Amphiphilic and Hydrophilic Block Copolymers from Aliphatic N-Substituted 8-Membered Cyclic Carbonates: A Versatile Macromolecular Platform for Biomedical Applications.

Introduction of hydrophilic components, particularly amines and zwitterions, onto a degradable polymer platform, while maintaining precise control over the polymer composition, has been a challenge. Recognizing the importance of these hydrophilic residues in multiple aspects of the nanobiomedicine field, herein, a straightforward synthetic route to access well-defined amphiphilic and hydrophilic degradable block copolymers from diethanolamine-derived functional eight-membered N-substituted aliphatic cyclic carbonates is reported. By this route, tertiary amine, secondary amine, and zwitterion residues can be incorporated across the polymer backbone. Demonstration of pH-responsiveness of these hydrophilic residues and their utility in the development of drug-delivery vehicles, catered for the specific requirements of respective model drugs (doxorubicin and diclofenac sodium salt) are shown. As hydrophilic components in degradable polymers play crucial roles in the biological interactions, these materials offers opportunities to expand the scope and applicability of aliphatic cyclic carbonates. Our approach to these functional polycarbonates will expand the range of biocompatible and biodegradable synthetic materials available for nanobiomedicine, including drug and gene delivery, antimicrobials, and hydrophilic polymers as poly(ethylene glycol) (PEG) alternatives.

Cryptococcosis mimicking lung carcinoma with brain metastases in an immunocompetent patient.

Cryptococcosis is a fungal infection caused by Cryptococcus spp. that enters the body via inhalation. This ubiquitous yeast has gained notoriety as an opportunistic pathogen in the immunosuppressed population. The authors report a case of a previously-well adult male presented with left-sided weakness. Imaging demonstrated a pulmonary mass and 2 contrast-enhancing intracranial lesions-all features suggestive of a primary lung carcinoma with brain metastases. However, further investigations confirmed disseminated cryptococcosis, without evidence of malignancy. The patient was successfully treated with a course of antifungals. To the authors' knowledge, this is the first reported case of dissemintated cryptococcosis in an immunocompetent adult male, simulating as primary lung carcinoma with brain metastases.

A Simple and Facile Approach to Aliphatic N-Substituted Functional Eight-Membered Cyclic Carbonates and Their Organocatalytic Polymerization.

Aliphatic N-substituted functional eight-membered cyclic carbonates were synthesized from N-substituted diethanolamines by intramolecular cyclization. On the basis of the N-substituent, three major subclasses of carbonate monomers were synthesized (N-aryl, N-alkyl and N-carbamate). Organocatalytic ring opening polymerization (ROP) of eight-membered cyclic carbonates was explored as a route to access narrowly dispersed polymers of predictable molecular weights. Polymerization kinetics was highly dependent on the substituent on the nitrogen atom and the catalyst used for the reaction. The use of triazabicyclodecene (TBD), instead of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), as the catalyst for the N-alkyl substituted monomers significantly enhanced the rate of polymerizations. Computational studies were performed to rationalize the observed trends for TBD catalyzed polymerizations. With the optimal organocatalyst all monomers could be polymerized generating well-defined polymers within a timespan of ≤2 h with relatively high monomer conversion (≥80%) and low molar-mass dispersity (D(M) ≤ 1.3). Both the glass transition temperatures (T(g)) and onset of degradation temperatures (T(onset)) of these polymers were found to be N-substituent dependent and were in the range of about -45 to 35 °C and 230 to 333 °C, respectively. The copolymerization of the eight membered monomers with 6-membered cyclic comonomers including commercially available l-lactide and trimethylene carbonate produced novel copolymers. The combination of inexpensive starting materials, ease of ring-closure and subsequent polymerization makes this an attractive route to functional polycarbontes.

Codelivery of dual drugs from polymeric micelles for simultaneous targeting of both cancer cells and cancer stem cells.

