A new biodegradable crosslinked polyethylene oxide sulfide (PEOS) hydrogel for controlled drug release

Designing and In Vitro Characterization of pH-Sensitive Aspartic Acid-Graft-Poly(Acrylic Acid) Hydrogels as Controlled Drug Carriers

Acetaminophen is an odorless and white crystalline powder drug, used in the management of fever, pain, and headache. The half-life of acetaminophen is very short; thus, multiple intakes of acetaminophen are needed in a day to maintain a constant pharmacological action for an extended period of time. Certain severe adverse effects are produced due to the frequent intake of acetaminophen, especially hepatotoxicity and skin rashes. Therefore, a drug carrier system is needed which not only prolongs the release of acetaminophen, but also enhances the patient compliance. Therefore, the authors prepared novel aspartic acid-graft-poly(acrylic acid) hydrogels for the controlled release of acetaminophen. The novelty of the prepared hydrogels is based on the incorporation of pH-sensitive monomer acrylic acid with polymer aspartic acid in the presence of ethylene glycol dimethacrylate. Due to the pH-sensitive nature, the release of acetaminophen was prolonged for an extended period of time by the developed hydrogels. Hence, a series of studies was carried out for the formulated hydrogels including sol-gel fraction, FTIR, dynamic swelling, polymer volume analysis, thermal analysis, percent porosity, SEM, in vitro drug release studies, and PXRD analysis. FTIR analysis confirmed the grafting of acrylic acid onto the backbone of aspartic acid and revealed the development of hydrogels. The thermal studies revealed the high thermal stability of the fabricated hydrogels as compared to pure aspartic acid. An irregular surface with a few pores was indicated by SEM. PXRD revealed the amorphous state of the developed hydrogels and confirmed the reduction in the crystallinity of the unreacted aspartic acid by the formulated hydrogels. An increase in gel fraction was observed with the increasing concentration of aspartic acid, acrylic acid, and ethylene glycol dimethacrylate due to the availability of a high amount of free radicals. The porosity study was influenced by the various compositions of developed hydrogels. Porosity was increased due to the enhancement in the concentrations of aspartic acid and acrylic acid, whereas it decreased with the increase in ethylene glycol dimethacrylate concentration. Similarly, the pH-responsive properties of hydrogels were evaluated by dynamic swelling and in vitro drug release studies at two different pH levels (1.2 and 7.4), and a greater dynamic swelling and acetaminophen release were exhibited at pH 7.4 as compared to pH 1.2. An increase in swelling, drug loading, and drug release was seen with the increased incorporation of aspartic acid and acrylic acid, whereas a decrease was detected with the increase in the concentration of ethylene glycol dimethacrylate. Conclusively, the formulated aspartic acid-based hydrogels could be employed as a suitable nonactive pharmaceutical ingredient for the controlled delivery of acetaminophen.

Injectable Nanocomposite Hydrogels for Cancer Therapy

Hydrogel is a kind of 3D polymer network with strong swelling ability in water and appropriate mechanical and biological properties, which make it feasible to maintain bioactive substances and has promising applications in the fields of biomaterials, soft machines, and artificial tissues. Unfortunately, traditional hydrogels prepared by chemical crosslinking have poor mechanical properties and limited functions, which limit their further application. In recent years, with the continuous development of nanoparticle research, more and more studies have combined nanoparticles with hydrogels to make up for the shortcomings of traditional hydrogels. In this article, the types and functions of hydrogels and nanomaterials are introduced first, as well as the functions and applications of injectable nanocomposite hydrogels (INHs), then the latest progress of INHs for cancer treatment is reviewed, some existing problems are summarized, and the application prospect of NHs is prospected.

