Linear, Mannitol-Based Poly(anhydride-esters) with High Ibuprofen Loading and Anti-Inflammatory Activity.

Sugar alcohols, such as mannitol and xylitol, are biocompatible polyols that have been used to make highly cross-linked polyester elastomers and dendrimers for tissue engineering and drug delivery. However, research that utilizes the secondary hydroxyl groups as sites for pendant bioactive attachment and subsequent polymerization is limited. This work is the first report of a linear, completely biodegradable polymer with a sugar alcohol backbone and chemically incorporated pendant bioactives that exhibits sustained bioactive release and high bioactive loading (∼70%). With four pendant esters per repeat unit, this poly(anhydride-ester) has high loading and biodegrades into three biocompatible products: bioactive, sugar alcohol, and alkyl-based diacid. Ibuprofen serves as a representative bioactive, whereas mannitol is a representative polyol. Polymerization was achieved through reaction with (trimethylsilyl)ethoxyacetylene. Drug release via polymer degradation was quantified by high performance liquid chromatography. Additionally, a cytocompatibility study with fibroblast cells was performed to elucidate the polymer's suitability for in vivo use and a cyclooxygenase-2 (COX-2) assay was performed on the degradation media to ensure that released ibuprofen retained its anti-inflammatory activity. This work enables the future development of novel, biodegradable polymers exhibiting two key features: (i) polymer backbones with easily modified pendant groups, such as targeting moieties, and (ii) high drug loading using a multitude of bioactive classes.

Enzymatic Polymerization of an Ibuprofen-Containing Monomer and Subsequent Drug Release.

Novel ibuprofen-containing monomers comprising naturally occurring and biocompatible compounds were synthesized and subsequently polymerized via enzymatic methods. Through the use of a malic acid sugar backbone, ibuprofen was attached as a pendant group, and then subsequently polymerized with a linear aliphatic diol (1,3-propanediol, 1,5-pentanediol, or 1,8-octanediol) as comonomer using lipase B from Candida antarctica, a greener alternative to traditional metal catalysts. Polymer structures were elucidated by nuclear magnetic resonance and infrared spectroscopies, and thermal properties and molecular weights were determined. All polymers exhibited sustained ibuprofen release, with the longer chain, more hydrophobic diols exhibiting the slowest release over the 30 d study. Polymers were deemed cytocompatible using mouse fibroblasts, when evaluated at relevant therapeutic concentrations. Additionally, ibuprofen retained its chemical integrity throughout the polymerization and in vitro hydrolytic degradation processes. This methodology of enzymatic polymerization of a drug presents a more environmentally friendly synthesis and a novel approach to bioactive polymer conjugates.

Antibiotic-containing polymers for localized, sustained drug delivery.

Many currently used antibiotics suffer from issues such as systemic toxicity, short half-life, and increased susceptibility to bacterial resistance. Although most antibiotic classes are administered systemically through oral or intravenous routes, a more efficient delivery system is needed. This review discusses the chemical conjugation of antibiotics to polymers, achieved by forming covalent bonds between antibiotics and a pre-existing polymer or by developing novel antibiotic-containing polymers. Through conjugating antibiotics to polymers, unique polymer properties can be taken advantage of. These polymeric antibiotics display controlled, sustained drug release and vary in antibiotic class type, synthetic method, polymer composition, bond lability, and antibacterial activity. The polymer synthesis, characterization, drug release, and antibacterial activities, if applicable, will be presented to offer a detailed overview of each system.

Poly(anhydride-esters) comprised exclusively of naturally occurring antimicrobials and EDTA: antioxidant and antibacterial activities.

Carvacrol, thymol, and eugenol are naturally occurring phenolic compounds known to possess antimicrobial activity against a range of bacteria, as well as antioxidant activity. Biodegradable poly(anhydride-esters) composed of an ethylenediaminetetraacetic acid (EDTA) backbone and antimicrobial pendant groups (i.e., carvacrol, thymol, or eugenol) were synthesized via solution polymerization. The resulting polymers were characterized to confirm their chemical composition and understand their thermal properties and molecular weight. In vitro release studies demonstrated that polymer hydrolytic degradation was complete after 16 days, resulting in the release of free antimicrobials and EDTA. Antioxidant and antibacterial assays determined that polymer release media exhibited bioactivity similar to that of free compound, demonstrating that polymer incorporation and subsequent release had no effect on activity. These polymers completely degrade into components that are biologically relevant and have the capability to promote preservation of consumer products in the food and personal care industries via antimicrobial and antioxidant pathways.

Biodegradable coumaric acid-based poly(anhydride-ester) synthesis and subsequent controlled release.

To overcome drug delivery issues associated with its short half-life in vivo, p-coumaric acid (pCA), a naturally occurring bioactive, has been chemically incorporated into a poly(anhydride-ester) backbone through solution polymerization. Nuclear magnetic resonance and Fourier transform infrared spectroscopies indicated that pCA was successfully incorporated without noticeable alterations in structural integrity. The polymer's weight-average molecular weight and thermal properties were determined, exhibiting a molecular weight of over 26 000 Da and a glass transition temperature of 57 °C. In addition, in vitro hydrolytic release studies demonstrated pCA release over 30 d with maintained antioxidant activity, demonstrating the polymer's potential as a controlled release system.

Synthesis of biotinylated c-di-gmp and c-di-amp using click conjugation.

The biotinylated c-di-GMP and c-di-AMP conjugates 10a/b were synthesized by a straightforward set of procedures from standard, commercially available phosphoramidites. Their availability should allow isolation and characterization of new protein and RNA receptors for these key bacterial signaling molecules.

Biodegradable ferulic acid-containing poly(anhydride-ester): degradation products with controlled release and sustained antioxidant activity.

Ferulic acid (FA) is an antioxidant and photoprotective agent used in biomedical and cosmetic formulations to prevent skin cancer and senescence. Although FA exhibits numerous health benefits, physicochemical instability leading to decomposition hinders its efficacy. To minimize inherent decomposition, a FA-containing biodegradable polymer was prepared via solution polymerization to chemically incorporate FA into a poly(anhydride-ester). The polymer was characterized using nuclear magnetic resonance and infrared spectroscopies. The molecular weight and thermal properties were also determined. In vitro studies demonstrated that the polymer was hydrolytically degradable, thus providing controlled release of the chemically incorporated bioactive with no detectable decomposition. The polymer degradation products were found to exhibit antioxidant and antibacterial activity comparable to that of free FA, and in vitro cell viability studies demonstrated that the polymer is noncytotoxic toward fibroblasts. This renders the polymer a potential candidate for use as a controlled release system for skin care formulations.