The fabrication of 3D cell microenvironments exploiting versatile, long‐term stable passivating poly(acryl amide) brushes in a microwell format and the study of the behavior of fibroblast and pancreatic tumor cells in wells of systematically varied shape and size is reported. The microwells, which are obtained by combining micromolding in capillaries with microcontact printing of initiator monolayers for subsequent surface‐initiated polymerization of acrylamide and controlled functionalization with fibronectin (FN), expose cell adhesive areas inside the wells and protein and cell resistant brushes on the topside plateaus. NIH 3T3 fibroblast and pancreatic tumor (Patu 8988T) cells adhere and remain viable in the FN coated microwells for more than 1 week. Compared to 2D patterns, both cell lines are observed to attach to the bottom as well as the sidewalls of the microwells. The cytoskeleton alignment is found to be less pronounced compared to 2D patterned substrates, independent of microwell size and geometry.
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.
This study describes the development and cell culture application of nanometer thick photocrosslinkable thermoresponsive polymer films prepared by physical adsorption. Two thermoresponsive polymers, poly(N‐isopropylacrylamide (NIPAm)‐co‐acrylamidebenzophenone (AcBzPh)) and poly(NIPAm‐co‐AcBzPh‐co‐N‐tertbutylacrylamide) are investigated. Films are prepared both above and below the polymers' lower critical solution temperatures (LCSTs) and cross‐linked, to determine the effect, adsorption preparation temperature has on the resultant film. The films prepared at temperatures below the LCST are smoother, thinner, and more hydrophilic than those prepared above. Human pulmonary microvascular endothelial cell (HPMEC) adhesion and proliferation are superior on the films produced below the polymers LCST compared to those produced above. Cells sheets are detached by simply lowering the ambient temperature to below the LCST. Transmission electron, scanning electron, and light microscopies indicate that the detached HPMEC sheets maintain their integrity.
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.
Control over biointerfacial interactions on material surfaces is of significant interest in many biomedical applications and extends from the modulation of protein adsorption and cellular responses to the inhibition of bacterial attachment and biofilm formation. Effective control over biointerfaces is best achieved by reducing nonspecific interactions on the surface while also displaying specific bioactive signals. A poly(ethylene glycol) (PEG)‐based multifunctional coating has been developed that provides effective reduction of protein fouling while enabling covalent immobilization of peptides in a one or two‐step manner. The highly protein resistant properties of the coating, synthesized via the crosslinking of PEG diepoxide and diaminopropane, are confirmed via europium‐labeled fibronectin adsorption and cell attachment assays. The ability to covalently incorporate bioactive signals is demonstrated using the cyclic peptides cRGDfK and cRADfK. L929 cells show enhanced attachment on the biologically active cRGDfK containing surfaces, while the surface remains nonadhesive when the nonbiologically active cRADfK peptide is immobilized. The crosslinked PEG‐based coating also demonstrates excellent resistance toward Staphylococcus aureus attachment in a 48 h biofilm assay, achieving a >96% reduction compared to the control surface. Additionally, incorporation of the antimicrobial peptide melimine during coating formation further significantly decreases biofilm formation (>99%).
Bone related problems are increasing as a consequence of increased life expectancy, disorders in life style, and other medical conditions enforcing the need for functional bones prepared in vitro at affordable cost. Lack of suitable surface which promotes growth of both osteogenic and nonosteogenic cells is a major limitation. Here a novel biomaterial is reported that is synthesized from natural polysaccharide, namely, tamarind kernel polysaccharide (TKP), which is grafted with hydrophilic acrylic acid (AA) by radical polymerization. Modification in surface functionality removes unwanted proteins and alters hydrophilic/hydrophobic balance. TKP‐AA is suitable for the growth of different nonosteogenic and osteogenic cells. This material is suitable for osteoblasts and promotes in vitro mineralization and differentiation without the addition of exogenous growth factors. TKP‐AA can be used for the growth of mesenchymal stem cell‐derived osteoblasts. It is suggested that TKP‐AA can potentially be used as a scaffold for diverse cell types and particularly for bone tissue engineering at low cost.
