Star Poly Research Articles

Digital Light Processing of Thermoresponsive Hydrogels from Polyproline-Based Star Polypeptides.

The first report of star poly(L-proline) crosslinkers is disclosed for digital light processing 3D printing of thermoresponsive hydrogels. Through chain end functionalization of star poly(L-proline)s with methacryloyl groups, access to high-resolution defined 3D hydrogel structures via digital light processing is achieved through photoinitiated free radical polymerization. Changing the poly(L-proline) molecular weight has a direct influence on both thermoresponsiveness and printability, while shape-morphing behavior can be induced thermally.

Star poly(lactide-co-glycolide) and poly(ε-caprolactone) polyurethanes with shape memory properties for biomedical applications

Shape memory polyurethane (SMPU) have the capacity to alter and regain their form in reaction to a stimulus (eg. temperature, pH) and have been investigated in biomedical applications. In this work, the shape memory properties of poly(ester-urethane)s (PEU) are studied as a function of the functionality of the poly(lactide-co-glycolide) (PLGA) and poly(e-caprolactone) (PCL) pre-polymers. Two distinct series of PEU are synthesized by reaction between linear and star-shaped PLGA polyols initiated by pentaerythritol (4-arms PLGA) or dipentaerythritol (6-arms PLGA) with PCL di-isocyanate prepolymers. The different PEUs exhibit thermally actuated shape memory properties and tunable mechanical properties with Young’s moduli reaching up to 96 MPa and elongation at break reaching 930 %. The integration of low amounts of PLGA star within the PEU structure increases the material’s shape memory properties, enhancing both fixity (from 45 % to 96 %) and recovery ratios (from 88 % to 92 %). Further exploration into potential applications led to the formulation of porous foams via the solvent casting/particles leaching (SC/PL) process. These foams exhibited high porosity ranging from 74 % to 83 % with pore sizes spanning from 100 to 300 µm. Their mechanical properties are close to the human meniscus with Young’s modulus ranging from 0.13 MPa to 0.53 MPa. Moreover, integration of PLGA star within the PEU scaffold decreases the flexural strength that is an important parameter for potential mini-invasive surgery.

Engineering Low Volume Resuscitants for the Prehospital Care of Severe Hemorrhagic Shock

AbstractGlobally, traumatic injury is a leading cause of suffering and death. The ability to curtail damage and ensure survival after major injury requires a time‐sensitive response balancing organ perfusion, blood loss, and portability, underscoring the need for novel therapies for the prehospital environment. Currently, there are few options available for damage control resuscitation (DCR) of trauma victims. We hypothesize that synthetic polymers, which are tunable, portable, and stable under austere conditions, can be developed as effective injectable therapies for trauma medicine. In this work, we design injectable polymers for use as low volume resuscitants (LVRs). Using RAFT polymerization, we evaluate the effect of polymer size, architecture, and chemical composition upon both blood coagulation and resuscitation in a rat hemorrhagic shock model. Our therapy is evaluated against a clinically used colloid resuscitant, Hextend. We demonstrate that a radiant star poly(glycerol monomethacrylate) polymer did not interfere with coagulation while successfully correcting metabolic deficit and resuscitating animals from hemorrhagic shock to the desired mean arterial pressure range for DCR – correcting a 60 % total blood volume (TBV) loss when given at only 10 % TBV. This highly portable and non‐coagulopathic resuscitant has profound potential for application in trauma medicine.

Engineering Low Volume Resuscitants for the Prehospital Care of Severe Hemorrhagic Shock.

Globally, traumatic injury is a leading cause of suffering and death. The ability to curtail damage and ensure survival after major injury requires a time-sensitive response balancing organ perfusion, blood loss, and portability, underscoring the need for novel therapies for the prehospital environment. Currently, there are few options available for damage control resuscitation (DCR) of trauma victims. We hypothesize that synthetic polymers, which are tunable, portable, and stable under austere conditions, can be developed as effective injectable therapies for trauma medicine. In this work, we design injectable polymers for use as low volume resuscitants (LVRs). Using RAFT polymerization, we evaluate the effect of polymer size, architecture, and chemical composition upon both blood coagulation and resuscitation in a rat hemorrhagic shock model. Our therapy is evaluated against a clinically used colloid resuscitant, Hextend. We demonstrate that a radiant star poly(glycerol monomethacrylate) polymer did not interfere with coagulation while successfully correcting metabolic deficit and resuscitating animals from hemorrhagic shock to the desired mean arterial pressure range for DCR - correcting a 60 % total blood volume (TBV) loss when given at only 10 % TBV. This highly portable and non-coagulopathic resuscitant has profound potential for application in trauma medicine.

