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.
Poly(di(ethylene glycol)methyl ether methacrylate) (PDEGMA) brushes, which are known to suppress protein adsorption and prevent cell attachment, are reported here to possess interesting and tunable thermoresponsive behavior, if the brush thickness is reduced or the grafting density is altered. PDEGMA brushes with a dry ellipsometric thickness of 5 ± 1 nm can be switched from cell adherent behavior at 37 °C to cell nonadherent at 25 °C. This behavior coincides with the temperature‐dependent irreversible adsorption of fibronectin from phosphate saline buffer and proteins present in the cell culture medium, as unveiled by surface plasmon resonance measurements. Unlike for tissue culture polystyrene reference surfaces, swelling of the PDEGMA chains below the lower critical solution temperature results in the absence of paxillin and actin containing cellular filaments responsible for cell attachment. These tunable properties of very thin homopolymer PDEGMA brushes render this system interesting as an alternative thermoresponsive layer for continuous cell culture or enzyme‐free cell culture systems.
In this study, heparin‐mimicking hydrogel thin films are covalently attached onto poly(ether sulfone) membrane surfaces to improve anticoagulant property. The hydrogel films display honeycomb‐like porous structure with well controlled thickness and show long‐term stability. After immobilizing the hydrogel films, the membranes show excellent anticoagulant property confirmed by the activated partial thromboplastin time values exceeding 600 s. Meanwhile, the thrombin time values increase from 20 to 61 s as the sodium allysulfonate proportions increase from 0 to 80 mol%. In vitro investigations of protein adsorption and blood‐related complement activation also confirm that the membranes exhibit super‐anticoagulant property. Furthermore, gentamycin sulfate is loaded into the hydrogel films, and the released drug shows significant inhibition toward E. coli bacteria. It is believed that the surface attached heparin‐mimicking hydrogel thin films may show high potential for the applications in various biological fields, such as blood contacting materials and drug loading materials.
Cell sorting is important for cell biology and regenerative medicine. A visible light‐responsive cell scaffold is produced using gold nanoparticles and collagen gel. Various kinds of cells are cultured on the visible light‐responsive cell scaffold, and the target cells are selectively detached by photoirradiation without any cytotoxicity. This is a new image‐guided cell sorting system.
Antimicrobial polymeric films that are both mechanically robust and function renewable would have broad technological implications for areas ranging from medical safety and bioengineering to foods industry; however, creating such materials has proven extremely challenging. Here, a novel strategy is reported to create high‐strength N‐halamine incorporated poly(vinyl alcohol‐co‐ethylene) films (HAF films) with renewable antimicrobial activity by combining melt radical graft polymerization and reactive extrusion technique. The approach allows here the intrinsically rechargeable N‐halamine moieties to be covalently incorporated into polymeric films with high biocidal activity and durability. The resulting HAF films exhibit integrated properties of robust mechanical strength, high transparency, rechargeable chlorination capability (>300 ppm), and long‐term durability, which can effectively offer 3–5 logs CFU reduction against typical pathogenic bacterium Escherichia coli within a short contact time of 1 h, even at high organism conditions. The successful synthesis of HAF films also provides a versatile platform for exploring the applications of antimicrobial N‐halamine moieties in a self‐supporting, structurally adaptive, and function renewable form.
In arterial tissue engineering, mimicking native structure and mechanical properties is essential because compliance mismatch can lead to graft failure and further disease. With bottom‐up tissue engineering approaches, designing tissue components with proper microscale mechanical properties is crucial to achieve the necessary macroscale properties in the final implant. This study develops a thermoresponsive cell culture platform for growing aligned vascular smooth muscle cell (VSMC) sheets by photografting N‐isopropylacrylamide (NIPAAm) onto micropatterned poly(dimethysiloxane) (PDMS). The grafting process is experimentally and computationally optimized to produce PNIPAAm–PDMS substrates optimal for VSMC attachment. To allow long‐term VSMC sheet culture and increase the rate of VSMC sheet formation, PNIPAAm–PDMS surfaces were further modified with 3‐aminopropyltriethoxysilane yielding a robust, thermoresponsive cell culture platform for culturing VSMC sheets. VSMC cell sheets cultured on patterned thermoresponsive substrates exhibit cellular and collagen alignment in the direction of the micropattern. Mechanical characterization of patterned, single‐layer VSMC sheets reveals increased stiffness in the aligned direction compared to the perpendicular direction whereas nonpatterned cell sheets exhibit no directional dependence. Structural and mechanical anisotropy of aligned, single‐layer VSMC sheets makes this platform an attractive microstructural building block for engineering a vascular graft to match the in vivo mechanical properties of native arterial tissue.
A new class of thermoresponsive random polyurethanes is successfully synthesized and characterized. Poly(ethylene glycol) diol (Mn = 1500 Da) and 2,2‐dimethylolpropionic acid are reacted with isophorone diisocyanate in the presence of methane sulfonic acid catalyst. It is found that these polyurethanes are thermoresponsive in aqueous media and manifest a lower critical solution temperature (LCST) that can be easily tuned from 30 °C to 70 °C by increasing the poly(ethylene glycol) content. Their sharp LCST transitions make these random polyurethanes ideal candidates for stimuli‐responsive drug delivery applications. To that end, the ability of these systems to efficiently sequester doxorubicin (up to 36 wt%) by means of a sonication/dialysis method is successfully demonstrated. Additionally, it is also demonstrated that accelerated doxorubicin release kinetics from the nanoparticles can be attained above the LCST.
