Novel trifluoromethylated 9-amino-3,4-dihydroacridin-1(2H)-ones act as covalent poisons of human topoisomerase IIα

A number of topoisomerase II-targeted anticancer drugs, including amsacrine, utilize an acridine or related aromatic core as a scaffold. Therefore, to further explore the potential of acridine-related compounds to act as topoisomerase II poisons, we synthesized a series of novel trifluoromethylated 9-amino-3,4-dihydroacridin-1(2H)-one derivatives and examined their ability to enhance DNA cleavage mediated by human topoisomerase IIα. Derivatives containing a H, Cl, F, and Br at C7 enhanced enzyme-mediated double-stranded DNA cleavage ∼5.5- to 8.5-fold over baseline, but were less potent than amsacrine. The inclusion of an amino group at C9 was critical for activity. The compounds lost their activity against topoisomerase IIα in the presence of a reducing agent, displayed no activity against the catalytic core of topoisomerase IIα, and inhibited DNA cleavage when incubated with the enzyme prior to the addition of DNA. These findings strongly suggest that the compounds act as covalent, rather than interfacial, topoisomerase II poisons

Redox-responsive hyaluronic acid-based nanogels for the topical delivery of the visual chromophore to retinal photoreceptors

Delivering therapeutics to the posterior segment of the eye is challenging due to various anatomical and physical barriers. While significant improvements have been realized by introducing direct injections to diseased sites, these approaches come with potential side effects that can range from simple inflammation to severe retinal damage. The topical instillation of drugs remains a safer and preferred alternative for patients compliance. Here, we report the synthesis of penetratin-complexed, redox-responsive hyaluronic acid-based nanogels for the triggered release and delivery of therapeutics to the posterior part of the eye via topical application. The synthesized nanogels were shown to release their load only when exposed to a reducing environment, similar to the cytoplasm. As a model drug, visual chromophore analog, 9-cis-retinal, was loaded into nanogels and efficiently delivered to the mouse retinas photoreceptors when applied topically. Electroretinogram measurements showed a partial recovery of photoreceptor function in all treated eyes versus untreated controls. To the best of our knowledge, this report constitutes the first attempt to use a topically applied triggered-release drug delivery system to target the pigmented layer of the retina, in addition to the first attempt to deliver the visual chromophore topically

Bioinspired thermosensitive hydrogel as a vitreous substitute: Synthesis, properties, and progress of animal studies

In many vitreal diseases, the surgeon removes the natural vitreous and replaces it with silicone oils, gases, or balanced salt solutions to fill the eyeball and hold the retina in position. However, these materials are often associated with complications and have properties that differ from natural vitreous. Herein, we report an extension of our previous work on the synthesis of a biomimetic hydrogel that is composed of thiolated gellan as an analogue of type II collagen and poly(methacrylamide-co-methacrylate-co-bis(methacryloyl)cystamine), a polyelectrolyte, as an analogue of hyaluronic acid. This thermosensitive hydrogel can be injected into the eye as a viscous solution at 45 °C. It then forms a physical gel in situ when it reaches body temperature, and later forms disulfide covalent crosslinks. In this article, we evaluated two different formulations of the biomimetic hydrogels for their physical, mechanical, and optical properties, and we determined their biocompatibility with several cell lines. Finally, we report on the progress of the four-month preclinical evaluation of our bio-inspired vitreous substitute in comparison to silicone oil or a balanced salt solution. We assessed the eyes with a slit-lamp examination, intraocular pressure measurements, electroretinography, and optical coherence tomography. Preliminary results are very encouraging for the continuing evaluation of our bio-inspired hydrogel in clinical trials

Synthesis of novel acridone derivatives as potential biologically active compounds

