Injectable Hydrogels Prepared Using Novel Synthetic Short Peptides with Defined Structure and Gelatin as Scaffolds to Support Cell and Tissue Growth.

Animal-derived basement-membrane matrices such as Geltrex are used to grow cells and tissues. Particularly, these are commonly applied to support tumor growth in animals for cancer research. However, a material derived from an animal source has an undefined composition, and may thus have unavoidable batch-to-batch variation in properties. To overcome these issues, a series of synthetic short peptides to form hydrogels is designed in combination with gelatin to promote cell adhesion and growth. The peptides have sequences of (X1Y1X2Y2)2 , where X1 and X2 are hydrophobic residues, while Y1 and Y2 are hydrophilic residues. The peptides spontaneously fold and self-assemble into a ß-sheet secondary structure upon contact with salts, and then aggregate to form hydrophilic networks of hydrogels. Hybrid hydrogels formed by mixing the peptide IEVEIRVK (IVK8) with gelatin are injectable and enzymatically degradable. The hybrid hydrogels at optimal compositions support SW480 and HepG2 tumor spheroid growth in vitro as effectively as Geltrex. More importantly, the peptide/gelatin hydrogels support tumor growth in a SW480 human colorectal adenocarcinoma xenograft mouse model. Altogether, the results illustrate that the synthetic peptide/gelatin hybrid hydrogel is a promising scaffold that can be used to support cell and tissue growth both in vitro and in vivo.

Drug-free neutrally charged polypeptide nanoparticles as anticancer agents.

Cationic synthetic anticancer polymers and peptides have attracted increasing attention for advancing cancer treatment without causing drug resistance development. To circumvent in vivo instability and toxicity caused by cationic charges of the anticancer polymers/peptides, we report, for the first time, a nanoparticulate delivery system self-assembled from a negatively charged pH-sensitive polypeptide poly(ethylene glycol)-b-poly(ʟ-lysine)-graft-cyclohexene-1,2-dicarboxylic anhydride and a cationic anticancer polypeptide guanidinium-functionalized poly(ʟ-lysine) (PLL-Gua) via electrostatic interaction. The formation of nanoparticles (Gua-NPs) neutralized the positive charges of PLL-Gua. Both PLL-Gua and Gua-NPs killed cancer cells in a dose- and time-dependent manner, and induced cell death via apoptosis. Confocal microscopic studies demonstrated that PLL-Gua and Gua-NPs readily entered cancer cells, and Gua-NPs were taken up by the cells via endocytosis. Notably, Gua-NPs and PLL-Gua exhibited similar in vitro anticancer efficacy against MCF-7 and resistant MCF-7/ADR. PLL-Gua and Gua-NPs also induced similar morphological changes in MCF-7/ADR cells compared to MCF-7 cells, further indicating their ability to bypass drug resistance mechanisms in the MCF-7/ADR cells. More importantly, Gua-NPs with higher LD50 and enhanced tumor accumulation significantly inhibited tumor growth with negligible side effects in vivo. Our findings shed light on the in vivo delivery of anticancer peptides and opened a new avenue for cancer treatment.

Biodegradable Cationic Polycarbonates as Vaccine Adjuvants.

In this study, biodegradable cationic polycarbonate and polylactide block copolymers were synthesized and successfully used as novel vaccine adjuvants to provide enhanced anticancer immunity. The polymers formed nanoparticles with the model vaccine, ovalbumin (OVA), and the immunostimulant toll-like receptor 3 agonist poly(I:C) (a synthetic analog of the double-stranded RNA). Higher uptake of poly(I:C) by the bone marrow-derived dendritic cells and macrophages and OVA by dendritic cells was observed when delivered using the polymer adjuvant. In vivo experiments showed that these nanoparticles remained longer in the subcutaneous injection site as compared to OVA alone and led to higher production of anti-OVA specific antibodies with prolonged immunostimulation. When OVA was combined with poly(I:C) that was either co-entrapped in the same particles or as separate particles, a comparable level of anti-OVA IgG1 antibodies and interleukin-6 (IL-6) was produced in mouse blood plasma, and a similar level of cytotoxic T lymphocyte (CTL) response in mice was stimulated as compared to OVA/Alum particles. Furthermore, tumor rejection in the mice that were vaccinated for 9 months with the formulations containing the polymer adjuvant was stronger than the other treatment groups without the polymer. Notably, the cationic polycarbonates were not associated with any adverse in vivo effects. Thus, these biodegradable polymers may be promising substitutes for aluminum-based adjuvants in vaccine formulations.

