Sustained delivery of paclitaxel using thermogelling poly(PEG/PPG/PCL urethane)s for enhanced toxicity against cancer cells

Electrospun PEO/PEG fibers as potential flexible phase change materials for thermal energy regulation

Polyethylene glycol (PEG) is widely used as phase change materials (PCM) due to their versatile working temperature and high latent heat. However, the low molecular weight of PEG prevents from the formation of flexible microfibers, and the common leakage problem associated with solid-liquid PCM further hinders their applications in various fields. To address these challenges, polyethylene oxide (PEO) is incorporated as the supporting matrix for PEG, leading to a successful electrospinning of fibrous mats. Due to the similar chemical nature of both PEG and PEO, the blended composites show great compatibility and produce uniform electrospun fibers. The thermal properties of these fibers are characterized by DSC and TGA, and supercooling for the PEG(1050) component is effectively reduced by 75-85%. The morphology changes before and after leakage test are analyzed by SEM. Tensile and DMA tests show that the presence of PEG(1050) component contributes to plasticization effect, improving mechanical and thermomechanical strength. The ratio of PEO(600K):PEG(1050) at 7:3 affords the optimal performance with good chemical and form-stability, least shrinkage, and uniformity. These fibrous mats have potential applications in areas of food packaging, flexible wearable devices, or textiles to aid in thermal regulation.

Research Advances of Injectable Functional Hydrogel Materials in the Treatment of Myocardial Infarction

Myocardial infarction (MI) has become one of the serious diseases threatening human life and health. However, traditional treatment methods for MI have some limitations, such as irreversible myocardial necrosis and cardiac dysfunction. Fortunately, recent endeavors have shown that hydrogel materials can effectively prevent negative remodeling of the heart and improve the heart function and long-term prognosis of patients with MI due to their good biocompatibility, mechanical properties, and electrical conductivity. Therefore, this review aims to summarize the research progress of injectable hydrogel in the treatment of MI in recent years and to introduce the rational design of injectable hydrogels in myocardial repair. Finally, the potential challenges and perspectives of injectable hydrogel in this field will be discussed, in order to provide theoretical guidance for the development of new and effective treatment strategies for MI.

A bio-functional polymer that prevents retinal scarring through modulation of NRF2 signalling pathway

One common cause of vision loss after retinal detachment surgery is the formation of proliferative and contractile fibrocellular membranes. This aberrant wound healing process is mediated by epithelial-mesenchymal transition (EMT) and hyper-proliferation of retinal pigment epithelial (RPE) cells. Current treatment relies primarily on surgical removal of these membranes. Here, we demonstrate that a bio-functional polymer by itself is able to prevent retinal scarring in an experimental rabbit model of proliferative vitreoretinopathy. This is mediated primarily via clathrin-dependent internalisation of polymeric micelles, downstream suppression of canonical EMT transcription factors, reduction of RPE cell hyper-proliferation and migration. Nuclear factor erythroid 2-related factor 2 signalling pathway was identified in a genome-wide transcriptomic profiling as a key sensor and effector. This study highlights the potential of using synthetic bio-functional polymer to modulate RPE cellular behaviour and offers a potential therapy for retinal scarring prevention.

Supramolecular Hydrogels: Design Strategies and Contemporary Biomedical Applications

Self-assembly of supramolecular hydrogels is driven by dynamic, non-covalent interactions between molecules. Considerable research effort has been exerted to fabricate and optimise supramolecular hydrogels that display shear-thinning, self-healing, and reversibility, in order to develop materials for biomedical applications. This review provides a detailed overview of the chemistry behind the dynamic physicochemical interactions that sustain hydrogel formation (hydrogen bonding, hydrophobic interactions, ionic interactions, metal-ligand coordination, and host-guest interactions). Novel design strategies and methodologies to create supramolecular hydrogels are highlighted, which offer promise for a wide range of applications, specifically drug delivery, wound healing, tissue engineering and 3D bioprinting. To conclude, future prospects are briefly discussed, and consideration given to the steps required to ultimately bring these biomaterials into clinical settings.