An open-source handheld extruder loaded with pore-forming bioink for in situ wound dressing

The increasing demand in rapid wound dressing and healing has promoted the development of intraoperative strategies, such as intraoperative bioprinting, which allows deposition of bioinks directly at the injury sites to conform to their specific shapes and structures. Although successes have been achieved to varying degrees, either the instrumentation remains complex and high-cost or the bioink is insufficient for desired cellular activities. Here, we report the development of a cost-effective, open-source handheld bioprinter featuring an ergonomic design, which was entirely portable powered by a battery pack. We further integrated an aqueous two-phase emulsion bioink based on gelatin methacryloyl with the handheld system, enabling convenient shape-controlled in situ bioprinting. The unique pore-forming property of the emulsion bioink facilitated liquid and oxygen transport as well as cellular proliferation and spreading, with an additional ability of good elasticity to withstand repeated mechanical compressions. These advantages of our pore-forming bioink-loaded handheld bioprinter are believed to pave a new avenue for effective wound dressing potentially in a personalized manner down the future.

Temperature-sensitive gel-loaded composite nanomedicines for the treatment of cervical cancer by vaginal delivery

In this study, toad venom (TV) and realgar were loaded into a poloxamer 188/407 (F127/F188)-based temperature-sensitive in situ gel (TISG) and encapsulated in solid lipid nanoparticles (TV-SLN) or ground nano-realgar (NR) to improve drug release and reduce local irritation after vaginal administration. The combination of TV-SLN and NR (TV-SLN/NR) greatly enhanced the inhibition of tumor cell proliferation and was most effective at a dose ratio of 2:3 (w/w). After TV-SLN/NR treatment, S and G0/G1 phase arrest were observed in HeLa and SKOV-3 cells and the inhibitory effects on proliferation were stronger than those in the conventional powder group. The gelation temperature of TV-SLN and NR-loaded TISG (TV-SLN/NR-TISG) using the selected formulation was 33 ± 0.91 °C. The cumulative release of the drug increased as the dissolution of gel progressed, showing a linear relationship (r > 0.99). TV-SLN/NR-TISG enabled the sustained release of cargo by adhesion to the vaginal mucosa and showed excellent biocompatibility during continuous administration for 7 days. We specifically demonstrated the effectiveness of the TISG for the vaginal delivery of TV-SLN and NR, supporting its important clinical implications for the treatment of cervical cancer.

Scaffold-mediated delivery for non-viral mRNA vaccines

mRNA is increasingly being recognized as a promising alternative to pDNA in gene vaccinations. Only recently, owing to the needs of cancer immunotherapies, has the biomaterials/gene delivery community begun to develop new biomaterial strategies for immunomodulation. Here, we report a novel way to use implantable porous scaffolds as a local gene delivery depot to enhance mRNA vaccine immunization in vitro, and in vivo when compared with conventional bolus injections. We first evaluated transfection efficiencies of single-stranded mRNA condensed and charge neutralized with two lipids (Lipofectamine Messenger MAX^TM LM-MM and Stemfect^TM SF) and two cationic polymers (in vivo-jetPEI™, Poly (β-amino ester)) as gene carriers. As SF demonstrated highest in vitro transfection and cell viability, it was selected for subsequent porous polymer scaffold-loading trials. Enhanced in vitro transfection of SF:mRNA nanoparticle-loaded poly (2-hydroxyethyl methacrylate) (pHEMA) scaffolds was also observed with a DC2.4 cell line. Improved sustained local release and local transgene expression were also demonstrated with SF:mRNA nanoparticle-loaded pHEMA scaffolds in vivo compared with bolus injections. Our results suggest that mRNA polyplex-loaded scaffolds may be a superior alternative to either repeated bolus immunizations or ex vivo transfection cell immunotherapies.

Reductively Degradable Poly(2-hydroxyethyl methacrylate) Hydrogels with Oriented Porosity for Tissue Engineering Applications

