Encapsulation of <i>N</i>‑Diazeniumdiolates within Liposomes for Enhanced Nitric Oxide Donor Stability and Delivery

The rapid decomposition of nitric oxide (NO) donors in aqueous environments remains a limitation for applications requiring extended NO release. Herein, we report the synthesis of dipalmitoyl­phosphatidylcholine-based liposomes capable of extended NO release using low molecular weight NO donors and a reverse-phase evaporation technique. The encapsulation of the NO donors within the liposomes enabled both prolonged NO release and enhanced storage compared to free NO donors alone. The NO-releasing liposomes also demonstrated enhanced efficacy against human pancreatic cancer cells. These NO-release vehicles represent attractive anticancer therapeutics due to their potential to store the majority of their NO payload until reaching cancerous tissue at which time the lower pH inherent to such environments will trigger an avalanche of NO

Controlled Release of Nitric Oxide from Liposomes

We report the ability to readily tune NO release from <i>N</i>-diazeniumdiolate-encapsulated liposomal structures by altering the NO donor molecule structure and/or phospholipid composition (independently or in combination). While encapsulating more stable NO donors expectedly enhanced the NO release (up to 48 h) from the liposomes, the phospholipid headgroup surface area proved equally useful in controlling NO-release kinetics by influencing the proton uptake and concomitant <i>N</i>-diazeniumdiolate NO donor breakdown (to NO). The potential therapeutic utility of the NO-releasing liposomes was further assessed in biological/proteinaceous fluids. The NO-release kinetics were similar in buffer and serum

Antibacterial Activity of Nitric Oxide-Releasing Hyperbranched Polyamidoamines

Hyperbranched polyamidoamines (h-PAMAM) were prepared using a one-pot reaction to have similar molecular weight to third generation PAMAM (G3-PAMAM) dendrimers, and then functionalized with <i>N</i>-diazeniumdiolate nitric oxide (NO) donors. A wide range of NO storage capacities (∼1–2.50 μmol mg^–1) and NO-release kinetics (<i>t</i>_1/2 ∼30–80 min) were achieved by changing the extent of propylene oxide (PO) modification. The therapeutic potential of these materials was evaluated by studying their antibacterial activities and toxicity against common dental pathogens and human gingival fibroblast cells, respectively. Our results indicate that the combination of NO release and PO modification is necessary to yield h-PAMAM materials with efficient bactericidal action without eliciting unwarranted cytotoxicity. Of importance, NO-releasing PO-modified h-PAMAM polymers exhibited comparable biological properties (i.e., antibacterial action and cytotoxicity) to defect-free G3-PAMAM dendrimers, but at a substantially lower synthetic burden

Nitric Oxide-Releasing Alginates

Low and high molecular weight alginate biopolymers were chemically modified to store and release potentially therapeutic levels of nitric oxide (NO). Carbodiimide chemistry was first used to modify carboxylic acid functional groups with a series of small molecule alkyl amines. The resulting secondary amines were subsequently converted to <i>N</i>-diazeniumdiolate NO donors via reaction with NO gas under basic conditions. NO donor-modified alginates stored between 0.4–0.6 μmol NO·mg^–1. In aqueous solution, the NO-release kinetics were diverse (0.3–13 h half-lives), dependent on the precursor amine structure. The liberated NO showed bactericidal activity against <i>Pseudomonas aeruginosa</i> and <i>Staphylococcus aureus</i> with pathogen eradication efficiency dependent on both molecular weight and NO-release kinetics. The combination of lower molecular weight (∼5 kDa) alginates with moderate NO-release durations (half-life of ∼4 h) resulted in enhanced killing of both planktonic and biofilm-based bacteria. Toxicity against human respiratory epithelial (A549) cells proved negligible at NO-releasing alginate concentrations required to achieve a 5-log reduction in viability in the biofilm eradication assay