Antimicrobial nanogels, aggregates, and films are prepared by complexation of the antiseptic and bacteriostatic agent chlorhexidine (CHX) for medical and dental applications. A series of α‐, β‐, and γ‐cyclodextrin methacrylate (CD‐MA) containing hydrophobic poly(methyl methacrylate) (PMMA) based nanogels are loaded quantitatively with CHX in aqueous dispersion. The results show that CHX is enhancedly complexed by the use of CD‐MA domains in the particles structure. β‐CD‐MA nanogels present the highest uptake of CHX. Furthermore, it is observed that the uptake of CHX in nanogels is influenced by the hydrophobic PMMA structure. CHX acts as external cross‐linker of nanogels by formation of 1:2 (CHX:CD‐MA) inclusion complexes of two β‐CD‐MA units on the surfaces of two different nanogels. The nanogels adsorb easily onto glass surfaces by physical self‐bonding and formation of a dense crosslinked nanogel film. Biological tests of the applied CHX nanogels with regard to antimicrobial efficiency are successfully performed against Staphylococcus aureus .
The synthesis, tunable thermoresponsive properties, and self‐assembly of dual redox and thermoresponsive double hydrophilic block copolymers having pendant disulfide linkages (DHBCss) are reported. Well‐defined DHBCss composed of a hydrophilic poly(ethylene oxide) block and a dual thermo‐ and reduction‐responsive random copolymer block containing pendant disulfide linkages are synthesized by atom transfer radical polymerization. Their lower critical solution temperature (LCST) transitions are adjusted through modulating pendant hydrophobic–hydrophilic balance with disulfide–thiol–sulfide chemistry. Further, these DHBCss derivatives are converted to disulfide‐crosslinked nanogels at temperatures above LCST through temperature‐driven self‐assembly and in situ disulfide crosslinking. They exhibit enhanced colloidal stability and further reduction‐responsive degradability, thus demonstrating versatility of dual thermo‐ and reduction‐responsive smart materials.
Graphene oxide (GO) has received increasing attention in bioengineering fields due to its unique biophysical and electrical properties, along with excellent biocompatibility. The application of GO nanoparticles (GO‐NPs) to engineer self‐renewal and differentiation of human fetal neural stem cells (hfNSCs) is reported. GO‐NPs added to hfNSC culture during neurosphere formation substantially promote cell‐to‐cell and cell‐to‐matrix interactions in neurospheres. Accordingly, GO‐NP‐treated hfNSCs show enhanced self‐renewal ability and accelerated differentiation compared to untreated cells, indicating the utility of GO in developing stem cell therapies for neurogenesis.
Aggregation‐caused quenching (ACQ) is a general phenomenon that is faced by traditional fluorescent polymers. Aggregation‐induced emission (AIE) is exactly opposite to ACQ. AIE molecules are almost nonemissive in their molecularly dissolved state, but they can be induced to show high fluorescence in the aggregated or solid state. Incorporation of AIE phenomenon into polymer design has yielded various polymers with AIE characteristics. In this review, the recent progress of AIE polymers for biological applications is summarized.
Photoinitiated reversible addition‐fragmentation chain transfer (RAFT) dispersion polymerization of 2‐hydroxypropyl methacrylate is conducted in water at low temperature using thermoresponsive copolymers of 2‐(2‐methoxyethoxy) ethyl methacrylate and oligo(ethylene glycol) methacrylate (Mn = 475 g mol−1) as the macro‐RAFT agent. Kinetic studies confirm that quantitative monomer conversion is achieved within 15 min of visible‐light irradiation (405 nm, 0.5 mW cm−2), and good control is maintained during the polymerization. The polymerization can be temporally controlled by a simple “ON/OFF” switch of the light source. Finally, thermoresponsive diblock copolymer nano‐objects with a diverse set of complex morphologies (spheres, worms, and vesicles) are prepared using this particular formulation.
A new methacrylic fructose glycomonomer is synthesized and copolymerized with N‐isopropyl acrylamide by reversible addition fragmentation chain transfer (RAFT) polymerization. By additional copolymerization of the analog mannose, glucose, and galactose glycomonomers, a set of glycopolymers is obtained which vary in the type of sugar attached to the polyacrylamide backbone. The glycopolymers are subsequently deprotected and characterized by size exclusion chromatography, FT‐IR and NMR spectroscopy, elemental analysis, as well as turbidimetry, revealing the thermoresponsive character of all synthesized glycopolymers. The deprotected glycopolymers are subsequently labeled with a Rhodamine B derivative, utilizing the thiol‐functionalities derived from the RAFT endgroups. As concluded from the ArlamaBlue assay, the glycopolymers are not cytotoxic. Finally, cellular uptake studies reveal a higher uptake of the fructose polymer into MDA?MB?231 breast cancer cells compared to the other glycopolymers, which demonstrates the high potential of fructosylated polymers for potential applications in the targeted treatment of breast cancer.