High molecular weight hyper-branched PCL-based thermogelling vitreous endotamponades

Vitreous endotamponades play essential roles in facilitating retina recovery following vitreoretinal surgery, yet existing clinically standards are suboptimal as they can cause elevated intra-ocular pressure, temporary loss of vision, and cataracts while also requiring prolonged face-down positioning and removal surgery. These drawbacks have spurred the development of next-generation vitreous endotamponades, of which supramolecular hydrogels capable of in-situ gelation have emerged as top contenders. Herein, we demonstrate thermogels formed from hyper-branched amphiphilic copolymers as effective transparent and biodegradable vitreous endotamponades for the first time. These hyper-branched copolymers are synthesised via polyaddition of polyethylene glycol, polypropylene glycol, poly(ε-caprolactone)-diol, and glycerol (branch inducing moiety) with hexamethylene diisocyanate. The hyper-branched thermogels are injected as sols and undergo spontaneous gelation when warmed to physiological temperatures in rabbit eyes. We found that polymers with an optimal degree of hyper-branching showed excellent biocompatibility and was able to maintain retinal function with minimal atrophy and inflammation, even at absolute molecular weights high enough to cause undesirable in-vivo effects for their linear counterparts. The hyper-branched thermogel is cleared naturally from the vitreous through surface hydrogel erosion and negates surgical removal. Our findings expand the scope of polymer architectures suitable for in-vivo intraocular therapeutic applications beyond linear constructs.

Biomaterials by design: Harnessing data for future development

Biomaterials is an interdisciplinary field of research to achieve desired biological responses from new materials, regardless of material type. There have been many exciting innovations in this discipline, but commercialization suffers from a lengthy discovery to product pipeline, with many failures along the way. Success can be greatly accelerated by harnessing machine learning techniques to comb through large amounts of data. There are many potential benefits of moving from an unstructured empirical approach to a development strategy that is entrenched in data. Here, we discuss the recent work on the use of machine learning in the discovery and design of biomaterials, including new polymeric, metallic, ceramics, and nanomaterials, and how machine learning can interface with emerging use cases of 3D printing. We discuss the steps for closer integration of machine learning to make this exciting possibility a reality.

(Macro)molecular self-assembly for hydrogel drug delivery

Hydrogels prepared via self-assembly offer scalable and tunable platforms for drug delivery applications. Molecular-scale self-assembly leverages an interplay of attractive and repulsive forces; drugs and other active molecules can be incorporated into such materials by partitioning in hydrophobic domains, affinity-mediated binding, or covalent integration. Peptides have been widely used as building blocks for self-assembly due to facile synthesis, ease of modification with bioactive molecules, and precise molecular-scale control over material properties through tunable interactions. Additional opportunities are manifest in stimuli-responsive self-assembly for more precise drug action. Hydrogels can likewise be fabricated from macromolecular self-assembly, with both synthetic polymers and biopolymers used to prepare materials with controlled mechanical properties and tunable drug release. These include clinical approaches for solubilization and delivery of hydrophobic drugs. To further enhance mechanical properties of hydrogels prepared through self-assembly, recent work has integrated self-assembly motifs with polymeric networks. For example, double-network hydrogels capture the beneficial properties of both self-assembled and covalent networks. The expanding ability to fabricate complex and precise materials, coupled with an improved understanding of biology, will lead to new classes of hydrogels specifically tailored for drug delivery applications.

A Morphable Ionic Electrode Based on Thermogel for Non-Invasive Hairy Plant Electrophysiology

Plant electrophysiology lays the foundation for smart plant interrogation and intervention. However, plant trichomes with hair-like morphologies present topographical features that challenge stable and high-fidelity non-invasive electrophysiology, due to the inadequate dynamic shape adaptability of conventional electrodes. Here, this issue is overcome using a morphable ionic electrode based on a thermogel, which gradually transforms from a viscous liquid to a viscoelastic gel. This transformation enables the morphable electrode to lock into the abrupt hairy surface irregularities and establish a conformal and adhesive interface. It achieves down to one tenth of the impedance and 4-5 times the adhesive strengths of conventional hydrogel electrodes on hairy leaves. As a result of the improved electrical and mechanical robustness, the morphable electrode can record more than one order of magnitude higher signal-to-noise ratio on hairy plants and maintains high-fidelity recording despite plant movements, achieving superior performance to conventional hydrogel electrodes. The reported morphable electrode is a promising tool for hairy plant electrophysiology and may be applied to diversely textured plants for advanced sensing and modulation.

