The Production of Polysarcosine-Containing Nanoparticles by Ring-Opening Polymerization-Induced Self-Assembly.

N-carboxyanhydride ring-opening polymerization-induced self-assembly (NCA ROPISA) offers a convenient route for generating poly(amino acid)-based nanoparticles in a single step, crucially avoiding the need for post-polymerization self-assembly. Most examples of NCA ROPISA make use of a poly(ethylene glycol) (PEG) hydrophilic stabilizing block, however this non-biodegradable, oil-derived polymer may cause an immunological response in some individuals. Alternative water-soluble polymers are therefore highly sought. This work reports the synthesis of wholly poly(amino acid)-based nanoparticles, through the chain-extension of a polysarcosine macroinitiator with L-Phenylalanine-NCA (L-Phe-NCA) and Alanine-NCA (Ala-NCA), via aqueous NCA ROPISA. The resulting polymeric structures comprise of predominantly anisotropic, rod-like nanoparticles, with morphologies primarily influenced by the secondary structure of the hydrophobic poly(amino acid) that enables their formation.

An injectable, self-healing and MMP-inhibiting hyaluronic acid gel via iron coordination.

Regulating the activity of matrix metalloproteinases (MMPs) is a potential strategy for osteoarthritis (OA) therapy, although delivering this effect in a spatially and temporally localised fashion remains a challenge. Here, we report an injectable and self-healing hydrogel enabling factor-free MMP regulation and biomechanical competence in situ. The hydrogel is realised within 1 min upon room temperature coordination between hyaluronic acid (HA) and a cell-friendly iron-glutathione complex in aqueous environment. The resultant gel displayed up to 300% in shear strain and tolerance towards ATDC 5 chondrocytes, in line with the elasticity and biocompatibility requirements for connective tissue application. Significantly enhanced inhibition of MMP-13 activity was achieved after 12 h in vitro, compared with a commercial HA injection (OSTENIL® PLUS). Noteworthy, 24-hour incubation of a clinical synovial fluid sample collected from a late-stage OA patient with the reported hydrogel was still shown to downregulate synovial fluid MMP activity (100.0 ± 17.6% ➔ 81.0 ± 7.5%), with at least comparable extent to the case of the OSTENIL® PLUS-treated SF group (100.0 ± 17.6% ➔ 92.3 ± 27.3%). These results therefore open up new possibilities in the use of HA as both mechanically-competent hydrogel as well as a mediator of MMP regulation for OA therapy.

The facile and additive-free synthesis of a cell-friendly iron(iii)-glutathione complex.

The straightfoward creation of an unreported glutathione-stabilised iron(iii) complex is disclosed. In contrast to previous reports, glutathione was shown to coordinate and stabilise iron directly under physiological conditions in the absence of additional sulfur containing molecules, such as sodium sulfide. The complex was extensively characterised; the molecular geometry was determined as two inequivalent octahedra, approximately 2/3 of which are slightly distorted towards more tetrahedral in character, with the remaining 1/3 more regularly octahedral. The dispersion of the iron(iii)-glutathione complex in aqueous solution yielded particles of 255 ± 4 nm in diameter that enhanced the growth and proliferation of L929 fibroblast cells over 7 days, and inhibited the activity of matrix metalloproteinase-13. Consequently, the unprecedented glutathione-stabilised iron(iii) complex disclosed has potential use as a simple-to-prepare growth factor for inclusion within cell culture media, and is an excellent candidate as a therapeutic for the treatment of metalloproteinase-13-associated diseases.

Covalent polyester colouration by in situ chromophore creation.

The permanent colouration of a polyester by straightforward azo coupling is disclosed. Uniquely, the chromophore is created only upon successful polymer modification with a non-coloured molecule (in situ colouration), which confirms successful polymer adaptation and ensures that coloured waste is not produced. The method of colouration, which may feasibly be applied for the coloration of a wide-range of step-growth polyesters, yielded a polymer capable of preventing indigo deposition onto a range of fabrics, offering potential use within advanced detergent formulations.

Meticulous Doxorubicin Release from pH-Responsive Nanoparticles Entrapped within an Injectable Thermoresponsive Depot.

