Smart assembly behaviors of hydroxypropylcellulose-graft-poly(4-vinyl pyridine) copolymers in aqueous solution by thermo and pH stimuli

Iron-containing poly(ionic liquid) membranes: a heterogeneous Fenton reaction and enhanced anti-fouling ability

Iron-containing poly(ionic liquid) membranes were prepared by Cu(0)-mediated reversible deactivation radical polymerization, which was achieved to catalyze a heterogeneous Fenton reaction and realize self-cleaning of the membrane surface.

Well-Defined Thermo- and pH-Responsive Double Hydrophilic Graft Copolymer Bearing a Pyridine-Containing Backbone

Graft copolymers have extensive applications in material science because of their tunable composition of backbone and side chains and diverse morphologies of aggregates. Recent studies mainly focused on the amphiphilic...

Morphology-controllable amphiphilic cellulose microgels made from self-assembly of hydrophobic long-chain bromide-alkylated-cellulose/gelatin copolymer

A cellulose-based microgel is firstly synthesized via chemically coupling gelatin and cellulose, and then amphiphilic cellulose copolymers (HMGC) are prepared by alkylated cellulose-based microgel from different long-chain alkyl groups. The long-chain alkyl group is mainly bonded onto the residual hydroxyl group at C₆ from the AGU of cellulose and the imino groups of gelatin, respectively. The results of self-assembly behavior of HMGC demonstrate that the critical aggregation concentrations of the microgels are in the range from 0.628 to 0.075 mg/mL, and the corresponding hydrodynamic diameters are between 104-1000 nm. Besides, the HMGC can self-assemble into microgels of various morphologies including cotton flocculence, sphere, rod-like, vesicle, flower-like cluster, snowflake-like, urchin-like, and coral shapes. These novel morphologies can be controlled by adjusting the degree of alkylation, the length of the alkyl chain, and the concentration of microgel. Furthermore, the possible formation mechanism of the multiform microgels is proposed from the chain conformation.

Stimuli responsive dynamic transformations in supramolecular gels

Supramolecular gels are formed by the self-assembly of small molecules under the influence of various non-covalent interactions. As the interactions are individually weak and reversible, it is possible to perturb the gels easily, which in turn enables fine tuning of their properties. Synthetic supramolecular gels are kinetically trapped and usually do not show time variable changes in material properties after formation. However, such materials potentially become switchable when exposed to external stimuli like temperature, pH, light, enzyme, redox, and chemical analytes resulting in reconfiguration of gel matrix into a different type of network. Such transformations allow gel-to-gel transitions while the changes in the molecular aggregation result in alteration of physical and chemical properties of the gel with time. Here, we discuss various methods that have been used to achieve gel-to-gel transitions by modifying a pre-formed gel material through external perturbation. We also describe methods that allow time-dependent autonomous switching of gels into different networks enabling synthesis of next generation functional materials. Dynamic modification of gels allows construction of an array of supramolecular gels with various properties from a single material which eventually extend the limit of applications of the gels. In some cases, gel-to-gel transitions lead to materials that cannot be accessed directly. Finally, we point out the necessity and possibility of further exploration of the field.

Recent advances in celluloses and their hybrids for stimuli-responsive drug delivery

The limitations of existing drug delivery systems (DDS) such as non-specific bio-distribution and poor selectivity have led to the exploration of a variety of carrier platforms to facilitate highly desirable and efficient drug delivery. Stimuli-responsive DDS are one of the most versatile and innovative approach to steer the compounds to the intended sites by exploiting their responsiveness to a range of various triggers. Preparation of stimuli-responsive DDS using celluloses and their derivatives offer a remarkable advantage over conventional polymer materials. In this review, we highlight on state-of-art progress in developing cellulose/cellulose hybrid stimuli-responsive DDS, which covers the preparation techniques, physicochemical properties, basic principles and, mechanisms of stimuli effect on drug release from various types of cellulose based carriers, through recent innovative investigations. Attention has been paid to endogenous stimuli (pH, temperature, redox gradient and ionic-strength) responsive DDS and exogenous stimuli (light, magnetic field and electric field) responsive DDS, where the cellulose-based materials have been extensively employed. Furthermore, the current challenges and future prospects of these DDS are also discussed at the end.

Stimuli-responsive self-assembly of cellulose nanocrystals (CNCs): Structures, functions, and biomedical applications

Cellulose nanocrystals (CNCs) have received a significant amount of attention from the researchers. It is used as a nanomaterial for various applications due to its excellent physiochemical properties for the last few decades. Self-assembly is a phenomenon where autonomous reorganization of randomly oriented species occurs elegantly. Self-assembly is responsible for the formation of the hierarchical cholesteric structure of CNCs. This process is highly influenced by several factors, such as the surface chemistry of the nanoparticles, intermolecular forces, and the fundamental laws of thermodynamics. Various conventional experimental designs and molecular dynamics (MD) studies have been applied to determine the possible mechanism of self-assembly in CNCs. Different external factors, like pH, temperature, magnetic/electric fields, vacuum, also influence the self-assembly process in CNCs. Notably, better responses have been observed in CNCs-grafted polymer nanocomposites. These functionalized CNCs with stimuli-responsive self-assembly have immense practical applications in modern biotechnology and medicine. Herein, we have concisely discussed the mechanism of the self-assembled CNCs in the presence of different external factors such as pH, temperature, electric/magnetic fields, and their biomedical applications.

