Characterization of nitric oxide-releasing microparticles for the mucosal delivery

Fabrication and Optimization of Poly(ε-caprolactone) Microspheres Loaded with S-Nitroso-N-Acetylpenicillamine for Nitric Oxide Delivery

Heart disease is one of the leading causes of death in the United States and throughout the world. While there are different techniques for reducing or preventing the impact of heart disease, nitric oxide (NO) is administered as nitroglycerin for reversing angina or chest pain. Unfortunately, due to its gaseous and short-lived half-life, NO can be difficult to study or even administer. Therefore, controlled delivery of NO is desirable for therapeutic use. In the current study, the goal was to fabricate NO-releasing microspheres (MSs) using a donor molecule, S-Nitroso-N-Acetyl penicillamine, (SNAP), and encapsulating it in poly(ε-caprolactone) (PCL) using a single-emulsion technique that can provide sustained delivery of NO to cells over time without posing any toxicity risks. Optimization of the fabrication process was performed by varying the duration of homogenization (5, 10, and 20 min) and its effect on entrapment efficiency and size. The optimized SNAP-MS had an entrapment efficiency of ˃50%. Furthermore, we developed a modified method for NO detection by using NO microsensors to detect the NO release from SNAP-MSs in real time, showing sustained release behavior. The fabricated SNAP-MSs were tested for biocompatibility with HUVECs (human umbilical vein endothelial cells), which were found to be biocompatible. Lastly, we tested the effect of controlled NO delivery to human induced pluripotent stem-derived cardiomyocytes (hiPSC-CMs) via SNAP-MSs, which showed a significant improvement in the electrophysiological parameters and alleviated anoxic stress.

Preventing Staphylococci Surgical Site Infections with a Nitric Oxide-Releasing Poly(lactic acid-co-glycolic acid) Suture Material

Of the 27 million surgeries performed in the United States each year, a reported 2.6% result in a surgical site infection (SSI), and Staphylococci species are commonly the culprit. Alternative therapies, such as nitric oxide (NO)-releasing biomaterials, are being developed to address this issue. NO is a potent antimicrobial agent with several modes of action, including oxidative and nitrosative damage, disruption of bacterial membranes, and dispersion of biofilms. For targeted antibacterial effects, NO is delivered by exogenous donor molecules, like S-nitroso-N-acetylpenicillamine (SNAP). Herein, the impregnation of SNAP into poly(lactic-co-glycolic acid) (PLGA) for SSI prevention is reported for the first time. The NO-releasing PLGA copolymer is fabricated and characterized by donor molecule loading, leaching, and the amount remaining after ethylene oxide sterilization. The swelling ratio, water uptake, static water contact angle, and tensile strength are also investigated. Furthermore, its cytocompatibility is tested against 3T3 mouse fibroblast cells, and its antimicrobial efficacy is assessed against multiple Staphylococci strains. Overall, the NO-releasing PLGA copolymer holds promise as a suture material for eradicating surgical site infections caused by Staphylococci strains. SNAP impregnation affords robust antibacterial properties while maintaining the cytocompatibility and mechanical integrity.

Bacteria-Adhesive Nitric Oxide-Releasing Graphene Oxide Nanoparticles for MRPA-Infected Wound Healing Therapy

A bacteria-infected wound can lead to being life-threatening and raises a great economic burden on the patient. Here, we developed polyethylenimine 1.8k (PEI_1.8k) surface modified NO-releasing polyethylenimine 25k (PEI_25k)-functionalized graphene oxide (GO) nanoparticles (GO-PEI_25k/NO-PEI_1.8k NPs) for enhanced antibacterial activity and infected wound healing via binding to the bacterial surface. In vitro antibacterial activity and in vivo wound healing efficacy in an infected wound model were evaluated compared with NO-releasing NPs (GO-PEI_25k/NO NPs). Surface modification with PEI_1.8k can enhance the ability of nanoparticles to adhere to bacteria. GO-PEI_25k/NO-PEI_1.8k NPs released NO in a sustained manner for 48 h and exhibited the highest bactericidal activity (99.99% killing) against methicillin-resistant Staphylococcus aureus (MRSA) and multidrug-resistant Pseudomonas aeruginosa (MRPA) without cytotoxicity to L929 mouse fibroblast cells at 0.1 mg/mL. In the MRPA-infected wound model, GO-PEI_25k/NO-PEI_1.8k NPs showed 87% wound size reduction while GO-PEI_25k/NO NPs showed 23% wound size reduction at 9 days postinjury. Masson trichrome and hematoxylin and eosin staining revealed that GO-PEI_25k/NO-PEI_1.8k NPs enhanced re-epithelialization and collagen deposition, which are comparable to healthy mouse skin tissue. GO-PEI_25k/NO-PEI_1.8k NPs hold promise as effective antibacterial and wound healing agents.