The dual stimuli-controlled release of doxorubicin from gel-embedded nanoparticles is reported. Non-cytotoxic polymer nanoparticles are formed from poly(ethylene glycol)-b-poly(benzyl glutamate) that, uniquely, contain a central ester link. This connection renders the nanoparticles pH-responsive, enabling extensive doxorubicin release in acidic solutions (pH 6.5), but not in solutions of physiological pH (pH 7.4). Doxorubicin-loaded nanoparticles were found to be stable for at least 31 days and lethal against the three breast cancer cell lines tested. Furthermore, doxorubicin-loaded nanoparticles could be incorporated within a thermoresponsive poly(2-hydroxypropyl methacrylate) gel depot, which forms immediately upon injection of poly(2-hydroxypropyl methacrylate) in dimethyl sulfoxide solution into aqueous solution. The combination of the poly(2-hydroxypropyl methacrylate) gel and poly(ethylene glycol)-b-poly(benzyl glutamate) nanoparticles yields an injectable doxorubicin delivery system that facilities near-complete drug release when maintained at elevated temperatures (37 °C) in acidic solution (pH 6.5). In contrast, negligible payload release occurs when the material is stored at room temperature in non-acidic solution (pH 7.4). The system has great potential as a vehicle for the prolonged, site-specific release of chemotherapeutics.

A redox-responsive hyaluronic acid-based hydrogel for chronic wound management.

Polymer-based hydrogels have been widely applied for chronic wound therapeutics, due to their well-acclaimed wound exudate management capability. At the same time, there is still an unmet clinical need for simple wound diagnostic tools to assist clinical decision-making at the point of care and deliver on the vision of patient-personalised wound management. To explore this challenge, we present a one-step synthetic strategy to realise a redox-responsive, hyaluronic acid (HA)-based hydrogel that is sensitive to wound environment-related variations in glutathione (GSH) concentration. By selecting aminoethyl disulfide (AED) as a GSH-sensitive crosslinker and considering GSH concentration variations in active and non-self-healing wounds, we investigated the impact of GSH-induced AED cleavage on hydrogel dimensions, aiming to build GSH-size relationships for potential point-of-care wound diagnosis. The hydrogel was also found to be non-cytotoxic and aided L929 fibroblast growth and proliferation over seven days in vitro. Such a material offers a very low-cost tool for the visual detection of a target analyte that varies dependent on the status of the cells and tissues (wound detection), and may be further exploited as an implant for fibroblast growth and tissue regeneration (wound repair).

Exploiting poly(α-hydroxy acids) for the acid-mediated release of doxorubicin and reversible inside-out nanoparticle self-assembly.

Biodegradable poly(α-hydroxy acid) copolyesters consisting of benzyl-protected glutamic acid and carboxybenzyl-protected lysine derived blocks possess the capability to self-assemble to form stable nanoparticles in aqueous solution (pH 7.4), that are able to withhold doxorubicin, prior to its directed release in acidic solution. Such pH-responsive nanoparticles are non-toxic against a panel of human breast cancer cell lines, but demonstrated comparable toxicities to free doxorubicin when loaded with doxorubicin. Significantly, comparable efficacy to free doxorubicin was observed even against triple negative breast cancer cells, highlighting the potential of the materials generated as drug delivery vehicles for cancer treatment. Facile block copolymer deprotection resulted in a polymer that presents an altered self-assembly/disassembly profile; forming nanoparticles when stored in either acidic or alkaline solution, but undergoing self-disassembly when added to aqueous solution of pH 7.4. This second polymer highlights the considerable versatility that poly(α-hydroxy acids) inherently possess.

Poly(amino acid)-polyester graft copolymer nanoparticles for the acid-mediated release of doxorubicin.

Biodegradable polymers have emerged as highly effective drug delivery vehicles. We combine N-carboxyanhydride and O-carboxyanhydride ring opening polymerisations to synthesise a poly(amino acid)-polyester graft copolymer capable of encapsulating, and subsequently releasing doxorubicin via acid-mediated hydrolysis. Consequently, the nanoparticles detailed are extremely promising vehicles for the controlled delivery of chemotherapeutic agents.

