Injectable Micelle-Incorporated Hydrogels for the Localized Chemo-Immunotherapy of Breast Tumors

Injectable Hydrogels: A Paradigm Tailored with Design, Characterization, and Multifaceted Approaches

Biomaterials denoting self-healing and versatile structural integrity are highly curious in the biomedicine segment. The injectable and/or printable 3D printing technology is explored in a few decades back, which can alter their dimensions temporarily under shear stress, showing potential healing/recovery tendency with patient-specific intervention toward the development of personalized medicine. Thus, self-healing injectable hydrogels (IHs) are stunning toward developing a paradigm for tissue regeneration. This review comprises the designing of IHs, rheological characterization and stability, several benchmark consequences for self-healing IHs, their translation into tissue regeneration of specific types, applications of IHs in biomedical such as anticancer and immunomodulation, wound healing and tissue/bone regeneration, antimicrobial potentials, drugs, gene and vaccine delivery, ocular delivery, 3D printing, cosmeceuticals, and photothermal therapy as well as in other allied avenues like agriculture, aerospace, electronic/electrical industries, coating approaches, patents associated with therapeutic/nontherapeutic avenues, and numerous futuristic challenges and solutions.

Engineered Bio-Based Hydrogels for Cancer Immunotherapy

Immunotherapy represents a revolutionary paradigm in cancer management, showcasing its potential to impede tumor metastasis and recurrence. Nonetheless, challenges including limited therapeutic efficacy and severe immune-related side effects are frequently encountered, especially in solid tumors. Hydrogels, a class of versatile materials featuring well-hydrated structures widely used in biomedicine, offer a promising platform for encapsulating and releasing small molecule drugs, biomacromolecules, and cells in a controlled manner. Immunomodulatory hydrogels present a unique capability for augmenting immune activation and mitigating systemic toxicity through encapsulation of multiple components and localized administration. Notably, hydrogels based on biopolymers have gained significant interest owing to their biocompatibility, environmental friendliness, and ease of production. This review delves into the recent advances in bio-based hydrogels in cancer immunotherapy and synergistic combinatorial approaches, highlighting their diverse applications. It is anticipated that this review will guide the rational design of hydrogels in the field of cancer immunotherapy, fostering clinical translation and ultimately benefiting patients.

Photothermal hyaluronic acid composite hydrogel targeting cancer stem cells for inhibiting recurrence and metastasis of breast cancer

Recurrence and metastasis have been recognized as a great challenge in cancer treatment. Cancer stem cells (CSCs), as a small subset of cancer cells, are closely associated with tumor metastasis and recurrence due to their resistance and multi-differentiation characteristics. Herein, we developed a local injectable hyaluronic acid (HA) composite hydrogel (HAAG) that targets CSCs, which can continuously release all-trans retinoic acid (ATRA) and gold nanoparticles (AuNPs) at tumor sites. The composite hydrogel was endowed with the ability to target CSCs through the specific binding of HA to CD44. ATRA was loaded into HA micelles to induce CSCs to differentiate into normal cancer cells, while AuNPs was incorporated into the hydrogel for photothermal therapy (PTT). HAAG exhibited good injectability, photothermal properties and CSCs targeting ability. HAAG not only significantly inhibited the growth of 4T1 mouse breast cancer cells and 4T1-CSCs in vitro, but also effectively inhibited tumor recurrence and metastasis in a 4T1-CSC mouse model in vivo. Our study provides a novel strategy of local differentiation combined with PTT for inhibiting the recurrence and metastasis of breast cancer.

Architecturally designed sequential-release hydrogels

Drug synergy has made significant strides in clinical applications in recent decades. However, achieving a platform that enables "single administration, multi-stage release" by emulating the natural physiological processes of the human body poses a formidable challenge in the field of molecular pharmaceutics. Hydrogels, as the novel generation of drug delivery systems, have gained widespread utilization in drug platforms owing to their exceptional biocompatibility and modifiability. Sequential drug delivery hydrogels (SDDHs), which amalgamate the advantages of hydrogel and sequential release platforms, offer a promising solution for effectively navigating the intricate human environment and accomplishing drug sequential release. Inspired by architectural design, this review establishes connections between three pivotal factors in SDDHs construction, namely mechanisms, carrier spatial structure, and stimuli-responsiveness, and three aspects of architectural design, specifically building materials, house structures, and intelligent interactive furniture, aiming at providing insights into recent developments in SDDHs. Furthermore, the dual-drug collocation and cutting-edge hydrogel preparation technologies as well as the prevailing challenges in the field were elucidated.