AIM: Phenformin-loaded micelles (Phen M) were used in combination with gemcitabine-loaded micelles (Gem M) to study their combined effect against H460 human lung cancer cells and cancer stem cells (CSCs) in vitro and in vivo. MATERIALS & METHODS: Gem M and Phen M were prepared via self-assembly of a mixture of a diblock copolymer of PEG and urea-functionalized polycarbonate (PEG-PUC) and a diblock copolymer of PEG and acid-functionalized polycarbonate (PEG-PAC) through hydrogen bonding and ionic interactions. Gem M and Phen M were characterized and tested for efficacy both in vitro and in vivo against cancer cells and CSCs. RESULTS: The combination of Gem M/Phen M exhibited higher cytotoxicity against CSCs and non-CSCs than Gem M and Phen M alone, and showed significant cell cycle growth arrest in vitro. The combination therapy had superior tumor suppression and apoptosis in vivo without inducing toxicity to liver and kidney. CONCLUSION: The combination of Gem M and Phen M may be potentially used in lung cancer therapy.

d(1) Oxosulfido-Mo(V) Compounds: First Isolation and Unambiguous Characterization of an Extended Series.

Reaction of Tp(iPr)Mo(VI)OS(OAr) with cobaltocene in toluene results in the precipitation of brown, microcrystalline oxosulfido-Mo(V) compounds, [CoCp2][Tp(iPr)Mo(V)OS(OAr)] (Cp(-) = η(5)-C5H5(-), Tp(iPr)(-) = hydrotris(3-isopropylpyrazol-1-yl)borate, OAr(-) = phenolate or 2-(s)Bu, 2-(t)Bu, 3-(t)Bu, 4-(s)Bu, 4-Ph, 3,5-(s)Bu2, 2-CO2Me, 2-CO2Et or 2-CO2Ph derivative thereof). The compounds are air- and water-sensitive and display ν(Mo═O) and ν(Mo[Formula: see text]S) IR absorption bands at ca. 890 and 435 cm(-1), respectively, 20-40 cm(-1) lower in energy than the corresponding bands in Tp(iPr)MoOS(OAr). They are electrochemically active and exhibit three reversible cyclovoltammetric waves (E(Mo(VI)/Mo(V)) = -0.40 to -0.66 V, E([CoCp2](+)/CoCp2) = -0.94 V and E(CoCp2/[CoCp2](-)) = -1.88 V vs SCE). Structural characterization of [CoCp2][Tp(iPr)MoOS(OC6H4CO2Et-2)]·2CH2Cl2 revealed a distorted octahedral Mo(V) anion with Mo═O and Mo[Formula: see text]S distances of 1.761(5) and 2.215(2) Å, respectively, longer than corresponding distances in related Tp(iPr)MoOS(OAr) compounds. The observation of strong S(1s) → (S(3p) + Mo(4d)) S K-preedge transitions indicative of a d(1) sulfido-Mo(V) moiety and the presence of short Mo═O (ca. 1.72 Å) and Mo[Formula: see text]S (ca. 2.25 Å) backscattering contributions in the Mo K-edge EXAFS further support the oxosulfido-Mo(V) formulation. The compounds are EPR-active, exhibiting highly anisotropic (Δg 0.124-0.150), rhombic, frozen-glass spectra with g1 close to the value observed for the free electron (ge = 2.0023). Spectroscopic studies are consistent with the presence of a highly covalent Mo[Formula: see text]S π* singly occupied molecular orbital. The compounds are highly reactive, with reactions localized at the terminal sulfido ligand. For example, the compounds react with cyanide and PPh3 to produce thiocyanate and SPPh3, respectively, and various (depending on solvent) oxo-Mo(V) species. Reactions with copper reagents also generally lead to desulfurization and the formation of oxo-Mo(V) or -Mo(IV) complexes.

Co-delivery of antiviral and antifungal therapeutics for the treatment of sexually transmitted infections using a moldable, supramolecular hydrogel.