Star poly(ionic liquid)s: Chain architecture‐property relationships

AbstractIn this study, we report the synthesis of 3‐, 4‐, and 6‐arm star poly(ionic liquid)s (PILs) (specifically, star poly(vinylbenzyl methylimidazolium bis(trifluoromethane)sulfonimide) (poly(VBMIm‐TFSI))) via reversible addition‐fragmentation chain transfer (RAFT) polymerization with a core‐first approach, followed by quaternization and anion exchange. The impact of star polymer architecture on properties was explored by measuring the thermal, mechanical, and ion transport properties of each star PIL compared to those of an analogous linear PIL. The star PILs exhibited up to 2‐fold higher ionic conductivity, 150% higher elastic modulus, and 465% higher ultimate tensile strength compared to the analogous linear PIL. The Williams‐Landel‐Ferry (WLF) equation was employed to explore the effect of increased free volume on the improved ion transport properties of the star PILs. These results highlight the impact of star polymer architecture on PILs and star PILs as promising materials for electrochemical energy devices.

Efficient gene delivery by multifunctional star poly (β-amino ester)s into difficult-to-transfect macrophages for M1 polarization

Gene delivery to macrophages holds great promise for cancer immunotherapy. However, traditional gene delivery methods exhibit low transfection efficiency in macrophages. The star-shaped topological structure of polymers is known to encapsulate genes inside their cores, thereby facilitating sustained release of the genetic material. Herein, combining the structural advantages of star polymers and the transfection advantages of poly (β-amino ester)s (PAEs), we developed a novel linear oligomer grafting-onto strategy to synthesize a library of multi-terminal star structured PAEs (SPAEs), and evaluated their gene delivery efficiency in various tissue cells. The transfection with human hepatocellular carcinoma cells (HepG2, HCC-LM3 cells and MHCC-97H cells), rat normal liver cells (BRL-3 A cells), human ovarian cancer cells (A2780 cells), African green monkey kidney cells (Vero cells), human cervical cancer cells (HeLa cells), human chondrosarcoma cells (SW1353 cells), and difficult-to-transfect human epidermal keratinocytes (HaCaT cells) and normal human fibroblast cells (NHF cells) showed that SPAEs exhibited superior transfection profile. The GFP transfection efficiency of top-performing SPAEs in HeLa cells (96.1%) was 2.1-fold, and 3.2-fold higher compared to jetPEI and Lipo3000, respectively, indicating that the star-shaped topological structure can significantly enhance the transfection efficiency of PAEs. More importantly, the top-performing SPAEs could efficiently deliver Nod2 DNA to difficult-to-transfect RAW264.7 macrophages, with a high transfection efficiency of 33.9%, which could promote macrophage M1 polarization and enhanced CD8+ T cell response in co-incubation experiments. This work advances gene therapy by targeting difficult-to-transfect macrophages and remodeling the tumor immune microenvironment.

Photo-induced synthesis of star poly(DL-Lactide)-templated Au and Ag nanoparticles and evaluation of their catalytic performance

