The design of drug delivery systems capable of efficiently delivering poorly soluble drugs to target sites still remains a major challenge. Such materials require several different functionalities; typically, these materials should be biodegradable and nontoxic, nonimmunogenic, responsive to their environment, and soluble in aqueous solution while retaining the ability to solubilize hydrophobic drugs. Here, a polypeptide‐polymer hybrid of elastin‐like polypeptides (ELPs) and poly(2‐oxazoline)s (POx) is reported. This paper describes the chemical synthesis, physical characteristics, and drug loading potential of these novel hybrid macromolecules. A novel method is introduced for terminal functionalization of POx with protected maleimide moieties. Following recovery of the maleimide group via a retro Diels–Alder reaction, the consecutive Michael addition of thiol‐functionalized ELPs yields the desired protein‐polymer conjugate. These conjugates form nanoparticles in aqueous solution capable of solubilizing the anti‐cancer drug paclitaxel with up to 8 wt% loading.
Polyelectrolyte block copolymer micelles assembled thin film is switched in response to local photocatalytic reactions on titanium dioxide, resulting in a layer of variable height, stiffness in response to visible light irradiation. Preosteoblasts migrate toward stiffer side of the substrates.
Pinosylvin is a natural stilbenoid known to exhibit antibacterial bioactivity against foodborne bacteria. In this work, pinosylvin is chemically incorporated into a poly(anhydride‐ester) (PAE) backbone via melt‐condensation polymerization, and characterized with respect to its physicochemical and thermal properties. In vitro release studies demonstrate that pinosylvin‐based PAEs hydrolytically degrade over 40 d to release pinosylvin. Pseudo‐first order kinetic experiments on model compounds, butyric anhydride and 3‐butylstilbene ester, indicate that the anhydride linkages hydrolyze first, followed by the ester bonds to ultimately release pinosylvin. An antibacterial assay shows that the released pinosylvin exhibit bioactivity, while in vitro cytocompatibility studies demonstrate that the polymer is noncytotoxic toward fibroblasts. These preliminary findings suggest that the pinosylvin‐based PAEs can serve as food preservatives in food packaging materials by safely providing antibacterial bioactivity over extended time periods.
Adhesion and proliferation of cells are often suppressed in rigid hydrogels as gel stiffness induces mechanical stress to embedded cells. Herein, the composite hydrogel systems to facilitate high cellular activities are described, while maintaining relatively high gel stiffness. This unusual property is obtained by harmonizing gelatin‐poly(ethylene glycol)‐tyramine (GPT, semisynthetic polymer) and gelatin‐hydroxyphenyl propionic acid conjugates (GH, natural polymer) into hydrogels. A minimum GH concentration of 50% is necessary for cells to be proliferative. GPT is utilized to improve biological stability (>1 week) and gelation time (<20 s) of the hydrogels. These results suggest that deficiency in cellular activity driven by gel stiffness could be overcome by finely tuning the material properties in the microenvironments.
The preparation of novel macromolecular prodrugs via the conjugation of two platinum(IV) complexes to suitably functionalized poly(organo)phosphazenes is presented. The inorganic/organic polymers provide carriers with controlled dimensions due to the use of living cationic polymerization and allow the preparation of conjugates with excellent aqueous solubility but long‐term hydrolytic degradability. The macromolecular Pt(IV) prodrugs are designed to undergo intracellular reduction and simultaneous release from the macromolecular carrier to present the active Pt(II) drug derivatives. In vitro investigations show a significantly enhanced intracellular uptake of Pt for the macromolecular prodrugs when compared to small molecule Pt complexes, which is also reflected in an increase in cytotoxicity. Interestingly, drug‐resistant sublines also show a significantly smaller resistance against the conjugates compared to clinically established platinum drugs, indicating that an alternative uptake route of the Pt(IV) conjugates might also be able to overcome acquired resistance against Pt(II) drugs. In vivo studies of a selected conjugate show improved tumor shrinkage compared to the respective Pt(IV) complex.
