Local Retention and Combination Effects of Biocompatible Doxorubicin-Loaded and Radioiodine-Labeled Microhydrogels in Cancer Therapy

Advancements in hydrogel-based embolic agents: Categorized by therapeutic mechanisms

BACKGROUND

Transcatheter arterial embolization (TAE) is a crucial technique in interventional radiology. Hydrogel-based embolic agents show promise due to their phase transition and drug-loading capabilities. However, existing categorizations of these agents are confusing.

AIMS

This review tackles the challenge of categorizing hydrogel-based embolic agents based on their therapeutic mechanisms, including transportation, accumulation, interaction, and elimination. It also addresses current challenges and controversies in the field while highlighting future directions for hydrogel-based embolicagents.

MATERIALS AND METHODS

We conducted a systematic review of papers published in PUBMED from 2004 to 2024, focusing primarily on preclinical trials.

RESULTS

Various kinds of hydrogel embolic agents were introduced according to their therapeutic mechanisms.

DISCUSSION

Most hydrogel embolic agents were specifically designed for effective accumulation and interaction. Recent advancement highlight the potential of multifunctional hydrogel embolic agents.

CONCLUSION

This new categorizations provided valuable insights into hydrogel embolic agents, potentially guiding material scientists and interventional radiologists in the development of novel hydrogel embolic agents in transarterial embolization.

One Stone Several Birds: Self-Localizing Submicrocages With Dual Loading Points for Multifunctional Drug Delivery

As the core index, how to improve bioavailability of loaded cargoes is a hot topic of drug carriers. In this study, aminated β-cyclodextrin (β-CD) as a cross-linking points is first integrated into 3D poly(acrylamide-co-acrylonitrile) (P(AAm-co-AN)) network to build up a unique submicrocage (466.2 ± 47.6 nm), featuring upper critical solution temperature (UCST; ≈40 °C), high volume expansion coefficient, and excellent biocompatibility. Hereinto, hydrophobic β-elemene (ELE) is locally loaded in β-CD with high loading efficiency (8.72%) and encapsulation efficiency (78.60%) through hydrophobic desolvation and host-guest interaction. Above UCST, the release of the loaded ELE is accelerated to 72.87% in 24 h, together with the enhanced sensitization effect of synergized radiotherapy. Given spontaneous long-lasting delivery, targeted embolization, and post-treatment removal of such UCST-type submicrocage, it is anticipated to provide a novel, facile, efficient, and versatile strategy of comprehensive anticancer treatments for high drug bioavailability.

Injectable hydrogels as emerging drug-delivery platforms for tumor therapy

Tumor therapy continues to be a prominent field within biomedical research. The development of various drug carriers has been propelled by concerns surrounding the side effects and targeting efficacy of various chemotherapeutic drugs and other therapeutic agents. These carriers strive to enhance drug concentration at tumor sites, minimize systemic side effects, and improve therapeutic outcomes. Among the reported delivery systems, injectable hydrogels have emerged as an emerging candidate for the in vivo delivery of chemotherapeutic drugs due to their minimal invasive drug delivery properties. This review systematically summarizes the composition and preparation methodologies of injectable hydrogels and further highlights the delivery mechanisms of diverse drugs using these hydrogels for tumor therapy, along with an in-depth discussion on the optimized therapeutic efficiency of drugs encapsulated within the hydrogels. The work concludes by providing a dynamic forward-looking perspective on the potential challenges and possible solutions of the in situ injectable hydrogels for non-surgical and real-time diagnostic applications.

Smart "Thrombus": Self-Localizing UCST-Type Microcage

Embolization is often used to block blood supply for controlling the growth of fibroids and malignant tumors, but limited by embolic agents lacking spontaneous targeting and post-treatment removal. So we first adopted nonionic poly(acrylamide-co-acrylonitrile) with an upper critical solution temperature (UCST) to build up self-localizing microcages by inverse emulsification. The results showed that these UCST-type microcages behaved with the appropriate phase-transition threshold value around 40 °C, and spontaneously underwent an expansion-fusion-fission cycle under the stimulus of mild temperature hyperthermia. Given the simultaneous local release of cargoes, this simple but smart microcage is expected to act as a multifunctional embolic agent for tumorous starving therapy, tumor chemotherapy, and imaging.

