proposed TLNS can passively target intestinal M cells, in which they are transcytosed and then transported into the pancreatic tissues via the intestinal lymphatic system. The pancreases in rats that are treated with the TLNS yield approximately 12 times stronger CUR signals than their counterparts receiving free CUR, potentially improving the recovery of AP. These findings demonstrate that the proposed TLNS can markedly increase the intestinal drug dissolution, making oral delivery a favorable noninvasive means of administering poorly water-soluble drugs.

An In Situ Depot for Continuous Evolution of Gaseous H2 Mediated by a Magnesium Passivation/Activation Cycle for Treating Osteoarthritis

Inflammation is involved in many human pathologies, including osteoarthritis (OA). Hydrogen (H₂ ) is known to have anti-inflammatory effects; however, the bioavailability of directly administered H₂ gas is typically poor. Herein, a local delivery system that can provide a high therapeutic concentration of gaseous H₂ at inflamed tissues is proposed. The delivery system comprises poly(lactic-co-glycolic acid) microparticles that contain magnesium powder (Mg@PLGA MPs). Mg@PLGA MPs that are intra-muscularly injected close to the OA knee in a mouse model can act as an in situ depot that can evolve gaseous H₂ continuously, mediated by the cycle of passivation/activation of Mg in body fluids, at a concentration that exceeds its therapeutic threshold. The analytical data that are obtained in the biochemical and histological studies indicate that the proposed Mg@PLGA MPs can effectively mitigate tissue inflammation and prevent cartilage from destruction, arresting the progression of OA changes.

In Situ Self-Assembling Micellar Depots that Can Actively Trap and Passively Release NO with Long-Lasting Activity to Reverse Osteoporosis

Treatment with exogenous nitric oxide (NO) donors is regarded as being effective against osteoporosis. However, NO has a short half-life, limiting its clinical usefulness. To overcome this limitation, an injectable microparticle (MP) system is developed that consists of phase-change materials capric acid (CA) and octadecane, and encapsulates a NO donor. The therapeutic efficacy of the MPs is evaluated in ovariectomized (OVX) rats with osteoporosis. Upon subcutaneous administration, the MPs undergo a phase transition, leaching out the NO donor and generating NO bubbles that are instantly covered by a layer of tightly packed CA surfactant molecules, forming micellar depots. The in situ self-assembling micellar depots can actively protect the NO bubbles, prolonging their half-life, while the entrapped NO may passively diffuse through the micellar depots over time, performing a long-lasting therapeutic function, reversing the OVX-induced osteoporosis. It is possible to use the concept of in situ self-assembling micellar depots developed herein to expand the therapeutic effect of NO in its diverse range of clinical applications.

Polypyrrole-chitosan conductive biomaterial synchronizes cardiomyocyte contraction and improves myocardial electrical impulse propagation

Background: The post-myocardial infarction (MI) scar interrupts electrical impulse propagation and delays regional contraction, which contributes to ventricular dysfunction. We investigated the potential of an injectable conductive biomaterial to restore scar tissue conductivity and re-establish synchronous ventricular contraction.

Methods: A conductive biomaterial was generated by conjugating conductive polypyrrole (PPY) onto chitosan (CHI) backbones. Trypan blue staining of neonatal rat cardiomyocytes (CMs) cultured on biomaterials was used to evaluate the biocompatibility of the conductive biomaterials. Ca²⁺ imaging was used to visualize beating CMs. A cryoablation injury rat model was used to investigate the ability of PPY:CHI to improve cardiac electrical propagation in the injured heart in vivo. Electromyography was used to evaluate conductivity of scar tissue ex vivo.

Results: Cell survival and morphology were similar between cells cultured on biomaterials-coated and uncoated-control dishes. PPY:CHI established synchronous contraction of two distinct clusters of spontaneously-beating CMs. Intramyocardial PPY:CHI injection into the cryoablation-induced injured region improved electrical impulse propagation across the scarred tissue and decreased the QRS interval, whereas saline- or CHI-injected hearts continued to have delayed propagation patterns and significantly reduced conduction velocity compared to healthy controls. Ex vivo evaluation found that scar tissue from PPY:CHI-treated rat hearts had higher signal amplitude compared to those from saline- or CHI-treated rat heart tissue.

Conclusions: The PPY:CHI biomaterial is electrically conductive, biocompatible and injectable. It improved synchronous contraction between physically separated beating CM clusters in vitro. Intra-myocardial injection of PPY:CHI following cardiac injury improved electrical impulse propagation of scar tissue in vivo.