Recombinant protein design allows modular protein domains with different functionalities and responsive behaviors to be easily combined. Inclusion of these protein domains can enable recombinant proteins to have complex responses to their environment (e.g., temperature‐triggered aggregation followed by enzyme‐mediated cleavage for drug delivery or pH‐triggered conformational change and self‐assembly leading to structural stabilization by adjacent complementary residues). These “smart” behaviors can be tuned by amino acid identity and sequence, chemical modifications, and addition of other components. A wide variety of domains and peptides have smart behavior. This review focuses on protein designs for self‐assembly or conformational changes due to stimuli such as shifts in temperature or pH.
The marine sulfated polysaccharide fucoidan displays superior ability to induce platelet aggregation compared to other sulfated polysaccharides. As such, it is an attractive tool for studying molecular and cellular responses in activated platelets. The heterogeneous structure, however, poses a problem in such applications. This study describes the synthesis of sulfated α‐l ‐fucoside‐pendant poly(methacryl amides) with homogeneous structures. By using both thiol‐mediated chain transfer and reversible addition‐fragmentation chain transfer polymerization techniques, glycopolymers with different chain lengths are obtained. These glycopolymers show platelet aggregation response and surface changes similar to those of fucoidan, and cause platelet activation through intracellular signaling as shown by extensive protein tyrosine phosphorylation. As the platelet activating properties of the glycopolymers strongly mimic those of fucoidan, this study concludes these fucoidan‐mimetic glycopolymers are unique tools for studying molecular and cellular responses in human blood platelets.
A nanoassembled drug delivery system for anticancer treatment, formed by the host–guest interactions between paclitaxel (PTX) and β‐cyclodextrin (β‐CD) modified poly(acrylic acid) (PCDAA), is successfully prepared. After such design, the aqueous solubility of PTX is greatly increased from 0.34 to 36.02 μg mL?1, and the obtained PCDAA‐PTX nanoparticles (PCDAA‐PTX NPs) exhibit a sustained PTX release behavior in vitro. In vitro cytotoxicity finds that PCDAA‐PTX NPs can accumulate significantly in tumor cells and remain the pharmacological activity of PTX. The in vivo real‐time biodistribution of PCDAA‐PTX NPs is investigated using near‐infrared fluorescence imaging, indicating that the PCDAA‐PTX NPs can effectively target to the tumor site by the enhanced permeability and retention effect in H22 tumor‐bearing mice. Through in vivo antitumor examination, PCDAA‐PTX NPs exhibit superior efficacy in impeding the tumor growth compared to the commercially available Taxol®.
Overcoming drug resistance is a major challenge for cancer therapy. Tumor necrosis factor α‐related apoptosis‐inducing ligand (TRAIL) is a potent therapeutic as an activator of apoptosis, particularly in tumor but not in healthy cells. However, its efficacy is limited by the resistance of tumor cell populations to the therapeutic substance. Here, we have addressed this limitation through the development of a controlled release system, matrix‐metalloproteinase (MMP)‐sensitive and arg‐gly‐asp‐ser (RGDS) peptide functionalized poly (ethylene‐glycol) (PEG) particles which are synthesized via visible‐light‐induced water‐in‐water emulsion polymerization. Quinacrine (QC), a recently discovered TRAIL sensitizer drug, is loaded into the hydrogel carriers and the influence of this system on the apoptosis of a malignant type of brain cancer, glioblastoma multiforme (GBM), has been investigated in detail. The results suggest that MMP‐sensitive particles are cytocompatible and superior to promote TRAIL‐induced apoptosis in GBM cells when loaded with QC. Compared to QC and TRAIL alone, combination of QC‐loaded PEG hydrogel and TRAIL demonstrates synergistic apoptotic inducing behavior. Furthermore, QC‐loaded particles, but not QC or PEG‐hydrogels alone, enhance apoptosis as is measured through expression of apoptosis‐related genes. This system is promising to significantly improve the efficacy of chemotherapeutic drugs and suggests a combination treatment for GBM therapy.
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.