Injectable, Self-Healing, and Biocompatible N,O-Carboxymethyl Chitosan/Multialdehyde Guar Gum Hydrogels for Sustained Anticancer Drug Delivery

Local delivery of anticancer agents via injectable hydrogels could be a promising method for achieving spatiotemporal control on drug release as well as minimizing the disadvantages related to the systemic mode of drug delivery. Keeping this in mind, we report the development of N,O-carboxymethyl chitosan (N,O-CMCS)-guar gum-based injectable hydrogels for the sustained delivery of anticancer drugs. The hydrogels were synthesized by chemical crosslinking of multialdehyde guar gum (MAGG) and N,O-CMCS through dynamic Schiff base linkages, without requiring any external crosslinker. Fabrication of injectable hydrogels, involving N,O-CMCS and MAGG via Schiff base crosslinking, is being reported for the first time. The hydrogels exhibited pH-responsive swelling behavior and good mechanical properties with a storage modulus of about 1625 Pa. Due to the reversible nature of Schiff base linkages, hydrogels displayed excellent self-healing and thixotropic properties. Doxorubicin (Dox), an anticancer agent, was loaded onto these hydrogels and its release studies were conducted at pH 7.4 (physiological) and pH 5.5 (tumoral). A sustained release of about 67.06% Dox was observed from the hydrogel after 5 days at pH 5.5 and about 32.13% at pH 7.4. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay on the human embryonic kidney cell line (HEK-293) and the hemolytic assay demonstrated the biocompatible nature of the hydrogels. The Dox-loaded hydrogel exhibited a significant killing effect against breast cancer cells (MCF-7) with a cytotoxicity of about 72.13%. All the data presented support the efficiency of the synthesized N,O-CMCS/MAGG hydrogel as a biomaterial that may find promising applications in anticancer drug delivery.

Supramolecular Nanofibrils Formed by Coassembly of Clinically Approved Drugs for Tumor Photothermal Immunotherapy

Pancreatic cancer, one of the most lethal malignancies, compromises the performance of traditional therapeutic regimens in the clinic because of stromal resistance to systemic drug delivery and poor prognosis caused by tumor metastasis. Therefore, a biocompatible therapeutic paradigm that can effectively inhibit pancreatic tumor growth while simultaneously eliminating tumor metastasis is urgently needed. Herein, supramolecular nanofibrils are fabricated through coassembly of clinically approved immunomodulatory thymopentin and near-infrared indocyanine green for localized photothermal immunotherapy of pancreatic tumors. The resulting long-range ordered fibrous nanodrugs show improved photophysical capabilities for fluorescence imaging and photothermal conversion and significantly promote the proliferation and differentiation of antitumor immune cells. Hence, the integration of rapid photothermal therapy and moderate immunomodulation for inhibiting tumor growth and eliminating tumor metastasis is promising. The utilization of clinically approved molecules to construct nanodrugs administered via localized injection amplifies the complementary photothermal immunotherapeutic effects of the components, creating opportunities for clinical translation as a treatment for pancreatic cancer.

Development of injectable thermosensitive polypeptide hydrogel as facile radioisotope and radiosensitizer hotspot for synergistic brachytherapy