ID:4005 Injectable Cell Delivery Constructs for Myocardial Tissue Engineering

Cell transplantation via direct intramuscular injection is a promising therapy for patients with ischemic diseases. However, following injections, retention of transplanted cells in engrafted areas remains problematic, and can be deleterious to cell-transplantation therapy. In this presentation, a thermo-responsive hydrogel system composed of aqueous methylcellulose (MC) blended with phosphate-buffered saline is constructed to grow cell sheet fragments and cell bodies for the treatment of ischemic diseases. The as-prepared MC hydrogel system undergoes a sol–gel reversible transition upon heating or cooling at approximately 32 °C. Via this unique property, the grown cell sheet fragments (cell bodies) can be harvested without using proteolytic enzymes; consequently, their inherent extracellular matrices (ECMs) and integrative adhesive agents remain well preserved. In animal studies using rats and pigs with experimentally created myocardial infarction, the injected cell sheet fragments (cell bodies) become entrapped in the interstices of muscular tissues and adhere to engraftment sites, while a minimal number of cells exist in the group receiving dissociated cells. Moreover, transplantation of cell sheet fragments (cell bodies) significantly increases vascular density, thereby improving the function of an infarcted heart. These experimental results demonstrate that cell sheet fragments (cell bodies) function as a cell-delivery construct by providing a favorable ECM environment to retain transplanted cells locally and consequently, improving the efficacy of therapeutic cell transplantation

In situ depot comprising phase-change materials that can sustainably release a gasotransmitter H2S to treat diabetic wounds

Patients with diabetes mellitus are prone to develop refractory wounds. They exhibit reduced synthesis and levels of circulating hydrogen sulfide (H₂S), which is an ephemeral gaseous molecule. Physiologically, H₂S is an endogenous gasotransmitter with multiple biological functions. An emulsion method is utilized to prepare a microparticle system that comprises phase-change materials with a nearly constant temperature of phase transitions to encapsulate sodium hydrosulfide (NaHS), a highly water-labile H₂S donor. An emulsion technique that can minimize the loss of water-labile active compounds during emulsification must be developed. The as-prepared microparticles (NaHS@MPs) provide an in situ depot for the sustained release of exogenous H₂S under physiological conditions. The sustained release of H₂S promotes several cell behaviors, including epidermal/endothelial cell proliferation and migration, as well as angiogenesis, by extending the activation of cellular ERK1/2 and p38, accelerating the healing of full-thickness wounds in diabetic mice. These experimental results reveal the strong potential of NaHS@MPs for the sustained release of H₂S for the treatment of diabetic wounds.

Diverse Applications of Nanomedicine

The design and use of materials in the nanoscale size range for addressing medical and health-related issues continues to receive increasing interest. Research in nanomedicine spans a multitude of areas, including drug delivery, vaccine development, antibacterial, diagnosis and imaging tools, wearable devices, implants, high-throughput screening platforms, etc. using biological, nonbiological, biomimetic, or hybrid materials. Many of these developments are starting to be translated into viable clinical products. Here, we provide an overview of recent developments in nanomedicine and highlight the current challenges and upcoming opportunities for the field and translation to the clinic.

H2O2-Depleting and O2-Generating Selenium Nanoparticles for Fluorescence Imaging and Photodynamic Treatment of Proinflammatory-Activated Macrophages

Macrophages have a pivotal role in chronic inflammatory diseases (CIDs), so imaging and controlling activated macrophage is critical for detecting and reducing chronic inflammation. In this study, photodynamic selenium nanoparticles (SeNPs) with photosensitive and macrophage-targeting bilayers were developed. The first layer of the photosensitive macromolecule was composed of a conjugate of a photosensitizer (rose bengal, RB) and a thiolated chitosan (chitosan-glutathione), resulting in a plasmonic coupling-induced red shift and broadening of RB absorption bands with increased absorption intensity. Electron paramagnetic resonance (EPR) and diphenylanthracene (DPA) quenching studies revealed that the SeNPs that were coated with the photosensitive layer were more effective than RB alone in producing singlet oxygen (¹O₂) under photoirradiation. The second layer of the activated macrophage-targetable macromolecule was synthesized by conjugation of hyaluronic acid with folic acid using an ethylenediamine linker. Proinflammatory-activated macrophages rapidly internalized the SeNPs that were covered with the targeting ligand, exhibiting a much stronger fluorescence signal of the SeNPs than did the nonactivated macrophages. Since proinflammatory-activated macrophage was known to generate a substantial amount of H₂O₂ while the inflamed site generally caused inflammation-associated tissue hypoxia, the SeNPs were further modified with O₂ self-sufficient function for photodynamic therapy. Catalase was immobilized on the SeNPs by the formation of disulfide bonds. Intracellular reduction of disulfide bonds induced the subsequent release of catalase, which catalyzed the decomposition of H₂O₂. The H₂O₂-depleting and O₂-generating photodynamic SeNPs efficiently killed activated macrophages and quenched the intracellular H₂O₂ and NO that are associated with inflammation. The SeNPs may have potential as a theranostic nanomaterial to image and control the activation of macrophages.

