pH-Responsive Copolymeric Network Gel Using Methacrylated β-Cyclodextrin for Controlled Codelivery of Hydrophilic and Hydrophobic Drugs

In medical science, sometimes two drugs with different solubilities are simultaneously required in combination to treat various diseases. Herein, a pH-responsive, copolymeric, antioxidant, biocompatible, and chemically crosslinked network gel is prepared to explore its capability as a matrix for controlled release of both hydrophobic [ibuprofen (IB)] and hydrophilic [tetracycline hydrochloride (TCH)] drugs, simultaneously. This three-dimensional β-CD-Meth-cl-(PHPMA-co-PAAc) network hydrogel is synthesized via two steps: (I) methacrylation of β-cyclodextrin and (II) grafting of poly(hydroxypropyl methacrylate) and poly(acrylic acid), followed by crosslinking of poly(ethylene glycol) diacrylate onto the backbone of methacrylated β-cyclodextrin (β-CD-Meth). The successful synthesis of the hydrogel is confirmed using several physiochemical characterizations. The β-CD-Meth-cl-(PHPMA-co-PAAc) hydrogel has an excellent network-like surface morphology. The potential pH-responsive high swelling behavior and excellent shrinking features suggest the reversible nature of the synthesized gel. Besides, rheological analyses affirm its excellent viscoelastic nature. This network gel is biodegradable and its non-cytotoxic nature toward human dermal fibroblast cells is demonstrated. Moreover, the dual drug release pattern from the copolymer under both in vitro and in vivo conditions portrays that this hydrogel has superior ability to be used as a controlled release matrix for both hydrophobic and hydrophilic drugs (TCH and IB) with varying solubilities concurrently.

Stimuli-responsive cyclodextrin-based supramolecular assemblies as drug carriers

Cyclodextrins (CDs) are widely employed in biomedical applications because of their unique structures. Various biomedical applications can be achieved in a spatiotemporally controlled manner by integrating the host-guest chemistry of CDs with stimuli-responsive functions. In this review, we summarize the recent advances in stimuli-responsive supramolecular assemblies based on the host-guest chemistry of CDs. The stimuli considered in this review include endogenous (pH, redox, and enzymes) and exogenous stimuli (light, temperature, and magnetic field). We mainly discuss the mechanisms of the stimuli-responsive ability and present typical designs of the corresponding supramolecular assemblies for drug delivery and other potential biomedical applications. The limitations and perspectives of CD-based stimuli-responsive supramolecular assemblies are discussed to further promote the translation of laboratory products into clinical applications.

Upconverting Nanocarriers Enable Triggered Microtubule Inhibition and Concurrent Ferroptosis Induction for Selective Treatment of Triple-Negative Breast Cancer

Despite the resistance of triple-negative breast cancer (TNBC) to targeted hormone therapy, the discovery of azobenzene combretastatin A4 (Azo-CA4) provides therapeutic opportunities for TNBC. Here, Azo-CA4 was loaded in upconverting nanocarriers that could convert near-infrared (NIR) light to UV light to activate Azo-CA4. Upon irradiation, Azo-CA4-loaded nanocarriers significantly reduced the viability of TNBC cells via both apoptosis and ferroptosis. The former was induced by photoisomerization of Azo-CA4, accompanied by microtubule breakdown and cell cycle arrest at G₂/M phase. The latter was caused by the UV light-induced reduction of Fe³⁺ to Fe²⁺ that facilitates the peroxidation of tailored lipids. The cooperation between apoptosis and ferroptosis in eliminating TNBC was demonstrated in a xenograft mice model in terms of histological staining, tumor growth inhibition, and animal survival. Since the NIR light is only applied to the tumor site, the adverse effects of such triggered nanocarriers to the healthy organs are negligible.

