Wearable nitric oxide-releasing antibacterial insert for preventing device-associated infections

Medical device-associated infections are a pervasive global healthcare concern, often leading to severe complications. Bacterial biofilms that form on indwelling medical devices, such as catheters, are significant contributors to infections like bloodstream and urinary tract infections. This study addresses the challenge of biofilms on medical devices by introducing a portable antimicrobial catheter insert (PACI) designed to be efficient, biocompatible, and anti-infective. The PACI utilizes nitric oxide (NO), known for its potent antimicrobial properties, to deter bacterial adhesion and biofilm formation. To achieve this, a photoinitiated NO donor, S-nitroso-N-acetylpenicillamine (SNAP), is covalently linked to a polydimethylsiloxane (PDMS) polymer. This design allows for higher NO loading for long-term impact and prevents premature donor leaching, a common challenge with SNAP-blended polymers. The SNAP-PDMS material was applied to a side-glowing fiber optic and connected to a wearable light module emitting 450 nm light, creating a functional antimicrobial insert. Activation of the fiber optic, accomplished with a one-click mechanism, enables real-time NO release, maintaining controlled NO levels for a minimum of 24  hours. The therapeutic levels of NO released via photocatalysis from the PACI demonstrated remarkable efficacy, with >90 % reduction in bacterial viability against S. aureus, S. epidermidis, and P. mirabilis without any cytotoxic impact on mammalian cells. This study underscores the potential of the NO-releasing insert in clinical settings, providing a portable and adaptable solution for preventing catheter-associated infections.

Recent advances on the development of NO-releasing molecules (NORMs) for biomedical applications

Nitric oxide (NO) is an important biological messenger as well as a signaling molecule that participates in a broad range of physiological events and therapeutic applications in biological systems. However, due to its very short half-life in physiological conditions, its therapeutic applications are restricted. Efforts have been made to develop an enormous number of NO-releasing molecules (NORMs) and motifs for NO delivery to the target tissues. These NORMs involve organic nitrate, nitrite, nitro compounds, transition metal nitrosyls, and several nanomaterials. The controlled release of NO from these NORMs to the specific site requires several external stimuli like light, sound, pH, heat, enzyme, etc. Herein, we have provided a comprehensive review of the biochemistry of nitric oxide, recent advancements in NO-releasing materials with the appropriate stimuli of NO release, and their biomedical applications in cancer and other disease control.

Smartphone compatible nitric oxide releasing insert to prevent catheter-associated infections

A large fraction of nosocomial infections is associated with medical devices that are deemed life-threatening in immunocompromised patients. Medical device-related infections are a result of bacterial colonization and biofilm formation on the device surface that affects >1 million people annually in the US alone. Over the past few years, light-based antimicrobial therapy has made substantial advances in tackling microbial colonization. Taking the advantage of light and antibacterial properties of nitric oxide (NO), for the first time, a robust, biocompatible, anti-infective approach to design a universal disposable catheter disinfection insert (DCDI) that can both prevent bacterial adhesion and disinfect indwelling catheters in situ is reported. The DCDI is engineered using a photo-initiated NO donor molecule, incorporated in polymer tubing that is mounted on a side glow fiber optic connected to an LED light source. Using a smartphone application, the NO release from DCDI is photoactivated via white light resulting in tunable physiological levels of NO for up to 24 h. When challenged with microorganisms S. aureus and E. coli, the NO-releasing DCDI statistically reduced microbial attachment by >99% versus the controls with just 4 h of exposure. The DCDI also eradicated ∼97% of pre-colonized bacteria on the CVC catheter model demonstrating the ability to exterminate an established catheter infection. The smart, mobile-operated novel universal antibacterial device can be used to both prevent catheter infections or can be inserted within an infected catheter to eradicate the bacteria without complex surgical interventions. The therapeutic levels of NO generated via illuminating fiber optics can be the next-generation biocompatible solution for catheter-related bloodstream infections.

