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.
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.
The preparation of physically crosslinked hydrogels from quasi ABA‐triblock copolymers with a water‐soluble middle block and hydrophobic end groups is reported. The hydrophilic monomer N‐acryloylmorpholine is copolymerized with hydrophobic isobornyl acrylate via a one‐pot sequential monomer addition through reversible addition fragmentation chain‐transfer (RAFT) polymerization in an automated parallel synthesizer, allowing systematic variation of polymer chain length and hydrophobic–hydrophilic ratio. Hydrophobic interactions between the outer blocks cause them to phase‐separate into larger hydrophobic domains in water, forming physical crosslinks between the polymers. The resulting hydrogels are studied using rheology and their self‐healing ability after large strain damage is shown.
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 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.
Multivalent aptamer–siRNA conjugates containing multiple mucin‐1 aptamers and BCL2‐specific siRNA are synthesized, and doxorubicin, an anthracycline anticancer drug, is loaded into these conjugates through intercalation with nucleic acids. These doxorubicin‐incorporated multivalent aptamer–siRNA conjugates are transfected to mucin‐1 overexpressing MCF‐7 breast cancer cells and their multidrug‐resistant cell lines. Doxorubicin‐incorporated multivalent aptamer–siRNA conjugates exert promising anticancer effects, such as activation of caspase‐3/7 and decrease of cell viability, on multidrug‐resistant cancer cells because of their high intracellular uptake efficiency. Thus, this delivery system is an efficient tool for combination oncotherapy with chemotherapeutics and nucleic acid drugs to overcome multidrug resistance.
Well‐defined poly(ethylene glycol)‐b‐allyl functional polylactide‐b‐polylactides (PEG‐APLA‐PLAs) are synthesized through sequential ring‐opening polymerization. PEG‐APLA‐PLAs that have amphiphilic properties and reactive allyl side chains on their intermediate blocks are successfully transferred to core–shell interface cross‐linked micelles (ICMs) by micellization and UV‐initiated irradiation. ICMs have demonstrated enhanced colloidal stability in physiological‐mimicking media. Hydrophobic molecules such as Nile Red or doxorubicin (Dox) are readily loaded into ICMs; the resulting drug‐ICM formulations possess slow and sustained drug release profiles under physiological‐mimicking conditions. ICMs exhibit negligible cytotoxicity in human uterine sarcoma cancer cells by using biodegradable aliphatic polyester as the hydrophobic segments. Relative to free Dox, Dox‐loaded ICMs show a reduced cytotoxicity due to the late intracellular release of Dox from ICMs. Overall, ICMs represent a new type of biodegradable cross‐linked micelle and can be employed as a promising platform for delivering a broad variety of hydrophobic drugs.
Enzyme immobilization is of high interest for industrial applications. However, immobilization may compromise enzyme activity or stability due to the harsh conditions which have to be applied. The authors therefore present a new and improved crosslinked layer‐by‐layer (cLbL) approach. Two different model enzymes (acid phosphatase and β‐galactosidase) are immobilized under mild conditions on biocompatible, monodisperse, sub‐micrometer poly(lactide‐co‐glycolide) (PLGA) particles. The resulting PLGA enzyme systems are characterized regarding their size, surface charge, enzyme activity, storage stability, reusability, and stability under various conditions such as changing pH and temperature. The developed and characterized cLbL protocol can be easily adapted to different enzymes. Potential future uses of the technology for biomedical applications are discussed. PLGA‐enzyme particles are therefore injected into the blood circulation of zebrafish embryos in order to demonstrate the in vivo stability and activity of the designed system.
Highly efficient functionalization and cross‐linking of polypeptides is achieved via tyrosine‐triazolinedione (TAD) conjugation chemistry. The feasibility of the reaction is demonstrated by the reaction of 4‐phenyl‐1,2,4‐triazoline‐3,5‐dione (PTAD) with tyrosine containing block copolymer poly(ethylene glycol)‐Tyr4 as well as a statistical copolymer of tyrosine and lysine (poly(Lys40‐st‐Tyr10)) prepared form N‐carboxyanhydride polymerization. Selective reaction of PTAD with the tyrosine units is obtained and verified by size exclusion chromatography and NMR spectroscopy. Moreover, two monofunctional and two difunctional TAD molecules are synthesized. It is found that their stability in the aqueous reaction media significantly varied. Under optimized reaction conditions selective functionalization and cross‐linking, yielding polypeptide hydrogels, can be achieved. TAD‐mediated conjugation can offer an interesting addition in the toolbox of selective (click‐like) polypeptide conjugation methodologies as it does not require functional non‐natural amino acids.
A novel PEGylation polypeptide, poly(ethylene glycol)‐b‐poly(l ‐lysine)‐b‐poly(l ‐cysteine) (PEG‐PLL‐PCys) triblock copolymer is synthesized via the sequential ring‐opening polymerization of amino acid N‐carboxyanhydrides initiated by methoxypolyethylene glycol amine (mPEG‐NH2, M w is 2 kDa). Subsequently, the obtained polypeptide is partially conjugated with fluorocarbon chains via disulfide exchange reaction. PLL segment can condense plasmid DNA through an electrostatic force to form a complex core, PEG segment surrounding the complex like a corona can prevent the complex from precipitation and reduce the adsorption of serum, while PCys segment with fluorocarbon can enhance the cellular uptake and the stability of the formed polyplex micelles in physiological conditions. Experiment results exhibit that the fluorinated polypeptides have low cytotoxicity and good gene transfection efficiency even in the presence of 50% fetal bovine serum.
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®.
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.