Synthetic peptide hydrogels as 3D scaffolds for tissue engineering.

The regeneration of tissues and organs poses an immense challenge due to the extreme complexity in the research work involved. Despite the tissue engineering approach being considered as a promising strategy for more than two decades, a key issue impeding its progress is the lack of ideal scaffold materials. Nature-inspired synthetic peptide hydrogels are inherently biocompatible, and its high resemblance to extracellular matrix makes peptide hydrogels suitable 3D scaffold materials. This review covers the important aspects of peptide hydrogels as 3D scaffolds, including mechanical properties, biodegradability and bioactivity, and the current approaches in creating matrices with optimized features. Many of these scaffolds contain peptide sequences that are widely reported for tissue repair and regeneration and these peptide sequences will also be discussed. Furthermore, 3D biofabrication strategies of synthetic peptide hydrogels and the recent advances of peptide hydrogels in tissue engineering will also be described to reflect the current trend in the field. In the final section, we will present the future outlook in the design and development of peptide-based hydrogels for translational tissue engineering applications.

A Macromolecule Reversing Antibiotic Resistance Phenotype and Repurposing Drugs as Potent Antibiotics.

In order to mitigate antibiotic resistance, a new strategy to increase antibiotic potency and reverse drug resistance is needed. Herein, the translocation mechanism of an antimicrobial guanidinium-functionalized polycarbonate is leveraged in combination with traditional antibiotics to afford a potent treatment for drug-resistant bacteria. Particularly, this polymer-antibiotic combination approach reverses rifampicin resistance phenotype in Acinetobacter baumannii demonstrating a 2.5 × 105-fold reduction in minimum inhibitory concentration (MIC) and a 4096-fold reduction in minimum bactericidal concentration (MBC). This approach also enables the repurposing of auranofin as an antibiotic against multidrug-resistant (MDR) Gram-negative bacteria with a 512-fold MIC and 128-fold MBC reduction, respectively. Finally, the in vivo efficacy of polymer-rifampicin combination is demonstrated in a MDR bacteremia mouse model. This combination approach lays foundational ground rules for a new class of antibiotic adjuvants capable of reversing drug resistance phenotype and repurposing drugs against MDR Gram-negative bacteria.

Subcutaneous vaccination using injectable biodegradable hydrogels for long-term immune response.

Prolonged vaccine release enables gradual immunostimulation, providing long-term immunity. Herein, Vitamin E-PEG-Vitamin E triblock 'ABA' hydrogel, which is formed through physical cross-linking of flower-shaped micelles and can reside in vivo for >17 weeks, was employed for delivery of cancer preventive vaccines to provide sustained anticancer immunity. Mice vaccinated with hydrogel formulations produced a significantly higher quantity of antibodies compared to solution formulations. OVA was used to study EG.7-OVA tumor rejection in vaccinated mice. Among all formulations, OVA-loaded hydrogel containing aluminum-based adjuvant had the best therapeutic outcome, and only 2/10 mice developed solid tumors with significantly smaller tumor size. Moreover, no adverse effect on liver and kidney was detected with the hydrogel formulation. In a lymphoma metastasis mouse model, vaccination with the OVA-loaded hydrogel and adjuvant resulted in increased survival (66.7%) compared to other formulations (12.5-50%) over 100 days. This hydrogel is a promising formulation for sustained delivery of vaccines.