Development of Light-Responsive Poly(γ-Benzyl-L-Glutamate) as Photo Switches by a One-Step NCA Method

Synthesized polypeptide is attracting an increased interests due to its excellent biological characteristic and adjustable chemical properties in bio-related fields. But polypeptide itself has no switching properties, which is harmful to the development of its application as a control component. Herein, light-responsive poly(γ-benzyl-L-glutamate)s (PBLGs) is synthesized by a one-step NCA method using p-aminoazobenzene (m-AZO) and p-diaminoazobenzene (m-DAZO) as initiators. PBLGs exhibit amorphous characteristics with obvious T_g transition, which are 14°C for PBLG1 and 21°C for PBLG2. In order to forecast the structure-property information of PBLGs, theoretical UV-vis spectra as well as the energy gap between HOMO and LUMO is calculated by DFT calculation. Experimental results of UV-vis spectra exhibit similar characteristics to those of theorical UV-vis spectra except for the 40–50 nm red-shifting of absorbance peak. Furthermore, the absorbance intensities of PBLGs have a good linear relationship with their concentration, but their linearity range depending on concentration is completely different. Then, trans–cis transition under a different excitation source and cis–trans recovery in a dark environment are tracked in real-time by UV-vis spectra to evaluate the light response performances. It is found that UV light is the only effective excitation source for PBLG1, and blue light is another effective excitation source for PBLG2 besides UV light. Furthermore, the addition of alcohol and water as cosolvents has little effect on trans→cis transition in UV-light-excited systems, but it shortens recovery time of the cis→trans process in a dark environment. By contrast, the detectable isomerization process becomes unclear with the addition of alcohol in blue-light-excited system. Furthermore, either alcohol or water in solvents accelerate both the trans→cis and cis→trans process in a blue-light-excited system.

Azobenzene Photoswitch for Isomerization-Dependent Cancer Therapy via Azo-Combretastatin A4 and Phototrexate

The adverse effects of chemotherapeutic drugs to healthy organs/cells greatly limit their clinical efficacy and patient compliance. The unique behavior of azobenzene photoswitch offers a remarkable tool to address the side effects of chemotherapeutic drugs. The azobenzene moiety has been integrated within some chemotherapeutic drugs to realize photo-triggered activation of drug cytotoxicity. However, the clinical translation of these agents has been facing a few barriers. In this short review, we present our viewpoints on potential solutions to address the following challenges associated with azobenzene-based photoswitchable chemotherapeutic drugs, including poor tissue penetration of light, hypoxia-induced drug degradation in solid tumor and the autonomous cis-trans relaxation.

Stimuli-Responsive Polymeric Nanocarriers for Drug Delivery, Imaging, and Theragnosis

In the past few decades, polymeric nanocarriers have been recognized as promising tools and have gained attention from researchers for their potential to efficiently deliver bioactive compounds, including drugs, proteins, genes, nucleic acids, etc., in pharmaceutical and biomedical applications. Remarkably, these polymeric nanocarriers could be further modified as stimuli-responsive systems based on the mechanism of triggered release, i.e., response to a specific stimulus, either endogenous (pH, enzymes, temperature, redox values, hypoxia, glucose levels) or exogenous (light, magnetism, ultrasound, electrical pulses) for the effective biodistribution and controlled release of drugs or genes at specific sites. Various nanoparticles (NPs) have been functionalized and used as templates for imaging systems in the form of metallic NPs, dendrimers, polymeric NPs, quantum dots, and liposomes. The use of polymeric nanocarriers for imaging and to deliver active compounds has attracted considerable interest in various cancer therapy fields. So-called smart nanopolymer systems are built to respond to certain stimuli such as temperature, pH, light intensity and wavelength, and electrical, magnetic and ultrasonic fields. Many imaging techniques have been explored including optical imaging, magnetic resonance imaging (MRI), nuclear imaging, ultrasound, photoacoustic imaging (PAI), single photon emission computed tomography (SPECT), and positron emission tomography (PET). This review reports on the most recent developments in imaging methods by analyzing examples of smart nanopolymers that can be imaged using one or more imaging techniques. Unique features, including nontoxicity, water solubility, biocompatibility, and the presence of multiple functional groups, designate polymeric nanocues as attractive nanomedicine candidates. In this context, we summarize various classes of multifunctional, polymeric, nano-sized formulations such as liposomes, micelles, nanogels, and dendrimers.