Affinity‐based cell separation is label‐free and highly specific, but it is difficult to efficiently and gently release affinity‐captured cells due to the multivalent nature of cell‐material interactions. To address this challenge, we have developed a platform composed of a capture substrate and a cell‐releasing molecular trigger. The capture substrate is functionalized with a cell‐capture antibody and a coiled‐coil A . The cell‐releasing molecular trigger B ‐PEG (polyethylene glycol), a conjugate of a coiled‐coil B and polyethylene glycol, can drive efficient and gentle release of the captured cells, because A / B heterodimerization brings B ‐PEG to the substrate and PEG chains adopt extended conformations and break nearby multivalent antibody‐biomarker interactions. No enzymes or excessive shear stress are involved, and the released cells have neither external molecules attached nor endogenous cell‐surface molecules cleaved, which is critical for the viability, phenotype, and function of sensitive cells.
Polysaccharides are abundant in nature, renewable, nontoxic, and intrinsically biodegradable. They possess a high level of functional groups including hydroxyl, amino, and carboxylic acid groups. These functional groups can be utilized for further modification of polysaccharides with small molecules, polymers, and crosslinkers; the modified polysaccharides have been used as effective building blocks in fabricating novel biomaterials for various biomedical applications such as drug delivery carriers, cell‐encapsulating biomaterials, and tissue engineering scaffolds. This review describes recent strategies to modify polysaccharides for the development of polysaccharide‐based biomaterials; typically self‐assembled micelles, crosslinked microgels/nanogels, three‐dimensional hydrogels, and fibrous meshes. In addition, the outlook is briefly discussed on the important aspects for the current and future development of polysaccharide‐based biomaterials, particularly tumor‐targeting intracellular drug delivery nanocarriers.
A facile and efficient methodology for the formation of polymer‐fullerene networks via a light‐induced reaction is reported. The photochemical crosslinking is based on a nitrile imine‐mediated tetrazole‐ene cycloaddition reaction, which proceeds catalyst‐free under UV‐light irradiation (λmax = 320 nm) at ambient temperature. A tetrazole‐functionalized polymer (Mn = 6500 g mol−1, Ð = 1.3) and fullerene C60 are employed for the formation of the hybrid networks. The tetrazole‐functionalized polymer as well as the fullerene‐containing networks are carefully characterized by NMR spectrometry, size exclusion chromatography, infrared spectroscopy, and elemental analysis. Furthermore, thermal analysis of the fullerene networks and their precursors is carried out. The current contribution thus induces an efficient platform technology for fullerene‐based network formation.
In this contribution, amphiphilic star copolymers (H40‐star‐PCL‐a‐PEG) with an H40 hyperbranched polyester core and poly(ε‐caprolactone)‐a‐poly(ethylene glycol) copolymer arms linked with acetal groups are synthesized using ring‐opening polymerization and a copper (I)‐catalyzed alkyne‐azide cycloaddition click reaction. The acid‐cleavable acetal groups between the hydrophilic and hydrophobic segments of the arms endow the amphiphilic star copolymers with pH responsiveness. In aqueous solution, unimolecular micelles can be formed with good stability and a unique acid degradability, as is desirable for anticancer drug carriers. For the model drug of doxorubicin, the in vitro release behavior, intracellular release, and inhibition of proliferation of HeLa cells show that the acid‐cleavable unimolecular micelles with anticancer activity can be dissociated in an acidic environment and efficiently internalized by HeLa cells. Due to the acid‐cleavable and biodegradable nature, unimolecular micelles from amphiphilic star copolymers are promising for applications in intracellular drug delivery for cancer chemotherapy.
The development of delivery systems efficiently uptaken by cells is of due importance since sites of drug action are generally localized in subcellular compartments. Herein, naked and core–shell polymeric nanoparticles (NPs) have been produced from poly(lactic‐co‐glycolic acid)—PLGA, poly(ethylene oxide)‐b‐poly(ε‐caprolactone)—PEO‐b‐PCL, and poly(ethylene oxide)‐b‐poly(lactic acid)—PEO‐b‐PLA. The nanostructures are characterized and the cellular uptake behavior is evaluated. The data evidence that cellular uptake is enhanced as the length of the hydrophilic PEO‐stabilizing shell reduces and that high negative surface charge restricts cellular uptake. Furthermore, NPs of higher degree of hydrophobicity (PEO‐b‐PCL) are more efficiently internalized as compared to PEO‐b‐PLA NPs. Accordingly, taking into account our recent published results 1 and the findings of the current investigation, there should be a compromise regarding protein fouling and cellular uptake as resistance to nonspecific protein adsorption and enhanced cellular uptake are respectively directly and inversely related to the length of the PEO‐stabilizing shell.
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.
Producing meiosis‐competent germ cells (GCs) from embryonic stem cells (ESCs) is essential for developing advanced therapies for infertility. Here, a novel approach is presented for generation of GCs from ESCs. In this regard, microparticles (MPs) have been developed from alginate sulfate loaded with bone morphogenetic protein 4 (BMP4). The results here show that BMP4 release from alginate sulfate MPs is significantly retarded by the sulfated groups compared to neat alginate. Then, BMP4‐laden MPs are incorporated within the aggregates during differentiation of GCs from ESCs. It is observed that BMP4‐laden MPs increase GC differentiation from ESCs at least twofold compared to the conventional soluble delivery method. Interestingly, following meiosis induction, Dazl , an intrinsic factor that enables GCs to enter meiosis, and two essential meiosis genes (Stra8 and Smc1b ) are upregulated significantly in MP‐induced aggregates compared to aggregates, which are formed by the conventional method. Together, these data show that controlled delivery of BMP4 during ESC differentiation into GC establish meiosis‐competent GCs which can serve as an attractive GC source for reproductive medicine.
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