Degradable antimicrobial polycarbonates with unexpected activity and selectivity for treating multidrug-resistant Klebsiella pneumoniae lung infection in mice.

Multidrug resistant (MDR) Klebsiella pneumoniae is a major cause of healthcare-associated infections around the world, with attendant high rates of morbidity and mortality. Progressive reduction in potency of antibiotics capable of treating MDR K. pneumoniae infections - including lung infection - as a consequence of escalating drug resistance provides the motivation to develop drug candidates targeting MDR K. pneumoniae. We recently reported degradable broad-spectrum antimicrobial guanidinium-functionalized polycarbonates with unique antimicrobial mechanism - membrane translocation followed by precipitation of cytosolic materials. These polymers exhibited high potency against bacteria with negligible toxicity. The polymer with ethyl spacer between the quanidinium group and the polymer backbone (pEt_20) showed excellent in vivo efficacy for treating MDR K. pneumoniae-caused peritonitis in mice. In this study, the structures of the polymers were optimized for the treatment of MDR Klebsiella pneumoniae lung infection. Specifically, in vitro antimicrobial activity and selectivity of guanidinium-functionalized polycarbonates containing the same number of guanidinium groups but of a shorter chain length and a structural analogue containing a thiouronium moiety as the pendent cationic group were evaluated. The polymers with optimal compositions and varying hydrophobicity were assessed against 25 clinically isolated K. pneumonia strains for antimicrobial activity and killing kinetics. The results showed that the polymers killed the bacteria more efficiently than clinically used antibiotics, and repeated use of the polymers did not cause drug resistance in K. pneumonia. Particularly, the polymer with butyl spacer (pBut_20) self-assembled into micelles at high concentrations, where the hydrophobic component was shielded in the micellar core, preventing interacting with mammalian cells. A subtle change in the hydrophobicity increased the antimicrobial activity while reducing in vivo toxicity. The in vivo efficacy studies showed that pBut_20 alleviated K. pneumonia lung infection without inducing damage to major organs. Taken together, pBut_20 is promising for treating MDR Klebsiella pneumoniae lung infection in vivo. STATEMENT OF SIGNIFICANCE: Multidrug resistant (MDR) Klebsiella pneumoniae is a major cause of healthcare-associated infections, with attendant high rates of morbidity and mortality. The progressive reduction in antibiotics capable of treating MDR K. pneumoniae infections - including lung infection - as a consequence of escalating drug resistance rates provides the motivation to develop drug candidates. In this study, we report a degradable guanidinium-functionalized polycarbonate with unexpected antimicrobial activity and selectivity towards MDR Klebsiella pneumoniae. A subtle change in polymer hydrophobicity increases antimicrobial activity while reducing in vivo toxicity due to self-assembly at high concentrations. The polymer with optimal composition alleviates Klebsiella pneumonia lung infection without inducing damage to major organs. The polymer is promising for treating MDR Klebsiella pneumoniae lung infection in vivo.

Hydrogels with prolonged release of therapeutic antibody: Block junction chemistry modification of 'ABA' copolymers provides superior anticancer efficacy.

In this study, we report a new series of vitamin E-functionalized 'ABA' triblock copolymers with carbamate block junction, which can form hydrogen-bonds. These polymers were synthesized via solvent- and catalyst-free nucleophilic addition between PEG-diamine and vitamin E-functionalized cyclic carbonate. The catalyst-free synthesis enabled an easy purification step and recycling of excess monomers. The polymers formed hydrogels through self-assembly by simply dissolving in aqueous solution. The hydrogel stiffness was easily tuned by varying polymer concentration, PEG molecular weight and number of vitamin E molecules. The triblock copolymer with one vitamin E molecule on each end of PEG (20 kDa) formed hydrogel at a concentration of 4.0 wt% and above. The hydrogel showed pronounced shear-thinning behavior, and was injectable. Particularly, the hydrogel formed with carbamate block junction was stiffer than that with carbonate block junction, and provided more sustained antibody release. The hydrogel with carbamate block junction was loaded with the anticancer antibody Herceptin, which suppressed tumor growth over a significantly longer period of time as compared to the Herceptin-loaded hydrogel with carbonate block junction (90 days vs. 40 days). This hydrogel has potential for use as matrix for sustained delivery of antibodies.