Degradable poly(2-hydroxyethyl methacrylate) hydrogels were prepared from a linear copolymer (M_w = 49 kDa) of 2-hydroxyethyl methacrylate (HEMA), 2-(acethylthio)ethyl methacrylate (ATEMA), and zwitterionic 2-methacryloyloxyethyl phosphorylcholine (MPC). The deprotection of ATEMA thiol groups by triethylamine followed by their gentle oxidation with 2,2'-dithiodipyridine resulted in the formation of reductively degradable polymers with disulfide bridges. Finally, a hydrogel 3D structure with an oriented porosity was obtained by gelation of the polymer in the presence of needle-like sodium acetate crystals. The pore diameter and porosity of resulting poly(2-hydroxyethyl methacrylate-co-2-(acethylthio)ethyl methacrylate-co-2-methacryloyloxyethyl phosphorylcholine) [P(HEMA-ATEMA-MPC)] hydrogels varied between 59 and 65 μm and between 70 and 79.6 vol % according to Hg porosimetry, and complete degradation of these materials was reached in 86 days in 0.33 mmol solution of l-cysteine/L in phosphate buffer. The cross-linked P(HEMA-ATEMA-MPC) hydrogels were evaluated as a possible support for human mesenchymal stem cells (MSCs). No cytotoxicity was found for the un-cross-linked thiol-containing and protected P(HEMA-ATEMA-MPC) chains up to a concentration of 5 and 1 wt % in α-minimum essential medium, respectively.

Enhancement of curcumin wound healing ability by complexation with 2-hydroxypropyl-γ-cyclodextrin in sacran hydrogel film

Curcumin is one of promising agents to accelerate the wound-healing process. However, the efficacy of curcumin is limited due to its poor water solubility and stability. To enhance the properties of curcumin, 2-hydroxypropyl-γ-cyclodextrin (HP-γ-CyD) can be used through complexation. Recently, we revealed that sacran has the potential to form a hydrogel film (HGF) as a wound dressing material. Therefore, in the present study, we investigated the wound healing ability of curcumin/HP-γ-CyD (Cur/HP-γ-CyD) complex in sacran-based HGF (Sac-HGF). We prepared the Cur/HP-γ-CyD complex in Sac-HGF without surface roughness. Additionally, the amorphous form in the Cur/HP-γ-CyD complex in Sac-HGF were observed. In contrast, the curcumin in Sac-HGF and curcumin/HP-γ-CyD physical mixture in Sac-HGF formed inhomogeneous films due to crystallization of curcumin. Furthermore, HP-γ-CyD played an important role to increase the elastic modulus of the Sac-HGF with high re-swelling ability. The Cur/HP-γ-CyD complex in Sac-HGF maintained antioxidant properties of curcumin. Curcumin was gradually released from the HP-γ-CyD complex in Sac-HGF. Notably, the Cur/HP-γ-CyD complex in Sac-HGF provided the highest wound healing ability in hairless mice. These results suggest that the Cur/HP-γ-CyD complex in Sac-HGF has the potential for use as a new transdermal therapeutic system to promote the wound-healing process.

Redox and pH Responsive Poly (Amidoamine) Dendrimer-Heparin Conjugates via Disulfide Linkages for Letrozole Delivery

Heparin (Hep) conjugated to poly (amidoamine) dendrimer G3.5 (P) via redox-sensitive disulfide bond (P-SS-Hep) was studied. The redox and pH dual-responsive nanocarriers were prepared by a simple method that minimized many complex steps as previous studies. The functional characterization of G3.5 coated Hep was investigated by the proton nuclear magnetic resonance spectroscopy. The size and formation were characterized by the dynamic light scattering, zeta potential, and transmission electron microscopy. P-SS-Hep was spherical in shape with average diameter about 11 nm loaded with more than 20% letrozole. This drug carrier could not only eliminate toxicity to cells and improve the drugs solubility but also increase biocompatibility of the system under reductive environment of glutathione. In particular, P-SS-Hep could enhance the effectiveness of cancer therapy after removing Hep from the surface. These results demonstrated that the P-SS-Hep conjugates could be a promising candidate as redox and pH responsive nanocarriers for cancer chemotherapy.