SMA-BmobaSNO: an intelligent photoresponsive nitric oxide releasing polymer for drug nanoencapsulation and targeted delivery

Nitric oxide (NO) is an important biological signalling molecule that acts to vasodilate blood vessels and change the permeability of the blood vessel wall. Due to these cardiovascular actions, co-administering NO with a therapeutic could enhance drug uptake. However current NO donors are not suitable for targeted drug delivery as they systemically release NO. To overcome this limitation we report the development of a smart polymer, SMA-BmobaSNO, designed to release NO in response to a photostimulus. The polymer's NO releasing functionality is an S-nitrosothiol group that, at 10 mg ml^-1, is highly resistant to both thermal (t_1/216 d) and metabolic (t_1/232 h) decomposition, but rapidly brakes down under photoactivation (2700 W m^-2, halogen source) to release NO (t_1/225 min). Photoresponsive NO release from SMA-BmobaSNO was confirmed in a cardiovascular preparation, where irradiation resulted in a 12-fold decrease in vasorelaxation EC₅₀(from 5.2μM to 420 nM). To demonstrate the polymer's utility for drug delivery we then used SMA-BmobaSNO to fabricate a nanoparticle containing the probe Nile Red (NR). The resulting SMA-BmobaSNO-NR nanoparticle exhibited spherical morphology (180 nm diameter) and sustained NR release (≈20% over 5 d). Targeted delivery was characterised in an abdominal preparation, where photoactivation (450 W m^-2) caused localized increases in vasodilation and blood vessel permeability, resulting in a 3-fold increase in NR uptake into photoactivated tissue. Nanoparticles fabricated from SMA-BmobaSNO therefore display highly photoresponsive NO release and can apply the Trojan Horse paradigm by using endogenous NO signalling pathways to smuggle a therapeutic cargo into target tissue.

Visible-to-NIR-Light Activated Release: From Small Molecules to Nanomaterials

Photoactivatable (alternatively, photoremovable, photoreleasable, or photocleavable) protecting groups (PPGs), also known as caged or photocaged compounds, are used to enable non-invasive spatiotemporal photochemical control over the release of species of interest. Recent years have seen the development of PPGs activatable by biologically and chemically benign visible and near-infrared (NIR) light. These long-wavelength-absorbing moieties expand the applicability of this powerful method and its accessibility to non-specialist users. This review comprehensively covers organic and transition metal-containing photoactivatable compounds (complexes) that absorb in the visible- and NIR-range to release various leaving groups and gasotransmitters (carbon monoxide, nitric oxide, and hydrogen sulfide). The text also covers visible- and NIR-light-induced photosensitized release using molecular sensitizers, quantum dots, and upconversion and second-harmonic nanoparticles, as well as release via photodynamic (photooxygenation by singlet oxygen) and photothermal effects. Release from photoactivatable polymers, micelles, vesicles, and photoswitches, along with the related emerging field of photopharmacology, is discussed at the end of the review.

Nanoscale lipid vesicles functionalized with a nitro-aniline derivative for photoinduced nitric oxide (NO) delivery

Nanoscale vesicles functionalized with a nitric oxide (NO) releasing molecule 4-nitro-3-(trifluoromethyl)aniline have been reported. The new NO-nano-vesicular donor material shows an effective photo-release of NO upon irradiation with blue light at 410 nm. The kinetics of NO release has been monitored by using simple spectroscopic techniques such as UV-Vis and fluorescence methods. Colorimetric Griess assay and fluorescence DAF assay have been used for the detection and quantification of NO released from vesicles. This new vesicular nanoscale NO donor has the advantages of facile preparation in water, capable of releasing NO in a pure aqueous medium, photo-controlled NO release, bio-compatibility and capacity to modulate the NO donor loading to achieve an essential amount of NO.

Magnetic and light-responsive nanogels based on chitosan functionalized with Au nanoparticles and poly(N-isopropylacrylamide) as a remotely triggered drug carrier

Synthesis of thermosensitive nanogels based on functionalized chitosan with Au nanoparticles (NPs) and poly(NIPAM) to release of drug molecules under light exposure.

Nitric oxide-releasing molecules at the interface of inorganic chemistry and biology: a concise overview

The useful aspects of nitric oxide (NO) are nowadays widely known. Due to the need for this molecule in the maintenance of homeostasis, NO-releasing compounds are tested every year to optimize its levels in a patient suffering from low NO production. This manuscript is an update of some important historical concerns about nitrosyl complexes having the ability to act as NO-releasing compounds under the influence of different chemically modified environments. At present, the search for efficient and less harmful NO-releasing molecules at desirable targets and concentrations has gained considerable momentum in nitrosyl chemistry. Iron, ruthenium, and manganese nitrosyls have been investigated elitely to disentangle their electronic transition (excitation) under visible light to act as NO donors without harming the healthy cells of a target. There is much evidence supporting the increase of NO lability if amino acids are used as complexing ligands, the design of a reduction center close to an NO grouping, and the development of porphyrin system-based nitrosyl complexes. From the overall survey, it may be concluded that the desirable properties of such scaffolds need to be evaluated further to complement the biological milieu.