Brachytherapy is considered to be an unparalleled form of conformal radiation therapy, which involves the delivery of radiation directly to tumor lesions or the postoperative cavity. With the development of specific applicators, the exploitation of in situ drug-delivery platform introduces opportunities for the synchronous administration of radiosensitizers. In this study, an iodine-131 (I¹³¹)-labeled injectable thermosensitive methoxy poly(ethylene glycol)-b-poly(tyrosine) hydrogel (denoted as PETyr-I¹³¹) was developed via a facile method. The radioactive source of I¹³¹ was immobilized at the subcutaneous injection site and monitored via single-photon emission computed tomography in real time, and hematological and histopathological analyses revealed no obvious side effects. Additionally, the SmacN7 peptide conjugated with cell membrane-permeable oligosarginine (denoted as SmacN7-R9) was used to enhance the radiosensitivity of cancer cells, as confirmed by the results of reactive oxygen species detection, DNA damage assay, cell apoptosis assay, and clonogenic evaluation. Importantly, a synergistic brachytherapy treatment effect on tumor-bearing nude mice was achieved. The proposed thermosensitive supramolecular hydrogel platform, which conformally immobilizes radionuclides and delivers radiosensitizers by virtue of its proximity to the site of the primary tumor or the postoperative cavity, has great potential for achieving synergistic treatment outcomes with reduced radiation-related side effects. STATEMENT OF SIGNIFICANCE: In this work, a kind of radioiodinated thermosensitive supramolecular hydrogel was developed, which was facilely used as the radioactive source for brachytherapy. Meanwhile, SmacN7-R9 peptide was combined as a model radiosensitizer to facilitate the activation of tumor cell apoptosis pathways and promotion of radiation-induced cytotoxicity. Synergistic brachytherapy outcomes were achieved from the in vitro and in vivo evaluations. Therefore, from the practical standpoint, this thermosensitive supramolecular hydrogel platform holds great potential for the 3D-conformally immobilizing radionuclide and delivering radiosensitizer by virtue of its proximity to the site of primary tumor lesions or postoperative cavity, resulting in synergetic treatment outcomes with reduced radiation associated side effects.

Spatiotemporally Coupled Photoactivity of Phthalocyanine-Peptide Conjugate Self-Assemblies for Adaptive Tumor Theranostics

Spatiotemporally coupled tumor phototheranostic platforms offer a flexible and precise system that takes the biological interaction between tumors and photoactive agents into consideration for optimizing treatment, which is highly consistent with precision medicine. However, the fabrication of monocomponent-based photoactive agents applicable to multifold imaging techniques and multiple therapies in a facile way remains challenging. In this study, we developed simple phthalocyanine-peptide (PF) conjugate-based monocomponent nanoparticles with spatiotemporally coupled photoactivity for adaptive tumor theranostics. The self-assembled PF nanoparticles possess well-defined spherical nanostructures and excellent colloidal stability along with supramolecular photothermal effects. Importantly, the PF nanoparticles showed switchable photoactivity triggered by their interactions with the cell membrane, which enables an adaptive transformation from photothermal therapy (PTT) and photoacoustic imaging (PAI) to photodynamic therapy (PDT) and corresponding fluorescence imaging (FI). Theranostic modalities are integrated in a spatiotemporally coupled manner, providing a facile, biocompatible and effective route for localized tumor phototherapy. This study offers a flexible and versatile strategy to integrate multiple theranostic modalities into a single component so that it can realize its full potential and thereby amplify its therapeutic efficacy, creating promising opportunities for the design of theranostics and further highlighting their clinical prospects to the diagnosis and treatment of cancers.

Injectable Hydrogels as Unique Platforms for Local Chemotherapeutics-Based Combination Antitumor Therapy

Different strategies of chemotherapeutics-based combination cancer therapy have presented enhanced antitumor efficiency and are widely used in clinical cancer treatments. However, several drawbacks of the systems for systemic administration, including low drug accumulation at tumor sites and significant systemic side effects limit their efficacy and application in the clinic. Local drug co-delivery systems based on injectable hydrogels may have considerable advantages, such as a facile drug-delivery procedure, targeted delivery of antitumor agents to tumor sites in a sustained manner, and markedly reduced systemic toxicities. Thus, in recent years, these systems have received increasing attention and consequently various injectable hydrogels have been tested as platforms for local chemotherapeutics-based combination antitumor therapy. In this review, the focus is on recent advances in injectable hydrogel-based drug co-delivery systems for local combination antitumor therapy, including multiple chemotherapeutics combination therapy, chemo-immunotherapy, chemo-radiotherapy, and hyperthermia-chemotherapy. Moreover, the rationale and preparation of local co-delivery systems are summarized and discussed.

Chitosan-Based Hydrogel Microparticles for Treatment of Carcinoma in a Rabbit VX2 Liver Tumor Model

PURPOSE

To investigate potential of chitosan hydrogel microparticles (CHI) for treatment of VX2 carcinoma.

