Shape memory polymers (SMPs), with the capability to change from one or more temporary shapes to predetermined shapes in response to an external stimulus, have attracted much interest from both academia and industries. When introducing supramolecular interactions that have been featured as dynamic and reversible into the design of novel SMPs, intriguing and unique functionalities have been engendered and thereby broaden the potential applications of the SMPs to new territories. In this review, we summarize recent progress made in SMPs based on supramolecular interactions, provide insight into the material design and shape memory mechanism, elucidate and evaluate their properties and performance, and point out opportunities and applications of SMPs.

NIR laser-induced photothermal therapy (PTT) through near-infrared agents has demonstrated the great potential in solid tumor ablation. However, the nonuniform heat distribution over tumors from PTT makes it insufficient to kill all tumor cells, resulting in tumor recurrence and inferior outcomes. To improve the tumor treatment efficacy, it is highly desirable to develop the combinational treatment of PTT with other modalities, especially with chemotherapeutic agents. Here we report a smart DOX/IR-780-loaded temperature-sensitive-liposome (DITSL) which can achieve NIR-laser-controlled drug release for chemo-photothermal synergistic tumor therapy. In this system, the liposoluble IR-780 was incorporated into the temperature-sensitive lipid bilayer and the soluble chemotherapeutic doxorubicin (DOX) was encapsulated in the hydrophilic core. The resulting DITSL is proved to be physiologically stable and can provide a fast and laser irradiation-controllable DOX release in the PBS and cellular conditions. We further employed this nanoparticle for tumor treatment, demonstrating significantly higher tumor inhibition efficacy than that of DOX-loaded temperature-sensitive-liposome (DTSL) or IR780-loaded temperature-sensitive-liposome (ITSL) in the in vitro cells and in vivo animals. Histological analysis further revealed much more apoptotic cells, confirming the advantageous anti-tumor effect of DITSL over DTSL or ITSL. Our study provides a promising strategy to realize chemo-photothermal synergistic combination therapy for breast tumors.

Sonodynamic therapy (SDT) has become a new modality for cancer therapy through activating certain chemical sensitizers by ultrasound (US). Discovery and development of novel sonosensitizers are attracting extensive attentions. Here, we introduce IR-780 iodide, a lipophilic heptamethine dye with a peak optical absorption of 780 nm wavelength, which can function as SDT agents for breast cancer treatment. The in vitro cellular uptake, cell viability, and the generation levels of reactive oxygen species (ROS) were examined by using 4T1 breast cancer cells incubated with various concentrations of IR-780 followed by US irradiation. Our results showed a dose- and time-dependent cellular uptake of IR-780 iodide in 4T1 cancer cells. Significant lower viabilities and more necrotic/apoptotic cells were found when these cancer cells were treated with IR-780 iodide with US irradiation. Further analyzing the generation of ROS demonstrated significant increase of 1O2 level and H2O2, but not ⋅OH in the SDT-treated cells. The in vivo anti-tumor efficacy of SDT with IR-780 revealed significant tumor growth inhibition of xenografts of 4T1 cancer cells; it was further confirmed by histological analysis and TUNEL staining. Our results strongly suggest that SDT combined with IR-780 may provide a promising strategy for tumor treatment with minimal side effects.

No abstract

In principle, polymeric materials are endowed with shape-memory properties by two approaches. The fi rst, and most common way is based on phase transition. [5][6][7][8][9][10][11] A material having one or more reversible phase transitions can switch off or on the molecular mobility so as to freeze or release the temporary shape. The phase transitions are largely related to a thermal effect, therefore the shape memory effect of these materials is triggered by direct or indirect heat (such as light, magnetic fi eld, moisture, ultrasound, etc.). [12][13][14][15] The second approach is to design molecular switches. Various reversible bonds (including reversible covalent bonding and supramolecular interaction) in response to different stimuli have been utilized for the construction of shape materials, bringing more options in terms of triggering stimulus. [16][17][18][19][20] So far, direct heating is the most common trigger, while other stimuli, like light, have attracted more and more interest due to the advantage of remote activation, as well as spatial and precise control. Generally, lightinduced shape-memory effect is achieved via photothermal effect or photochemical reactions. [ 21 ] The use of the photothermal effect requires the introduction of light-sensitive components, such as nanotubes, graphene oxide, gold particles, dyes and metal-ligand complexes A thermo-, photo-and chemoresponsive shape-memory material is successfully prepared by introducing α-cyclodextrin (αCD) and azobenzene (Azo) into a poly(acrylate acid)/ alginate (PAA/Alg) network. The tri-stimuli-responsive formation/dissociation of αCD-Azo acts as molecular switches freezing or increasing the molecular mobility. The resulting fi lm herein can be processed into temporary shapes as needed and recovers its initial shape upon the application of light irradiation, heating, or chemical agent independently. Furthermore, the agar diffusion test suggests that the α-CD-Alg/Azo-PAA has good biocompatibility for L929 fi broblast-like cells.

No abstract

No abstract

A multistimuli sensitive shape memory hydrogel with dual and triple shape memory properties was prepared by grafting dansyl groups into the network of polyacrylamide (PAAM). The hydrophobic aggregation of dansyl groups acted as molecular switches, which showed reversible aggregationdisaggregation transition in aqueous solution in response to the pH or temperature change.KEYWORDS: multishape memory, multistimuli sensitivity, hydrogel, hydrophobic aggregation, dansyl groups S hape memory polymers (SMPs) are an important class of stimuli-responsive materials, which can be deformed and fixed into a temporary shape, and recover to their original shape when exposed to a specific external stimulus. The capacities of remembering two or more shapes under different conditions are called dual-shape memory effect (dual-SME) and mutishape memory effect (multi-SME), which give the SMPs great potential for a wide range of applications, such as smart devices, sensors, and actuators. To realize more complex actuation and to expand the technical potential of SMPs, exploring new triggering mechanisms and multishape memory processes have been the focus of SMP research. 1−4 So far, the most common stimulus for shape memory effect is heating, but other stimuli like pH have also become increasingly attractive in recent years. pH is of important environmental value in typical physiological, biological and/or chemical systems. It can also be utilized in the applications where large temperature swings are undesirable. For example, an SMP using pH-sensitive host−guest complexes as the molecular switches was reported by our group. It could be processed into a temporary shape at pH 11.5 and was found to be able to recover to the original shape at pH 7.0. 5 Subsequently, a kind of pH-sensitive polyurethane using hydrogen bonding as molecular switches, which could recover its initial shape at pH 1.5, was prepared by Zhou et al. 6 These works, however, only focused on the pH-induced shape memory effect. Although a few reports have developed some multi-stimuli-responsive behaviors of materials, 7−9 seldom SMP has been reported in response to multistimuli of pH values and other stimuli up to now; however, it is obvious that the feedback behavior of materials usually occurs because of a combination of multiple factors in nature.To develop multishape memory polymers that are capable of remembering more than one temporary state, therefore more flexible and able to meet more complex demand of applications, is another attractive subject in the field of SMPs. Generally, multishape SMPs need to have two or more distinct thermal phase switches, or a single broad thermal transition, and the multishape memory effect is triggered by heating. 4,10−13 Although Hu et al. 14 and Zhou et al. 15 reported triple SMP being responsive to thermal and water stimuli, respectively, a combination of both multistimuli and multishape memory effect in one material is still a big challenge.In this letter, we synthesized a versatile pH-and thermalresponsive mult...