Enhancing effect of γ-cyclodextrin on wound dressing properties of sacran hydrogel film

A wound dressing is one of the essential approaches for preventing further harm to cutaneous wounds as well as promoting wound healing. Therefore, to achieve ideal wound healing, the development of advanced dressing materials is necessary. Recently, we revealed that a novel megamolecular polysaccharide, sacran, has potential properties as a biomaterial in a physically cross-linked hydrogel film (HGF) for wound dressing application. In this study, to enhance the wound-healing properties of sacran hydrogel film (Sac-HGF) further, we fabricated and characterized novel Sac-HGFs containing cyclodextrins (CyDs). The sacran/α-CyD film (Sac/α-CyD-HGF) and sacran/γ-CyD HGF (Sac/γ-CyD-HGF), but not sacran/β-CyD HGF (Sac/β-CyD-HGF), were well prepared without surface roughness. Powder X-ray diffraction (XRD) patterns of the Sac/γ-CyD-HGFs showed a totally amorphous state compared to that shown by Sac/α-CyD-HGFs. Furthermore, the addition of γ-CyD to Sac-HGFs significantly increased the swelling ratio, porosity, and moisture content of the HGFs, compared to those of the Sac-HGF without CyDs. The Sac/γ-CyD-HGFs were not cytotoxic against NIH3T3 cells, a murine fibroblast cell line. Notably, the Sac/γ-CyD-HGFs significantly improved wound healing in mice, compared to that achieved with the Sac-HGF without γ-CyD. These results suggest that γ-CyD has the potential to promote the wound healing ability of Sac-HGF.

Physically crosslinked-sacran hydrogel films for wound dressing application

The thin hydrogel films consisting of water-swollen polymer networks can potentially be applied for biomedical fields. Recently, natural polysaccharides have great attentions to be developed as wound healing and protection. In the present study, we newly prepared and characterized a physically crosslinked-hydrogel film composed of a novel megamolecular polysaccharide sacran for wound dressing application. We successfully fabricated a physically crosslinked-sacran hydrogel film by a solvent-casting method. The thickness of a sacran hydrogel film was lower than that of a sodium alginate (Na-alginate) film. Importantly, the swollen ratio of a sacran hydrogel film in water at 24h was 19-fold, compared to initial weight. Meanwhile, a Na-alginate hydrogel film was completely broken apart after rehydration. Moreover, a sacran hydrogel film did not show any cytotoxicity on NIH3T3 cells, a murine fibroblast cell line. The in vivo skin hydration study revealed that a sacran hydrogel film significantly increased the moisture content on hairless mice skin and considerably improved wound healing ability, compared to control (non-treated), probably due to not only the moisturing effect but also the anti-inflammatory effect of sacran. These results suggest that sacran has the potential properties as a basic biomaterial in a hydrogel film for wound dressing application.

Fabrication and Characterization of a Glucose-sensitive Antibacterial Chitosan-Polyethylene Oxide Hydrogel

A novel glucose-sensitive chitosan-polyethylene oxide (CS/PEO =1:0.5~1:2.5) hydrogel with controlled release of metronidazole (MNZ) was obtained by chemical cross-linking and immobilization of glucose oxidase (GOx). The hydrogel was characterized by Fourier-transformed infrared spectroscopy (FTIR), compressive mechanical test, rheological analysis, cytotoxicity test, and antibacterial test against Porphyromonas gingivalis. The study found that the CS-PEO composite hydrogel possessed significantly better mechanical properties and biocompatibility than a single-component hydrogel. This might result from the physical cross-linking and formation of semi-interpenetrating network (semi-IPN). In addition, this novel hydrogel has self-regulate ability to release MNZ in response to the environmental glucose stimulus. Specifically, it released more drugs at higher glucose concentration, thus can lead to a greater ability to inhibit Porphyromonas gingivalis. This study has demonstrated the glucose-sensitive antibacterial hydrogel has a great potential as a new therapeutic material for treatment or prevention of periodontitis in diabetic patients.