MATERIALS AND METHODS

Two weeks after liver VX2 implantation, contrast-enhanced computerized tomographic scanning was conducted. Rabbits (n = 2) with successful tumor growth were treated with different sizes of ^99mTc-labeled CHI (60-80 μm and 100-120 μm) via intra-arterial hepatic catheterization. Liver distribution of ^99mTc-labeled CHI was determined by means of autoradiography, a radiation-based photographic technique. In the next part of this study, therapeutic effectiveness was examined with the use of CHI with the size range of 60-80 μm (n = 11). Tumor growth response and levels of blood liver enzymes were studied at baseline and 1 and 2 weeks after CHI treatment.

RESULTS

Successful tumor growth was confirmed in all rabbits (24/24). Intrahepatic CHI with the size range of 60-80 μm resulted in liver localization in more close proximity to tumor nodule versus 100-120 μm. Baseline tumor volume was 1,909 ± 575 mm³ in animals receiving CHI versus 1,831 ± 249 mm³ in control animals (P = .342). In control animals, tumor volume markedly increased by 1,544 ± 512% at 2 weeks after sham operation versus baseline. In animals receiving CHI, tumor volume remained relatively unchanged (54 ± 6% increase; P = .007 vs control). Levels of blood aspartate transaminase (AST) and alanine transaminase (ALT) in animals receiving CHI increased 1 week after treatment (P = .032 vs control for AST; P = .000 vs control for ALT), but returned to control levels at 2 weeks.

CONCLUSIONS

CHI embolization suppressed tumor growth without appreciable damages in liver function.

Development of silver nanoparticle-doped adsorbents for the separation and recovery of radioactive iodine from alkaline solutions

Removing radioactive iodine from solutions containing fission products is essential for nuclear facility decontamination, radioactive waste treatment, and medical isotope production. For example, the production of high-purity fission ⁹⁹Mo by irradiation of ²³⁵U with neutrons involves the removal of iodine from an alkaline solution of the irradiated target (which contains numerous fission products and a large quantity of aluminate ions) using silver-based materials or anion-exchange resins. To be practically applicable, the utilized iodine adsorbent should exhibit a decontamination factor of at least 200. Herein, the separation of radioactive iodine from alkaline solutions was achieved using alumina doped with silver nanoparticles (Ag NPs). Ag NPs have a larger surface area than Ag powder/wires and can thus adsorb iodine more effectively and economically, whereas alumina is a suitable inert support that does not adsorb ⁹⁹Mo and is stable under basic conditions. The developed adsorbents with less impurities achieved iodine removal and recovery efficiencies of 99.7 and 62%, respectively, thus being useful for the production of ¹³¹I, a useful medical isotope.

Radiolabelled Polymeric Materials for Imaging and Treatment of Cancer: Quo Vadis?

Owing to their tunable blood circulation time and suitable plasma stability, polymer-based nanomaterials hold a great potential for designing and utilising multifunctional nanocarriers for efficient imaging and effective treatment of cancer. When tagged with appropriate radionuclides, they may allow for specific detection (diagnosis) as well as the destruction of tumours (therapy) or even customization of materials, aiming to both diagnosis and therapy (theranostic approach). This review provides an overview of recent developments of radiolabelled polymeric nanomaterials (natural and synthetic polymers) for molecular imaging of cancer, specifically, applying nuclear techniques such as positron emission tomography (PET) and single-photon emission computed tomography (SPECT). Different approaches to radiolabel polymers are evaluated from the methodical radiochemical point of view. This includes new bifunctional chelating agents (BFCAs) for radiometals as well as novel labelling methods. Special emphasis is given to eligible strategies employed to evade the mononuclear phagocytic system (MPS) in view of efficient targeting. The discussion encompasses promising strategies currently employed as well as emerging possibilities in radionuclide-based cancer therapy. Key issues involved in the clinical translation of radiolabelled polymers and future scopes of this intriguing research field are also discussed.

