Surface Engineering for Endothelium-Mimicking Functions to Combat Infection and Thrombosis in Extracorporeal Life Support Technologies.

Blood-contacting medical devices routinely fail from the cascading effects of biofouling toward infection and thrombosis. Nitric oxide (NO) is an integral part of endothelial homeostasis, maintaining platelet quiescence and facilitating oxidative/nitrosative stress against pathogens. Recently, it is shown that the surface evolution of NO can mediate cell-surface interactions. However, this technique alone cannot prevent the biofouling inherent in device failure with dynamic blood-contacting applications. This work proposes an endothelium-mimicking surface design pairing controlled NO release with an inherently antifouling polyethylene glycol interface (NO+PEG). This simple, robust, and scalable platform develops surface-localized NO availability with surface hydration, leading to a significant reduction in protein adsorption as well as bacteria/platelet adhesion. Further in vivo thrombogenicity studies show a decrease in thrombus formation on NO+PEG interfaces, with preservation of circulating platelet and white blood cell counts, maintenance of activated clotting time, and reduced coagulation cascade activation. It is anticipated that this bio-inspired surface design will enable a facile alternative to existing surface technologies to address clinical manifestations of infection and thrombosis in dynamic blood-contacting environments.

Bioinspired superhydrophobic surfaces with silver and nitric oxide-releasing capabilities to prevent device-associated infections and thrombosis.

Bacteria-associated infections and thrombus formation are the two major complications plaguing the application of blood-contacting medical devices. Therefore, functionalized surfaces and drug delivery for passive and active antifouling strategies have been employed. Herein, we report the novel integration of bio-inspired superhydrophobicity with nitric oxide release to obtain a functional polymeric material with anti-thrombogenic and antimicrobial characteristics. The nitric oxide release acts as an antimicrobial agent and platelet inhibitor, while the superhydrophobic components prevent non-specific biofouling. Widely used medical-grade silicone rubber (SR) substrates that are known to be susceptible to biofilm and thrombus formation were dip-coated with fluorinated silicon dioxide (SiO2) and silver (Ag) nanoparticles (NPs) using an adhesive polymer as a binder. Thereafter, the resulting superhydrophobic (SH) SR substrates were impregnated with S-nitroso-N-acetylpenicillamine (SNAP, an NO donor) to obtain a superhydrophobic, Ag-bound, NO-releasing (SH-SiAgNO) surface. The SH-SiAgNO surfaces had the lowest amount of viable adhered E. coli (> 99.9 % reduction), S. aureus (> 99.8 % reduction), and platelets (> 96.1 % reduction) as compared to controls while demonstrating no cytotoxic effects on fibroblast cells. Thus, this innovative approach is the first to combine SNAP with an antifouling SH polymer surface that possesses the immense potential to minimize medical device-associated complications without using conventional systemic anticoagulation and antibiotic treatments.

Superhydrophobic and Conductive Foams with Antifouling and Oil-Water Separation Properties.

Hybrid organic-inorganic materials are attracting enormous interest in materials science due to the combination of multiple advantageous properties of both organic and inorganic components. Taking advantage of a simple, scalable, solvent-free hard-sacrificial method, we report the successful fabrication of three-dimensional hybrid porous foams by integrating two types of fillers into a poly(dimethylsiloxane) (PDMS) framework. These fillers consist of hydrophobic electrically conductive graphene (GR) nanoplatelets and hydrophobic bactericidal copper (Cu) microparticles. The fillers were utilized to create the hierarchical rough structure with low-surface-energy properties on the PDMS foam surfaces, leading to remarkable superhydrophobicity/superoleophilicity with contact angles of 158 and 0° for water and oil, respectively. The three-dimensional interconnected porous foam structures facilitated high oil adsorption capacity and excellent reusability as well as highly efficient oil/organic solvent-water separation in turbulent, corrosive, and saline environments. Moreover, the introduction of the fillers led to a significant improvement in the electrical conductivity and biofouling resistance (vs whole blood, fibrinogen, platelet cells, and Escherichia coli) of the foams. We envision that the developed composite strategy will pave a facile, scalable, and effective way for fabricating novel multifunctional hybrid materials with ideal properties that may find potential use in a broad range of biomedical, energy, and environmental applications.

Derivatization of graphene oxide nanosheets with tunable nitric oxide release for antibacterial biomaterials.