In this report, photochemical synthesis of monodispersed gold (Au) and silver (Ag) nanoparticles (NPs) was reported using cholic acid functionalized star poly(DL-lactide) (CA-(PDLLA)) as a capping and reducing agent. CA-(PDLLA) was synthesized by ring-opening polymerization (ROP) of DL-lactide with a feed ratio of 1:120 (cholic acid: DL-lactide). The molecular weight of CA-(PDLLA) was measured by using the gel permeation chromatography (GPC) technique. The thermal properties of the polymer and its nanocomposite materials were studied by thermogravimetric analysis (TGA). The optical properties of Ag and Au NPs were studied by UV–visible absorption spectroscopy. Morphological studies and size of the polymer-nanocomposites were assessed by using field emission scanning electron microscopy (FE-SEM) and high-resolution transmission electron microscopy (HR-TEM) techniques. The percentage composition of Au and Ag present in the polymer-nanocomposites was calculated using energy-dispersive X-ray spectroscopic (EDX) analysis. Finally, the synthesized polymer-metal nanocomposites were used as heterogeneous catalysts for the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) as a model reaction and the apparent rate constant (kapp) values of CA-(PDLLA)-AuNPs and CA-(PDLLA)-AgNPs were found to be 5.76 × 10−4 s−1 and 19.7 × 10−4 s−1, respectively.

Synthesis of star poly (L-lactic acid) and its copolymers catalyzed by lipase in supercritical carbon dioxide

Synthesis of star poly (L-lactic acid) and its copolymers catalyzed by lipase in supercritical carbon dioxide

Synthesis, Thermal and Mechanical Properties of Linear and Star Poly(L‐lactide)s

AbstractPoly(L‐lactide) with various architectures and molecular weights have been studied with respect to their thermal and mechanical properties. Their synthesis has been performed with an aluminum salen catalyst, which allows to obtain linear chains, tetrahedral 4‐arm stars and stars with two linked tetrahedra with 3 arms each, all with defined molecular weights. The polymers are characterized by their molecular weight distributions and then subjected to differential scanning calorimetry and thermogravimetric analyses, which show differences in the characteristic temperatures of not more than 10 degrees. The crystallinity index clearly increases with the weight of the chains with only a minor dependency on the topology. Thin films of the polymers are studied with respect to their elongation at break, their tensile strength, and their moduli. The elongation is most sensitive to the polymer type with a 15‐fold increase between the shortest linear polymer and the 6‐arm star polymer with the longest chains.

Precision Synthesis of End-Functionalized Star Poly(vinyl alcohol)s by RAFT Polymerization and Post-polymerization Modification

Precision Synthesis of End-Functionalized Star Poly(vinyl alcohol)s by RAFT Polymerization and Post-polymerization Modification

A Tumor Microenvironment Model of Pancreatic Cancer to Elucidate Responses toward Immunotherapy (Adv. Healthcare Mater. 14/2023)

3D Cancer Models In article 2201907 by Daniela Loessner and co-workers, the tumor microenvironment of pancreatic cancer is engineered using star poly(ethylene glycol) (PEG)–heparin hydrogels, that are functionalized with integrin-binding and protease-responsive peptides to stimulate cell proliferation and migration. The coculture of cancer cells and patient-derived stromal cells mimics the multicellular composition of tumor tissues and cancer–immune interactions and allows the testing of immunomodulatory treatments in combination with chemotherapy.

Synthesis of 3-, 4-, and 6-arm star poly(ionic liquid)s

In this study, we report the synthesis of 3-, 4-, and 6-arm star poly(vinylbenzyl methylimidazolium chloride) via reversible addition-fragmentation chain transfer (RAFT) polymerization with a core-first approach, which results in uniform number and length of polymer arms. The effect of initial radical initiator concentration and number of functional groups per multifunctional RAFT agent on polymerization reaction kinetics was systematically investigated. Increasing the initial radical initiator concentration resulted in faster monomer conversion, while decreasing the number of functional groups per multifunctional RAFT agent resulted in a decrease in the initial rate retardation in reaction kinetics. This work demonstrates a facile method for synthesizing ion-containing star polymers, specifically star poly(ionic liquids) or star PILs, with uniform number and length of polymer arms, where star PILs may be a promising new material for electrochemical energy devices due to property enhancements associated with their star polymer architecture.

Ultrasensitive hydrogel grating detector for real-time continuous-flow detection of trace threat Pb2.