Poly(amido amine)s' (PAAs) versatility are nearly unique among stepwise polymers. Different functional groups can be easily introduced into these polymers to add functionality such as cell internalization, charge‐shift, bioreducibility, “stealth” properties, and targeting moieties, while maintaining the bulk structural integrity of these polymers. The poly(amido amine)s are used as a unique research platform to elucidate their complex structure–function relationship. It is shown that guanidinium group, carboxyl group, disulfide bond, alkyl chain, branching, acetyl groups, benzoyl groups, and quaternary nicotinamide moieties can influence many steps of gene delivery, such as DNA condensation, cellular uptake, endosomal escape, nuclear entry, and finally gene expression. The authors systematically discuss the structure–function correlations of PAAs for gene delivery, and elaborate how the properties of polymers can be adjusted by changing the polymeric structure.
Biocompatible polymeric coatings for metallic stents are desired, as currently used materials present limitations such as deformation during degradation and exponential loss of mechanical properties after implantation. These concerns, together with the present risks of the drug‐eluting stents, namely, thrombosis and restenosis, require new materials to be studied. For this purpose, novel poly(polyol sebacate)‐derived polymers are investigated as coatings for metallic stents. All pre‐polymers reveal a low molecular weight between 3000 and 18 000 g mol?1. The cured polymers range from flexible to more rigid, with E‐modulus between 0.6 and 3.8 MPa. Their advantages include straightforward synthesis, biodegradability, easy processing through different scaffolding techniques, and easy transfer to industrial production. Furthermore, electrospraying and dip‐coating procedures are used as proof‐of‐concept to create coatings on metallic stents. Biocompatibility tests using adipose stem cells lead to promising results for the use of these materials as coatings for metallic coronary stents.
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.
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.
A simple and rapid process for multiscale printing of bioinks with dot widths ranging from hundreds of microns down to 0.5 μm is presented. The process makes use of spontaneous surface charges generated pyroelectrically that are able to draw little daughter droplets directly from the free meniscus of a mother drop through jetting (“p‐jet”), thus avoiding time‐consuming and expensive fabrication of microstructured nozzles. Multiscale can be easily achieved by modulating the parameters of the p‐jet process. Here, it is shown that the p‐jet allows us to print well‐defined adhesion islands where NIH‐3T3 fibroblasts are constrained to live into cluster configurations ranging from 20 down to single cell level. The proposed fabrication approach can be useful for high‐throughput studies on cell adhesion, cytoskeleton organization, and stem cell differentiation.
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.
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.
Synthesis and novel applications of biofunctional polymers for diagnosis and therapy are promising area involving various research domains. Herein, three fluorescent polymers, poly(p‐phenylene‐co‐thiophene), poly(p‐phenylene), and polythiophene with amino groups (PPT‐NH2, PPP‐NH2, and PT‐NH2, respectively) are synthesized and investigated for cancer cell targeted imaging, drug delivery, and radiotherapy. Polymers are conjugated to anti‐HER2 antibody for targeted imaging studies in nontoxic concentrations. Three cell lines (A549, Vero, and HeLa) with different expression levels of HER2 are used. In a model of HER2 expressing cell line (A549), radiotherapy experiments are carried out and results show that all three polymers increase the efficacy of radiotherapy. This effect is even more increased when conjugated to anti‐HER2. In the second part of this work, one of the selected polymers (PT‐NH2) is conjugated with a drug model; methotrexate via pH responsive hydrazone linkage and a drug carrier property of PT‐NH2 is demonstrated on neuroblastoma (SH‐SY5Y) cell model. Our results indicate that, PPT‐NH2, PPP‐NH2, and PT‐NH2 have a great potential as biomaterials for various bioapplications in cancer research.
Thermoresponsive linear polymers and their corresponding aggregates or nanogels typically show similar thermoresponsive profiles. In this study, the authors demonstrate reversible chemical switching between linear polymers and their cross‐linked nanogels. The linear polymers exhibit sharp thermal transitions typical of common thermoresponsive polymers but the cross‐linked nanogels exhibit “linear” thermal transitions over a relatively broad temperature range. The reversible switching between these two different polymer architectures with distinct thermoresponses represents a unique example of how the responsive properties of smart polymers can be significantly manipulated via polymer architecture engineering.
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