Preparation and performance of poly(4-vinylpyridine)-b-polysulfone-b-poly(4-vinylpyridine) triblock copolymer/polysulfone blend membrane for separation of palladium (II) from electroplating wastewaters

In order to separate palladium (II) from electroplating wastewaters, poly(4-vinylpyridine)-b-polysulfone-b-poly(4-vinylpyridine) (P4VP-PSF-P4VP) / polysulfone blend membranes were fabricated by combining non-solvent induced phase separation, surface segregation and self-assembly of block copolymer. Amphiphilic P4VP-PSF-P4VP was used as the membrane base material, which was synthesized by introducing the functional monomer of 4-vinylpyridine (4-VP), and polysulfone as the additive. Effects of blend ratio and 4-VP content on membrane performance, such as structure, hydrophilicity, pure water flux and adsorption capacity towards Pd (II), were investigated. The membranes exhibited dense surface structure and low roughness due to surface segregation and self-assembly of P4VP-PSF-P4VP. The presence of 4-VP increased hydrophilicity and water flux of membrane, and it also provided good adsorption capacity towards Pd (II) (up to 103.1 ± 5.15 mg/g). Further, the membrane was used to separate Pd (II) from simulated wastewaters during filtration. It showed good rejection ability and high selectivity towards Pd (II) in co-existence of Cu (II) and Ni (II), and selectivity coefficients of Pd/Cu and Pd/Ni are 41.9 ± 1.88 and 97.8 ± 4.32, respectively. In filtration process of actual electroplating wastewater, the membrane also exhibited excellent rejection performance (Pd (II) rejection reached up to 96.8 ± 2.71%). Perhaps it is suitable for future practice applications.

Advances in thermosensitive polymer-grafted platforms for biomedical applications

Studies on "smart" polymeric material performing environmental stimuli such as temperature, pH, magnetic field, enzyme and photo-sensation have recently paid much attention to practical applications. Among of them, thermo-responsive grafted copolymers, amphiphilic steroids as well as polyester molecules have been utilized in the fabrication of several multifunctional platforms. Indeed, they performed a strikingly functional improvement comparing to some original materials and exhibited a holistic approach for biomedical applications. In case of drug delivery systems (DDS), there has been some successful proof of thermal-responsive grafted platforms on clinical trials such as ThermoDox®, BIND-014, Cynviloq IG-001, Genexol-PM, etc. This review would detail the recent progress and highlights of some temperature-responsive polymer-grafted nanomaterials or hydrogels in the 'smart' DDS that covered from synthetic polymers to nature-driven biomaterials and novel generations of some amphiphilic functional platforms. These approaches could produce several types of smart biomaterials for human health care in future.

An efficient route to synthesize thermoresponsive molecular bottlebrushes of poly[o-aminobenzyl alcohol-graft-poly(N-isopropylacrylamide)]

The thermoresponsive molecular bottlebrushes of poly[o-aminobenzyl alcohol-graft-poly(N-isopropylacrylamide)] [P(oABA-g-PNIPAM)] were synthesized and their characteristic thermoresponse was demonstrated.

Synthesis of Novel Temperature- and pH-Sensitive ABA Triblock Copolymers P(DEAEMA-co-MEO₂MA-co-OEGMA)-b-PEG-b-P(DEAEMA-co-MEO₂MA-co-OEGMA): Micellization, Sol⁻Gel Transitions, and Sustained BSA Release

Novel temperature- and pH-responsive ABA-type triblock copolymers, P(DEAEMA-co-MEO₂MA-co-OEGMA)-b-PEG-b-P(DEAEMA-co-MEO₂MA-co-OEGMA), composed of a poly(ethylene glycol) (PEG) middle block and temperature- and pH-sensitive outer blocks, were synthesized by atom transfer radical polymerization (ATRP). The composition and structure of the copolymer were characterized by ¹H NMR and gel permeation chromatography (GPC). The temperature- and pH-sensitivity, micellization, and the sol⁻gel transitions of the triblock copolymers in aqueous solutions were studied using transmittance measurements, surface tension, viscosity, fluorescence probe technique, dynamic light scattering (DLS), zeta-potential measurements, and transmission electron microscopy (TEM). The lower critical solution temperature (LCST) of the triblock copolymer, which contains a small amount of a weak base group, (N,N-diethylamino) ethyl methacrylate (DEAEMA), can be tuned precisely and reversibly by changing the solution pH. When the copolymer concentration was sufficiently high, increasing temperature resulted in the free-flowing solution transformation into a micellar gel. The sol-to-gel transition temperature (Tsol⁻gel) in aqueous solution will continue to decrease as solution concentration increases.

One-pot preparation of BAB triblock copolymer nano-objects through bifunctional macromolecular RAFT agent mediated dispersion polymerization

Nano-assemblies of a BAB triblock copolymer containing a solvophilic A block and two solvophobic B blocks were prepared through dispersion RAFT polymerization.