Thermohydrogel Containing Melanin for Photothermal Cancer Therapy

Melanin is an effective absorber of light and can extend to near infrared (NIR) regions. In this study, a natural melanin is presented as a photothermal therapeutic agent (PTA) because it provides a good photothermal conversion efficiency, shows biodegradability, and does not induce long-term toxicity during retention in vivo. Poloxamer solution containing melanin (Pol-Mel) does not show any precipitation and shows sol-gel transition at body temperature. After irradiation from 808 nm NIR laser at 1.5 W cm^-2 for 3 min, the photothermal conversion efficiency of Pol-Mel is enough to kill cancer cells in vitro and in vivo. The tumor growth of mice bearing CT26 tumors treated with Pol-Mel injection and laser irradiation is suppressed completely without recurrence postirradiation. All these results indicate that Pol-Mel can become an attractive PTA for photothermal cancer therapy.

The Alginate Layer for Improving Doxorubicin Release and Radiolabeling Stability of Chitosan Hydrogels

PURPOSE

Chitosan hydrogels (CSH) formed through ionic interaction with an anionic molecule are suitable as a drug carrier and a tissue engineering scaffold. However, the initial burst release of drugs from the CSH due to rapid swelling after immersing in a biofluid limits their wide application as a drug delivery carrier. In this study, alginate layering on the surface of the doxorubicin (Dox)-loaded and I-131-labeled CSH (DI-CSH) was performed. The effect of the alginate layering on drug release behavior and radiolabeling stability was investigated.

METHODS

Chitosan was chemically modified using a chelator for I-131 labeling. After labeling of I-131 and mixing of Dox, the chitosan solution was dropped into tripolyphosphate (TPP) solution using an electrospinning system to prepare spherical microhydrogels. The DI-CSH were immersed into alginate solution for 30 min to form the crosslinking layer on their surface. The formation of alginate layer on the DI-CSH was confirmed by Fourier transform infrared spectroscopy (FT-IR) and zeta potential analysis. In order to investigate the effect of alginate layer, studies of in vitro Dox release from the hydrogels were performed in phosphate buffered in saline (PBS, pH 7.4) at 37 °C for 12 days. The radiolabeling stability of the hydrogels was evaluated using ITLC under different experimental condition (human serum, normal saline, and PBS) at 37 °C for 12 days.

RESULTS

Formatting the alginate-crosslinked layer on the CSH surface did not change the spherical morphology and the mean diameter (150 ± 10 μm). FT-IR spectra and zeta potential values indicate that alginate layer was formed successfully on the surface of the DI-CSH. In in vitro Dox release studies, the total percentage of the released Dox from the DI-CSH for 12 days were 60.9 ± 0.8, 67.3 ± 1.4, and 71.8 ± 2.5 % for 0.25, 0.50, and 1.00 mg Dox used to load into the hydrogels, respectively. On the other hand, after formatting alginate layer, the percentage of the released Dox for 12 days was decreased to 47.6 ± 1.4, 51.1 ± 1.4, and 57.5 ± 1.6 % for 0.25, 0.50, and 1.00 mg Dox used, respectively. The radiolabeling stability of DI-CSH in human serum was improved by alginate layer.

CONCLUSIONS

The formation of alginate layer on the surface of the DI-CSH is useful for improving the drug release behavior and radiolabeling stability.

Injectable and Biodegradable pH-Responsive Hydrogels for Localized and Sustained Treatment of Human Fibrosarcoma

Injectable hydrogels are an important class of biomaterials, and they have been widely used for controlled drug release. This study evaluated an injectable hydrogel formed in situ system by the reaction of a polyethylene glycol derivative with α,β-polyaspartylhydrazide for local cancer chemotherapy. This pH-responsive hydrogel was used to realize a sol-gel phase transition, where the gel remained a free-flowing fluid before injection but spontaneously changed into a semisolid hydrogel just after administration. As indicated by scanning electron microscopy images, the hydrogel exhibited a porous three-dimensional microstructure. The prepared hydrogel was biocompatible and biodegradable and could be utilized as a pH-responsive vector for drug delivery. The therapeutic effect of the hydrogel loaded with doxorubicin (DOX) after intratumoral administration in mice with human fibrosarcoma was evaluated. The inhibition of tumor growth was more obvious in the group treated by the DOX-loaded hydrogel, compared to that treated with the free DOX solution. Hence, this hydrogel with good syringeability and high biodegradability, which focuses on local chemotherapy, may enhance the therapeutic effect on human fibrosarcoma.