A number of acridine and acridone derivatives have been reported to exhibit potent anticancer and antiviral properties. Amsacrine is currently being used in the clinic for the treatment of leukemia. Based on the above literature report, along with the research interest of the Okoro group in the chemistry of cyclic β-diketone, we became motivated to synthesize a diverse library of heterocyclic ring systems and to evaluate them for cytotoxic and other activities, such as antioxidant and antimicrobial activities. The major highlight of this work is the incorporation of a trifluoromethyl group in all the compounds synthesized. The trifluoromethyl group enjoys a privileged role in medicinal chemistry, because its introduction often enhances efficacy by promoting electrostatic interactions with protein targets, improving membrane penetration, as well as increasing robustness towards oxidative metabolism by liver enzyme. Substitued-(3-Oxo-5-trifluoromethyl-cyclohex-1-enylamino)-benzonitrile 75-85 were prepared from substituted-2-aminobenzonitrile by treatment with 5-trifluoromethyl-1,3-cyclohexanedione 18 in dilute aqueous hydrochloric acid. Compounds 75-85 were each reacted with a mixture of cuprous chloride and potassium carbonate in toluene to furnish novel fluorinated acridone derivatives (86-96). The structures of the above compounds were established by IR, NMR and LC-MS. Preliminary biochemical evaluation in collaboration with the Osheroff group at Vanderbilt University School of Medicine delineated 86 (9-amino-3-trifluoromethyl-acridone) as a poison of human topoisomerase II. 86 enhances enzyme-mediated DNA cleavage 6-fold (similar to levels seen in established anticancer drugs such as etoposide and amsacrine) in a concentration-dependent manner. Compounds 86-96 will be submitted to the National Cancer Institute (NCI) Chemotherapeutic Agents Repository Fisher BioServices for in vitro cytotoxicity testing in a panel of 60 cancer cell lines. In silico analysis indicate drug-like properties and absence of mutagenic and tumorigenic properties compared to THA. Our studies have identified a potent lead compound (86) that will guide further synthesis and structure-activity relationship (SAR) studies. In addition, the acridone derivatives could be derivatized to tacrine derivatives in a future exciting research leading to novel fluorinated tacrines for the treatment of AD (Alzheimer\u27s disease) patients

Hyaluronic Acid-Based Gold Nanoparticles for the Topical Delivery of Therapeutics to the Retina and the Retinal Pigment Epithelium.

The ocular immune privilege is a phenomenon brought about by anatomical and physiological barriers to shield the eye from immune and inflammation responses. While this phenomenon is beneficial for eyes protection, it is, at the same time, a hindrance for drug delivery to the posterior segment of the eye to treat retinal diseases. Some ocular barriers can be bypassed by intravitreal injections, but these are associated with several side effects and patient noncompliance, especially when frequent injections are required. As an alternative, applying drugs as an eye drop is preferred due to the safety and ease. This study investigated the possible use of topically-applied hyaluronic acid-coated gold nanoparticles as drug delivery vehicles to the back of the eye. The coated gold nanoparticles were topically applied to mouse eyes, and results were compared to topically applied uncoated gold nanoparticles and phosphate-buffered saline (PBS) solution. Retina sections from these mice were then analyzed using fluorescence microscopy, inductively coupled plasma mass spectrometry (ICP-MS), and transmission electron microscopy (TEM). All characterization techniques used in this study suggest that hyaluronic acid-coated gold nanoparticles have higher distribution in the posterior segment of the eye than uncoated gold nanoparticles. Electroretinogram (ERG) analysis revealed that the visual function of mice receiving the coated gold nanoparticles was not affected, and these nanoparticles can, therefore, be applied safely. Together, our results suggest that hyaluronic acid-coated gold nanoparticles constitute potential drug delivery vehicles to the retina when applied noninvasively as an eye drop

Adhesion and Stability of Nanocellulose Coatings on Flat Polymer Films and Textiles