Copper iodide nanoparticles supported on magnetic aminomethylpyridine functionalized cellulose: a new heterogeneous and recyclable nanomagnetic catalyst for facile access to N-sulfonylamidines under solvent free conditions

A highly active catalyst based on CuI nanoparticles supported on magnetic aminomethylpyridine functionalized cellulose has been synthesized. It well catalyzes the multicomponent synthesis of N-sulfonylamidines under solvent free conditions.

A dual stimuli responsive fluorescent probe carrier from a double hydrophilic block copolymer capped with β-cyclodextrin

A β-cyclodextrin terminated triblock copolymer with both hydrophilic temperature and pH sensitive segments was prepared and characterized in terms of self-assembling and encapsulation behaviors.

Biomedical coatings on polyethylene terephthalate artificial ligaments

This review comprehensively covers research conducted to enhance polyethylene terephthalate (PET) artificial ligament osseointegration in the bone tunnel. These strategies, using biocompatible or bioactive coatings, had a positive effect in promoting PET ligament osseointegration by increasing bone formation and decreasing fibrous scar tissue at the ligament-to-bone interface. The improved osseointegration can be translated into a significant increase in the biomechanical pull-out loads. However, the load-to-failure of coated ligament is far lower than that of native ACL. Coatings to promote intra-articular ligamentization are also discussed in this study. Collectively, our investigations may arouse further study of the biological coating of PET artificial ligaments in order to effectively enhance ligament osseointegration and promote artificial ligament ligamentization.

The preparation of graft copolymers of cellulose and cellulose derivatives using ATRP under homogeneous reaction conditions

Atom transfer radical polymerisation (ATRP) is used to modify cellulose and cellulose derivatives under homogeneous conditions, yielding novel materials for application in areas such as drug delivery.

Graphene oxide/polyacrylamide/carboxymethyl cellulose sodium nanocomposite hydrogel with enhanced mechanical strength: preparation, characterization and the swelling behavior

A ternary GO/PAM/CMC nanocomposite hydrogel was fabricated by introducing GO into PAM/CMC hydrogels followed by ionically crosslinking of Al³⁺. The compressive strength of the ternary hydrogel was dramatically enhanced with the incorporation of only 1.6 wt% GO sheets.

"Smart" Materials Based on Cellulose: A Review of the Preparations, Properties, and Applications

Cellulose is the most abundant biomass material in nature, and possesses some promising properties, such as mechanical robustness, hydrophilicity, biocompatibility, and biodegradability. Thus, cellulose has been widely applied in many fields. "Smart" materials based on cellulose have great advantages-especially their intelligent behaviors in reaction to environmental stimuli-and they can be applied to many circumstances, especially as biomaterials. This review aims to present the developments of "smart" materials based on cellulose in the last decade, including the preparations, properties, and applications of these materials. The preparations of "smart" materials based on cellulose by chemical modifications and physical incorporating/blending were reviewed. The responsiveness to pH, temperature, light, electricity, magnetic fields, and mechanical forces, etc. of these "smart" materials in their different forms such as copolymers, nanoparticles, gels, and membranes were also reviewed, and the applications as drug delivery systems, hydrogels, electronic active papers, sensors, shape memory materials and smart membranes, etc. were also described in this review.

A new strategy to enhance artificial ligament graft osseointegration in the bone tunnel using hydroxypropylcellulose

PURPOSE

The aim of this study was to determine whether hydroxypropylcellulose (HPC) coating of polyethylene terephthalate (PET) artificial ligaments enhances graft osseointegration in the bone tunnel.

METHODS

Thirty New Zealand white rabbits underwent artificial ligament graft transplantation in the bilateral proximal tibia tunnels. One limb was implanted with an HPC-coated PET graft, and the contralateral limb was implanted with a non-HPC-coated PET graft as a control. The rabbits were then randomly sacrificed at weeks four and eight after surgery for biomechanical testing, histological examination, and histomorphometric and real-time polymerase chain reaction analysis.

RESULTS

At week four after surgery, there were no statistically significant differences in the load to failure or stiffness values between the experimental and control limbs (P = 0.328 and P = 0.128, respectively). At week eight after surgery, the mean load to failure and stiffness value of the experimental limbs was higher than that of the control limbs (P < 0.001 and P = 0.018, respectively). At week eight after surgery, some protruding new bone tissue from the host bone to the graft was found in the HPC-coated group, while a thick fibrous tissue band was observed at the interface between the graft and the host bone in the control group. Histomorphometric analysis showed that the graft-bone interface width in the HPC-coated group was significantly narrower than that in the control group at week eight after surgery (P < 0.001). At weeks four and eight after surgery, the mRNA expression level of bone morphogenetic protein-2 in the HPC group was higher than that in the control group (P = 0.001 and P = 0.010, respectively). The mRNA expression level of osteopontin in the HPC group was higher than that in the control group only at week four after surgery (P = 0.032).

CONCLUSIONS

Our data show that an HPC coating on the surface of PET artificial ligament grafts may induce artificial ligament graft osseointegration in the bone tunnel.