3D visualization of additive occlusion and tunable full-spectrum fluorescence in calcite.

From biomineralization to synthesis, organic additives provide an effective means of controlling crystallization processes. There is growing evidence that these additives are often occluded within the crystal lattice. This promises an elegant means of creating nanocomposites and tuning physical properties. Here we use the incorporation of sulfonated fluorescent dyes to gain new understanding of additive occlusion in calcite (CaCO3), and to link morphological changes to occlusion mechanisms. We demonstrate that these additives are incorporated within specific zones, as defined by the growth conditions, and show how occlusion can govern changes in crystal shape. Fluorescence spectroscopy and lifetime imaging microscopy also show that the dyes experience unique local environments within different zones. Our strategy is then extended to simultaneously incorporate mixtures of dyes, whose fluorescence cascade creates calcite nanoparticles that fluoresce white. This offers a simple strategy for generating biocompatible and stable fluorescent nanoparticles whose output can be tuned as required.

Glucose-bearing biodegradable poly(amino acid) and poly(amino acid)-poly(ester) conjugates for controlled payload release.

The glucoseamine-initiated ring-opening polymerisation of amino acid N-carboxyanhydrides and O-carboxanhydrides to yield amphiphilic block copolymers that are capable of self-assembly in aqueous solution to form well-defined, glucose-presenting, particles is reported. The particles formed are susceptible to enzyme-mediated (lipase and protease) and pH-induced degradation, and can selectively bind the lectin concanavalin A. Consequently, such glycoparticles are of significance for the controlled release of payload molecules in response to an acidic environment, for instance cancerous tissue, and upon interaction with target enzymes.

A vegetable oil-based organogel for use in pH-mediated drug delivery.

Organogels prepared with vegetable oils as the liquid organic phase present an excellent platform for the controlled delivery of hydrophobic guest molecules. We disclose a graft copolymer comprised of a poly(L-serine) backbone linked to alkane side-chains by hydrolytically susceptible ester bonds, that is capable of gelating edible safflower oil. The thermoresponsive organogel formed, which is non-cytotoxic, is capable of withholding guest molecules before undergoing targeted disassembly upon incubation in solutions of acidic pH, permitting the directed release of payload molecules. The presented material offers an extremely promising candidate for the controlled delivery of hydrophobic agents within acidic environments, such as cancer tumour sites.

The formation of biodegradable micelles from a therapeutic initiator for enzyme-mediated drug delivery.

The direct grafting of amphiphilic macromolecules by sequential n-carboxyanhydride ring-opening polymerisation (NCA ROP) from a therapeutic initiator enables the formation of monodisperse drug-containing micelles. The subsequent enzyme-mediated hydrolysis of the peptide component permits the programmed release of the encapsulated drug molecules, demonstrating a controlled drug delivery platform that negates any challenging payload loading procedures.

Mechanisms by which synthetic 6,7-annulated-4-substituted indole compounds with anti-proliferative activity disrupt mitosis and block cytokinesis in human HL-60 tumor cells in vitro.

BACKGROUND: Synthetic 6,7-annulated-4-substituted indole compounds, which elicit interesting antitumor effects in murine L1210 leukemia cells, were tested for their ability to inhibit human HL-60 tumor cell proliferation, disrupt mitosis and cytokinesis, and interfere with tubulin and actin polymerization in vitro. MATERIALS AND METHODS: Various markers of metabolic activity, mitotic disruption and cytokinesis were used to assess the effectiveness of the drugs in the HL-60 tumor cell system. The ability of annulated indoles to alter the polymerizations of purified tubulin and actin were monitored in cell-free assays and were compared to the effects of drugs known to disrupt the dynamic structures of the mitotic spindle and cleavage furrow. RESULTS: With one exception, annulated indoles inhibited the metabolic activity of HL-60 tumor cells in the low-micromolar range after two and four days in culture but these anti-proliferative effects were weaker than those of jasplakinolide, a known actin binder that blocks cytokinesis. After 24-48 h, antiproliferative concentrations of annulated indoles increased the mitotic index of HL-60 cells similarly to vincristine and stimulated the formation of many bi-nucleated cells, multi-nucleated cells and micronuclei, similarly to taxol and jasplakinolide, suggesting that these antitumor compounds might increase mitotic abnormality, induce chromosomal damage or missegregation, and block cytokinesis. Since annulated indoles mimicked the effect of vincristine on tubulin polymerization, but not that of taxol, these compounds might represent a new class of microtubule de-stabilizing agents that inhibit tubulin polymerization. Moreover, annulated indoles remarkably increased the rate and level of actin polymerization similarly to jasplakinolide, suggesting that they might also stabilize the cleavage furrow to block cytokinesis. CONCLUSION: Although novel derivatives with different substitutions must be synthesized to elucidate structure-activity relationships, identify more potent antitumor compounds and investigate different molecular targets, annulated indoles appear to interact with both tubulin to reduce microtubule assembly and actin to block cytokinesis, thereby inducing bi- and multinucleation, resulting in genomic instability and apoptosis.