Localized sequence-specific release of a chemopreventive agent and an anticancer drug in a time-controllable manner to enhance therapeutic efficacy

Combination chemotherapy with multiple drugs commonly requires several injections on various schedules, and the probability that the drug molecules reach the diseased tissues at the proper time and effective therapeutic concentrations is very low. This work elucidates an injectable co-delivery system that is based on cationic liposomes that are adsorbed on anionic hollow microspheres (Lipos-HMs) via electrostatic interaction, from which the localized sequence-specific release of a chemopreventive agent (1,25(OH)2D3) and an anticancer drug (doxorubicin; DOX) can be thermally driven in a time-controllable manner by an externally applied high-frequency magnetic field (HFMF). Lipos-HMs can greatly promote the accumulation of reactive oxygen species (ROS) in tumor cells by reducing their cytoplasmic expression of an antioxidant enzyme (superoxide dismutase) by 1,25(OH)2D3, increasing the susceptibility of cancer cells to the cytotoxic action of DOX. In nude mice that bear xenograft tumors, treatment with Lipos-HMs under exposure to HFMF effectively inhibits tumor growth and is the most effective therapeutic intervention among all the investigated. These empirical results demonstrate that the synergistic anticancer effects of sequential release of 1,25(OH)2D3 and DOX from the Lipos-HMs may have potential for maximizing DOX cytotoxicity, supporting more effective cancer treatment.

CD44-specific nanoparticles for redox-triggered reactive oxygen species production and doxorubicin release

CD44-specific and redox-responsive nanoparticles were prepared by coating a bioreducible chitosan-based nanoparticles with hyaluronic acid for intracellular glutathione-triggered reactive oxygen species (ROS) production and doxorubicin (DOX) release. Chitosan (CS) was conjugated with a copper chelator, D-penicillamine (D-pen), to obtain a CS-SS-D-pen conjugate through the formation of a disulfide bond. D-pen release from the conjugate was triggered by intracellular glutathione (GSH) via reducing biologically reversible disulfide bonds. Self-assembled CS-SS-D-pen nanoparticles were prepared through ionotropic gelation with tripolyphosphate and subsequently coated with hyaluronic acid (HA). The HA-coated CS-SS-D-pen NPs were reduced by GSH to release free D-pen and trigger ROS production via a series of reactions involving Cu(II)-catalyzed D-pen oxidation and H2O2 generation. DOX was loaded into the HA-coated CS-SS-D-pen NPs by a method involving the complexation of DOX with Cu(II) ions. The Cu(II)-DOX complex-loaded NPs exhibited redox-responsive release properties which accelerated DOX release at a higher glutathione level (10mM). Confocal fluorescence microscopy demonstrated that the Cu(II)-DOX-loaded NPs effectively delivered DOX to human colon adenocarcinoma cells (HT-29) by active targeting via HA-CD44 interactions. Intracellular ROS generated from the HA-coated CS-SS-D-pen NPs sensitized cancer cells to DOX-induced cytotoxicity. In vitro cytotoxicity assays revealed that Cu(II)-DOX-loaded NPs sensitized cells to DOX-induced cytotoxicity in CD44-overexpressing HT-29 cells compared to CD44 low-expressing HCT-15 cells.

STATEMENT OF SIGNIFICANCE

In this manuscript, we develop a CD44-targetable loaded with nanoparticles Cu(II)-DOX complex. The nanoparticles exhibited redox-responsive properties, which triggered reactive oxygen species (ROS) production and accelerated DOX release. The Cu(II)-DOX-loaded nanoparticle sensitized cells to DOX-induced cytotoxicity in CD44-overexpressing HT-29 cells. To our knowledge, this is the first report showing the combination of CD44-targeting and redox-responsive property for triggering ROS production and subsequent drug release. We believe our findings would appeal to the readership of Acta Biomaterialia because the study bring new and interesting ideals in the development of specific and stimuli-responsive nanoparticles as drug carrier for cancer therapy.

A Conductive Polymer Hydrogel Supports Cell Electrical Signaling and Improves Cardiac Function After Implantation into Myocardial Infarct

BACKGROUND

Efficient cardiac function requires synchronous ventricular contraction. After myocardial infarction, the nonconductive nature of scar tissue contributes to ventricular dysfunction by electrically uncoupling viable cardiomyocytes in the infarct region. Injection of a conductive biomaterial polymer that restores impulse propagation could synchronize contraction and restore ventricular function by electrically connecting isolated cardiomyocytes to intact tissue, allowing them to contribute to global heart function.