A macromolecular approach to eradicate multidrug resistant bacterial infections while mitigating drug resistance onset.

Polymyxins remain the last line treatment for multidrug-resistant (MDR) infections. As polymyxins resistance emerges, there is an urgent need to develop effective antimicrobial agents capable of mitigating MDR. Here, we report biodegradable guanidinium-functionalized polycarbonates with a distinctive mechanism that does not induce drug resistance. Unlike conventional antibiotics, repeated use of the polymers does not lead to drug resistance. Transcriptomic analysis of bacteria further supports development of resistance to antibiotics but not to the macromolecules after 30 treatments. Importantly, high in vivo treatment efficacy of the macromolecules is achieved in MDR A. baumannii-, E. coli-, K. pneumoniae-, methicillin-resistant S. aureus-, cecal ligation and puncture-induced polymicrobial peritonitis, and P. aeruginosa lung infection mouse models while remaining non-toxic (e.g., therapeutic index-ED50/LD50: 1473 for A. baumannii infection). These biodegradable synthetic macromolecules have been demonstrated to have broad spectrum in vivo antimicrobial activity, and have excellent potential as systemic antimicrobials against MDR infections.

Injectable Coacervate Hydrogel for Delivery of Anticancer Drug-Loaded Nanoparticles in vivo.

In this study, bortezomib (BTZ, a cytotoxic water-insoluble anticancer drug) was encapsulated in micellar nanoparticles having a catechol-functionalized polycarbonate core through a pH-sensitive covalent bond between phenylboronic acid (PBA) in BTZ and catechol, and these drug-loaded micelles were incorporated into hydrogels to form micelle/hydrogel composites. A series of injectable, biodegradable hydrogels with readily tunable mechanical properties were formed and optimized for sustained delivery of the BTZ-loaded micelles through ionic coacervation between PBA-functionalized polycarbonate/poly(ethylene glycol) (PEG) "ABA" triblock copolymer and a cationic one having guanidinium- or thiouronium-functionalized polycarbonate as "A" block. An in vitro release study showed the pH dependence in BTZ release. At pH 7.4, the BTZ release from the micelle/hydrogel composite remained low at 7%, whereas in an acidic environment, ∼85% of BTZ was released gradually over 9 days. In vivo studies performed in a multiple myeloma MM.1S xenograft mouse model showed that the tumor progression of mice treated with BTZ-loaded micelle solution was similar to that of the control group, whereas those treated with the BTZ-loaded micelle/hydrogel composite resulted in significant delay in the tumor progression. The results demonstrate that this hydrogel has great potential for use in subcutaneous and sustained delivery of drug-loaded micelles with superior therapeutic efficacy.

Biodegradable Strain-Promoted Click Hydrogels for Encapsulation of Drug-Loaded Nanoparticles and Sustained Release of Therapeutics.

Biodegradable polycarbonate-based ABA triblock copolymers were synthesized via organocatalyzed ring-opening polymerization and successfully formulated into chemically cross-linked hydrogels by strain-promoted alkyne-azide cycloaddition (SPAAC). The synthesis and cross-linking of these polymers are copper-free, thereby eliminating the concern over metallic contaminants for biomedical applications. Gelation occurs rapidly within a span of 60 s by simple mixing of the azide- and cyclooctyne-functionalized polymer solutions. The resultant hydrogels exhibited pronounced shear-thinning behavior and could be easily dispensed through a 22G hypodermic needle. To demonstrate the usefulness of these gels as a drug delivery matrix, doxorubicin (DOX)-loaded micelles prepared using catechol-functionalized polycarbonate copolymers were incorporated into the polymer solutions to eventually form micelle/hydrogel composites. Notably, the drug release rate from the hydrogels was significantly more gradual compared to the solution formulation. DOX release from the micelle/hydrogel composites could be sustained for 1 week, while the release from the micelle solution was completed rapidly within 6 h of incubation. Cellular uptake of the released DOX from the micelle/hydrogel composites was observed at 3 h of incubation of human breast cancer MDA-MB-231 cells. A blank hydrogel containing PEG-(Cat)12 micelles showed almost negligible toxicity on MDA-MB-231cells where cell viability remained high at >80% after treatment. When the cells were treated with the DOX-loaded micelle/hydrogel composites, there was a drastic reduction in cell viability with only 25% of cells surviving the treatment. In all, this study introduces a simple method of formulating hydrogel materials with incorporated micelles for drug delivery applications.