Diversity by divergence: Solution-phase parallel synthesis of a library of N-diversified 1-oxa-7-azaspiro[4.5]decan-2-yl-propanes and -butanes.

The synthesis of a 162-member compound library derived from a single precursor via a multistage divergence strategy is described. Divergence is sequentially introduced in three ways: (1) by early preparation of two separable spirocyclic diastereomers, (2) by elaboration of each spirocyclic diastereomer to a different scaffold using four Horner-Emmons-Wadsworth reagents, and (3) by employing three different modes of nitrogen diversification with each scaffold to afford the final compounds. This 2 diastereomers × 4 reagents × 3 modes of diversification strategy leads to 24 unique synthetic pathways that ultimately afforded, in parallel format, the 162-compound set.

Synthesis of a family of spirocyclic scaffolds: building blocks for the exploration of chemical space.

This report describes the preparation of a series of 17 novel racemic spirocyclic scaffolds that are intended for the creation of compound libraries by parallel synthesis for biological screening. Each scaffold features two points of orthogonal diversification. The scaffolds are related to each other in four ways: (1) through stepwise changes in the size of the nitrogen-bearing ring; (2) through the oxidation state of the carbon-centered point of diversification; (3) through the relative stereochemical orientation of the two diversification sites in those members that are stereogenic; and (4) through the provision of both saturated and unsaturated versions of the furan ring in the scaffold series derived from 3-piperidone. The scaffolds provide incremental changes in the relative orientation of the diversity components that would be introduced onto them. The scaffolds feature high sp(3) carbon content which is essential for the three-dimensional exploration of chemical space. This characteristic is particularly evident in those members of this family that bear two stereocenters, i.e., the two series derived from 3-piperidone and 3-pyrrolidinone. In the series derived from 3-piperidone we were able to "split the difference" between the two diastereomers by preparation of their corresponding unsaturated version.

Enzyme-degradable self-assembled hydrogels from polyalanine-modified poly(ethylene glycol) star polymers.

The generation of a range of star-shaped block copolymers composed of a biocompatible poly(ethylene glycol) (PEG) core tethered to a polyalanine (PAla) shell that possesses the capability to (reversibly) self-assemble in water is described. The hydrogels formed offer a hydrophilic environment ideal for biological processes involving proteins and are able to withhold albumin for prolonged periods before its triggered release following the targeted material degradation by the proteolytic enzyme elastase. Consequently, the materials formed offer significant promise for the delivery of proteins, and possibly inhibitors, in response to a proteolytic enzyme overexpressed in chronic wounds.

Antitumor effects of synthetic 6,7-annulated-4-substituted indole compounds in L1210 leukemic cells in vitro.