Graphene oxide (GO) nanosheets are a promising class of carbon-based materials suitable for application in the construction of medical devices. These materials have inherent antimicrobial properties based on sheet size, but these effects must be carefully traded off to maintain biocompatibility. Chemical modification of functional groups to the lattice structure of GO nanosheets enables unique opportunities to introduce new surface properties to bolster biological effects. Herein, we have developed nitric oxide (NO)-releasing GO nanosheets via immobilization of S-nitrosothiol (RSNO) moieties to GO nanosheets (GO-[NH]x -SNO). These novel RSNO-based GO nanosheets were characterized for chemical functionality via Fourier transform infrared spectroscopy, x-ray photoelectron spectroscopy, and colorimetric assays for functional group quantification. Stoichiometric control of the available RSNO groups functionalized onto the nanosheets was studied using chemiluminescence-based NO detection methods, showing highly tunable NO release kinetics. Studies of electrical stimulation and subsequent electrochemical reduction of the nanosheets demonstrated further tunability of the NO release based on stimuli. Finally, nanosheets were evaluated for cytotoxicity and antibacterial effects, showing strong cytocompatibility with human fibroblasts in parallel to broad antibacterial and anti-biofilm effects against both Gram-positive and Gram-negative strains. In summary, derivatized GO-(NH)x -SNO nanosheets were shown to have tunable NO release properties, enabling application-specific tailoring for diverse biomedical applications such as antimicrobial coatings and composite fillers for stents, sensors, and other medical devices.

Dual Action Nitric Oxide and Fluoride Ion-Releasing Hydrogels for Combating Dental Caries.

Demineralization and breakdown of tooth enamel are characterized by a condition called dental caries or tooth decay, which is caused by two main factors: (1) highly acidic food intake without proper oral hygiene and (2) overactive oral bacteria generating acidic metabolic byproducts. Fluoride treatments have been shown to help rebuild the hydroxyapatite structures that make up 98% of enamel but do not tackle the bacterial overload that continues to threaten future demineralization. Herein, we have created a dual-function Pluronic F127-alginate hydrogel with nitric oxide (NO)- and fluoride-releasing capabilities for the two-pronged treatment of dental caries. Analysis of the hydrogels demonstrated porous, shear-thinning behaviors with tunable mechanical properties. Varying the weight percent of the NO donor S-nitrosoglutathione (GSNO) within the hydrogel enabled physiologically actionable NO release over 4 h, with the fabricated gels demonstrating storage stability over 21 days. This NO-releasing capability resulted in a 97.59% reduction of viable Streptococcus mutans in the planktonic state over 4 h and reduced the preformed biofilm mass by 48.8% after 24 h. Delivery of fluoride ions was confirmed by a fluoride-sensitive electrode, with release levels resulting in the significant prevention of demineralization of hydroxyapatite discs after treatment with an acidic demineralization solution. Exposure to human gingival fibroblasts and human osteoblasts showed cytocompatibility of the hydrogel, demonstrating the potential for the successful treatment of dental caries in patients.

Nitric Oxide-Releasing Lock Solution for the Prevention of Catheter-Related Infection and Thrombosis.

Although frequently used, venous catheters are often associated with serious complications such as infection and thrombosis. Lock solution therapies are clinically used to deter these issues but generally address only infection or thrombosis with limited success. Here, we report the development of a dual-functional lock therapy using nitric oxide (NO) donor molecule, S-nitrosoglutathione (GSNO). NO is a potent, broad-spectrum antimicrobial agent that also temporarily inhibits platelet activation, preventing thrombosis. Furthermore, NO has antibiofilm actions, an ability that traditional antibiotic lock solutions lack, thus limiting their efficacy. In this work, different concentrations of GSNO were characterized via NO analysis to determine a range of NO-releasing lock solution (NOreLS) concentrations to investigate and to demonstrate prolonged potential efficacy. Tested against clinically used vancomycin and gentamicin lock solutions, GSNO-based NOreLS repeatedly outperformed in models of different stages of catheter infections. NOreLS also prevented clot formation when exposed to whole blood, showing increased efficacy compared to a heparin lock solution. Moreover, NOreLS was demonstrated to be biocompatible via hemolysis and cytotoxicity assays. NOreLS has excellent potential for safely and effectively preventing infection and thrombosis related to catheter usage.

Reduction in Foreign Body Response and Improved Antimicrobial Efficacy via Silicone-Oil-Infused Nitric-Oxide-Releasing Medical-Grade Cannulas.