3D-printed gelatin methacrylate (GelMA)/silanated silica scaffold assisted by two-stage cooling system for hard tissue regeneration

Among many biomaterials, gelatin methacrylate (GelMA), a photocurable protein, has been widely used in 3D bioprinting process owing to its excellent cellular responses, biocompatibility and biodegradability. However, GelMA still shows a low processability due to the severe temperature dependence of viscosity. To overcome this obstacle, we propose a two-stage temperature control system to effectively control the viscosity of GelMA. To optimize the process conditions, we evaluated the temperature of the cooling system (jacket and stage). Using the established system, three GelMA scaffolds were fabricated in which different concentrations (0, 3 and 10 wt%) of silanated silica particles were embedded. To evaluate the performances of the prepared scaffolds suitable for hard tissue regeneration, we analyzed the physical (viscoelasticity, surface roughness, compressive modulus and wettability) and biological (human mesenchymal stem cells growth, western blotting and osteogenic differentiation) properties. Consequently, the composite scaffold with greater silica contents (10 wt%) showed enhanced physical and biological performances including mechanical strength, cell initial attachment, cell proliferation and osteogenic differentiation compared with those of the controls. Our results indicate that the GelMA/silanated silica composite scaffold can be potentially used for hard tissue regeneration.

Polymeric hydrogels as a vitreous replacement strategy in the eye

Vitreous endo-tamponades are commonly used in the treatment of retinal detachments and tears. They function by providing a tamponading force to support the retina after retina surgery. Current clinical vitreous endo-tamponades include expansile gases (such as sulfur hexafluoride (SF₆) and perfluoropropane (C₃F₈)) and also sislicone oil (SiO). They are effective in promoting recovery but are disadvantaged by their lower refractive indices and lower densities as compared to the native vitreous, resulting in immediate blurred vision after surgery and necessitating patients to assume prolonged face-down positioning respectively. While the gas implants diffuse out over time, the SiO implants are non-biodegradable and require surgical removal. Therefore, there is much demand to develop an ideal vitreous endo-tamponade that can combine therapeutic effectiveness with patient comfort. Polymeric hydrogels have since attracted much attention due to their favourable properties such as high water content, high clarity, suitable refractive indices, suitable density, tuneable rheological properties, injectability, and biocompatibility. Many design strategies have been employed to design polymeric hydrogel-based vitreous endo-tamponades and they can be classified into four main strategies. This review seeks to analyse these various strategies and evaluate their effectiveness and also propose the key criteria to design successful polymeric hydrogel vitreous endo-tamponades.

RETRACTED: A review on biomacromolecular hydrogel classification and its applications

This article has been retracted: please see Elsevier Policy on Article Withdrawal (https://www.elsevier.com/locate/withdrawalpolicy). This article has been retracted at the request of the Editor-in-Chief and Author. The work included substantial parts copied without attribution from a prior work by Varaprasad et al (2017): https://doi.org/10.1016/j.msec.2017.05.096

Self-Healable, Fast Responsive Poly(ω-Pentadecalactone) Thermogelling System for Effective Liver Cancer Therapy

A polyurethane based thermogelling system comprising poly(ω-pentadecalactone) (PPDL), poly(ethylene glycol) (PEG), and poly(propylene glycol) (PPG), termed as PDEP, was synthesized. The incorporation of PPDL lowers critical micelle concentration (CMC) as well as critical gelation concentration (CGC) of the novel copolymers compared to commercial Pluronic® F127. The thermogels showed excellent thermal stability at high temperature up to 80°C, fast response to temperature change in a time frame of less than second, as well as remarkable self-healing properties after being broken at high strain. In vitro drug release studies using docetaxel (DTX) and cell uptake studies using doxorubicin (DOX) show high potential of the hydrogel as drug reservoir for sustainable release profile of payloads, while the in vivo anti-tumor evaluation using mice model of hepatocellular carcinoma further demonstrated the significant inhibition on the growth of tumor. Together with its excellent biocompatibility in different organs, the novel PDPE thermogelling copolymers reported in this work could potentially be utilized as in situ-forming hydrogels for liver cancer therapy.