Three‐dimensional hydrogel supports for mesenchymal and neural stem cells (NSCs) are promising materials for tissue engineering applications such as spinal cord repair. This study involves the preparation and characterization of superporous scaffolds based on a copolymer of 2‐hydroxyethyl and 2‐aminoethyl methacrylate (HEMA and AEMA) crosslinked with ethylene dimethacrylate. Ammonium oxalate is chosen as a suitable porogen because it consists of needle‐like crystals, allowing their parallel arrangement in the polymerization mold. The amino group of AEMA is used to immobilize RGDS and SIKVAVS peptide sequences with an N‐γ‐maleimidobutyryloxy succinimide ester linker. The amount of the peptide on the scaffold is determined using 125I radiolabeled SIKVAVS. Both RGDS‐ and SIKVAVS‐modified poly(2‐hydroxyethyl methacrylate) scaffolds serve as supports for culturing human mesenchymal stem cells (MSCs) and human fetal NSCs. The RGDS sequence is found to be better for MSC and NSC proliferation and growth than SIKVAVS.
Thin polymer films that prevent the adhesion of bacteria are of interest as coatings for the development of infection‐resistant biomaterials. This study investigates the influence of grafting density and film thickness on the adhesion of Staphylococcus epidermidis to poly(poly(ethylene glycol)methacrylate) (PPEGMA) and poly(2‐hydroxyethyl methacrylate) (PHEMA) brushes prepared via surface‐initiated atom transfer radical polymerization (SI‐ATRP). These brushes are compared with poly(ethylene glycol) (PEG) brushes, which are obtained by grafting PEG onto an epoxide‐modified substrate. Except for very low grafting densities (ρ = 1%), crystal violet staining experiments show that the PHEMA and PPEGMA brushes are equally effective as the PEG‐modified surfaces in preventing S. epidermis adhesion and do not reveal any significant variations as a function of film thickness or grafting density. These results indicate that brushes generated by SI‐ATRP are an attractive alternative to grafted‐onto PEG films for the preparation of surface coatings that resist bacterial adhesion.
A new type of bioreducible poly(amido amine) copolymer is synthesized by the Michael addition polymerization of cystamine bisacrylamide (CBA) with 4‐aminobutylguanidine (agmatine, AGM) and 4‐aminobutanol (ABOL). Since the positively charged guanidinium groups of AGM and the hydroxybutyl groups of ABOL in the side chains have shown to improve the overall transfection efficiency of poly(amido amine)s, it is hypothesized that poly(CBA‐ABOL/AGM) synthesized at the optimal ratio of both components would result in high transfection efficiency and minimal toxicity. In this study, a series of the poly(CBA‐ABOL/AGM) copolymers is synthesized as gene carriers. The polymers are characterized and luciferase transfection efficiencies of the polymers in various cell lines are investigated to select the ideal ratio between AGM and ABOL. The poly(CBA‐ABOL/AGM) containing 80% AGM and 20% ABOL has shown the best transfection efficiency with the lowest cytotoxicity, indicating that this polymer is very promising as a potent and nontoxic gene carrier.
Poly(2‐alkenyl‐2‐oxazoline)s are promising functional polymers for a variety of biomedical applications, such as drug delivery systems, peptide conjugates, or gene delivery. In this study, poly(2‐isopropenyl‐2‐oxazoline) (PIPOx) is prepared through free‐radical polymerization initiated with azobisisobutyronitrile. Reactive 2‐oxazoline units in the side chain support an addition reaction with different compounds containing a carboxylic group, which facilitates the preparation of polymers labeled with two different fluorescent dyes. The cytotoxicities of 2‐oxazoline monomers, PIPOx, and fluorescently labeled PIPOx are evaluated in vitro using an 3‐(4,5‐Dimethyldiazol‐2‐yl)‐2,5‐diphenyl tetrazolium bromide assay and ex vivo using a cell proliferation assay with adenosine triphosphate bioluminescence. The cell uptake of labeled PIPOx is used to determine the colocalization of PIPOx with cell organelles that are part of the endocytic pathway. For the first time, it is shown that poly(2‐isopropenyl‐2‐oxazoline) is a biocompatible material and is suitable for biomedical applications; further, its immunomodulative properties are evaluated.
Reactive oxygen species (ROS) play important roles in cell signaling pathways, while increased production of ROS may disrupt cellular homeostasis, giving rise to oxidative stress and a series of diseases. Utilizing these cell‐generated species as triggers for selective tuning polymer structures and properties represents a promising methodology for disease diagnosis and treatment. Recently, significant progress has been made in fabricating biomaterials including nanoparticles and macroscopic networks to interact with this dynamic physiological condition. These ROS‐responsive platforms have shown potential in a range of biomedical applications, such as cancer targeted drug delivery systems, cell therapy platforms for inflammation related disease, and so on.