In this investigation, a therapeutic co-delivery hydrogel system is developed to provide effective HIV prophylaxis, alongside the prevention and/or treatment of candidiasis. Two components-a HIV reverse transcriptase inhibitor, tenofovir, and a cationic macromolecular antifungal agent derived from a vitamin D-functionalized polycarbonate (VD/BnCl (1:30))-are formulated into biodegradable vitamin D-functionalized polycarbonate/PEG-based supramolecular hydrogels. The hydrogels exhibit thixotropic properties and can be easily spread across surfaces for efficient drug absorption. Sustained release of tenofovir from the hydrogel is observed, where approximately 85% tenofovir is released within 3 h. VD/BnCl (1:30) does not impede drug diffusion from the hydrogel as the drug release profiles are similar with and without the polycation. Antimicrobial efficacy studies indicate that the hydrogels kill C. albicans efficiently with a minimum bactericidal concentration (MBC) of 0.25-0.5 g L(-1) . These hydrogels also eradicate C. albicans biofilm effectively at 4× MBC. When human dermal fibroblasts (as model mammalian cells) are treated with these hydrogels, cell viability remains high at above 80%, demonstrating excellent biocompatibility. When applied topically, this dual-functional hydrogel can potentially prevent HIV transmission and eliminate microbes that cause infections in the vulvovagina region.

Injectable biodegradable hydrogels from vitamin D-functionalized polycarbonates for the delivery of avastin with enhanced therapeutic efficiency against metastatic colorectal cancer.

Humanized vascular endothelial growth factor (VEGF) antibody (bevacizumab; Avastin) is a highly effective monoclonal antibody against metastatic colorectal cancer and several other advanced late stage cancers. However, limited aqueous solubility and short circulation half-life of the antibody result in long infusion time (30-90 min) and frequent injections. Such direful medical procedures often cause considerable patient inconvenience and prolonged pharmacy preparation. Subcutaneous delivery of Avastin using injectable hydrogels can continuously provide Avastin to treat the malignancy and mitigate antibody degradation. In this study, ABA triblock copolymers of vitamin D-functionalized polycarbonate and poly(ethylene glycol), that is, VDm-PEG-VDm were synthesized and employed to form physically cross-linked injectable hydrogels for encapsulation and subcutaneous delivery of Avastin in a sustained fashion. Antitumor studies were performed using two different HCT116 xenograft mouse models: a subcutaneous and an intraperitoneal metastatic tumor models. The therapeutic efficacy of Avastin-loaded hydrogel injected subcutaneously (s.c.) was compared to an Avastin solution injected via either intravenous (i.v.) or intraperitoneal (i.p.) route. In the subcutaneous tumor model, the Avastin-loaded hydrogel resulted in greater tumor suppression as compared to i.v. and i.p. administration of Avastin solution. The biodistribution pattern of the hydrogel delivery system was also different from the other formulations as there was significantly higher accumulation in the tumor tissue and lesser accumulation within the liver and kidneys as compared to Avastin delivered through i.v. and i.p. administration. Furthermore, in vivo studies carried out on mice with peritoneal metastasis demonstrated that Avastin-loaded hydrogel and weekly administration of Avastin solution resulted in higher survival (87 and 77% over 62 days, respectively) when compared to the control, blank hydrogel and bolus Avastin solution (i.v.; 50-60%). The antimetastatic activity of Avastin delivered using a one-time injection of the hydrogel was as effective as that of 4× weekly injections (i.v.) of Avastin. The reduced injection frequency provided by the subcutaneous formulation may enhance patient convenience and compliance for metastatic cancer therapy.

Antimicrobial hydrogels: a new weapon in the arsenal against multidrug-resistant infections.

The rapid emergence of antibiotic resistance in pathogenic microbes is becoming an imminent global public health problem. Treatment with conventional antibiotics often leads to resistance development as the majority of these antibiotics act on intracellular targets, leaving the bacterial morphology intact. Thus, they are highly prone to develop resistance through mutation. Much effort has been made to develop macromolecular antimicrobial agents that are less susceptible to resistance as they function by microbial membrane disruption. Antimicrobial hydrogels constitute an important class of macromolecular antimicrobial agents, which have been shown to be effective in preventing and treating multidrug-resistant infections. Advances in synthetic chemistry have made it possible to tailor molecular structure and functionality to impart broad-spectrum antimicrobial activity as well as predictable mechanical and rheological properties. This has significantly broadened the scope of potential applications that range from medical device and implant coating, sterilization, wound dressing, to antimicrobial creams for the prevention and treatment of multidrug-resistant infections. In this review, advances in both chemically and physically cross-linked natural and synthetic hydrogels possessing intrinsic antimicrobial properties or loaded with antibiotics, antimicrobial polymers/peptides and metal nanoparticles are highlighted. Relationships between physicochemical properties and antimicrobial activity/selectivity, and possible antimicrobial mechanisms of the hydrogels are discussed. Approaches to mitigating toxicity of metal nanoparticles that are encapsulated in hydrogels are reviewed. In addition, challenges and future perspectives in the development of safe and effective antimicrobial hydrogel systems especially involving co-delivery of antimicrobial polymers/peptides and conventional antimicrobial agents for eventual clinical applications are presented.

