Directed assembly of triblock copolymer worms to produce nanostructured fibers is achieved via colloid electrospinning. These copolymer worms are conveniently prepared by polymerization‐induced self‐assembly in concentrated aqueous dispersion. Addition of a second water‐soluble component, poly(vinyl alcohol), is found to be critical for the production of well‐defined fibers: trial experiments performed using the worms alone produce only spherical microparticles. Transmission electron microscopy studies confirm that the worm morphology survives electrospinning and the worms become orientated parallel to the main axis of the fibers during their generation. The average deviant angle (θdev) between the worm orientation and fiber axis decreases from 17° to 9° as the worm/PVA mass ratio increases from 1.15:1 to 5:1, indicating a greater degree of worm alignment within fibers with higher worm contents and smaller fiber diameters. Thus triblock copolymer fibers of ≈300 ± 120 nm diameter can be readily produced that comprise aligned worms on the nanoscale.
The present study delves into a combined bio‐nano‐macromolecular approach for bone tissue engineering. This approach relies on the properties of an ideal scaffold material imbued with all the chemical premises required for fostering cellular growth and differentiation. A tannic acid based water dispersible hyperbranched polyurethane is fabricated with bio‐nanohybrids of carbon dot and four different peptides (viz. SVVYGLR, PRGDSGYRGDS, IPP, and CGGKVGKACCVPTKLSPISVLYK) to impart target specific in vivo bone healing ability. This polymeric bio‐nanocomposite is blended with 10 wt% of gelatin and examined as a non‐invasive delivery vehicle. In vitro assessment of the developed polymeric system reveals good osteoblast adhesion, proliferation, and differentiation. Aided by this panel of peptides, the polymeric bio‐nanocomposite exhibits in vivo ectopic bone formation ability. The study on in vivo mineralization and vascularization reveals the occurrence of calcification and blood vessel formation. Thus, the study demonstrates carbon dot/peptide functionalized hyperbranched polyurethane gel for bone tissue engineering application.
Oligo(Glu70‐co‐Leu30), a peptide synthesized by protease catalysis, is functionalized at the N‐terminus with a 4‐pentenoyl unit and grafted to polyLSL[6′Ac,6″Ac], a glycopolymer prepared by ring‐opening metathesis polymerization of lactonic sophorolipid diacetate. First, polyLSL[6'Ac,6”Ac] fiber mats are fabricated by electrospinning. Oxidation of the fiber mats and subsequent reaction with cysteamine lead to thiol‐functionalized fiber mats with no significant morphology changes. Grafting of the alkene‐modified oligopeptide to thiol‐functionalized polyLSL[6′Ac,6″Ac] fiber mats is achieved via “thiol‐ene” click reaction. X‐ray photoelectron spectroscopy analysis to characterize peptide grafting reveals that about 50 mol% of polyLSL[6′Ac,6′′Ac] repeat units at fiber surfaces are decorated with a peptide moiety, out of which about 1/3 of the oligo(Glu70‐co‐Leu30) units are physically adsorbed to polyLSL[6′Ac,6′′Ac]. The results of this work pave the way to precise engineering of polyLSL fiber mats that can be decorated with a potentially wide range of molecules that tailor surface chemistry and biological properties.
Here, it is demonstrated that X‐ray nanotomography with Zernike phase contrast can be used for 3D imaging of cells grown on electrospun polymer scaffolds. The scaffold fibers and cells are simultaneously imaged, enabling the influence of scaffold architecture on cell location and morphology to be studied. The high resolution enables subcellular details to be revealed. The X‐ray imaging conditions were optimized to reduce scan times, making it feasible to scan multiple regions of interest in relatively large samples. An image processing procedure is presented which enables scaffold characteristics and cell location to be quantified. The procedure is demonstrated by comparing the ingrowth of cells after culture for 3 and 6 days.