Nitric Oxide Uncaging from a Hydrophobic Chromium(III) PhotoNORM: Visible and Near-Infrared Photochemistry in Biocompatible Polymer Disks

Devices consisting of polymer disks (PDs) of optically clear or translucent, medical-grade silicone loaded with a new hydrophobic, oxygen-stable, photoactivated nitric oxide-releasing moiety (photoNORM) are described. The photoNORM is the new O-nitrito chromium(III) complex trans-[Cr(PetA)(ONO)2](BF4) (PetA = 5,14-dimethyl-7,12-diphenyl-1,4,8,11-tetraaza-cyclotetradecane), of which the synthesis, X-ray crystal structure, and solution-phase photochemistry are described. Several different commercially available silicone polymers were tested with this photoNORM, and nitric oxide photouncaging with 451 nm light from these systems is compared. In addition, PDs were loaded with the photoNORM and neodymium-sensitized upconverting nanoparticles (Nd-UCNPs). The Nd-UCNPs absorb NIR light at ∼800 nm and activate NO release from the trans-[Cr(PetA)(ONO)2]+ cation. The use of such ensembles as implants provides a potential strategy for the in vivo uncaging of NO at physiological targets triggered by tissue-transmitting NIR excitation. Also reported are the X-ray crystal structures of cis- and trans-{Cr(PetA)Cl2]Cl.

Solution or solid - it doesn't matter: visible light-induced CO release reactivity of zinc flavonolato complexes

Two types of zinc flavonolato complexes ([(6-Ph₂TPA)Zn(flavonolato)]ClO₄ and Zn(flavonolato)₂) of four extended flavonols have been prepared, characterized, and evaluated for visible light-induced CO release reactivity. Zinc coordination of each flavonolato anion results in a red-shift of the lowest energy absorption feature and in some cases enhanced molar absorptivity relative to the free flavonol. The zinc-coordinated flavonolato ligands undergo visible light-induced CO release with enhanced reaction quantum yields relative to the neutral flavonols. Most notable is the discovery that both types of zinc flavonolato derivatives undergo similar visible light-induced CO release reactivity in solution and in the solid state. A solid film of a Zn(flavonolato)₂ derivative was evaluated as an in situ CO release agent for aerobic oxidative palladium-catalyzed alkoxycarbonylation to produce esters in ethanol. The CO release product was found to undergo ester alcolysis under the conditions of the carbonylation reaction.

Uncaging carbon disulfide. Delivery platforms for potential pharmacological applications: a mechanistic approach

We describe the kinetics of the formation and decay of a series of dithiocarbamates under physiological conditions. The goal is to provide a toolbox of compounds that release CS2 by well-defined kinetics in such media. Carbon disulfide is a known environmental toxin, but there is fragmentary evidence suggesting that CS2 may have bioregulatory and/or therapeutic roles in mammalian biology. Further investigation of such roles will require methodologies for controlled delivery of this bioactive small molecule to specific targets. Reported here are mechanistic and computational studies of CS2 release from a series of dithiocarbamate anions (DTCs), where R2N represents several different secondary amido groups. The various DTCs under physiologically relevant conditions show a tremendous range of reactivities toward CS2 dissociation with decay lifetimes ranging from ∼2 s for imidazolidyldithiocarbamate (ImDTC-) to ∼300 s for diisopropyldithiocarbamate (DIDTC-) to >24 h for pyrrolidinyldithiocarbamate (PDTC-) in pH 7.4 phosphate buffer solution at 37 °C. Thus, by making the correct choice of these tools, one can adjust the flux of CS2 in a biological experiment, while the least reactive DTCs could serve as controls for evaluating the potential effects of the dithiocarbamate functionality itself. Kinetics studies and density functional calculations are used to probe the mechanism of DTC- decay. In each case, the rate of CS2 dissociation is acid dependent; however, the DFT studies point to a mechanistic pathway for ImDTC- that is different than those for DIDTC-. The role of general acid catalysis is also briefly probed.

Near infrared light-mediated photoactivation of cytotoxic Re(i) complexes by using lanthanide-doped upconversion nanoparticles

Photoactivation of cytotoxic Re(i) complexes by using lanthanide doped upconversion nanoparticles upon near infrared illumination was demonstrated to selectively activate Re(i) complexes in tumor cells for enhanced anti-cancer effect.

Near-IR mediated intracellular uncaging of NO from cell targeted hollow gold nanoparticles

NIR light triggers NO delivery with unprecedented spatio-temporal control inside prostate cancer cells from surface-modified hollow gold nanoshells.