Phenformin-loaded polymeric micelles for targeting both cancer cells and cancer stem cells in vitro and in vivo.

Conventional cancer chemotherapy often fails as most anti-cancer drugs are not effective against drug-resistant cancer stem cells. These surviving cancer stem cells lead to relapse and metastasis. In this study, an anti-diabetic drug, phenformin, capable of eliminating cancer stem cells was loaded into micelles via self-assembly using a mixture of a diblock copolymer of poly(ethylene glycol) (PEG) and urea-functionalized polycarbonate and a diblock copolymer of PEG and acid-functionalized polycarbonate through hydrogen bonding. The phenformin-loaded micelles, having an average diameter of 102 nm with narrow size distribution, were stable in serum-containing solution over 48 h and non-cytotoxic towards non-cancerous cells. More than 90% of phenformin was released from the micelles over 96 h. Lung cancer stem cells (side population cells, i.e. SP cells) and non-SP cells were sorted from H460 human lung cancer cell line, and treated with free phenformin and phenformin-loaded micelles. The results showed that the drug-loaded micelles were more effective in inhibiting the growth of both SP and non-SP cells. In vivo studies conducted in an H460 human lung cancer mouse model demonstrated that the drug-loaded micelles had greater anti-tumor efficacy, and reduced the population of SP cells in the tumor tissues more effectively than free phenformin. Liver function analysis was performed following drug treatments, and the results indicated that the drug-loaded micelles did not cause liver damage, a harmful side-effect of phenformin when used clinically. These phenformin-loaded micelles may be used to target both cancer cells and cancer stem cells in chemotherapy for the prevention of relapse and metastasis.

Antimicrobial polycarbonates: investigating the impact of balancing charge and hydrophobicity using a same-centered polymer approach.

Biodegradable antimicrobial polymers are a promising solution for combating drug resistant microbes. When designing these materials, the balance between charge and hydrophobicity significantly affects the antimicrobial activity and selectivity toward microbes over mammalian cells. Furthermore, where the charge and hydrophobicity is located on the molecules has also proven to be significant. A series of antimicrobial homopolymer polycarbonates were synthesized, where the hydrophobic/hydrophilic balance was controlled by varying the spacer between the charged quaternary ammonium moiety and the polymer backbone (a "same-centered" structure where the hydrophobic moiety is directly attached to the charged moiety). These homopolymers were active against all microbes tested but depending on the spacer length some hemolytic activity was observed. To reduce the polymer hemolytic activity we systematically varied the polymer composition by copolymerizing the different monomers used in the "same center" homopolymers. By maintaining charge on each repeat unit but copolymerizing monomers having varied hydrophobic side chain lengths, polymers with high activity and selectivity were achieved. In addition, these macromolecules act via a membrane disruption mechanism, making them less likely to induce resistance.

Block copolymer mixtures as antimicrobial hydrogels for biofilm eradication.