Conductive polymers are interesting materials for a number of biological and medical applications requiring electrical stimulation of cells or tissues. Highly conductive polymers (polypyrrole and polyaniline)/Antheraea mylitta silk fibroin coated fibers are fabricated successfully by in situ polymerization without any modification of the native silk fibroin. Coated fibers characterized by scanning electron microscopy confirm the silk fiber surface is covered by conductive polymers. Thermogravimetric analysis reveals preserved thermal stability of silk fiber after coating process. X‐ray diffraction of degummed fiber diffraction peaks at around 2θ = 20.4 and 16.5 confirms the preservation of the β‐sheet structure typical of degummed silk II fibers. This phenomenon implies that both polypyrrole and polyaniline chains form interactions with peptide linkages in degummed fiber macromolecules, without significantly disrupting protein assembly. Fourier transform infrared spectroscopy of coated fibers indicates hydrogen bonding and electrostatic interactions exist between silk fibroin macromolecules and conductive polymers. Resulting fibers display good conductive properties compared to corresponding conjugated polymers. In vitro analysis (live/dead assay) of the behavior of human immortalized keratinocytes (HaCaTs) on coated fibers demonstrates improved cell‐adhesive properties and viability after polymers coating. Hence, polypyrrole‐ and polyaniline‐coated A. mylitta silk fibers are suitable for application in cell culture and for tissue engineering, where electrical conduction properties are required.
The phase behavior of a dendritic amphiphile containing a Newkome‐type dendron as the hydrophilic moiety and a cholesterol unit as the hydrophobic segment is investigated at the air–liquid interface. The amphiphile forms stable monomolecular films at the air–liquid interface on different subphases. Furthermore, the mineralization of calcium phosphate beneath the monolayer at different calcium and phosphate concentrations versus mineralization time shows that at low calcium and phosphate concentrations needles form, whereas flakes and spheres dominate at higher concentrations. Energy‐dispersive X‐ray spectroscopy, X‐ray photoelectron spectroscopy, and electron diffraction confirm the formation of calcium phosphate. High‐resolution transmission electron microscopy and electron diffraction confirm the predominant formation of octacalcium phosphate and hydroxyapatite. The data also indicate that the final products form via a complex multistep reaction, including an association step, where nano‐needles aggregate into larger flake‐like objects.
This blinded controlled prospective randomized study investigates the biocompatibility of polypyrrole (PPy) polymer that will be used for intracranial triggered release of anti‐epileptic drugs (AEDs). Three by three millimeters PPy are implanted subdurally in six adult female genetic absence epilepsy rats from Strasbourg. Each rat has a polymer implanted on one side of the cortex and a sham craniotomy performed on the other side. After a period of seven weeks, rats are euthanized and parallel series of coronal sections are cut throughout the implant site. Four series of 15 sections are histological (hematoxylin and eosin) and immunohistochemically (neuron‐specific nuclear protein, glial fibrillary acidic protein, and anti‐CD68 antibody) stained and evaluated by three investigators. The results show that implanted PPy mats do not induce obvious inflammation, trauma, gliosis, and neuronal toxicity. Therefore the authors conclude the PPy used offer good histocompatibility with central nervous system cells and that PPy sheets can be used as intracranial, AED delivery implant.
Stimuli‐sensitive polymeric vesicles or polymersomes as self‐assembled colloidal nanocarriers have received paramount importance for their integral role as delivery system for therapeutics and biotherapeutics. This work describes spontaneous polymersome formation at pH 7, as evidenced by surface tension, steady state fluorescence, dynamic light scattering, and microscopic studies, by three hydrophilic random cationic copolymers synthesized using N ,N‐(dimethylamino)ethyl methacrylate (DMAEM) and methoxy poly(ethylene glycol) monomethacrylate in different mole ratios. The results suggest that methoxy poly(ethylene glycol) chains constitute the bilayer membrane of the polymersomes and DMAEM projects toward water constituting the positively charged surface. The polymersomes have been observed to release their encapsulated guest at acidic pH as a result of transformation into polymeric micelles. All these highly biocompatible cationic polymers show successful gene transfection ability as nonviral vector on human cell line with different potential. Thus these polymers prove their utility as a potential delivery system for hydrophilic model drug as well as genetic material.