METHODS AND RESULTS

We created a conductive polymer by grafting pyrrole to the clinically tested biomaterial chitosan to create a polypyrrole (PPy)-chitosan hydrogel. Cyclic voltammetry showed that PPy-chitosan had semiconductive properties lacking in chitosan alone. PPy-chitosan did not reduce cell attachment, metabolism, or proliferation in vitro. Neonatal rat cardiomyocytes plated on PPy-chitosan showed enhanced Ca(2+) signal conduction in comparison with chitosan alone. PPy-chitosan plating also improved electric coupling between skeletal muscles placed 25 mm apart in comparison with chitosan alone, demonstrating that PPy-chitosan can electrically connect contracting cells at a distance. In rats, injection of PPy-chitosan 1 week after myocardial infarction decreased the QRS interval and increased the transverse activation velocity in comparison with saline or chitosan, suggesting improved electric conduction. Optical mapping showed increased activation in the border zone of PPy-chitosan-treated rats. Echocardiography and pressure-volume analysis showed improvement in load-dependent (ejection fraction, fractional shortening) and load-independent (preload recruitable stroke work) indices of heart function 8 weeks after injection.

CONCLUSIONS

We synthesized a biocompatible conductive biomaterial (PPy-chitosan) that enhances biological conduction in vitro and in vivo. Injection of PPy-chitosan better maintained heart function after myocardial infarction than a nonconductive polymer.

Enhancement of cell adhesion, retention, and survival of HUVEC/cbMSC aggregates that are transplanted in ischemic tissues by concurrent delivery of an antioxidant for therapeutic angiogenesis

A recurring obstacle in cell-base strategies for treating ischemic diseases is the significant loss of viable cells that is caused by the elevated levels of regional reactive oxygen species (ROS), which ultimately limits therapeutic capacity. In this study, aggregates of human umbilical vein endothelial cells (HUVECs) and cord-blood mesenchymal stem cells (cbMSCs), which are capable of inducing therapeutic angiogenesis, are prepared. We hypothesize that the concurrent delivery of an antioxidant N-acetylcysteine (NAC) may significantly increase cell retention following the transplantation of HUVEC/cbMSC aggregates in a mouse model with hindlimb ischemia. Our in vitro results demonstrate that the antioxidant NAC can restore ROS-impaired cell adhesion and recover the reduced angiogenic potential of HUVEC/cbMSC aggregates under oxidative stress. In the animal study, we found that by scavenging the ROS generated in ischemic tissues, NAC is likely to be able to establish a receptive cell environment in the early stage of cell transplantation, promoting the adhesion, retention, and survival of cells of engrafted aggregates. Therapeutic angiogenesis is therefore enhanced and blood flow recovery and limb salvage are ultimately achieved. The combinatory strategy that uses an antioxidant and HUVEC/cbMSC aggregates may provide a new means of boosting the therapeutic efficacy of cell aggregates for the treatment of ischemic diseases.

Controlled Release of an Anti-inflammatory Drug Using an Ultrasensitive ROS-Responsive Gas-Generating Carrier for Localized Inflammation Inhibition

Inflammation is associated with many diseases, in which activated inflammatory cells produce various reactive oxygen species (ROS), including H2O2. This work proposes an ultrasensitive ROS-responsive hollow microsphere (HM) carrier that contains an anti-inflammatory drug, an acid precursor consisting of ethanol and FeCl2, and sodium bicarbonate (SBC) as a bubble-generating agent. In cases of inflamed osteoarthritis, the H2O2 at low concentration diffuses through the HMs to oxidize their encapsulated ethanol in the presence of Fe(2+) by the Fenton reaction, establishing an acidic milieu. In acid, SBC decomposes to form CO2 bubbles, disrupting the shell wall of the HMs and releasing the anti-inflammatory drug to the problematic site, eventually protecting against joint destruction. These results reveal that the proposed HMs may uniquely exploit biologically relevant concentrations of H2O2 and thus be used for the site-specific delivery of therapeutics in inflamed tissues.

A pH-Responsive Carrier System that Generates NO Bubbles to Trigger Drug Release and Reverse P-Glycoprotein-Mediated Multidrug Resistance

Multidrug resistance (MDR) resulting from the overexpression of drug transporters such as P-glycoprotein (Pgp) increases the efflux of drugs and thereby limits the effectiveness of chemotherapy. To address this issue, this work develops an injectable hollow microsphere (HM) system that carries the anticancer agent irinotecan (CPT-11) and a NO-releasing donor (NONOate). Upon injection of this system into acidic tumor tissue, environmental protons infiltrate the shell of the HMs and react with their encapsulated NONOate to form NO bubbles that trigger localized drug release and serve as a Pgp-mediated MDR reversal agent. The site-specific drug release and the NO-reduced Pgp-mediated transport can cause the intracellular accumulation of the drug at a concentration that exceeds the cell-killing threshold, eventually inducing its antitumor activity. These results reveal that this pH-responsive HM carrier system provides a potentially effective method for treating cancers that develop MDR.