Current antimicrobial strategies have mostly been developed to manage infections due to planktonic cells. However, microbes in their nature state will tend to exist by attaching to and growing on living and inanimate surfaces that result in the formation of biofilms. Conventional therapies for treating biofilm-related infections are likely to be insufficient due to the lower susceptibility of microbes that are embedded in the biofilm matrix. In this study, we report the development of biodegradable hydrogels from vitamin E-functionalized polycarbonates for antimicrobial applications. These hydrogels were formed by incorporating positively-charged polycarbonates containing propyl and benzyl side chains with vitamin E moiety into physically cross-linked networks of "ABA"-type polycarbonate and poly(ethylene glycol) triblock copolymers. Investigations of the mechanical properties of the hydrogels showed that the G' values ranged from 1400 to 1600 Pa and the presence of cationic polycarbonate did not affect the stiffness of the hydrogels. Shear-thinning behavior was observed as the hydrogels displayed high viscosity at low shear rates that dramatically decreased as the shear rate increased. In vitro antimicrobial studies revealed that the more hydrophobic VE/BnCl(1:30)-loaded hydrogels generally exhibited better antimicrobial/antifungal effects compared to the VE/PrBr(1:30) counterpart as lower minimum biocidal concentrations (MBC) were observed in Staphylococcus aureus (Gram-positive), Escherichia coli (Gram-negative) and Candida albicans (fungus) (156.2, 312.5, 312.5 mg/L for VE/BnCl(1:30) and 312.5, 2500 and 625 mg/L for VE/PrBr(1:30) respectively). Similar trends were observed for the treatment of biofilms where VE/BnCl(1:30)-loaded hydrogels displayed better efficiency with regards to eradication of biomass and reduction of microbe viability of the biofilms. Furthermore, a high degree of synergistic antimicrobial effects was also observed through the co-delivery of antimicrobial polycarbonates with a conventionally-used antifungal agent, fluconazole. These hydrogels also displayed excellent compatibility with human dermal fibroblasts with cell viability >80% after treatment with hydrogels loaded with cationic polymers and/or fluconazole at minimum biocidal concentrations (MBC).

Structural characterization and unusual reactivity of oxosulfido-Mo(V) compounds: implications for the structure and electronic description of the very rapid form of xanthine oxidase.

The first structural characterization of a mononuclear, EPR-active, oxosulfido-Mo(V) compound related to the very rapid form of xanthine oxidase (VR-XnO) is reported. The compound, [CoCp2][Tp(iPr)Mo(V)OS(2-OC6H4CO2Et)] [Cp = cyclopentadienyl; Tp(iPr) = hydrotris(3-isopropylpyrazol-1-yl)borate], exhibits a distorted octahedral geometry with Mo═O and Mo=/--S distances of 1.761(5) and 2.215(2) Å, respectively, and an O═Mo=/--S angle of 107.33(14)°. Significantly, the Mo(V)=/--S distance is much shorter than the value of 2.36 Å reported for oxosulfido-Mo(V) compounds (Singh, R.; et al. Inorg. Chem. 1989, 28, 8) but close to the range established for VR-XnO by protein crystallography. The methyl and phenyl esters were also prepared but the latter is highly reactive and undergoes an intramolecular, radical-based cyclization/elimination reaction to form [CoCp2][Tp(iPr)Mo(IV)O{2-OC6H4C(O)S-κO,κS}]. This study provides the first definitive measurement of the Mo(V)=/--S bond distance in an unambiguously characterized oxosulfido-Mo(V) compound and supports the presence of a short (ca. 2.22 Å) Mo=/--S bond in VR-XnO. It also demonstrates that the Mo(V)=/--S moiety participates in radical-based reactions that are facilitated by the facile redox interplay of Mo and S and by substrates susceptible to radical eliminations.

Bipyridine Adducts of Molybdenum Imido Alkylidene and Imido Alkylidyne Complexes.