Highly potent antimicrobial polyionenes with rapid killing kinetics, skin biocompatibility and in vivo bactericidal activity.

Effective antimicrobial agents are important arsenals in our perennial fight against communicable diseases, hospital-acquired and surgical site multidrug-resistant infections. In this study, we devise a strategy for the development of highly efficacious and skin compatible yet inexpensive water-soluble macromolecular antimicrobial polyionenes by employing a catalyst-free, polyaddition polymerization using commercially available monomers. A series of antimicrobial polyionenes are prepared through a simple polyaddition reaction with both polymer-forming reaction and charge installation occurring simultaneously. The compositions and structures of polymers are modulated to study their effects on antimicrobial activity against a broad spectrum of pathogenic microbes. Polymers with optimized compositions have potent antimicrobial activity with low minimum inhibitory concentrations of 1.95-7.8 µg/mL and high selectivity over mammalian cells. In particular, a killing efficiency of more than 99.9% within 2 min is obtained. Moreover, the polymers demonstrate high antimicrobial efficacy against various clinically-isolated multidrug-resistant microbes, yet exhibit vastly superior skin biocompatibility in mice as compared to other clinically used surgical scrubs (chlorhexidine and betadine). Microbicidal activity of the polymer is mediated via membrane lysis as demonstrated by confocal microscopy. Unlike small molecular antibiotics, repeated use of the polymer does not induce drug resistance. More importantly, the polymer shows excellent bactericidal activity in a P. aeruginosa-contaminated mouse skin model. Given their rapid and efficacious microbicidal activity and skin compatibility, these polymers have tremendous potential to be developed as surgical scrubs/hand sanitizers to prevent multidrug-resistant infections.

Self-Assembled, Biodegradable Magnetic Resonance Imaging Agents: Organic Radical-Functionalized Diblock Copolymers.

We report the design, synthesis, and evaluation of biodegradable amphiphilic poly(ethylene glycol)-b-polycarbonate-based diblock copolymers containing pendant persistent organic radicals (e.g., PROXYL). These paramagnetic radical-functionalized polymers self-assemble into micellar nanoparticles in aqueous media, which preferentially accumulate in tumor tissue via the enhanced permeability and retention (EPR) effect. Through T1 relaxation NMR studies, as well as magnetic resonance imaging (MRI) studies on mice, we show that these nanomaterials are effective as metal-free, biodegradable MRI contrast agents. We also demonstrate anticancer drugs can be readily loaded into the nanoparticles, conferring therapeutic delivery properties in addition to their imaging properties making these materials potential theranostic agents in the treatment of cancer.

Modular composite hydrogels from cholesterol-functionalized polycarbonates for antimicrobial applications.

