beta-Cyclodextrin hydrogels containing naphthaleneacetic acid for pH-sensitive release

Stimulus-Responsive Hydrogels for Targeted Cancer Therapy

Cancer is a highly heterogeneous disease and remains a global health challenge affecting millions of human lives worldwide. Despite advancements in conventional treatments like surgery, chemotherapy, and immunotherapy, the rise of multidrug resistance, tumor recurrence, and their severe side effects and the complex nature of the tumor microenvironment (TME) necessitates innovative therapeutic approaches. Recently, stimulus-responsive nanomedicines designed to target TME characteristics (e.g., pH alterations, redox conditions, enzyme secretion) have gained attention for their potential to enhance anticancer efficacy while minimizing the adverse effects of chemotherapeutics/bioactive compounds. Among the various nanocarriers, hydrogels are intriguing due to their high-water content, adjustable mechanical characteristics, and responsiveness to external and internal stimuli, making them promising candidates for cancer therapy. These properties make hydrogels an ideal nanocarrier for controlled drug release within the TME. This review comprehensively surveys the latest advancements in the area of stimulus-responsive hydrogels for cancer therapy, exploring various stimuli-responsive mechanisms, including biological (e.g., pH, redox), chemical (e.g., enzymes, glucose), and physical (e.g., temperature, light), as well as dual- or multi-stimuli responsiveness. Furthermore, this review addresses the current developments and challenges in hydrogels in cancer treatment. Our aim is to provide readers with a comprehensive understanding of stimulus-responsive hydrogels for cancer treatment, offering novel perspectives on their development for cancer therapy and other medical applications.

pH-Sensitive Self-Assembled Microspheres Composed of Poly(Ethyleneimine) and Cinnamic Acid

Microspheres which were sensitive to pH change were developed by utilizing cinnamic acid (CA) as a physical cross-linker for poly(ethyleneimine) (PEI). At pH 7.0, the microspheres were efficiently formed at the PEI/CA ratio of 1:3.4, 1:5.1, and 1:7.1 (w/w), which corresponded to the protonated amino group/deprotonated carboxyl group ratio of 5:5, 4:6, and 3:7. The mean diameter of wet microspheres was 3.2 ± 0.3 to 8.8 ± 0.5 μm and that of dry ones was 1.7 ± 0.2 to 2.7 ± 0.2 μm. The microspheres were disappeared upon the alkalification, possibly because the electrostatic interaction between PEI and CA was slackened down and the hydrophobic interaction among CA molecules was weakened. At pH 5.0 and 7.0, the microsphere released its content in a sustained manner and the release degree in 24 h was less than 40%. Whereas, at pH 8.0 and 9.0, the microsphere exhibited a burst release and the release degree in 24 h was greater than 80%. In the alkali condition, not only the electrostatic interaction between PEI and CA but also the hydrophobic interaction among CA molecules became weaker, leading to the disintegration of the microsphere and resulting in a burst and intensive release.

Novel thermogelling dispersions of polymer nanoparticles for controlled protein release

A novel poly(oligo(ethylene glycol) methyl ether methacrylate-co-oligo(ethylene glycol) ethyl ether methacrylate)-poly(acrylic acid) interpenetrating network (IPN) nanoparticle was synthesized. The temperature-responsive properties of the IPN nanoparticles were investigated by a dynamic light scattering method. Atomic force microscopic images confirmed the homogenous and monodisperse morphology of the IPN nanoparticles. Both visual observation and viscosity testing demonstrated that the IPN nanoparticles exhibit thermogelling properties at body temperature, 37 °C. Subsequent studies verified that such temperature-sensitive properties of IPN nanoparticles allow their ease of injection and then slow release of model proteins, both in vitro and in vivo. Histological analysis showed that our IPN implants exerted minimal inflammation following subcutaneous implantation. Our results support the idea that, by simply mixing with proteins of interest, the novel IPN nanoparticles can be used to form in situ thermogelling devices for controlled protein release.

FROM THE CLINICAL EDITOR

This paper discusses a temperature responsive interpenetrating network (IPN) polymeric nanoparticle that can be used to form in situ thermogelling devices for controlled protein release by simply mixing them with proteins of interest.