Evaluation of micelles incorporated into thermosensitive hydrogels for intratumoral delivery and controlled release of docetaxel: A dual approach for in situ treatment of tumors

Implantation of In Situ Gelling Systems for the Delivery of Chemotherapeutic Agents

Implantation is a modern method of administering chemotherapeutic agents, with a highly targeted effect and better patient tolerance due to the low frequency of administration. Implants are capable of controlled release, which makes them a viable alternative to infusional chemotherapy, allowing patients to enjoy a better quality of life without the need for prolonged hospitalization. Compared to subcutaneous implantation, intratumoral implantation has a number of significant advantages in terms of targeting and side effects, but this area of chemotherapy is still poorly understood in terms of clinical trials. At the same time, there are more known developments of drugs in the form of implants and injections for intratumoral administration. The disadvantages of classical intratumoral implants are the need for surgical intervention to install the system and the increased risk of tumor rupture noted by some specialists. The new generation of implants are in situ implants-systems formed in the tumor due to a phase transition (sol-gel transition) under the influence of various stimuli. Among this systems some are highly selective for a certain type of malignant neoplasm. Such systems are injected and have all the advantages of intratumoral injections, but due to the phase transition occurring in situ, they form depot forms that allow the long-term release of chemotherapeutic agents.

Injectable Poloxamer Hydrogels for Local Cancer Therapy

The widespread push to invest in local cancer therapies comes from the need to overcome the limitations of systemic treatment options. In contrast to intravenous administration, local treatments using intratumoral or peritumoral injections are independent of tumor vasculature and allow high concentrations of therapeutic agents to reach the tumor site with minimal systemic toxicity. Injectable biodegradable hydrogels offer a clear advantage over other delivery systems because the former requires no surgical procedures and promotes drug retention at the tumor site. More precisely, in situ gelling systems based on poloxamers have garnered considerable attention due to their thermoresponsive behavior, biocompatibility, ease of preparation, and possible incorporation of different anticancer agents. Therefore, this review focuses on the use of injectable thermoresponsive hydrogels based on poloxamers and their physicochemical and biological characterization. It also includes a summary of these hydrogel applications in local cancer therapies using chemotherapy, phototherapy, immunotherapy, and gene therapy.

Chitosan-based high-strength supramolecular hydrogels for 3D bioprinting

The loss of tissues and organs is a major challenge for biomedicine, and the emerging 3D bioprinting technology has brought the dawn for the development of tissue engineering and regenerative medicine. Chitosan-based supramolecular hydrogels, as novel biomaterials, are considered as ideal materials for 3D bioprinting due to their unique dynamic reversibility and fantastic biological properties. Although chitosan-based supramolecular hydrogels have wonderful biological properties, the mechanical properties are still under early exploration. This paper aims to provide some inspirations for researchers to further explore. In this review, common 3D bioprinting techniques and the properties required for bioink for 3D bioprinting are firstly described. Then, several strategies to enhance the mechanical properties of chitosan hydrogels are introduced from the perspectives of both materials and supramolecular binding motifs. Finally, current challenges and future opportunities in this field are discussed. The combination of chitosan-based supramolecular hydrogels and 3D bioprinting will hold promise for developing novel biomedical implants.

A pH-sensitive and sustained-release oral drug delivery system: the synthesis, characterization, adsorption and release of the xanthan gum-graft-poly(acrylic acid)/GO-DCFP composite hydrogel

In this study, graphene oxide (GO) was successfully prepared using the improved Hummers method, and the prepared GO powder was dissolved in distilled water and subjected to ultrasonic stripping. Diclofenac potassium (DCFP) was selected as a model drug to systematically evaluate the adsorption mechanism of DCFP by GO. Different reaction models were constructed to fit the adsorption kinetics and adsorption isotherms of DCFP on GO, in order to further explore the underlying adsorption mechanism. The results demonstrated that the pseudo-second-order kinetic model and Freundlich model could better delineate the adsorption process of DCFP by GO. Both π–π stacking and hydrophobic interaction were mainly involved in the adsorption process, and there were electrostatic interaction and hydrogen bonding at the same time. Then, the xanthan gum-graft-poly(acrylic acid)/GO (XG-g-PAA/GO) composite hydrogel was synthesized by in situ polymerization as a slow-release drug carrier. For this reason, a XG-g-PAA/GO–DCFP composite hydrogel was synthesized, and its in vitro drug release and pharmacokinetic data were assessed. The results showed that the synthesized XG-g-PAA/GO composite hydrogel had a certain mechanical strength and uniform color, indicating that GO is evenly distributed in this composite hydrogel. Moreover, the results of a swelling ratio test demonstrated that the swelling ratios of the XG-g-PAA/GO composite hydrogel were significantly increased with increasing pH values, implying that this material is sensitive to pH. The in vitro drug release experiment showed that the cumulative release of DCFP after 96 h was significantly higher in artificial intestinal fluid than in artificial gastric fluid. These findings indicate that the XG-g-PAA/GO–DCFP composite hydrogel exhibits pH sensitivity under physiological conditions. Besides, the results of in vivo pharmacokinetic analysis revealed that the t_1/2 of DCFP group was 2.03 ± 0.35 h, while that of the XG-g-PAA/GO–DCFP composite hydrogel group was 10.71 ± 2.04 h, indicating that the synthesized hydrogel could effectively prolong the drug action time. Furthermore, the AUC_(0–t) of the DCFP group was 53.99 ± 3.18 mg L⁻¹ h⁻¹, while that of the XG-g-PAA/GO–DCFP composite hydrogel group was 116.79 ± 14.72 mg L⁻¹ h⁻¹, suggesting that the bioavailability of DCFP is greatly enhanced by this composite hydrogel. In conclusion, this study highlights that the XG-g-PAA/GO–DCFP composite hydrogel can be applied as a sustained-release drug carrier.