BACKGROUND: Because annulated indoles have almost no representation in the PubChem or MLSMR databases, an unprecedented class of an indole-based library was constructed, using the indole aryne methodology, and screened for antitumor activity. Sixty-six novel 6,7-annulated-4-substituted indole compounds were synthesized, using a strategic combination of 6,7-indolyne cycloaddition and cross-coupling reactions under both Suzuki-Miyaura and Buchwald-Hartwig conditions, and tested for their effectiveness against murine L1210 tumor cell proliferation in vitro. MATERIALS AND METHODS: Various markers of tumor cell metabolism, DNA degradation, mitotic disruption, cytokinesis and apoptosis were assayed in vitro to evaluate drug cytotoxicity. RESULTS: Most compounds inhibited the metabolic activity of leukemic cells in a time- and concentration-dependent manner but only 9 of them were sufficiently potent to inhibit L1210 tumor cell proliferation by 50% in the low-µM range after 2 (IC(50): 4.5-20.4 µM) and 4 days (0.5-4.0 µM) in culture. However, the antiproliferative compounds that were the most effective at day 4 were not necessarily the most potent at day 2, suggesting different speeds of action. A 3-h treatment with antiproliferative annulated indole was sufficient to inhibit, in a concentration-dependent manner, the rate of DNA synthesis measured in L1210 cells over a 0.5-h period of pulse-labeling with (3)H-thymidine. Four of the antiproliferative compounds had weak DNA-binding activities but one compound reduced the fluorescence of the ethidium bromide-DNA complex by up to 53%, suggesting that some annulated indoles might directly interact with double-stranded DNA to disrupt its integrity and prevent the dye from intercalating into DNA base pairs. However, all 9 antiproliferative compounds induced DNA cleavage at 24 h in L1210 cells, containing (3)H-thymidine-prelabeled DNA, suggesting that these antitumor annulated indoles might trigger an apoptotic pathway of DNA fragmentation. Indeed the antiproliferative annulated indoles caused a time-dependent increase of caspase-3 activity with a peak at 6 h. Interestingly, the compounds with the most potent antiproliferative IC(50) values at day 2 were consistently the most effective at inhibiting DNA synthesis at 3 h and inducing DNA fragmentation at 24 h. After 24-48 h, antiproliferative concentrations of annulated indoles increased the mitotic index of L1210 cells and stimulated the formation of many bi-nucleated cells, multi-nucleated cells, apoptotic cells and micronuclei, suggesting that these antitumor compounds might enhance mitotic abnormality, induce chromosomal damage or missegregation, and block cytokinesis to induce apoptosis. CONCLUSION: Although annulated indoles may have interesting bioactivity, novel derivatives with different substitutions must be synthesized to elucidate structure-activity relationships, identify more potent antitumor lead compounds, and investigate their molecular targets and mechanisms of action.

Block copolypeptides prepared by N-carboxyanhydride ring-opening polymerization.

N-Carboxyanhydride ring-opening polymerization (NCA ROP) is a synthetically straightforward methodology to generate homopolypeptides. Extensive control over the polymerization permits the production of highly monodisperse synthetic polypeptides to a targeted molecular weight in the absence of unfavorable side reactions. Sequential NCA ROP permits the creation of block copolypeptides composed of individual polypeptide blocks boasting different functionalities, secondary structures, and desirable chemical properties. Consequently, a plethora of novel materials have been generated that have found wide-range applicability. This review offers an insight into contemporary synthetic approaches toward NCA ROP before highlighting a number of block copolypeptide architectures generated.

The generation of hydrophilic polypeptide-siloxane conjugates via n-carboxyanhydride polymerisation.

A novel methodology to create covalently linked polypeptide-siloxane hybrid materials by controlled n-carboxyanhydride ring opening polymerisation is disclosed. Poly-L-glutamic acid and poly-L-lysine conjugated products were formed that possessed excellent surface wettability. In addition, the poly-L-lysine-siloxane hybrids formed demonstrated bactericidal attributes against gram-positive Staphylococcus aureus and gram-negative Escherichia coli. It is anticipated that these materials may be of significance for the generation of hydrophilic siloxane-containing polymers that are commonly employed in contemporary medical devices.

Selective formation of angular tricyclic compounds by ruthenium-mediated ring-rearrangement metathesis.

Unsaturated spirocyclic substrates bearing two alkenyl chains underwent ruthenium-mediated ring-rearrangement metathesis through relaying cyclohexene and cycloheptene moieties to give angularly fused tricyclics. In some instances where two products were expected, high degrees of selectivity were observed. In one instance the structural parameter leading to selectivity was very subtle; in others the transformation favoured the formation of products with a cis-fused cyclohexene moiety. An unusual transformation involving ring-opening, double-bond migration, and then ring-closing was observed.