Seven bipyridine adducts of molybdenum imido alkylidene bispyrrolide complexes of the type Mo(NR)(CHCMe(2)R')(Pyr)(2)(bipy) (1a-1g; R = 2,6-i-Pr(2)C(6)H(3) (Ar), adamantyl (Ad), 2,6-Me(2)C(6)H(3) (Ar'), 2-i-PrC(6)H(4) (Ar(iPr)), 2-ClC(6)H(4) (Ar(Cl)), 2-t-BuC(6)H(4) (Ar(t) (Bu)), and 2-MesitylC(6)H(4) (Ar(M)), respectively; R' = Me, Ph) have been prepared using three different methods. Up to three isomers of the adducts are observed that are proposed to be the trans and two possible cis pyrrolide isomers of syn alkylidenes. Sonication of a mixture containing 1a-1g, HMTOH (2,6-dimesitylphenol), and ZnCl(2)(dioxane) led to the formation of MAP species of the type Mo(NR)(CHCMe(2)R')(Pyr)(OHMT) (3a-3g). DCMNBD (2,3-dicarbomethoxynorbornadiene) is polymerized employing 3a-3g as initiators to yield >98% cis,syndiotactic poly(DCMNBD). Attempts to prepare bipy adducts of bisdimethylpyrrolide complexes led to formation of imido alkylidyne complexes of the type Mo(NR)(CCMe(2)R')(Me(2)Pyr)(bipy) (Me(2)Pyr = 2,5-dimethylpyrrolide; 4a - 4g) through a ligand-induced migration of an alkylidene α proton to a dimethylpyrrolide ligand. X-ray structures of Mo(NAr)(CHCMe(2)Ph)(Pyr)(2)(bipy) (1a), Mo(NAr(iPr))(CHCMe(2)Ph)(Pyr)(OHMT) (3d), Mo(NAr)(CCMe(2)Ph)(Me(2)Pyr)(bipy) (4a), and Mo(NAr(T))(CCMe(3))(Me(2)Pyr)(bipy) (Ar(T) = 2-(2,4,6-i-Pr(3)C(6)H(2))C(6)H(4); 4g) showed structures with the normal bond lengths and angles.

Synthesis of cis,syndiotactic ROMP polymers containing alternating enantiomers.

Ring-opening metathesis polymerization (ROMP) of rac-endo,exo-5,6-dicarbomethoxynorbornene (inter alia) yields a cis,syndio,alt-polymer, one in which the sequential units in the cis,syndiotactic polymer consist of alternating enantiomers. Cis selectivity arises through addition of the monomer to produce an all-cis-metallacyclobutane intermediate, while syndioselectivity and alternating enantiomer structures arise as a consequence of inversion of configuration at the metal center with each metathesis step.

cis-Dioxo- and cis-(hydroxo)oxo-Mo(V) complexes stabilized by intramolecular hydrogen-bonding.

The reactions of Tp(iPr)Mo(VI)O(2)Cl with salicylanilides and NEt(3) produce cis-Tp(iPr)Mo(VI)O(2)(2-OC(6)H(4)CONHR) (Tp(iPr) = hydrotris(3-isopropylpyrazol-1-yl)borate, R = Ph, 4-C(6)H(4)Cl, 4-C(6)H(4)OMe). The N-methyl complex, Tp(iPr)MoO(2){2-OC(6)H(4)CON(Me)Ph}, is similarly prepared. Reduction of the amido complexes by cobaltocene produces green, EPR-active compounds, [CoCp(2)][Tp(iPr)Mo(V)O(2)(2-OC(6)H(4)CONHR)], that exhibit strong, low energy, ν(MoO(2)) IR bands at ∼ 895 and 790 cm(-1) (cf. ∼ 935 and 900 cm(-1) for the Mo(VI) analogues). The X-ray structures of all seven complexes have been determined. In each case, the Mo center exhibits a distorted octahedral coordination geometry defined by mutually cis oxo and phenolate ligands and a tridentate fac-Tp(iPr) ligand. The Mo(V) anions exhibit greater Mo═O distances (av. 1.738 Å vs 1.695 Å) and O═Mo═O angles (av. 112.4° vs 102.9°) than their Mo(VI) counterparts, indicative of the presence of a three-center (MoO(2)), π* semioccupied molecular orbital in these d(1) complexes. The amido Mo(VI) and Mo(V) complexes exhibit an intramolecular hydrogen-bond between the NH and O(phenolate) atoms. Protonation of [CoCp(2)][Tp(iPr)Mo(V)O(2)(2-OC(6)H(4)CONHR)] by lutidinium tetrafluoroborate is quantitative and produces EPR-active, cis-(hydroxo)oxo-Mo(V) complexes, Tp(iPr)Mo(V)O(OH)(2-OC(6)H(4)CONHR), related to the low pH Mo(V) forms of sulfite oxidase.