Enhanced cell functions on graphene oxide incorporated 3D printed polycaprolactone scaffolds

For tissue engineering applications, a porous scaffold with an interconnected network is essential to facilitate the cell attachment and proliferation in a three dimensional (3D) structure. This study aimed to fabricate the scaffolds by an extrusion-based 3D printer using a blend of polycaprolactone (PCL), and graphene oxide (GO) as a favorable platform for bone tissue engineering. The mechanical properties, morphology, biocompatibility, and biological activities such as cell proliferation and differentiation were studied concerning the two different pore sizes; 400 μm, and 800 μm, and also with two different GO content; 0.1% (w/w) and 0.5% (w/w). The compressive strength of the scaffolds was not significantly changed due to the small amount of GO, but, as expected scaffolds with 400 μm pores showed a higher compressive modulus in comparison to the scaffolds with 800 μm pores. The data indicated that the cell attachment and proliferation were increased by adding a small amount of GO. According to the results, pore size did not play a significant role in cell proliferation and differentiation. Alkaline Phosphate (ALP) activity assay further confirmed that the GO increase the ALP activity and further Elemental analysis of Calcium and Phosphorous showed that the GO increased the mineralization compared to PCL only scaffolds. Western blot analysis showed the porous structure facilitate the secretion of bone morphogenic protein-2 (BMP-2) and osteopontin at both day 7 and 14 which galvanizes the osteogenic capability of PCL and PCL + GO scaffolds.

Sustained delivery of anti-VEGFs from thermogel depots inhibits angiogenesis without the need for multiple injections

Polyurethane thermogels show sustained delivery of bioactive anti-VEGFs therapeutics to the eye.

Synthesis and biological evaluation of redox/NIR dual stimulus-responsive polymeric nanoparticles for targeted delivery of cisplatin

Functional drug delivery systems enabling various favorable characteristics including specific targets, efficient cellular uptake and controllable release. At present work, a folate and cRGD dual modified nanoparticles based on NIR light and glutathione dual stimuli-responsive release system was successfully prepared and which simultaneously deliver cisplatin and ICG to tumor sites to enhance controllability. The prepared nanoparticles showed a stable uniform spherical morphology of 77.59 nm particle size range in PBS (pH = 7.4, 25 °C) and the encapsulated cisplatin were rapidly released in acidic environment especially added glutathione (GSH) and NIR irradiation. Moreover, the prepared nanoparticles can be efficiently internalized by tumor cells through the enhanced dual targeted ligands (folate and cRGD) for ICG imaging. The cytotoxicity assays showed that the cells viability decreased to 1.95% (SGC-7901) when been exposed to NIR light, and which further decreased to 1.25% in MCF-7 cells. Thus, the prepared nanoparticles showed excellent performance for photothermal conversion therapy of tumor cells and especially on human breast tumor cells. Our research highlights the great potential of stimuli-responsive smart nanoparticles in biomaterial and nano-biomedicine.

A Recent Perspective on Noncovalently Formed Polymeric Hydrogels

Chemically crosslinked covalent hydrogels form a permanent and often strong network, and have been extensively used so far in drug delivery and tissue engineering. However, it is more difficult to induce dynamic and highly tunable changes in these hydrogels. Noncovalently formed hydrogels show promise as inherently reversible systems with an ability to change in response to dynamic environments, and have garnered strong interest recently. In this Personal Account, we elucidate a few key attractive properties of noncovalent hydrogels and describe recent developments in hydrogels crosslinked using various different noncovalent interactions. These hydrogels offer huge control for modulating material properties and could be more relevant mimics for biological systems.

Biocompatible and mechanically robust nanocomposite hydrogels for potential applications in tissue engineering

The synergistic contributions of nanofillers and polymer matrix induce remarkable properties in nanocomposite hydrogels. Present article reports the facile synthesis of biocompatible nanocomposite hydrogels using microporous multi wall carbon nanotubes (MWCNTs) dispersed chitosan (CH)-Acrylonitrile (AN), N,N'-methylenebisacrylamide (MBAAm) and linseed polyol through solution blending method. Polyol and N,N'-methylenebisacrylamide (MBAAm) was used as the crosslinking agent. The structural characterization and formation of highly crosslinked network with dendrimer morphology was confirmed by FT-IR and scanning electron microscope (SEM) analysis. In addition, transmission electron microscope (TEM) was employed to visualize the size and proper dispersion of MWCNT in the polymer matrices. The strong mechanical strength exhibited by these hydrogel films was confirmed by the tensile strength analysis. The dispersion of the conductive nanofillers, like MWCNTs has significantly enhanced the strength, which revealed unique characteristics of these hydrogel films. The high swelling capacity and sustained expansion of hydrogel films were confirmed in the buffer solutions of pH4 and 7.4. The biodegradability of these films was estimated by hydrolytic and soil burial tests. The biocompatibility test was conducted on Human Embryonic Kidney (HEK-293) cell line, which confirmed the non-toxic and biocompatible nature of these films. Incorporation of carbon nanotubes (MWCNTs) in the polymer matrix enhanced the film forming properties, high modulus and tensile strength, swelling ability, biodegradable and biocompatibility. These properties can be finely tuned through the variation of MWCNT concentrations, as a result these nanostructure hydrogel films have potential scope for their diverse applications in the field of tissue engineering.