New macromolecules such as dendrimers are increasingly needed to drive breakthroughs in diverse areas, for example, healthcare. Here, the authors report hybrid antimicrobial dendrimers synthesized by functionalizing organometallic dendrimers with quaternary ammonium groups or 2‐mercaptobenzothiazole. The functionalization tunes the glass transition temperature and antimicrobial activities of the dendrimers. Electron paramagnetic resonance spectroscopy reveals that the dendrimers form free radicals, which have significant implications for catalysis and biology. In vitro antimicrobial assays indicate that the dendrimers are potent antimicrobial agents with activity against multidrug‐resistant pathogens such as methicillin‐resistant Staphylococcus aureus and vancomycin‐resistant Enterococcus faecium as well as other microorganisms. The functionalization increases the activity, especially in the quaternary ammonium group‐functionalized dendrimers. Importantly, the activities are selective because human epidermal keratinocytes cells and BJ fibroblast cells exposed to the dendrimers are viable after 24 h.
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.
The strand material in extrusion‐based bioprinting determines the microenvironments of the embedded cells and the initial mechanical properties of the constructs. One unmet challenge is the combination of optimal biological and mechanical properties in bioprinted constructs. Here, a novel bioprinting method that utilizes core–shell cell‐laden strands with a mechanically robust shell and an extracellular matrix‐like core has been developed. Cells encapsulated in the strands demonstrate high cell viability and tissue‐like functions during cultivation. This process of bioprinting using core–shell strands with optimal biochemical and biomechanical properties represents a new strategy for fabricating functional human tissues and organs.
The fabrication of nanodiamond (ND)‐based drug carriers for tumor‐targeted drug delivery is described. The ND clusters with an average size of 52.84 nm are fabricated using a simple fluidic device combined with a precipitation method and then conjugated with folic acid (FA) and doxorubicin (Dox) via carbodiimide chemistry to obtain FA/Dox‐modified ND (FA/Dox‐ND) clusters. Cell culture experiments revealed that KB (folate receptor‐positive) cells are preferentially ablated by FA/Dox‐ND clusters compared to A549 (folate receptor‐negative) cells. In vivo results revealed that FA/Dox‐ND clusters are specifically accumulated in tumor tissues after intravenous injection into tumor‐bearing mice, effectively reducing the volume of tumor. Based on these results, this study suggests that FA/Dox‐ND clusters can be a good candidate as tumor‐targeted nanovehicles for delivery of antitumor drug.
Aligned poly(l ‐lactide)/poly(methyl methacrylate) binary blend fibers and mats loaded with a chimeric green fluorescence protein having a bioactive peptide with hydroxyapatite binding and mineralization property are prepared by pressurized gyration. The effect of processing parameters on the product morphologies, and the shape memory properties of these samples are investigated. Integration of hydroxyapatite nanoparticles into the fiber assembly is self‐directed using the hydroxyapatite‐binding property of the peptide genetically engineered to green fluorescence protein. Fluorescence microscopy analysis corroborated with Fourier transform infrared spectroscopy (FTIR) data confirms the integration of the chimeric protein with the fibers. An enzyme based remineralization assay is conducted to study the effects of peptide‐mediated mineralization within the fiber mats. Raman and FTIR spectral changes observed following the peptide‐mediated mineralization provides an initial step toward a soft‐hard material transition. These results show that programmable shape memory properties can be obtained by incorporating genetically engineered bioactive peptide domains into polymer fibers.
This article reports the behavior of embryonic neural stem cells on a hydrogel that combines cationic, non‐specific cell adhesion motifs with glycine‐arginine‐glycine‐aspartic acid‐serine‐phenylalanine (GRGDSF)‐peptides as specific cell adhesion moieties. Therefore, three hydrogels are prepared by free radical polymerization that contains either a GRGDSF‐peptide residue ( P1 ), amino ethylmethacrylate as a cationic residue ( P2 ), or a combination of both motifs ( P3 ). For each gel, cross linker concentrations of 8 mol% is used to have a comparable gel stiffness of 8–9 kPa. The cell experiments indicate a synergistic effect of the non‐specific, cationic residues, and the specific GRGDSF‐peptides on embryonic neural stem cell behavior that is especially pronounced in the cell adhesion experiments by more than doubling the number of cells after 72 h when comparing P3 with P2 and is less pronounced in the proliferation and differentiation experiments.
The authors report a method to prepare cell‐laden, cell‐sized microparticles from various materials suitable for individual applications. The method includes a piezoelectric inkjetting technology and a horseradish peroxidase (HRP)‐catalyzed crosslinking reaction. The piezoelectric inkjetting technology enables production of cell‐laden, cell‐sized (20–60 μm) droplets from a polymer aqueous solution. The HRP‐catalyzed crosslinking of the polymer in the ejected solution enables production of spherical microparticles from various materials. Superior cytocompatibility of the microencapsulation method is confirmed from the viability and growth profiles of normal murine mammary gland epithelial cells.
下载免费PDF全文