A collagen sheet with highly aligned collagen fibers is fabricated by continuous cyclic stretch. The rearrangement of the collagen fibers depends on the different process parameters of the cyclic stretch, including magnitude, frequency, and period of stretch. The collagen fibers are aligned perpendicularly to the direction of the stretch. Corneal stromal cells and smooth muscle cells cultivated on the highly aligned collagen sheet show alignment along the collagen fibers without the stretch during culture. Thus, the sheet can be a suitable scaffold for use in regenerative medicine.
To simultaneously control inflammation and facilitate dentin regeneration, a copolymeric micelle‐in‐microsphere platform is developed in this study, aiming to simultaneously release a hydrophobic drug to suppress inflammation and a hydrophilic biomolecule to enhance odontogenic differentiation of dental pulp stem cells in a distinctly controlled fashion. A series of chitosan‐graft‐poly(lactic acid) copolymers is synthesized with varying lactic acid and chitosan weight ratios, self‐assembled into nanoscale micelle‐like core–shell structures in an aqueous system, and subsequently crosslinked into microspheres through electrostatic interaction with sodium tripolyphosphate. A hydrophobic biomolecule either coumarin‐6 or fluocinolone acetonide (FA) is encapsulated into the hydrophobic cores of the micelles, while a hydrophilic biomolecule either bovine serum albumin or bone morphogenetic protein 2 (BMP‐2) is entrapped in the hydrophilic shells and the interspaces among the micelles. Both hydrophobic and hydrophilic biomolecules are delivered with distinct and tunable release patterns. Delivery of FA and BMP‐2 simultaneously suppresses inflammation and enhances odontogenesis, resulting in significantly enhanced mineralized tissue regeneration. This result also demonstrates the potential for this novel delivery system to deliver multiple therapeutics and to achieve synergistic effects.
A visible light and pH responsive anticancer drug delivery system based on polymer‐coated mesoporous silica nanoparticles (MSNs) has been developed. Perylene‐functionalized poly(dimethylaminoethyl methacrylates) sensitive to visible light and pH are electrostatically attached on the surface of MSNs to seal the nanopores. Stimulation of visible light and acid can unseal the nanopores to induce controlled drug release from the MSNs. More interestingly, the release can be enhanced under the combined stimulation of the dual‐stimuli. The synergistic effect of visible light and acid stimulation on the efficient release of anticancer drugs from the nanohybrids endows the system with great potential for cancer therapy.
This paper provides a biomaterial derived from zwitterionic polymer for controlling macrophage phagocytosis of bacteria. A series of zwitterionic copolymers, named DMAPS‐co‐AA, are synthesized with 3‐dimethyl (methacryloyloxyethyl) ammonium propane sulfonate (DMAPS) and acrylic acid (AA). The biocompatibility of DMAPS‐co‐AA copolymers can be adjusted by adjusting the DMAPS‐content or pH value. As the DMAPS‐content increases, the biocompatibility of zwitterionic copolymer increases. The zwitterionic copolymers with DMAPS content above 30 wt% have higher biocompatibility. Moreover, the biocompatibility also increases significantly as the pH increases from 3.4 to 7.2. By adjusting the pH above 5.8, the zwitterionic copolymer with lower DMAPS‐content also shows higher biocompatibility. Importantly, after incubation with the DMAPS‐co‐AA copolymer solutions at different pH values, phagocytosis behavior of macrophage RAW264.7 cells can also be adjusted. The phagocytosis of bacteria is enhanced at pH = 7.2. Thus, it is proposed that zwitterionic copolymers can be used for controlling phagocytosis of bacteria.
Conventional cancer treatments such as chemotherapy, radiotherapy, or combination of these two result in side effects, which lower the quality of life of the patients. To overcome problems with these methods, altering the drug properties by conjugating them to carrier polymers has emerged. Such polymeric carriers also hold the potential to make tumor cells more sensitive to radiation therapy. Herein, poly(p‐phenylene) (PPP) polymer with poly(ethylene glycol) (PEG) chains and primary amino groups (PPP‐NH2‐g‐PEG) is synthesized and conjugated with anticancer drug Doxorubicin (DOX). pH dependent drug release experiments are performed at pH 5.3 and pH 7.4, respectively. Cell viability studies on human cervix adenocarcinoma cells show that lower doses of DOX inhibit cell proliferation when conjugated with nontoxic doses of PPP‐NH2‐g‐PEG polymer. Additionally, PPP‐NH2‐g‐PEG/Cys/DOX bioconjugate significantly increases radiosensitive properties of DOX. It is possible to use lower doses of DOX when conjugated to PPP‐NH2‐g‐PEG in combination with radiotherapy.