A review of recent progress in drug and protein encapsulation: Approaches, applications and challenges

Many drugs and proteins formulated for treatment of various diseases are not fully utilised due to environmentally problems such as degradation by enzymes or it being hydrophobic. To counter this problem, the drug and protein of interest are encapsulated by synthetic polymers where they are protected from the environment. This allows the molecule to reach its target safely and maximise its function. In this paper, we will discuss about the different techniques of encapsulation that includes emulsion evaporation, self-emulsifying drug delivery system and supercritical fluid. This will be followed by the drugs and proteins that are commonly encapsulated to counter life-threatening diseases such as cancer and diabetes. A novel method using foam was proposed and will be briefly discussed as it can play a huge role in future developments.

Nano-Star-Shaped Polymers for Drug Delivery Applications

With the advancement of polymer engineering, complex star-shaped polymer architectures can be synthesized with ease, bringing about a host of unique properties and applications. The polymer arms can be functionalized with different chemical groups to fine-tune the response behavior or be endowed with targeting ligands or stimuli responsive moieties to control its physicochemical behavior and self-organization in solution. Rheological properties of these solutions can be modulated, which also facilitates the control of the diffusion of the drug from these star-based nanocarriers. However, these star-shaped polymers designed for drug delivery are still in a very early stage of development. Due to the sheer diversity of macromolecules that can take on the star architectures and the various combinations of functional groups that can be cross-linked together, there remain many structure-property relationships which have yet to be fully established. This review aims to provide an introductory perspective on the basic synthetic methods of star-shaped polymers, the properties which can be controlled by the unique architecture, and also recent advances in drug delivery applications related to these star candidates.

Multi-responsive hydrogels with UCST- and LCST-induced shrinking and controlled release behaviors of rhodamine B

By using a disulfide-functionalized crosslinker, a pH- and thermo-responsive 2-(dimethylamino) ethyl methacrylate (DMAEMA) monomer and a zwitterionic sulfobetaine methacrylate (SBMA) monomer were conjugated to fabricate a multi-responsive P(DMAEMA-SS-SBMA) copolymeric hydrogel. Apparent UCST and LCST volume transitions were observed in the P(DMAEMA-SS-SBMA) hydrogels with equivalent weight fractions of monomers. Different pore size and response sensitivity of shrunken structures below UCST and above LCST were visualized by SEM images. The hydrogel exhibited a highly swollen state with a swelling ratio of 17.8 and a pore size of 106μm at 45°C, they deswelled unequally at 5°C with a compact surface with pore size of 30μm and a loose bulk with pore size of 83μm, while they deswelled uniformly at 65°C with dense shrunken structure with small pore size of 12μm. The dual-thermoresponsive hydrogel was promising in controlled drug release. The initial drug release was predominantly controlled by diffusion, and the long-term release was influenced by the swelling ratio. Below UCST, the relatively hydrophilic shrunken structure and slow diffusion had a synergistic effect on the sustained release. Above LCST, the fast diffusion and the rapid "off" effect of hydrophobic skin layer resulted in a burst release. Additionally, pH-tunable swelling and redox-sensitive degradation were also observed.