Foreign body response and infection are two universal complications that occur with indwelling medical devices. In response, researchers have developed different antimicrobial and antifouling surface strategies to minimize bacterial colonization and fibrous encapsulation. In this study, the nitric oxide (NO) donor S-nitroso-N-acetylpenicillamine (SNAP) and silicone oil were impregnated into silicone rubber cannulas (SR-SNAP-Si) using a solvent swelling method to improve the antimicrobial properties and decrease the foreign body response. The fabricated SR-SNAP-Si cannulas demonstrated a stable, prolonged NO release, exhibited minimal SNAP leaching, and maintained sliding angles < 15° for 21 days. SR-SNAP-Si cannulas displayed enhanced antimicrobial efficacy against Staphylococcus aureus in a 7-day biofilm bioreactor study, reducing the viability of adhered bacteria by 99.2 ± 0.2% compared to unmodified cannulas while remaining noncytotoxic toward human fibroblast cells. Finally, SR-SNAP-Si cannulas were evaluated for the first time in a 14- and 21-day subcutaneous mouse model, showing significantly enhanced biocompatibility compared to control cannulas by reducing the thickness of fibrous encapsulation by 60.9 ± 6.1 and a 60.8 ± 10.5% reduction in cell density around the implant site after 3 weeks. Thus, this work demonstrates that antifouling, NO-releasing surfaces can improve the lifetime and safety of indwelling medical devices.

Development of Novel Amphotericin B-Immobilized Nitric Oxide-Releasing Platform for the Prevention of Broad-Spectrum Infections and Thrombosis.

Indwelling medical devices currently used to diagnose, monitor, and treat patients invariably suffer from two common clinical complications: broad-spectrum infections and device-induced thrombosis. Currently, infections are managed through antibiotic or antifungal treatment, but the emergence of antibiotic resistance, the formation of recalcitrant biofilms, and difficulty identifying culprit pathogens have made treatment increasingly challenging. Additionally, systemic anticoagulation has been used to manage device-induced thrombosis, but subsequent life-threatening bleeding events associated with all available therapies necessitates alternative solutions. In this study, a broad-spectrum antimicrobial, antithrombotic surface combining the incorporation of the nitric oxide (NO) donor S-nitroso-N-acetylpenicillamine (SNAP) with the immobilization of the antifungal Amphotericin B (AmB) on polydimethylsiloxane (PDMS) was developed in a two-step process. This novel strategy combines the key advantages of NO, a bactericidal agent and platelet inhibitor, with AmB, a potent antifungal agent. We demonstrated that SNAP-AmB surfaces significantly reduced the viability of adhered Staphylococcus aureus (99.0 ± 0.2%), Escherichia coli (89.7 ± 1.0%), and Candida albicans (93.5 ± 4.2%) compared to controls after 24 h of in vitro exposure. Moreover, SNAP-AmB surfaces reduced the number of platelets adhered by 74.6 ± 3.9% compared to controls after 2 h of in vitro porcine plasma exposure. Finally, a cytotoxicity assay validated that the materials did not present any cytotoxic side effects toward human fibroblast cells. This novel approach is the first to combine antifungal surface functionalization with NO-releasing technology, providing a promising step toward reducing the rate of broad-spectrum infection and thrombosis associated with indwelling medical devices.

Combination strategies for antithrombotic biomaterials: an emerging trend towards hemocompatibility.

Surface-induced thrombosis is a frequent, critical issue for blood-contacting medical devices that poses a serious threat to patient safety and device functionality. Antithrombotic material design strategies including the immobilization of anticoagulants, alterations in surface chemistries and morphology, and the release of antithrombotic compounds have made great strides in the field with the ultimate goal of circumventing the need for systemic anticoagulation, but have yet to achieve the same hemocompatibility as the native endothelium. Given that the endothelium achieves this state through the use of many mechanisms of action, there is a rising trend in combining these established design strategies for improved antithrombotic actions. Here, we describe this emerging paradigm, highlighting the apparent advantages of multiple antithrombotic mechanisms of action and discussing the demonstrated potential of this new direction.

Reactive Oxygen Species-Triggered Dissociation of a Polyrotaxane-Based Nanochelator for Enhanced Clearance of Systemic and Hepatic Iron.