Magnetic Responsive Release of Nitric Oxide from an MOF-Derived Fe3O4@PLGA Microsphere for the Treatment of Bacteria-Infected Cutaneous Wound

Nitric oxide (NO) is an essential endogenous signaling molecule regulating multifaceted physiological functions in the (cardio)vascular, neuronal, and immune systems. Due to the short half-life and location-/concentration-dependent physiological function of NO, translational application of NO as a novel therapeutic approach, however, awaits a strategy for spatiotemporal control on the delivery of NO. Inspired by the magnetic hyperthermia and magneto-triggered drug release featured by Fe₃O₄ conjugates, in this study, we aim to develop a magnetic responsive NO-release material (MagNORM) featuring dual NO-release phases, namely, burst and steady release, for the selective activation of NO-related physiology and treatment of bacteria-infected cutaneous wound. After conjugation of NO-delivery [Fe(μ-S-thioglycerol)(NO)₂]₂ with a metal-organic framework (MOF)-derived porous Fe₃O₄@C, encapsulation of obtained conjugates within the thermo-responsive poly(lactic-co-glycolic acid) (PLGA) microsphere completes the assembly of MagNORM. Through continuous/pulsatile/no application of the alternating magnetic field (AMF) to MagNORM, moreover, burst/intermittent/slow release of NO from MagNORM demonstrates the AMF as an ON/OFF switch for temporal control on the delivery of NO. Under continuous application of the AMF, in particular, burst release of NO from MagNORM triggers an effective anti-bacterial activity against both Gram-positive Staphylococcus aureus (S. aureus) and Gram-negative Escherichia coli (E. coli). In addition to the magneto-triggered bactericidal effect of MagNORM against E. coli-infected cutaneous wound in mice, of importance, steady release of NO from MagNORM without the AMF promotes the subsequent collagen formation and wound healing in mice.

Polymeric Nitric Oxide Delivery Nanoplatforms for Treating Cancer, Cardiovascular Diseases, and Infection

The shortened Abstract is as follows: Therapeutic gas nitric oxide (NO) has demonstrated the unique advances in biomedical applications due to its prominent role in regulating physiological/pathophysiological activities in terms of vasodilation, angiogenesis, chemosensitizing effect, and bactericidal effect. However, it is challenging to deliver NO, due to its short half-life (<5 s) and short diffusion distances (20-160 µm). To address these, various polymeric NO delivery nanoplatforms (PNODNPs) have been developed for cancer therapy, antimicrobial and cardiovascular therapeutics, because of the important advantages of polymeric delivery nanoplatforms in terms of controlled release of therapeutics and the extremely versatile nature. This reviews highlights the recent significant advances made in PNODNPs for NO storing and targeting delivery. The ideal and unique criteria that are required for PNODNPs for treating cancer, cardiovascular diseases and infection, respectively, are summarized. Hopefully, effective storage and targeted delivery of NO in a controlled manner using PNODNPs could pave the way for NO-sensitized synergistic therapy in clinical practice for treating the leading death-causing diseases.

Inducing angiogenesis with the controlled release of nitric oxide from biodegradable and biocompatible copolymeric nanoparticles

PURPOSE

Nitric oxide (NO) can be clinically applied at low concentrations to regulate angiogenesis. However, studies using small molecule NO donors (N-diazeniumdiolate, S-nitrosothiol, etc) have yet to meet clinical requirements due to the short half-life and initial burst-release profile of NO donors. In this study, we report the feasibility of methoxy poly(ethylene glycol)-b-poly(lactic-co-glycolic acid) (mPEG-PLGA) nanoparticles (NPs) as NO-releasing polymers (NO-NPs) for inducing angiogenesis.

