Thermoresponsive and acid-cleavable amphiphilic copolymer micelles for controlled drug delivery

Physically stimulus-responsive nanoparticles for therapy and diagnosis

Nanoparticles offer numerous advantages in various fields of science, particularly in medicine. Over recent years, the use of nanoparticles in disease diagnosis and treatments has increased dramatically by the development of stimuli-responsive nano-systems, which can respond to internal or external stimuli. In the last 10 years, many preclinical studies were performed on physically triggered nano-systems to develop and optimize stable, precise, and selective therapeutic or diagnostic agents. In this regard, the systems must meet the requirements of efficacy, toxicity, pharmacokinetics, and safety before clinical investigation. Several undesired aspects need to be addressed to successfully translate these physical stimuli-responsive nano-systems, as biomaterials, into clinical practice. These have to be commonly taken into account when developing physically triggered systems; thus, also applicable for nano-systems based on nanomaterials. This review focuses on physically triggered nano-systems (PTNSs), with diagnostic or therapeutic and theranostic applications. Several types of physically triggered nano-systems based on polymeric micelles and hydrogels, mesoporous silica, and magnets are reviewed and discussed in various aspects.

Thermo-responsive polymers: Applications of smart materials in drug delivery and tissue engineering

Synthetic polymers are attracting great attention in the last decades for their use in the biomedical field as nanovectors for controlled drug delivery, hydrogels and scaffolds enabling cell growth. Among them, polymers able to respond to environmental stimuli have been recently under growing consideration to impart a "smart" behavior to the final product, which is highly desirable to provide it with a specific dynamic and an advanced function. In particular, thermo-responsive polymers, materials able to undergo a discontinuous phase transition or morphological change in response to a temperature variation, are among the most studied. The development of the so-called controlled radical polymerization techniques has paved the way to a high degree of engineering for the polymer architecture and properties, which in turn brought to a plethora of sophisticated behaviors for these polymers by simply switching the external temperature. These can be exploited in many different fields, from separation to advanced optics and biosensors. The aim of this review is to critically discuss the latest advances in the development of thermo-responsive materials for biomedical applications, including a highly controlled drug delivery, mediation of cell growth and bioseparation. The focus is on the structural and design aspects that are required to exploit such materials for cutting-edge applications in the biomedical field.

Preparation and controlled drug release ability of the poly[N-isopropylacryamide-co-allyl poly(ethylene glycol)]-b-poly(γ-benzyl-l-glutamate) polymeric micelles

The polymeric micelles were prepared through a copolymerization of allyl polyethylene glycol (APEG) and N-isopropylacrylamide in the presence of 2-aminoethanethiol (AET), followed by a ring opening polymerization of γ-benzyl-l-glutamate N-carboxyanhydride (BLG-NCA). Doxorubicin (DOX) as a model drug was covalently conjugated into the core of micelles via hydrazone bonds. The drug loading capacity could reach up to 15% with drug encapsulation efficiency of 80%. The pH/thermo sensitivities were observed in the process of in vitro drug release. The DOX-loaded micelles exhibited accelerated drug release behaviors in an acidic condition, and enhanced therapeutic efficacy was observed. Furthermore, the cytotoxicity of micelles against Hela and 3T3 cells was evaluated before and after drug loading. The DOX-loaded micelles showed strong cytotoxic activity to the cancer cells. But the blank micelles showed non-cytotoxicity. Therefore, the thermo/pH dual-responsive polymeric micelles have a promising future applied as a controlled drug delivery system for anticancer drugs.

Temperature, ultrasound and redox triple-responsive poly(N-isopropylacrylamide) block copolymer: synthesis, characterization and controlled release

Triple stimuli-responsive polymers PNiPAAm-S-S-PXCL containing a disulfide (–S–S–) bond as a junction point between hydrophilic and hydrophobic chains were synthesized and characterized.