Chronic blood transfusions are used to alleviate anemic symptoms in thalassemia and sickle cell anemia patients but can eventually result in iron overload (IO) and subsequently lead to severe oxidative stress in cells and tissues. Deferoxamine (DFO) is clinically approved to treat transfusional IO, but the use of the iron chelator is hindered by nonspecific toxicity and poor pharmacokinetic (PK) properties in humans, resulting in the need to administer the drug via long-term infusion regimens that can often lead to poor patient compliance. Herein, a nanochelator system that uses the characteristic IO physiological environment to dissociate was prepared through the incorporation of DFO and reactive oxygen species (ROS)-sensitive thioketal groups into an α-cyclodextrin-based polyrotaxane platform (rPR-DFO). ROS-induced dissociation of this nanochelator (ca. 10 nm) into constructs averaging 2 nm in diameter significantly increased urine and fecal elimination of excess iron in vivo. In addition to significantly improved PK properties, rPR-DFO was well-tolerated in mice and no adverse side effects were noted in single high dose or multiple dose acute toxicity studies. The overall features of rPR-DFO as a promising system for iron chelation therapy can be attributed to a combination of the nanochelator's improved PK, favorable distribution to the liver, and ROS-induced dissociation properties into constructs <6 nm for faster renal elimination. This ROS-responsive nanochelator design may serve as a promising alternative for safely prolonging the circulation of DFO and more rapidly eliminating iron chelates from the body in iron chelation therapy regimens requiring repeated dosing of nanochelators.

Nitric oxide and viral infection: Recent developments in antiviral therapies and platforms.

Nitric oxide (NO) is a gasotransmitter of great significance to developing the innate immune response to many bacterial and viral infections, while also modulating vascular physiology. The generation of NO from the upregulation of endogenous nitric oxide synthases serves as an efficacious method for inhibiting viral replication in host defense and warrants investigation for the development of antiviral therapeutics. With increased incidence of global pandemics concerning several respiratory-based viral infections, it is necessary to develop broad therapeutic platforms for inhibiting viral replication and enabling more efficient host clearance, as well as to fabricate new materials for deterring viral transmission from medical devices. Recent developments in creating stabilized NO donor compounds and their incorporation into macromolecular scaffolds and polymeric substrates has created a new paradigm for developing NO-based therapeutics for long-term NO release in applications for bactericidal and blood-contacting surfaces. Despite this abundance of research, there has been little consideration of NO-releasing scaffolds and substrates for reducing passive transmission of viral infections or for treating several respiratory viral infections. The aim of this review is to highlight the recent advances in developing gaseous NO, NO prodrugs, and NO donor compounds for antiviral therapies; discuss the limitations of NO as an antiviral agent; and outline future prospects for guiding materials design of a next generation of NO-releasing antiviral platforms.

Desferrioxamine:gallium-pluronic micelles increase outer membrane permeability and potentiate antibiotic activity against Pseudomonas aeruginosa.

The outer membrane of Pseudomonas aeruginosa functions primarily as a permeability barrier and imparts a broad spectrum of intrinsic antibiotic resistance. Herein, we describe the synthesis, characterization, and antimicrobial evaluation of a targeted polymeric micelle that specifically permeabilizes the outer membrane and potentiates antibiotic activity against P. aeruginosa.

Synthesis and biological evaluation of anti-cancer agents that selectively inhibit Her2 over-expressed breast cancer cell growth via down-regulation of Her2 protein.

Compound JCC76 selectively inhibited the proliferation of human epidermal growth factor 2 (Her2) over-expressed breast cancer cells. In the current study, a ligand based structural optimization was performed to generate new analogs, and we identified derivatives 16 and 17 that showed improved activity and selectivity against Her2 positive breast cancer cells. A structure activity relationship (SAR) was summarized. Compounds 16 and 17 were also examined by western blot assay to check their effect on Her2 protein. The results reveal that the compounds could decrease the Her2 protein, which explains their selectivity to Her2 over-expressed breast cancer cells. Furthermore, the compounds inhibited the chaperone activity of small chaperone protein that could stabilize Her2 protein.

Copalic acid analogs down-regulate androgen receptor and inhibit small chaperone protein.

Copalic acid, one of the diterpenoid acids in copaiba oil, inhibited the chaperone function of α-crystallin and heat shock protein 27kD (HSP27). It also showed potent activity in decreasing an HSP27 client protein, androgen receptor (AR), which makes it useful in prostate cancer treatment or prevention. To develop potent drug candidates to decrease the AR level in prostate cancer cells, more copalic acid analogs were synthesized. Using the level of AR as the readout, 15 of the copalic acid analogs were screened and two compounds were much more potent than copalic acid. The compounds also dose-dependently inhibited AR positive prostate cancer cell growth. Furthermore, they inhibited the chaperone activity of α-crystallin as well.