Strong poly(ethylene oxide) based gel adhesives via oxime cross-linking

There is a demand for materials to replace or augment the use of sutures and staples in surgical procedures. Currently available commercial surgical adhesives provide either high bond strength with biological toxicity or polymer and protein-based products that are biologically acceptable (though with potential sensitizing potential) but have much reduced bond strength. It is desirable to provide novel biocompatible and biodegradable surgical adhesives/sealants capable of high strength with minimal immune or inflammatory response. In this work, we report the end group derivatization of 8-arm star PEOs with aldehyde and amine end groups. Gels were prepared employing the Schiff-base chemistry between the aldehydes and the amines. Gel setting times, swelling behavior and rheological characterization were carried out for these gels. The mechanical-viscoelastic properties were found to be directly proportional to the crosslinking density of the gels, the 10K PEO gel was stiffer in comparison to the 20K PEO gel. The adhesive properties of these gels were tested using porcine skin and showed excellent adhesion properties. Cytotoxicity studies were carried out for the individual gel components using two different methods: (a) Crystal Violet Staining assay (CVS assay) and (b) impedance and cell index measurement by the xCELLigence system at concentrations >5%. Gels prepared by mixing 20% w/w solutions were also tested for cytotoxicity. The results revealed that the individual gel components as well as the prepared gels and their leachables were non-cytotoxic at these concentrations.

STATEMENT OF SIGNIFICANCE

This work presents a new type of glue that is aimed at surgery applications using a water soluble star shaped polymer. It show excellent adhesion to skin and is tough and easy to use. We show that it is very biocompatible based on tests on live human cells, and could therefore in principle be used for internal surgery. Comparison with other reported and commercial glues shows that it is stronger than most, and does not swell in water to the same degree as many other water based bioadhesives.

One-pot synthesis of highly mechanical and redox-degradable polyurethane hydrogels based on tetra-PEG and disulfide/thiol chemistry

A series of tetra-PEG polyurethane hydrogels with tunable redox-degradability and a high compressive fracture strength has been synthesized by a one-pot method.

Novel redox-responsive nanogels based on poly(ionic liquid)s for the triggered loading and release of cargos

A redox-responsive nanogel matrix was fabricated by one-step synthesis for the controlled loading and release of cargos.

Oxidation- and thermo-responsive poly(N-isopropylacrylamide-co-2-hydroxyethyl acrylate) hydrogels cross-linked via diselenides for controlled drug delivery

A novel diselenide crosslinked poly(NIPAM-co-HEA) hydrogel was successfully synthesized, which exhibits a dual-stimuli-responsive drug release behaviors,i.e., thermo-induced slow sustained release and oxidation-induced quick burst release.

Vitreous substitutes: the present and the future

Vitreoretinal surgery has advanced in numerous directions during recent years. The removal of the vitreous body is one of the main characteristics of this surgical procedure. Several molecules have been tested in the past to fill the vitreous cavity and to mimic its functions. We here review the currently available vitreous substitutes, focusing on their molecular properties and functions, together with their adverse effects. Afterwards we describe the characteristics of the ideal vitreous substitute. The challenges facing every ophthalmology researcher are to reach a long-term intraocular permanence of vitreous substitute with total inertness of the molecule injected and the control of inflammatory reactions. We report new polymers with gelification characteristics and smart hydrogels representing the future of vitreoretinal surgery. Finally, we describe the current studies on vitreous regeneration and cell cultures to create new intraocular gels with optimal biocompatibility and rheological properties.

Reversible maleimide-thiol adducts yield glutathione-sensitive poly(ethylene glycol)-heparin hydrogels

We have recently reported that retro Michael-type addition reactions can be employed for producing labile chemical linkages with tunable sensitivity to physiologically relevant reducing potentials. We reasoned that such strategies would also be useful in the design of glutathione-sensitive hydrogels for a variety of targeted delivery and tissue engineering applications. In this report, we describe hydrogels in which maleimide-functionalized low molecular weight heparin (LMWH) is crosslinked with various thiol-functionalized poly(ethylene glycol) (PEG) multi-arm star polymers. Judicious selection of the chemical identity of the thiol permits tuning of degradation via previously unstudied, but versatile chemical methods. Thiol pK_a and hydrophobicity affected both the gelation and degradation of these hydrogels. Maleimide-thiol crosslinking reactions and retro Michael-type addition reactions were verified with ¹H NMR during the crosslinking and degradation of hydrogels. PEGs esterified with phenylthiol derivatives, specifically 4-mercaptophenylpropionic acid or 2,2-dimethyl-3-(4-mercaptophenyl)propionic acid, induced sensitivity to glutathione as shown by a decrease in hydrogel degradation time of 4-fold and 5-fold respectively, measured via spectrophotometric quantification of LMWH. The degradation proceeded through the retro Michael-type addition of the succinimide thioether linkage, with apparent pseudo-first order reaction constants derived from oscillatory rheology experiments of 0.039 ± 0.006 h^-1 and 0.031 ± 0.003 h^-1. The pseudo-first order retro reaction constants were approximately an order of magnitude slower than the degradation rate constants for hydrogels crosslinked via disulfide linkages, indicating the potential use of these Michael-type addition products for reduction-mediated release and/or degradation, with increased blood stability and prolonged drug delivery timescales compared to disulfide moieties.