In this study, graphene oxide (GO) was successfully prepared using the improved Hummers method, and the prepared GO powder was dissolved in distilled water and subjected to ultrasonic stripping.

Stimuli-responsive hydrogels for intratumoral drug delivery

The ability of some hydrogels to exhibit a phase transition or change their structure in response to stimuli has been extensively explored for drug depot formation and controlled drug release. Taking advantage of the unique features of the tumor microenvironment (TME) or externally applied triggers, several injectable stimuli-responsive hydrogels have been described as promising candidates for intratumoral drug delivery. In this review, we provide a brief overview of the TME and highlight the advantages of intratumoral administration, followed by a summary of the reported strategies to endow hydrogels with responsiveness to physical (temperature and light), chemical (pH and redox potential), or biological (enzyme) stimuli.

Black phosphorus nanosheets and docetaxel micelles co-incorporated thermoreversible hydrogel for combination chemo-photodynamic therapy

The platform of the combination chemo-photodynamic therapy has received widespread attention for enhancing anticancer efficacy and inhibiting tumor growth, which supports thermosensitive and controlled drug release. Here, an injectable thermoreversible hydrogel (BPNSs/DTX-M-hydrogel) co-encapsulating black phosphorus nanosheets (BPNSs) and docetaxel (DTX) micelles was prepared to increase drug accumulation in tumor tissue and improve anticancer efficacy. BPNSs were prepared by liquid exfoliation method with a simple and rapid preparation, and DTX micelles were prepared by the thin film dispersion method. Hydrogel was prepared with F127 as hydrogel matrix for intratumoral injection. BPNSs, DTX micelles, and BPNSs/DTX-M-hydrogel were characterized by particle size, morphology, stability and degradation, phase transition feature, and photodynamic performance. And the in vivo anticancer efficacy was evaluated in 4T1 tumor-bearing Balb/c mice. The results showed that the particle size of DTX micelles and BPNSs were about 16 and 180 nm, respectively. The hydrogel with the transformation temperature at near body exhibited great photodynamic efficacy and good biodegradability. Moreover, BPNSs/DTX-M-hydrogel with the combination of chemotherapy and photodynamic therapy exhibited unique anticancer efficacy with low toxicity. In conclusion, the combination platform of chemo-photodynamic therapy based on BPNSs could be a prospective strategy in antitumor research. Graphical abstract.

NIR-triggered thermo-responsive biodegradable hydrogel with combination of photothermal and thermodynamic therapy for hypoxic tumor

Hypoxia is a typical feature of solid tumors, which highly limits the application of the oxygen-dependent therapy. Also, the dense and hyperbaric tumor tissues impede the penetration of nanoparticles into the deep tumor. Thereby, we designed a novel localized injectable hydrogel combining the photothermal therapy (PTT) and the thermodynamic therapy (TDT), which is based on the generation of free radicals even in the absence of oxygen for hypoxic tumor therapy. In our study, gold nanorods (AuNRs) and 2,2'-Azobis[2-(2-imidazalin-2-yl)propane] dihydrochlaride (AIPH) were incorporated into the hydrogel networks, which were formed by the copolymerization of hydrophobic N-isopropyl acrylamide (NIPAM) and hydrophilic glycidyl methacrylate modified hyaluronic acid (HA-GMA) to fabricate an injectable and near-infrared (NIR) responsive hydrogel. The crosslinked in situ forming hydrogel could not only realize PTT upon the NIR laser irradiation, but also generate free radicals even in hypoxic condition. Meanwhile the shrink of hydrogels upon thermal could accelerate the generation of free radicals to further damage the tumors, achieving the controlled drug release on demand. The designed hydrogel with a sufficient loading capacity, excellent biocompatibility and negligible systemic toxicity could serve as a long-acting implant for NIR-triggered thermo-responsive free radical generation. The in vitro cytotoxicity result and the in vivo antitumor activity illustrated the excellent therapeutic effect of hydrogels even in the absence of oxygen. Therefore, this innovative oxygen-independent platform combining the antitumor effects of PTT and TDT would bring a new insight into hypoxic tumor therapy by the application of alkyl free radical.