Cell sheet transplantation is a key tissue engineering technology. A vascular endothelial growth factor (VEGF)‐releasing fiber mat is developed for the transplantation of multilayered cardiomyocyte sheets. Poly(vinyl alcohol) fiber mats bearing poly(lactic‐co‐glycolic acid) nanoparticles that incorporate VEGF are fabricated using electrospinning and electrospray methods. Six‐layered cardiomyocyte sheets are transplanted with a VEGF‐releasing mat into athymic rats. After two weeks, these sheets produce thicker cardiomyocyte layers compared with controls lacking a VEGF‐releasing mat, and incorporate larger‐diameter blood vessels containing erythrocytes. Thus, local VEGF release near the transplanted cardiomyocytes induces vascularization, which supplies sufficient oxygen and nutrients to prevent necrosis. In contrast, cardiomyocyte sheets without a VEGF‐releasing mat do not survive in vivo, probably undergo necrosis, and are reduced in thickness. Hence, these VEGF‐releasing mats enable the transplantation of multilayered cardiomyocyte sheets in a single procedure, and should expand the potential of cell sheet transplantation for therapeutic applications.
Using systematic coarse‐grained (CG) techniques such as iterative Boltzmann inversion (IBI) is an efficient means to simulate high molecular weight polymer melts within reasonable computational time. One drawback of such an approach is however the need to carry out extensive atomistic simulations in order to extrapolate the necessary distributions to derive the inter and intrabead force field parameters. Here it is shown that it is possible to use atomistic simulations of relative short oligomers to develop the CG model for high molecular weight polymers. In particular for the specific case of polycarbonates, it is found that the structural properties (end‐to‐end distance, radius of gyration and their distributions) are similar irrespective of whether the CG potentials are derived from 5‐mer or 10‐mer melt systems. Dynamical properties of the CG systems are smoother and faster than the atomistic ones. Scaling factor, derived by overlapping the CG mean square displacement curves (obtained from different CG IBI potentials) over the atomistic ones, also scales the autocorrelation functions. A prediction of the dynamical scaling factor in the case of the unavailability of atomistic simulations is also discussed. The dynamical properties of the CG melts are modeled reasonably well by all the CG potentials derived from atomistic simulations of short oligomers.
A fully starch‐derived bioactive 3D porous scaffold is developed. The bioactivity is introduced through nanosized graphene oxide (nGO) derived from starch by microwave‐assisted degradation to carbon spheres and further oxidation to GO nanodots. nGO is covalently attached to starch to prepare functionalized starch (SNGO) via an esterification reaction. nGO and SNGO exhibit no cytotoxicity to MG63 at least up to 1000 µg mL−1 under (3‐(4,5‐Dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide) assay. Porous scaffolds consisting of starch and SNGO (S/SNGO) or nGO (S/nGO) are prepared by freeze drying. The porosity and water uptake ability of the scaffolds depend on the concentration of nGO. Moreover, nGO, as a bioactive nanofiller, functions as an effective anchoring site for inducing CaP recrystallization in simulated body fluid. Among all modified starch‐based scaffolds, the S/SNGO scaffold containing the highest concentration of covalently attached SNGO (50%) induces the largest amount of hydroxyapatite, a type of CaP crystal that is closest to bone. The prepared 3D porous nGO functionalized scaffold, thus, exhibits potential promise for bone/cartilage tissue engineering.
The structural determination and manipulation of bottle‐brush polymers, a class of polymers with serially grafted side‐chains, is challenging due to the interplay of side‐chain and backbone interactions over various length scales. The present work performs a detailed analysis, using molecular dynamics simulation techniques, to unravel these interactions by probing the distinct rod to a flexible real‐chain with self‐avoiding walk (SAW) type crossover in the backbone static structure factor. This analysis elucidates the deviation from flexible chain behavior, while also providing a quantitative measure of persistence length, . Significantly, the results identify a trend in which is consistent with the debated theoretical prediction of , where Ns is the number of monomers in each side‐chain of the bottle‐brush polymer.