Overcoming STC2 mediated drug resistance through drug and gene co-delivery by PHB-PDMAEMA cationic polyester in liver cancer cells

Stanniocalcin 2 (STC2) overexpression in hepatocellular carcinoma (HCC) could lead to poor prognosis, which might be due to its induced P-glycoprotein and Bcl-2 protein expression level increase. P-glycoprotein or membrane pump induced drug efflux and altered prosurvival Bcl-2 expression are key mechanisms for drug resistance leading to failure of chemotherapy in HCC. However, current strategy to overcome both P-glycoprotein and Bcl-2 protein induced drug resistance was rarely reported. In this work, we utilized an amphiphilic poly[(R)-3-hydroxybutyrate] (PHB)-b-poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) cationic polyester to encapsulate chemotherapeutic paclitaxel (PTX) in hydrophobic PHB domain and Bcl-2 convertor Nur77/ΔDBD gene (Nur77 without DNA binding domain for mitochondria localization) by formation of polyplex due to cationic PDMAEMA segment, to effectively inhibit the drug resistant HepG2/STC2 and SMCC7721/STC2 liver cancer cell growth. Thanks to the cationic nanoparticle complex formation ability and high transfection efficiency to express Bcl-2 conversion proteins, PHB-PDMAEMA/PTX@polyplex could partially impair P-glycoprotein induced PTX efflux and activate the apoptotic function of previous prosurvival Bcl-2 protein. This is the pioneer report of cationic amphiphilic polyester PHB-PDMAEMA to codeliver anticancer drug and therapeutic plasmid to overcome both pump and non-pump mediated chemotherapeutic resistance in liver cancer cells, which might be inspiring for the application of polyester in personalized cancer therapy.

Photodynamic effect of light-harvesting, long-lived triplet excited state Ruthenium(II)-polyimine-coumarin complexes: DNA binding, photocleavage and anticancer studies

Two coumarin based Ru^II-polyimine complexes (Ru-1 and Ru-2) showing intense absorption of visible light and long-lived triplet excited states (~12-15μs) were used for study of the interaction with DNA. The binding of the complexes with CT-DNA were studied by UV-vis, fluorescence and time-resolved nanosecond transient absorption (ns-TA) spectroscopy. The results suggesting that the complexes interact with CT-DNA by intercalation mode of binding, showing the binding constants (K_b) 6.47×10⁴ for Ru-1 and 5.94×10⁴ M^-1 for Ru-2, in contrast no such results were found for Ru-0. The nanosecond transient absorption spectra of these systems in the presence of CT-DNA showing a clear perturbation in the bleaching region was observed compare to buffer alone. Visible light photoirradiation DNA cleavage was investigated for these complexes by treating with the supercoiled pUC19 DNA and irradiated at 450nm. The reactive species produced upon irradiation of current agents is singlet oxygen (¹O₂), which results in the generation of other reactive oxygen species (ROS). The complexes shown efficient cleavage activity, converted complete supercoiled DNA to nicked circular at as low as 20μM concentration in 30min of light irradiation time. Significant amount of linear form was generated by Ru-1 at the same conditions. Even though Ru-0 has significant ¹O₂ quantum yield but shown lower cleavage activity compared to other two analogs is due the miserable interaction (binding) with DNA. The cytotoxicity in vitro of the complexes toward HeLa, BEL-7402 and MG-63 cells was assessed by MTT assay. The cellular uptake was observed on BEL-7402 cells under fluorescence microscope. The complexes shown appreciable cytotoxicity towards the cancer cell lines.

PCL-based thermo-gelling polymers for in vivo delivery of chemotherapeutics to tumors

The synthesis of a multiblock poly(ether ester urethane)s comprising poly(ε-caprolactone), poly(ethylene glycol), and poly(propylene glycol) segments is described. We found that this polymer possessed a critical thermo-gelation concentration of 4wt%. Molecular characterization of the polymer was performed in terms of molecular weight determination, chemical composition elucidation and functional group determination using GPC, NMR, and FTIR. We carried out in vitro paclitaxel and doxorubicin release studies and demonstrated that sustained therapeutic release of about 2weeks can be obtained with this system. A nude mice model of tumor was developed and intratumoral injection of therapeutic-loaded thermo-gel demonstrated that PTX-loaded thermo-gel effectively inhibited the growth of tumors.

Review of Adaptive Programmable Materials and Their Bioapplications

Adaptive programmable materials have attracted increasing attention due to their high functionality, autonomous behavior, encapsulation, and site-specific confinement capabilities in various applications. Compared to conventional materials, adaptive programmable materials possess unique single-material architecture that can maintain, respond, and change their shapes and dimensions when they are subjected to surrounding environment changes, such as alternation in temperature, pH, and ionic strength. In this review, the most-recent advances in the design strategies of adaptive programmable materials are presented with respect to different types of architectural polymers, including stimuli-responsive polymers and shape-memory polymers. The diverse functions of these sophisticated materials and their significance in therapeutic agent delivery systems are also summarized in this review. Finally, the challenges for facile fabrication of these materials and future prospective are also discussed.