MATERIALS AND METHODS

The mPEG-PLGA copolymers were synthesized by typical ring-opening polymerization of lactide, glycolide and mPEG as macroinitiators. Double emulsion methods were used to prepare mPEG-PLGA NPs incorporating hydrophilic NONOate (dieth-ylenetriamine NONOate).

RESULTS

This liposomal NP encapsulates hydrophilic diethylenetriamine NONOate (70%±4%) more effectively than other previously reported materials. The application of NO-NPs at different ratios resulted in varying NO-release profiles with no significant cytotoxicity in various cell types: normal cells (fibroblasts, human umbilical vein endothelial cells and epithelial cells) and cancer cells (C6, A549 and MCF-7). The angiogenic potential of NO-NPs was confirmed in vitro by tube formation and ex vivo through an aorta ring assay. Tubular formation increased 189.8% in NO-NP-treated groups compared with that in the control group. Rat aorta exhibited robust sprouting angiogenesis in response to NO-NPs, indicating that NO was produced by polymeric NPs in a sustained manner.

CONCLUSION

These findings provide initial results for an angiogenesis-related drug development platform by a straightforward method with biocompatible polymers.

Antimicrobial Activity of Nitric Oxide-Releasing Ti-6Al-4V Metal Oxide

Titanium and titanium alloy materials are commonly used in joint replacements, due to the high strength of the materials. Pathogenic microorganisms can easily adhere to the surface of the metal implant, leading to an increased potential for implant failure. The surface of a titanium-aluminum-vanadium (Ti-6Al-4V) metal oxide implant material was functionalized to deliver an small antibacterial molecule, nitric oxide. S-nitroso-penicillamine, a S-nitrosothiol nitric oxide donor, was covalently immobilized on the metal oxide surface using self-assembled monolayers. Infrared spectroscopy was used to confirm the attachment of the S-nitrosothiol donor to the Ti-Al-4V surface. Attachment of S-nitroso-penicillamine resulted in a nitric oxide (NO) release of 89.6 ± 4.8 nmol/cm² under physiological conditions. This low concentration of nitric oxide reduced Escherichia coli and Staphylococcus epidermidis growth by 41.5 ± 1.2% and 25.3 ± 0.6%, respectively. Combining the S-nitrosothiol releasing Ti-6Al-4V with tetracycline, a commonly-prescribed antibiotic, increased the effectiveness of the antibiotic by 35.4 ± 1.3%, which allows for lower doses of antibiotics to be used. A synergistic effect of ampicillin with S-nitroso-penicillamine-modified Ti-6Al-4V against S. epidermidis was not observed. The functionalized Ti-6Al-4V surface was not cytotoxic to mouse fibroblasts.

Drug- and Gene-eluting Stents for Preventing Coronary Restenosis

Coronary artery disease (CAD) has been reported to be a major cause of death worldwide. Current treatment methods include atherectomy, coronary angioplasty (as a percutaneous coronary intervention), and coronary artery bypass. Among them, the insertion of stents into the coronary artery is one of the commonly used methods for CAD, although the formation of in-stent restenosis (ISR) is a major drawback, demanding improvement in stent technology. Stents can be improved using the delivery of DNA, siRNA, and miRNA rather than anti-inflammatory/anti-thrombotic drugs. In particular, genes that could interfere with the development of plaque around infected regions are conjugated on the stent surface to inhibit neointimal formation. Despite their potential benefits, it is necessary to explore the various properties of gene-eluting stents. Furthermore, multifunctional electronic stents that can be used as a biosensor and deliver drug- or gene-based on physiological condition will be a very promising way to the successful treatment of ISR. In this review, we have discussed the molecular mechanism of restenosis, the use of drug- and gene-eluting stents, and the possible roles that these stents have in the prevention and treatment of coronary restenosis. Further, we have explained how multifunctional electronic stents could be used as a biosensor and deliver drugs based on physiological conditions.

Nitric oxide in paediatric respiratory disorders: novel interventions to address associated vascular phenomena?