Combined treatment is more effective than single treatment against most forms of cancer. In this work, doxorubicin loaded chitosan–W18O49 nanoparticles combined with the photothermal therapy and chemotherapy are fabricated through the electrostatic interaction between positively charged chitosan and negatively charged W18O49 nanoparticles. The in vitro and in vivo behaviors of these nanoparticles are examined by dynamic light scattering, transmission electron microscopy, cytotoxicity, near‐infrared fluorescence imaging, and tumor growth inhibition experiment. These nanoparticles have a mean size around 110 nm and show a pH sensitive drug release behavior. After irradiation by the 980 nm laser, these nanoparticles show more pronounced cytotoxicity against HeLa cells than that of free doxorubicin or photothermal therapy alone. The in vivo experiments confirm that their antitumor ability is significantly improved, resulting in superior efficiency in impeding tumor growth and extension of the lifetime of mice.
The unsatisfactory outcomes of typical multiple cytotoxic chemotherapeutic combination therapies used to treat patients have fostered a need for new unconventional combinations of therapeutic agents. Among the candidates, siRNA has been widely discussed and tested. However, the right time right place codelivery of siRNA with other types of active ingredients is challenging because of the possible differences among their physiochemical and pharmacodynamics properties. To accomplish a synergistic cytotoxic effect, a nanoassembly is thus designed to codeliver siRNA with other therapeutic agents. A siRNA, targeting prosurvival gene for the p75 neurotrophin receptor, and an organelle‐fusing peptide, targeting mitochondria, are layered onto a nanotemplate by charge–charge interaction, followed by a layer of CD44 targeting ligand. The formulated triple‐functional nanomedicine is efficiently internalized by the CD44 expressing triple‐negative breast cancer cells. The encapsulated siRNA and the pro‐apoptotic peptide are released inside cells, silencing the intended prosurvival gene, and inducing apoptosis by fusing the mitochondrial membrane, respectively. A synergistic effect is achieved by this three‐agent combination. The design of the developed multifunctional nanomedicine can be generalized to deliver other siRNA and drugs for a maximum therapeutic combination with minimal off‐targeting effects.
Solution behavior of thermo‐responsive polymers and their complexes with biological macromolecules may be affected by environmental conditions, such as the concentration of macromolecular components, pH, ion concentration, etc. Therefore, a thermo‐responsive polymer and its complexes should be characterized in detail to observe their responses against possible environments under physiological conditions before biological applications. To briefly indicate this important issue, thermo‐responsive block copolymer of quaternized poly(4‐vinylpyridine) and poly(oligoethyleneglycol methyl ether methacrylate) as a potential nonviral vector has been synthesized. Polyelectrolyte complexes of this copolymer with the antisense oligonucleotide of c‐Myc oncogene are also thermo‐responsive but, have lower LCST (lower critical solution temperature) values compared to individual copolymer. LCST values of complexes decrease with molar ratio of macromolecular components and presence of salt. Dilution of solutions also affects solution behavior of complexes and causes a significant decrease in size and an increase in LCST, which indicates possible effects of severe dilutions in the blood stream.
Hyperbranched polymer formation during step polymerization of AB2 type monomer with equal reactivity of two B's is investigated theoretically, focusing the attention to the degree of branching (DB) and the mean square radius of gyration for the unperturbed chains, . It is found that the DB‐value at large degree of polymerization (P) limit, = 0.5 is unchanged during the whole course of polymerization. The average value of having the same P is invariant throughout the polymerization. The universal curve between and P agrees perfectly with that for the self‐condensing vinyl polymerization (SCVP), another method to synthesize hyperbranched polymers, when the reactivity ratio for SCVP, rSCVP, is 2.589 that gives = 0.5. The power law, is found for large values of P.