Antiproliferative Drugs for Restenosis Prevention

Cardiovascular disease is a leading cause of death and disability worldwide. Current treatment strategies aimed at treating the symptoms and consequences of obstructive vascular disease have embraced both optimal medical therapy and catheter-based percutaneous coronary intervention with drug-eluting stents. Drug-eluting stents elute antiproliferative drugs inhibiting vascular smooth muscle cell proliferation, which occurs in response to injury and thus prevents restenosis. However, all drugs currently approved for use in drug-eluting stents do not discriminate between proliferating vascular smooth muscle cells and endothelial cells, thus delaying re-endothelialization and subsequent vascular healing.

A Thixotropic Polyglycerol Sebacate-Based Supramolecular Hydrogel as an Injectable Drug Delivery Matrix

We have developed a "self-healing" polyglycerol sebacate-polyethylene glycol methyl ether methacrylate (PGS-PEGMEMA)/α-Cyclodextrin (αCD) hydrogel which could be sheared into a liquid during injection and has the potential to quickly "heal" itself back into gel post-injection. This hydrogel was shown to be biocompatible and biodegradable and therefore appropriate for use in vivo. Furthermore, the storage and loss moduli of the hydrogels could be tuned (by varying the concentration of αCD) between a fraction of a kPa to a few 100 kPa, a range that coincides with the moduli of cells and human soft tissues. This property would allow for this hydrogel to be used in vivo with maximal mechanical compatibility with human soft tissues. In vitro experiments showed that the hydrogel demonstrated a linear mass erosion profile and a biphasic drug (doxorubicin) release profile: Phase I was primarily driven by diffusion and Phase II was driven by hydrogel erosion. The diffusion mechanism was modeled with the First Order equation and the erosion mechanism with the Hopfenberg equation. This established fitting model could be used to predict releases with other drugs and estimate the composition of the hydrogel required to achieve a desired release rate.

Nanodelivery systems for enhancing the immunostimulatory effect of CpG oligodeoxynucleotides

Synthetic oligodeoxynucleotides containing immunostimulatory CpG motif mimic bacterial DNA and are potent activator of innate and adaptive immune responses. Therefore, CpG ODNs have significant potentials as immunotherapeutic agent for treatment of infectious diseases, allergy and cancer. Many clinical trials involving CpG ODNs either used alone or as adjuvant have been initiated. However, delivery of CpG ODNs to target sites still remains a great challenge due to their extreme susceptibility to nuclease degradation in serum and poor cellular uptake. Chemical modification of CpG ODNs backbone can protect them against degradation by nucleases, but have raised concern regarding several severe side effects. Development of efficient CpG ODNs delivery systems to address these issues and enhance their immunostimulatory effect are highly desirable. In recent years, the emergence of nanotechnology has provided unprecedented opportunities to encapsulate CpG ODN into various nanocarriers or synthesize CpG ODNs nanostructures. This review provides an overview of the delivery systems based on nanomaterials and nanostructures newly developed for enhancing the immunostimulatory effect of CpG ODNs, together with a brief discussion on perspectives for future studies in this field.

Small molecule therapeutic-loaded liposomes as therapeutic carriers: from development to clinical applications

In this review, various methods and mechanisms for encapsulation of small therapeutic molecules in liposomes for targeted delivery and triggered release, as well as their potential in the clinical uses, are discussed.

Intraarterial gelation of injectable cationic pH/temperature-sensitive radiopaque embolic hydrogels in a rabbit hepatic tumor model and their potential application for liver cancer treatment

Radiopaque embolic solutions employing cationic poly(amino ester urethane)-based copolymers are injected into a rabbit hepatic tumor artery and form hydrogels in response to local temperature and pH for chemoembolization.

Organic–inorganic shape memory thermoplastic polyurethane based on polycaprolactone and polydimethylsiloxane

We report an organic–inorganic SMP comprising PCL and PDMS that exhibits extremely fast-response time at body temperature and thermoplasticity that allows for solvent processing. The SMP recovered to the programmed shape in less than 0.5 seconds.