Cisplatin-loaded polymeric complex micelles with a modulated drug/copolymer ratio for improved in vivo performance

This study aimed to evaluate the performance of cisplatin-loaded polymeric micelles (CDDP-PMs) with different drug/copolymer ratios of 1:1, 1:3 and 1:6 (w/w) prepared by coordinated complexation and self-assembly method. The mass ratio influenced the self-assembly behaviors and the complex degree, where both single- and double- complexation existed in CDDP-PMs. With the increase of CDDP/copolymer ratio, the particle size and drug loading increased, while encapsulation efficiency decreased. The PEG density of CDDP-PM_1-6, CDDP-PM_1-3 and CDDP-PM_1-1 were 0.20, 0.61 and 0.38 PEG/nm², respectively. CDDP-PM_1-3 and CDDP-PM_1-6 had similar sustained release behavior, while CDDP-PM_1-1 showed burst release. Pharmacokinetics showed the AUC of CDDP-PM_1-6, CDDP-PM_1-3 and CDDP-PM_1-1 was 27.2, 76.6 and 13.0 fold higher than CDDP solution. Tissue distribution presented the platinum concentration of CDDP-PM_1-6, CDDP-PM_1-3 and CDDP-PM_1-1 was 1.03, 0.80 and 0.48 times of CDDP solution in kidney at 10 min, and 17.61, 28.63 and 16.6 times in tumor at 48 h respectively, indicating CDDP-PMs significantly reduced nephrotoxicity and increased tumor-targeting accumulation. In vivo antitumor test showed that CDDP-PMs exhibited an improved antitumor efficacy and lower systemic toxicity compared with CDDP solution. From CDDP-PM_1-1 to CDDP-PM_1-6, the toxicity decreased with the increase of copolymer ratio, but the tumor inhibition rate also decreased. CDDP-PM_1-3 had relative high therapeutic effect and low toxicity compared with other formulations. CDDP-PM_1-3 could improve the antitumor efficacy by increasing the dose within systemic tolerability, but CDDP solution cannot. This work provides an effective strategy by modulating drug/copolymer ratio of CDDP-PMs to balance the antitumor efficacy and toxicity for better payoff. STATEMENT OF SIGNIFICANCE: Cancer chemotherapy always exists a contradiction between antitumor efficacy and toxicity. Higher efficacy against tumor often associated with larger toxicity for normal tissues. This work provides an important strategy by modulating the drug/copolymer ratios to balance the antitumor efficacy and toxicity to obtain better payoff. The cisplatin-loaded polymeric micelles (CDDP-PMs) based on the complexation between CDDP and copolymer with different mass ratios make differences in vitro and in vivo because of the single- or double-complexation degree. Most importantly, we found the balance at CDDP/copolymer ratio of 1:3, which has relative high therapeutic effect and low toxicity compared with other formulations. CDDP-PM_1-3 could improve the antitumor efficacy by increasing the dose within systemic tolerability, but CDDP solution cannot.

Preparation of injectable temperature-sensitive chitosan-based hydrogel for combined hyperthermia and chemotherapy of colon cancer

The purpose of this study was to design an injectable hydrogel with temperature-sensitive property for safe and high efficient in vivo colon cancer hyperthermia and chemotherapy. Chitosan (CS) solution was injected into the tumor at room temperature and automatically gelled after warming to body temperature in the present of β-glycerophosphate (β-GP). Combined localized tumor photothermal and chemotherapy were achieved by dissolving photothermal material MoS₂/Bi₂S₃-PEG (MBP) nanosheets and drug molecule doxorubicin (DOX) into the hydrogel, and the gel system could encapsulate DOX and MBP nanosheets and prevent them from entering the blood circulation and damaging normal tissues and cells. More importantly, the CS/MBP/DOX (CMD) hydrogel exhibited a photothermal efficiency of 22.18% and 31.42% in the first and second near infrared light (NIR I and NIR II) biowindows respectively at a low MBP concentration (0.5 mg/mL). Besides, the release of the DOX from CMD hydrogel was controllable since the gel temperature could be governed by NIR laser irradiation. Moreover, the chitosan-based hydrogel had antibacterial effects. The designed composite hydrogel is anticipated to act as a platform for the high efficient treatment of tumors owing to the different penetration depths of NIR I and NIR II.