Tissue engineering (TE) depends on the population of scaffolds with appropriate cells, arranged in a specific physiological direction using a variety of techniques. Here, a novel technique of creating “living threads” is described based on thin (poly(ε‐caprolactone) fibers of different diameters (23–243 μm). The fibers readily attract human mesenchymal stem cells (MSCs), which are firmly adhered. These versatile fibers can be used to produce dimensional shapes identical in shape to the cup‐like structure of a normal human valve, while preserving the specific orientation of both the cells and the fibers. The MSCs on leaflets and the cells cultured in flask shown similar epitopes expression when analyzed by fluorescence activated cell sorting. Together, these characteristics have important functional implications as living absorbable fibers can be a valuable resource in TE of living tissues, including heart valves.
A ternary complex comprising plasmid DNA, lipopolysaccharide‐binding peptide (LBP), and deoxycholic acid‐conjugated polyethylenimine (PEI‐DA) is prepared for combinational therapy of acute lung injury (ALI). The LBP is designed as an anti‐inflammatory peptide based on the lipopolysaccharide (LPS)‐binding domain of HMGB‐1. In vitro cytokine assays show that LBP reduces levels of proinflammatory cytokines by inhibiting LPS. PEI‐DA is synthesized as the gene carrier by conjugation of deoxycholic acid to low‐molecular weight polyethylenimine (2 kDa, PEI2k). PEI‐DA has higher transfection efficiency than high‐molecular weight polyethylenimine (25 kDa, PEI25k). The ternary complex of an HO‐1 plasmid (pHO‐1), PEI‐DA, and LBP is prepared as a combinational system to deliver the therapeutic gene and peptide. The transfection efficiency of the ternary complex is higher than that of the pHO‐1/PEI‐DA binary complex. The ternary complex also reduces TNF‐α secretion in LPS‐activated Raw264.7 macrophage cells. Administration of the ternary complex into the lungs of an animal ALI model by intratracheal injection induces HO‐1 expression and reduces levels of proinflammatory cytokines more efficiently than the pHO‐1/PEI‐DA binary complex or LBP alone. In addition, the ternary complex reduces inflammation in the lungs. Therefore, the pHO‐1/PEI‐DA/LBP ternary complex may be an effective treatment for ALI.
The molecular systems, modeling composite materials, are formed by the epoxy‐amine oligomers with covalently bound chromophore‐containing dendritic fragments ( EAD ) as a host and additional azo‐chromophores as guests. The relationship between the structure and quadratic nonlinear optical characteristics of the model systems is established by atomistic modeling and quantum chemistry. The effect of the chain length of the model systems and the choice of the dendron structure, in particular, the length of the groups tethering chromophores to the branching center, on the values of first hyperpolarizability is studied. Molecular dynamics, performed for the model systems at various temperatures, reveals chromophores local mobility at temperature close to 130 °C; the calculations being fulfilled with the force field MMFF94s modified in terms of the ESP partial charges estimate at B3LYP/6‐31G(d) level.
The condensation of nucleic acids into compact nanoparticles with cationic carriers is a powerful tool for translocating exogenous nucleic acids into cells. To date, most efforts have been focused on the development of novel gene carriers for safe and efficient gene delivery. However, small interfering RNA (siRNA) is generally not strongly associated with cationic carriers due to its stiff structure and low spatial charge density. To overcome this limitation, this work introduces a well‐defined dimeric conjugate of small internally segment interfering RNA (sisiRNA) linked via a disulfide bond for enhanced cellular uptake and gene silencing. Dimeric sisiRNA is synthesized through oxidizing two monomeric sisiRNA molecules, each of which consists of a sense strand carrying a nick and an antisense strand modified with a thiol group at the 3′‐end. The nick in the sense strand enables the dimeric sisiRNA to be more effectively condensed into nanosized complexes due to the increased structural flexibility, which results in a higher gene silencing efficiency compared with the dimeric siRNA containing the intact sense strands. The results indicate that the discontinuity of the sense strands is a simple method of adding more flexibility to various siRNA‐based nanostructures for enhanced gene silencing.
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