Nitric oxide (NO) has a significant role in modulating the respiratory system and is being exploited therapeutically. Neonatal respiratory failure can affect around 2% of all live births and is responsible for over one third of all neonatal mortality. Current treatment method with inhaled NO (iNO) has demonstrated great benefits to patients with persistent pulmonary hypertension, bronchopulmonary dysplasia and neonatal respiratory distress syndrome. However, it is not without its drawbacks, which include the need for patients to be attached to mechanical ventilators. Notably, there is also a lack of identification of subgroups amongst abovementioned patients, and homogeneity in powered studies associated with iNO, which is one of the limitations. There are significant developments in drug delivery methods and there is a need to look at alternative or supplementary methods of NO delivery that could reduce current concerns. The addition of NO-independent activators and stimulators, or drugs such as prostaglandins to work in synergy with NO donors might be beneficial. It is of interest to consider such delivery methods within the respiratory system, where controlled release of NO can be introduced whilst minimizing the production of harmful byproducts. This article reviews current therapeutic application of iNO and the state-of-the-art technology methods for sustained delivery of NO that may be adapted and developed to address respiratory disorders. We envisage this perspective would prompt active investigation of such systems for their potential clinical benefit.

Liposomal Aerosols of Nitric Oxide (NO) Donor as a Long-Acting Substitute for the Ultra-Short-Acting Inhaled NO in the Treatment of PAH

PURPOSE

This study seeks to develop a liposomal formulation of diethylenetriamine NONOate (DN), a long acting nitric oxide (NO) donor, with a goal to replace inhaled NO (iNO) in the treatment of pulmonary arterial hypertension (PAH).

METHODS

Liposomal formulations were prepared by a lipid film hydration method and modified with a cell penetrating peptide, CAR. The particles were characterized for size, polydispersity index (PDI), zeta potential, entrapment efficiency, storage and nebulization stability, and in-vitro release profiles. The cellular uptake and transport were assessed in rat alveolar macrophages (NR8383) and transforming growth factor β (TGF-β) activated rat pulmonary arterial smooth muscle cells (PASMCs). The fraction of the formulation that enters the systemic circulation, after intratracheal administration, was determined in an Isolated Perfused Rat Lung (IPRL) model. The safety of the formulations were assessed using an MTT assay and by measuring injury markers in the bronchoalveolar lavage (BAL) fluid; the pharmacological efficacy was evaluated by monitoring the changes in the mean pulmonary arterial (mPAP) and systemic pressure (mSAP) in a monocrotaline (MCT) induced-PAH rat model

RESULTS

Liposome size, zeta potential, and entrapment efficiency were 171 ± 4 nm, -37 ± 3 mV, and 46 ± 5%, respectively. The liposomes released 70 ± 5% of the drug in 8 h and were stable when stored at 4°C. CAR-conjugated-liposomes were taken up more efficiently by PASMCs than liposomes-without-CAR; the uptake of the formulations by rat alveolar macrophages was minimal. DN-liposomes did not increase lung weight, protein quantity, and levels of injury markers in the BAL fluid. Intratracheal CAR-liposomes reduced the entry of liposomes from the lung to blood; the formulations produced a 40% reduction in mPAP for 180 minutes.

CONCLUSION

This study establishes the proof-of-concept that peptide modified liposomal formulations of long-acting NO donor can be an alternative to short-acting iNO.

Biodegradable poly(lactic-co-glycolic acid) microspheres loaded with S-nitroso-N-acetyl-D-penicillamine for controlled nitric oxide delivery