Renewable nanocellulose materials received increased attention owing to their small dimensions, high specific surface area, high mechanical characteristics, biocompatibility, and compostability. Nanocellulose coatings are among many interesting applications of these materials to functionalize different by composition and structure surfaces, including plastics, polymer coatings, and textiles with broader applications from food packaging to smart textiles. Variations in porosity and thickness of nanocellulose coatings are used to adjust a load of functional molecules and particles into the coatings, their permeability, and filtration properties. Mechanical stability of nanocellulose coatings in a wet and dry state are critical characteristics for many applications. In this work, nanofibrillated and nanocrystalline cellulose coatings deposited on the surface of polymer films and textiles made of cellulose, polyester, and nylon are studied using atomic force microscopy, ellipsometry, and T-peel adhesion tests. Methods to improve coatings’ adhesion and stability using physical and chemical cross-linking with added polymers and polycarboxylic acids are analyzed in this study. The paper reports on the effect of the substrate structure and ability of nanocellulose particles to intercalate into the substrate on the coating adhesion

Grafting through Method for Implanting of Lysozyme Enzyme in Molecular Brush for Improved Biocatalytic Activity and Thermal Stability

We report a “grafting through” conjugation strategy to improve lysozyme catalytic activity and thermal stability by the synthesis of a synthetic polymer–enzyme hybrid. The lysozyme was first conjugated with glycidyl methacrylate via ring-opening reaction between epoxy groups and lysine residues of the enzyme to synthesize the enzyme macromonomer. The conjugation was followed by free radical copolymerization of the macromonomer with poly­(ethylene glycol) methyl ether acrylate (PEGMEA) (<i>M</i>_n = 5000 g/mol) and poly­(ethylene glycol) methyl ether methacrylate (PEGMEMA) (<i>M</i>_n = 500 g/mol). We demonstrated that implanting of a single lysozyme molecule in the molecular brush polymer chain resulted a significant improvement of the thermal stability up to 90 °C and 9-time extended half-life for this synthetic enzyme structure. The improved enzyme performance is explained by the crowding effect provided by molecular brush architecture of the synthetic hybrid

Robust, Solvent-Free, Catalyst-Free Click Chemistry for the Generation of Highly Stable Densely Grafted Poly(ethylene glycol) Polymer Brushes by the Grafting To Method and Their Properties

Herein we report a robust, highly selective, and efficient method to prepare dense poly­(ethylene glycol) (PEG) polymer brushes on silicon substrates via solvent-free, catalyst-free, strain-promoted acetylene–azide cycloaddition (SPAAC) reaction. First, poly­(glycidyl methacrylate) was grafted to the silicon substrate as an anchoring layer to immobilize cyclopropenone-caged dibenzo­cyclooctyne-amine (photo-DIBO-amine) via an epoxy ring-opening reaction providing protected, stable, and functionalized substrates. Next, three synthesized α-methoxy-ω-azido-PEGs of different molecular weights (5, 10, and 20 kg/mol) were successfully grafted to the photo-DIBO-modified silicon substrates from melt after the deprotection of DIBO with UV-irradiation. PEG molecular weight, reaction temperature, and reaction time were all used to control the grafting reaction for targeted brush thicknesses and grafting densities. The highest grafting density obtained was close to 1.2 chains/nm² and was achieved for 5 kg/mol PEG. The prepared PEG polymer brushes displayed efficient antifouling properties and stability in PBS buffer aqueous media for a period of at least two months

Thermal Stabilization of Enzymes with Molecular Brushes

Herein, we report a conjugation strategy, where we utilize a poly­(ethylene oxide) cylindrical molecular brush architecture to design a self-assembled structure for thermal stabilization of enzymes. We demonstrate that the proposed architecture of the moderately stiff polymer ligand results in a significant improvement of biocatalytic activity and thermal stability of lysozyme and trypsin that retain their activity, even upon heating to 100 °C and above. The molecular brush is bound via epoxy functional groups to the amino groups of the lysine on the surface of the enzyme globule, promoting the formation of stiff and crowded cages around the enzymes and preventing the water molecules access to the enzyme and enzymes agglomeration. The molecular dynamic simulations show that the high concentration of poly­(ethylene oxide) in the vicinity of the enzyme is critical for their stability. Monitoring of lysozyme–molecular brush conjugates for 6 and 12 months in lyophilized form and in solution, respectively, has shown that the conjugation does not compromise the shelf life of the enzyme