Ultrasensitive real-time detection of trace Pb2+ in continuous flow is vital to effectively and timely eliminate the potential hazards to ecosystem health and sustainability. This work reports on a micro-structured smart hydrogel grating with ultra-sensitivity, high selectivity, good transparency and mechanical property for real-time detection of Pb2+ in continuous flow. The hydrogel grating possesses uniform surface relief microstructures with periodic nano-height ridges made of poly(acrylamide-co-benzo-18-crown-6-acrylamide) networks that crosslinked by tetra-arm star poly(ethylene glycol)acrylamide. The hydrogel grating with good optical transparency and mechanical property can change its height via selective host-guest complexation with Pb2+ to output a changed diffraction efficiency. Meanwhile, the periodic nano-ridges with large specific area benefit the contact with Pb2+ for fast Pb2+-induced height change. Thus, with such rationally designed molecular structures and surface relief microstructures, the hydrogel grating integrated in a glass-based mini-chip allows real-time detection of Pb2+ in continuous flow with ultra-sensitivity and high selectivity. The hydrogel grating detector can achieve ultralow detection limit (10-9 M Pb2+), fast response (2min), and selective detection of Pb2+ from dozens of interfering ions even with high concentrations. This high-performance hydrogel grating detector is general and can be extended to detect many analytes due to the wide choice of responsive hydrogels, thus opening new areas for creating advanced smart detectors in analytical science.

Dynamics of polymer electrolyte with LiTFSI via Quasi-Elastic Neutron Scattering

Most lithium batteries offer a wide range of applications. However, safety issues are still an unresolved issue for several applications. To solve the safety issue of Li-ion batteries, solid polymer electrolyte is a promising candidate to replace commercial liquid electrolyte. A 4-arm star poly(ethylene oxide) polymer with LiTFSI salt as an electrolyte was studied. The dynamics of this polymer were explored with the Quasi-Elastic Neutron Scattering technique. Furthermore, the influence of temperature and Li salt concentration on the polymer dynamics was investigated. The dynamics of the polymer ends of the arm show much higher flexibility than the core parts making those types of polymers attractive for further studies in battery research.

Poly(2-oxazoline)-based core cross-linked star polymers: synthesis and drug delivery applications.

Poly(2-oxazoline)s (POxs) are promising platforms for drug delivery applications due to their biocompatibility and stealth properties. In addition, the use of core cross-linked star (CCS) polymers based on POxs is expected to enhance drug encapsulation and release performances. In this study, we employed the "arm-first" strategy to synthesize a series of amphiphilic CCS [poly(2-methyl-2-oxazoline)]n-block-poly(2,2'-(1,4-phenylene)bis-2-oxazoline)-cross-link/copolymer-(2-n-butyl-2-oxazoline)s (PMeOx)n-b-P(PhBisOx-cl/co-ButOx)s by using microwave-assisted cationic ring-opening polymerization (CROP). First, PMeOx, as the hydrophilic arm, was synthesized by CROP of MeOx using methyl tosylate as the initiator. Subsequently, the living PMeOx was used as the macroinitiator to initiate the copolymerization/core-crosslinking reaction of ButOx and PhBisOx to form CCS POxs having a hydrophobic core. The molecular structures of the resulting CCS POxs were characterized by size exclusion chromatography and nuclear magnetic resonance spectroscopy. The CCS POxs were loaded with the anti-cancer drug doxorubicin (DOX), and the loading was detected by UV-vis spectrometry, dynamic light scattering, and transmission electron microscopy. In vitro studies showed that DOX release at pH 5.2 was faster than that at pH 7.1. The in vitro cytotoxicity study using HeLa cells revealed that the neat CCS POxs are compatible with the cells. In contrast, the DOX-loaded CCS POxs exhibited a cytotoxic effect in a concentration-dependent manner in HeLa cells, which strongly supports that the CSS POxs are potential candidates for drug delivery applications.

Ultrafast synthesis of core cross-linked star poly(p-methylstyrene) with high syndiotacticity through living coordination polymerization

We synthesized for the first time star syndiotactic poly(p-methylstyrene) via coordination polymerization with a high yield of 93.5%.

Biodegradable, Solvent‐Free Photocrosslinkable PLLA Resin Formulations for Additive Manufacturing

AbstractAcrylate end‐functionalized linear and star poly l‐lactide (PLLA) based aliphatic, photocurable oligomeric crosslinkers are developed, which are formulated with hydroxyl (ethyl)methacrylate (HEMA) as a biodegradable reactive diluent to demonstrate successful application for solvent‐less 3D printing using digital light processing (DLP) technique as well as a custom‐designed direct ink writing 3D printer. The resin formulation for 3D printing is optimized using spot curing, photodifferential scanning calorimetry and cure depth analysis. The 3D printed parts exhibit promising mechanical property along with improved hydrophilicity and biodegradability. The development of new photocurable resin formulations are expected to meet the growing demand for raw materials that can be applied for developing custom designed bio implantable objects.