Nitric oxide (NO) is a fascinating and important endogenous free-radical gas with potent antimicrobial, vasodilating, smooth muscle relaxant, and growth factor stimulating effects. However, its wider biomedical applicability is hindered by its cumbersome administration, since NO is unstable especially in biological environments. In this work, to ultimately develop site-specific controlled release vehicles for NO, the NO donor S-nitroso-N-acetyl-D-penicillamine (SNAP) was encapsulated within poly(lactic-co-glycolic acid) 50:50 (PLGA) microspheres by using a solid-in-oil-in-water emulsion solvent evaporation method. The highest payload was 0.56(±0.01) μmol SNAP/mg microspheres. The in vitro release kinetics of the donor were controlled by the bioerosion of the PLGA microspheres. By using an uncapped PLGA (Mw=24,000-38,000) SNAP was slowly released for over 10days, whereas by using the ester capped PLGA (Mw=38,000-54,000) the release lasted for over 4weeks. The presence of copper ions and/or ascorbate in solution was necessary to efficiently decompose the released NO donor and obtain sustained NO release. It was also demonstrated that light can be used to induce rapid NO release from the microspheres over several hours. SNAP exhibited excellent storage stability when encapsulated in the PLGA microspheres. These new microsphere formulations may be useful for site-specific administration and treatment of pathologies associated with dysfunction in endogenous NO production, e.g. treatment of diabetic wounds, or in diseases involving other biological functions of NO including vasodilation, antimicrobial, anticancer, and neurotransmission.

Biomimicking Robust Hydrogel for the Mesenchymal Stem Cell Carrier

PURPOSE

This study was aimed to develop a hydrogel-nanofiber as an advanced carrier for adipose derived human mesenchymal stem cells (AD-MSCs) and evaluate its potential for immunomodulatory therapies applicable to surface coating of drug eluting stent (DES) against coronary artery diseases (CAD).

METHODS

A mixture of dispersing-nanofibers (dNFs) and poly (ethylene glycol)-diacrylate (PEGDA) were blended with sodium alginate to achieve robust mechanical strength. The effects of stem cell niche on cell viability and proliferation rates were evaluated using LDH assay and alamar blue assay, respectively. The amount of Nile-red microparticles (NR-MPs) remained in the hydrogel scaffolds was examined as an index for the physical strength of hydrogels. To evaluate the immunomodulatory activity of AD-MSCs as well as their influence by ROS, the level of L-Kynurenine was determined as tryptophan replacement compounds in parallel with IDO secreted from AD-MSCs using a colorimetric assay of L-amino acid.

RESULTS

Both SA-cys-PEG and SA-cys-dNF-PEG upon being coated on stents using electrophoretic deposition technique displayed superior mechanical properties against the perfused flow. d-NFs had a significant impact on the stability of SA-cys-dNF-PEG, as evidenced by the substantial amount of NR-MPs remained in them. An enhanced subcellular level of ROS by spheroidal cluster yielded the high concentrations of L-Kynurenine (1.67 ± 0.6 μM without H2O2, 5.2 ± 1.14 μM with 50 μM of H2O2 and 8.8 ± 0.51 μM with 100 μM of H2O2), supporting the IDO-mediated tryptophan replacement process.

CONCLUSION

The "mud-and-straw" hydrogels are robust in mechanical property and can serve as an ideal niche for AD-MSCs with immunomodulatory effects.

Nitric oxide-releasing poly(lactic-co-glycolic acid)-polyethylenimine nanoparticles for prolonged nitric oxide release, antibacterial efficacy, and in vivo wound healing activity

Nitric oxide (NO)-releasing nanoparticles (NPs) have emerged as a wound healing enhancer and a novel antibacterial agent that can circumvent antibiotic resistance. However, the NO release from NPs over extended periods of time is still inadequate for clinical application. In this study, we developed NO-releasing poly(lactic-co-glycolic acid)-polyethylenimine (PEI) NPs (NO/PPNPs) composed of poly(lactic-co-glycolic acid) and PEI/diazeniumdiolate (PEI/NONOate) for prolonged NO release, antibacterial efficacy, and wound healing activity. Successful preparation of PEI/NONOate was confirmed by proton nuclear magnetic resonance, Fourier transform infrared spectroscopy, and ultraviolet/visible spectrophotometry. NO/PPNPs were characterized by particle size, surface charge, and NO loading. The NO/PPNPs showed a prolonged NO release profile over 6 days without any burst release. The NO/PPNPs exhibited potent bactericidal efficacy against methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa concentration-dependently and showed the ability to bind on the surface of the bacteria. We also found that the NO released from the NO/PPNPs mediates bactericidal efficacy and is not toxic to healthy fibroblast cells. Furthermore, NO/PPNPs accelerated wound healing and epithelialization in a mouse model of a MRSA-infected wound. Therefore, our results suggest that the NO/PPNPs presented in this study could be a suitable approach for treating wounds and various skin infections.