Green polymer chemistry: Living oxidative polymerization of dithiols

Reduction sensitivity and mild synthetic conditions make disulfide-bonded materials ideal for degradable biomaterial applications. Both the degradation and the synthetic advantages of disulfide-bonded biomaterials have been applied to drug delivery vesicles, protein conjugation, and hydrogel biomaterials, but the synthetic advantages are rarely seen in the creation of biopolymers. A greener and highly efficient oxidative system is presented for the polymerization dithiols to high-molecular-weight poly(disulfide) polymers. The application of this system to 2-[2-(2-sulfanylethoxy)ethoxy]ethanethiol (DODT) produced corresponding degradable poly(disulfide) polymers with molecular weights as high as Mn = 250 000 g/mol and with a polydispersity index (PDI) as low as 1.15.

Protein polymer hydrogels by in situ, rapid and reversible self-gelation

Protein-based biomaterials are an important class of materials for applications in biotechnology and medicine. The exquisite control of their composition, stereochemistry, and chain length offers unique opportunities to engineer biofunctionality, biocompatibility, and biodegradability into these materials. Here, we report the synthesis of a thermally responsive peptide polymer-based hydrogel composed of a recombinant elastin-like polypeptide (ELP) that rapidly forms a reversibly cross-linked hydrogel by the formation of intermolecular disulfide cross-links. To do so, we designed and synthesized ELPs that incorporate periodic cysteine residues (cELPs), and show that cELPs are thermally responsive protein polymers that display rapid gelation under physiologically relevant, mild oxidative conditions. Gelation of cELPs, at concentrations as low as 2.5 wt%, occurs in ≈ 2.5 min upon addition a low concentration of hydrogen peroxide (0.3 wt%). We show the utility of these hydrogels for the sustained release of a model protein in vitro, and demonstrate the ability of this injectable biomaterial to pervade tumors to maximize tumor coverage and retention time upon intratumoral injection. cELPs represent a new class of injectable reversibly cross-linked hydrogels with properties intermediate between ELP coacervates and chemically cross-linked ELP hydrogels that will find useful applications in drug delivery and tissue engineering.

Drug loading into and drug release from pH- and temperature-responsive cylindrical hydrogels

Hydrogels that undergo deformation upon appropriate changes in pH or temperature have considerable promise as drug delivery vehicles. Drug uptake in swelling and nonswelling cylindrical hydrogels and drug release from these into a target fluid are investigated here. A mathematical model for hydrogel-solution composite, a composite of a distributed parameter system (cylindrical hydrogel) and a lumped parameter system (surrounding solution), is developed. The polymer network displacement in a swelling/deswelling hydrogel is described by a stress diffusion coupling model. The analytical solution for network displacement is used to predict solvent intake by swelling hydrogels, solvent efflux from deswelling hydrogels, and changes in pressure, porosity, and effective drug diffusivity. These in turn influence drug uptake during and after hydrogel swelling and drug release from hydrogel during and after deswelling. Numerical results illustrate benefits of hydrogel swelling for drug loading and merits of different modes of drug release. Drug uptake and drug release by temperature-responsive hydrogels are compared with those by hydrogels not subject to deformation.