Impact of Star Polyacid Branching on Polymer Diffusion within Multilayer Films

A series of linear and star poly(acrylic acids) (LPAA and star PAAs) were synthesized to explore the effect of molecular architecture on the stratification and polymer dynamics of electrostatic layer-by-layer (LbL) films. Studies of LbL deposition of LPAA and star PAAs with poly[2-(dimethylamino)ethyl methacrylate] (PDMAEMA) at acidic pH showed an ∼30% increase in film dry thickness with increased polymer branching. Consistent with a greater mass of star polymer deposited within the films, in situ ellipsometric measurements of PAA uptake from solution revealed ∼3.5-fold greater diffusion coefficients for 8-arm PAA in comparison to linear PAA. For comparison, the dynamics of the linear PDMAEMA partner was explored via neutron reflectometry (NR) studies of stacked multilayers containing hydrogenated and deuterated polycations, hPDMAEMA and dPDMAEMA. The stacked multilayers deposited from low-ionic-strength solutions were stratified, exhibiting interfacial widths between hydrogenated and deuterated stacks of ∼15 and 10 nm for films constructed with star and linear PAAs, respectively, suggesting relatively low mobility of the polycation in both assemblies. Further exposure of these films to 0.5 M sodium chloride solutions enhanced the mobility of PDMAEMA, revealing an order magnitude faster diffusion of PDMAEMA in films of 8-arm PAA relative to linear PAA. The faster diffusion of polymers within films of star polyacids was correlated not only with the compactness of star polymers but also with an ∼2-fold lower ionization of assembled 8-arm PAA as determined by Fourier transform infrared spectroscopy and thus a lower number of polycation–polyacid ionic contacts in the case of star polymers as compared to their linear counterparts. The significant influence of molecular architecture on the number of polymer–polymer contacts was further confirmed by isothermal titration calorimetry studies of polyelectrolyte complexes in solution.

High density star poly HEMA containing bis-indole rich dendrimer inner core for integrated anti-fouling and anti-bacterial coating applications

Multi-arm star polymers with controlled molecular architecture suitable to be used as biomaterials are rapidly developing area of research. Herein, G2 and G3 polyurethane dendrimers containing bio-active bis-indolyl building blocks were converted into corresponding multifunctional ATRP initiators via a single-step reaction and characterized thoroughly. Polymerization of 2-hydroxethyl methacrylate (HEMA) monomer for different time duration using these initiators and CuBr/2,2′-bpy ATRP system yielded star PHEMAs with molecular weight (Mn) in the range of 2.79 × 104 – 4.52 × 105 g mol−1; the poly dispersity indices were in the range of 1.16–1.49. Glass transition temperature of these star PHEMAs was found significantly low compared to the linear PHEMA. Contact angle measurements carried out on the surface of polyethylene terephthalate (PET) film coated with these polymers confirmed that these polymers are more hydrophilic compared to the un-coated PET surface. The integrated anti-fouling and anti-bacterial properties of these polymer coatings were studied with two common pathogens namely E. coli and P. aeruginosa and found that the binding of both of these bacterial cells either in live or dead form was negligibly low in the polymer coated PET surface compared to un-coated films and also found that the percentage of live cells was low compared to dead cells.

Synthesis and hydrodynamic properties of star poly(2-alkyl-2-oxazolines) and poly(2-alkyl-2-oxazines) based on sulfochlorinated calix[4]arene initiator

New four-arm star poly(2-alkyl-2-oxazolines) and poly(2-alkyl-2-oxazines) were synthesized using sulfochlorinated calix[4]arene derivative as a multifunctional initiator. Their characteristics were investigated by gel permeation chromatography, light scattering and viscometry. The polymer stars obtained were shown to have well-defined architecture and high intramolecular density.