Hyaluronic acid (HA) provides many advantages to regenerative implants through its bioactive properties, but it also has many limitations as a biomaterial if it is not chemically modified. In order to overcome some of these limitations, HA has been combined with poly(ethyl acrylate) in the form of interpenetrating polymeric networks (IPNs), in which the HA network is crosslinked with divinyl sulfone. Scaffolds of this IPN have been produced through a template‐leaching methodology, and their properties have been compared with those of single‐network scaffolds made of either PEA or crosslinked HA. A fibroblast cell line has been used to assess the in vitro performance of the scaffolds, revealing good cell response and a differentiated behavior on the IPN surface when compared to the individual polymers. Altogether, the results confirm that this type of material offers an interesting microenvironment for cells, which can be further improved toward its potential use in medical implants.
Furoxans, or 1,2,5‐oxadiazole‐N‐oxides, are a class of nitric oxide (NO)‐donating compounds that release NO in response to thiol‐containing molecules. In this study, polymeric micelles bearing furoxan moieties are prepared from an amphiphilic block copolymer consisting of a hydrophobic furoxan‐bearing block and a hydrophilic poly(N‐acryloylmorpholine) block. The block copolymer is prepared using a combination of the reversible addition–fragmentation chain transfer polymerization and the copper‐catalyzed Huisgen cycloaddition techniques. The block copolymers form spherical micelles with a diameter of 50 nm by self‐assembly in water. The micelles release NO in response to cysteine and show improved stability against hydrolytic decomposition. Furthermore, the micelles show a synergistic anti‐proliferative effect with ibuprofen in human colon cancer cells.
Molecularly Imprinted Polymers (MIPs) are highly advantageous in the field of analytical chemistry. However, interference from secondary molecules can also impede capture of a target by a MIP receptor. This greatly complicates the design process and often requires extensive laboratory screening which is time consuming, costly, and creates substantial waste products. Herein, is presented a new technique for screening of “virtually imprinted receptors” for rebinding of the molecular template as well as secondary structures, correlating the virtual predictions with experimentally acquired data in three case studies. This novel technique is particularly applicable to the evaluation and prediction of MIP receptor specificity and efficiency in complex aqueous systems.
Electrospun poly‐l ‐lactic acid (PLLA) nanofiber mats carrying surface amine groups, previously introduced by nitrogen atmospheric pressure nonequilibrium plasma, are embedded into aqueous solutions of oligomeric acrylamide‐end capped AGMA1, a biocompatible polyamidoamine with arg‐gly‐asp (RGD)‐reminiscent repeating units. The resultant mixture is finally cured giving PLLA‐AGMA1 hydrogel composites that absorb large amounts of water and, in the swollen state, are translucent, soft, and pliable, yet as strong as the parent PLLA mat. They do not split apart from each other when swollen in water and remain highly flexible and resistant, since the hydrogel portion is covalently grafted onto the PLLA nanofibers via the addition reaction of the surface amine groups to a part of the terminal acrylic double bonds of AGMA1 oligomers. Preliminary tested as scaffolds, the composites prove capable of maintaining short‐term undifferentiated cultures of human pluripotent stem cells in feeder‐free conditions.
A series of pH‐triggered charge‐reversal polyurethane copolymers (PS‐PUs) containing methoxyl‐poly(ethylene glycol) (mPEG), carboxylic acid groups, and piperazine groups is presented in this work. The obtained PS‐PUs copolymers can form into stable micelles at pH 7.4, which response to a narrow pH change (5.5–7.5) and show a tunable pH‐triggered charge‐reversal property. Doxorubicin (DOX) is encapsulated into the PS‐PU micelles as a model drug. The drug release of DOX‐loaded PS‐PU micelles shows an obviously stepped‐up with reducing the pH. Meanwhile, it is found that the charge‐reversal property can improve the cellular uptake behavior and intracellular drug release in both HeLa cells and MCF‐7 cells. Additionally, the time‐dependent cytotoxicity of the DOX‐loaded PS‐PU micelles is confirmed by MTT assay. Attributed to the tunable charge‐reversal property through changing the molar ratio of piperazine/carboxyl, the PS‐PU micelles will be a potential candidate as an intelligent drug delivery system in future studies.
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