In vitro and in vivo study of sustained nitric oxide release coating using diazeniumdiolate-oped poly(vinyl chloride) matrix with poly(lactide-co-glycolide) additive

Nitric oxide (NO) is an endogenous vasodilator as well as natural inhibitor of platelet adhesion and activation that can be released from a NO donor species, such as diazeniumdiolated dibutylhexanediamine (DBHD/N2O2) within a polymer coating. In this study, various Food and Drug Administration approved poly(lactic-co-glycolic acid) (PLGA) species were evaluated as additives to promote a prolonged NO release from DBHD/N2O2 within a plasticized poly(vinyl chloride) (PVC) matrix. When using an ester-capped PLGA additive with a slow hydrolysis time, the resulting coatings continuously release between 7-18×10-10 mol cm-2 min-1 NO for 14 d at 37°C in PBS buffer. The corresponding pH changes within the polymer films were visualized using pH sensitive indicators and are shown to correlate with the extended NO release pattern. The optimal combined diazeniumdiolate/PLGA-doped NO release (NOrel) PVC coating was evaluated in vitro and its effect on the hemodynamics was also studied within a 4 h in vivo extracorporeal circulation (ECC) rabbit model of thrombogenicity. Four out of 7 control circuits clotted within 3 h, whereas all the NOrel coated circuits were patent after 4 h. Platelet counts on the NOrel ECC were preserved (79 ± 11% compared to 54 ± 6% controls). The NOrel coatings showed a significant decrease in the thrombus area as compared to the controls. Results suggest that by using ester-capped PLGAs as additives to a conventional plasticized PVC material containing a lipophilic diazeniumdiolates, the NO release can be prolonged for up to 2 weeks by controlling the pH within the organic phase of the coating.

Optimization of cardiovascular stent against restenosis: factorial design-based statistical analysis of polymer coating conditions

The objective of this study was to optimize the physicodynamic conditions of polymeric system as a coating substrate for drug eluting stents against restenosis. As Nitric Oxide (NO) has multifunctional activities, such as regulating blood flow and pressure, and influencing thrombus formation, a continuous and spatiotemporal delivery of NO loaded in the polymer based nanoparticles could be a viable option to reduce and prevent restenosis. To identify the most suitable carrier for S-Nitrosoglutathione (GSNO), a NO prodrug, stents were coated with various polymers, such as poly (lactic-co-glycolic acid) (PLGA), polyethylene glycol (PEG) and polycaprolactone (PCL), using solvent evaporation technique. Full factorial design was used to evaluate the effects of the formulation variables in polymer-based stent coatings on the GSNO release rate and weight loss rate. The least square regression model was used for data analysis in the optimization process. The polymer-coated stents were further assessed with Differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy analysis (FTIR), Scanning electron microscopy (SEM) images and platelet adhesion studies. Stents coated with PCL matrix displayed more sustained and controlled drug release profiles than those coated with PLGA and PEG. Stents coated with PCL matrix showed the least platelet adhesion rate. Subsequently, stents coated with PCL matrix were subjected to the further optimization processes for improvement of surface morphology and enhancement of the drug release duration. The results of this study demonstrated that PCL matrix containing GSNO is a promising system for stent surface coating against restenosis.

Nanocarriers for nitric oxide delivery

Nitric oxide (NO) is a promising pharmaceutical agent that has vasodilative, antibacterial, and tumoricidal effects. To study the complex and wide-ranging roles of NO and to facilitate its therapeutic use, a great number of synthetic compounds (e.g., nitrosothiols, nitrosohydroxyamines, N-diazeniumdiolates, and nitrosyl metal complexes) have been developed to chemically stabilize and release NO in a controlled manner. Although NO is currently being exploited in many biomedical applications, its use is limited by several factors, including a short half-life, instability during storage, and potential toxicity. Additionally, efficient methods of both localized and systemic in vivo delivery and dose control are needed. One strategy for addressing these limitations and thus increasing the utility of NO donors is based on nanotechnology.