Gated Mesoporous Silica Nanocarriers for Hypoxia-Responsive Cargo Release

Mesoporous silica nanocarriers (MSNs) are appealing in terms of their large cavity surface area and high loading capacity, but they have been suffering from premature cargo release. Herein, we report a gated smart MSN that is sensitive to low oxygen concentration (i.e., hypoxia) via taking advantage of the superior electron-accepting ability of the azobenzene moiety. The azobenzene polymer was employed as the responsive gate-keeper that was deposited on the MSN surface, followed by coating with amphiphilic Pluronic F68 for steric stabilization. The obtained nanocarriers were less than 200 nm. The in vitro polymer degradation was spectrophotometrically witnessed via the employment of a reducing agent, namely, sodium dithionite, with a strong electron-donating ability. The hypoxia-responsive cargo release from the gated MSN was quantitatively demonstrated in breast cancer cells (MCF-7) using the fluorescence resonance energy transfer (FRET) technique where coumarin 6 and rhodamine B was selected as the FRET donor and acceptor, respectively. The FRET ratio was used as the index and decreased linearly over time under hypoxia, whereas it almost remained steady under normoxia. In addition, a model photosensitizer, namely, chlorin e6, was also loaded in the gated MSN whose toxicity under hypoxia was verified. This study developed a hypoxia-responsive MSN with the azobenzene polymer as the removable gate-keeper, which would expand the application of MSNs in pharmaceutical and biomedical areas since the low oxygen concentration is a unique trigger in many pathological conditions.

Complex systems that incorporate cyclodextrins to get materials for some specific applications

Cyclodextrins (CDs) are a family of biodegradable cyclic hydrocarbons composed of α-(1,4) linked glucopyranose subunits, the more common containing 6, 7 or 8 glucose units are named α, β and γ-cyclodextrins respectively. Since the discovery of CDs, they have attracted interest among scientists and the first studies were about the properties of the native compounds and in particular their use as catalysts of organic reactions. Characteristics features of different types of cyclodextrins stimulated investigation in different areas of research, due to its non-toxic and non-inmunogenic properties and also to the development of an improved industrial production. In this way, many materials with important properties have been developed. This mini-review will focus on chemical systems that use cyclodextrins, whatever linked covalently or mediated by the non covalent interactions, to build complex systems developed mainly during the last five years.

Design, Synthesis, Investigation, and Application of a Macromolecule Photoswitch

Azobenzene (AZO) has attracted increasing interest due to its reversible structural change upon a light stimulus. However, poor fatigue durability and the photobleaching phenomenon restricts its further application. Herein, the AZO domain as a pendent group, was incorporated into copolymers, which was synthesized by radical copolymerization in the research. Structure-properties of synthesized copolymer can be adjusted by monomer ratios. Emphatically, responsive properties of copolymer in different solutions were investigated. In the DMSO solution, copolymer exhibited effective structural change, stable rapid responsive time (1 min) upon UV light at room temperature, stable relative acceptable recovery time (100 min) upon white light at room temperature, and good fatigue resistance property. In an aqueous solution, even more controllable responsive properties and fatigue resistance properties for copolymer were verified by results. More pervasively, the recovery process could be controlled by light density and temperature. In order to clarify reasons for the difference between the AZO molecule and the AZO domain of copolymer, energy barrier or interactions between single atoms or even structural units was calculated using the density functional theory (DFT). Furthermore, the status of copolymer was characterized by dynamic light scattering (DLS) and transmission electron microscope (TEM). Finally, copolymer was further functionalized with bioactive protein (concanavalin, ConA) to reduce the cytotoxicity of the AZO molecule.

Synthesis, characterization, and formulation of poly-puerarin as a biodegradable and biosafe drug delivery platform for anti-cancer therapy

Poly-puerarin, a novel biodegradable biomaterial as a drug delivery platform in anti-tumour therapy.

NIR-triggered release of DOX from sophorolipid-coated mesoporous carbon nanoparticles with the phase-change material 1-tetradecanol to treat MCF-7/ADR cells

To prevent premature drug release from nanoparticles, it is vital to design and prepare controlled and site-specific drug release systems.

Hypoxia- and singlet oxygen-responsive chemo-photodynamic Micelles featured with glutathione depletion and aldehyde production

Triggered drug release from anti-tumor nanomedicine is an efficient approach to address the dilemma of systemic nanocarrier stability and on-demand drug liberation in tumor sites.