Vitreous substitutes: a comprehensive review

Vitreoretinal disorders constitute a significant portion of treatable ocular disease. Advances in vitreoretinal surgery have included the development and characterization of suitable substitutes for the vitreous. Air, balanced salt solutions, perfluorocarbons, expansile gases, and silicone oil serve integral roles in modern vitreoretinal surgery. Vitreous substitutes vary widely in their properties, serve different clinical functions, and present different shortcomings. Permanent vitreous replacement has been attempted with collagen, hyaluronic acid, hydroxypropylmethylcellulose, and natural hydrogel polymers. None, however, have proven to be clinically viable. A long-term vitreous substitute remains to be found, and recent research suggests promise in the area of synthetic polymers. Here we review the currently available vitreous substitutes, as well those in the experimental phase. We classify these compounds based on their functionality, composition, and properties. We also discuss the clinical use, advantages, and shortcomings of the various substitutes. In addition we define the ideal vitreous substitute and highlight the need for a permanent substitute with long-term viability and compatibility. Finally, we attempt to define the future role of biomaterials research and the various functions they may serve in the area of vitreous substitutes.

Bioactive inorganic-materials/alginate composite microspheres with controllable drug-delivery ability

Alginate microspheres are considered a promising material as a drug carrier in bone repair because of excellent biocompatibility, but their main disadvantage is low drug entrapment efficiency and noncontrollable release. The aim of this study was to investigate the effect of incorporating mesoporous bioglass (MBG), nonmesoporous bioglass (BG), or hydroxyapatite (HAp) into alginate microspheres on their drug-loading and release properties. X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and atomic emission spectroscopy (AES) were used to analyze the composition, structure, and dissolution of bioactive inorganic materials and their microspheres. Dexamethasone (DEX)-loading and release ability of four microspheres were tested in phosphate buffered saline with varying pH. Results showed that the drug-loading capacity was enhanced with the incorporation of bioactive inorganic materials into alginate microspheres. The MBG/alginate microspheres had the highest drug loading ability. DEX release from alginate microspheres correlated to the dissolution of MBG, BG, and HAp in PBS, and that the pH was an efficient factor in controlling the DEX release; a high pH resulted in greater DEX release, whereas a low pH delayed DEX release. In addition, MBG/alginate, BG/alginate, and HAp/alginate microspheres had varying apatite-formation and dissolution abilities, which indicate that the composites would behave differently with respect to bioactivity. The study suggests that microspheres made of a composite of bioactive inorganic materials and alginate have a bioactivity and degradation profile which greatly improves their drug delivery capacity, thus enhancing their potential applications as bioactive filler materials for bone tissue regeneration.

Primary cardiomyocyte-targeted bioreducible polymer for efficient gene delivery to the myocardium

A cardiomyocyte-targeted Fas siRNA delivery system was developed using primary cardiomyocyte (PCM) specific peptide-modified polymers with high transfection efficiency and low cytotoxicity. Primary cardiomyocyte (PCM) specific peptide, selected by phage display, was conjugated to bioreducible poly(cystamine bisacrylamide-diaminohexane, CBA-DAH) (PCD). The specificity of the PCM-modified polymer to cardiomyocytes was confirmed by competition study with free PCM ligand and by delivery to non-cardiomyocyte NIH 3T3 fibroblasts. The cellular binding and uptake of the PCM-polymer/pDNA polyplex was inhibited by addition of free PCM peptide. The impact of PCM conjugation on cellular uptake and transfection efficiency was greater in H9C2 rat cardiomyocytes than in NIH 3T3 cells. Fas siRNA/PCM-polymer polyplexes exhibited significant Fas gene silencing in rat cardiomyocytes under hypoxic conditions, leading to inhibition of cardiomyocyte apoptosis. These findings demonstrate the utility of the addition of a primary cardiomyocyte (PCM) specific peptide modification to a bioreducible polymer for targeted delivery of Fas siRNA to inhibit cardiomyocyte apoptosis.

Electrostatic Assembly of Poly(ethylene glycol) Nanotubes

Poly(ethylene glycol) (PEG)-based films, nanotubes, and nanotube arrays were successfully made using layer-by-layer (LbL) assembly ion-containing PEO derivatives on porous templates and planar substrates. PEG nanotubes are challenging to produce because PEG dissolves into solutions and solvents used during nanotube processing, but our techniques circumvent the issue. Nanotube dimensions were verified using microscopy and the average observed diameter was 155 nm. The PEG-based structures showed remarkable stability in water, salt water, and sodium hydroxide solution.