Micellar composite hydrogel systems represent a promising class of materials for biomolecule and drug delivery applications. In this work a system combining micellar drug delivery with supramolecular hydrogel assemblies is developed, representing an elegant marriage of aqueous hydrophobic drug delivery and next-generation injectable viscoelastic materials. Novel shear thinning and injectable micellar composite hydrogels were prepared using an amphiphilic ABA-type triblock copolymer consisting of a hydrophilic middle block and cholesterol-functionalized polycarbonates as terminal hydrophobic blocks. Varying the concentration and relative hydrophobic-hydrophilic content of the amphiphilic species conferred the ability to tune the storage moduli of these gels from 200 Pa to 3500 Pa. This tunable system was used to encapsulate drug-loaded polymeric micelles, demonstrating a straightforward and modular approach to developing micellar viscoelastic materials for a variety of applications such as delivery of hydrophobic drugs. These hydrogels were also mixed with cholesterol-containing cationic polycarbonates to render antimicrobial activity and capability for anionic drug delivery. Additionally, small-angle X-ray scattering (SAXS) and electron microscopy (EM) results probed the mesoscale structure of these micellar composite materials, lending molecular level insight into the self-assembly properties of these gels. The antimicrobial composite hydrogels demonstrated strong microbicidal activity against Gram-negative and Gram-positive bacteria, and C. albicans fungus. Amphotericin B (AmB, an antifungal drug)-loaded micelles embedded within the hydrogel demonstrated sustained drug release over 4 days and effective eradication of fungi. Our findings demonstrate that materials of different nature (i.e. small molecule drugs or charged macromolecules) can be physically combined with ABA-type triblock copolymer gelators to form hydrogels for potential pharmaceutical applications.

Biodegradable Block Copolyelectrolyte Hydrogels for Tunable Release of Therapeutics and Topical Antimicrobial Skin Treatment.

Biodegradable polycarbonate-based ABA triblock copolyelectrolytes were synthesized and formulated into physically cross-linked hydrogels. These biocompatible, cationically, and anionically charged hydrogel materials exhibited pronounced shear-thinning behavior, making them useful for a variety of biomedical applications. For example, we investigated the antimicrobial activity of positively charged thiouronium functionalized hydrogels by microbial growth inhibition assays against several clinically relevant Gram-negative and Gram-positive bacteria. It is noteworthy that these hydrogels exhibited broad spectrum killing efficiencies approaching 100%, thereby rendering these thixotropic materials attractive for treatment of skin and other surface bound infections. Finally, cationic trimethylammonium containing hydrogels and anionic carboxylic acid functionalized hydrogels were utilized to sustain the release of negatively charged (diclofenac) and positively charged (vancomycin) therapeutics, respectively. Collectively, the present work introduces a simple method for formulating charged hydrogel materials that are capable of interacting with various analytes of interest through noncovalent interactions.

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.

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).

Synergistic co-delivery of membrane-disrupting polymers with commercial antibiotics against highly opportunistic bacteria.

A series of vitamin E-containing biodegradable antimicrobial cationic polycarbonates is designed and synthesized via controlled organocatalytic ring-opening polymerization. The incorporation of vitamin E significantly enhances antimicrobial activity. These polymers demonstrate broad-spectrum antimicrobial activity against various microbes, e.g., S. aureus (Gram-positive), E-coli (Gram-negative) and C. albicans (fungi). More importantly, the co-delivery of such polymers with selected antibiotics (e.g., doxycycline) shows high synergism towards difficult-to-kill bacteria P. aeruginosa. These findings suggest that these vitamin E-functionalized polycarbonates are potentially useful antimicrobial agents against challenging bacterial/fungal infections.

Access to different nanostructures via self-assembly of thiourea-containing PEGylated amphiphiles.

Readily water-soluble PEGylated amphiphiles containing bis-thiourea-based molecular recognition units at the interface of hydrophobic and hydrophilic blocks are developed. Self-assembly of these amphiphiles is found to be dependent on the exact chemical composition of the hydrophobic component. Elongated, spherical, and disk-like micelles are formed with the change in hydrophobic group from stearyl (2A), oleyl (2B), and dodecanol (2C), respectively. The length of the rod-like elongated micelles formed by 2A could be tuned by thermal treatment as well. Synthesis and detailed structural characterization of these amphiphiles by TEM, DSC, synchrotron SAXS techniques are reported. Organic solvent-free direct aqueous encapsulation of doxorubicin, an anticancer drug into these nanostructures is demonstrated.