Polysaccharide-based tumor microenvironment-responsive drug delivery systems for cancer therapy

The biochemical indicators of tumor microenvironment (TME) that are different from normal tissues provide the possibility for constructing intelligent drug delivery systems (DDSs). Polysaccharides with good biocompatibility, biodegradability, and unique biological properties are ideal materials for constructing DDSs. Nanogels, micelles, organic-inorganic nanocomposites, hydrogels, and microneedles (MNs) are common polysaccharide-based DDSs. Polysaccharide-based DDSs enable precise control of drug delivery and release processes by incorporating TME-specific biochemical indicators. The classification and design strategies of polysaccharide-based TME-responsive DDSs are comprehensively reviewed. The advantages and challenges of current polysaccharide-based DDSs are summarized and the future directions of development are foreseen. The polysaccharide-based TME-responsive DDSs are expected to provide new strategies and solutions for cancer therapy and make important contributions to the realization of precision medicine.

Injectable Bioadhesive Hydrogels Scavenging ROS and Restoring Mucosal Barrier for Enhanced Ulcerative Colitis Therapy

Despite the progress in the therapy of ulcerative colitis (UC), long-lasting UC remission can hardly be achieved in the majority of UC patients. The key pathological characteristics of UC include an impaired mucosal barrier and local inflammatory infiltration. Thus, a two-pronged approach aiming at repairing damaged mucosal barrier and scavenging inflammatory mediators simultaneously might hold great potential for long-term remission of UC. A rectal formulation can directly offer preferential and effective drug delivery to inflamed colon. However, regular intestinal peristalsis and frequent diarrhea in UC might cause transient drug retention. Therefore, a bioadhesive hydrogel with strong interaction with intestinal mucosa might be preferable for rectal administration to prolong drug retention. Here, we designed a bioadhesive hydrogel formed by the cross-linking of sulfhydryl chondroitin sulfate and polydopamine (CS-PDA). The presence of PDA would ensure the mucosa-adhesive behavior, and the addition of CS in the hydrogel network was expected to achieve the restoration of the intestinal epithelial barrier. To scavenge the key player (excessive reactive oxygen species, ROS) in inflamed colon, sodium ferulic (SF), a potent ROS inhibitor, was incorporated into the CS-PDA hydrogel. After rectal administration, the SF-loaded CS-PDA hydrogel could adhere to the colonic mucosa to allow prolonged drug retention. Subsequently, sustained SF release could be achieved to persistently scavenge ROS in inflammatory areas. Meanwhile, the presence of CS would promote the restoration of the mucosal barrier. Ultimately, scavenging ROS and restoring the mucosal barrier could be simultaneously achieved via this SF-loaded bioadhesive hydrogel scaffold. Our two-pronged approach might provide new insight for effective UC treatment.

A self-healable metallohydrogel for drug encapsulations and drug release

A self-healable metallohydrogel (MOG) of Mn(ii) has been prepared using a low molecular weight gelator, Na₂HL {H₃L = l-(3,5-di-tert-butyl-2-hydroxy-benzyl)amino aspartic acid}. The MOG has been characterized by MALDI TOF mass spectrometry, rheological studies, IR spectroscopy, and microscopic techniques. Non-steroidal anti-inflammatory drug (NSAID), indomethacin (IND) and anti-cancer drug gemcitabine (GEM) were encapsulated into the metallohydrogel. The GEM-loaded metallogel (MOG_GEM) shows better delivery and more adverse cytotoxicity than the drug against breast cancer cell lines MDA-MB-468 and 4T1. The anti-cancer property was evaluated with in vitro MTT cytotoxic assay, live-dead assay and cell migration assay. In vitro cytotoxicity assay against RAW 264.7 cell line with the treatment of MOG_IND shows the improved anti-inflammatory response in the case of MOG_IND compared to the drug alone.

Injectable rhein-assisted crosslinked hydrogel for efficient local osteosarcoma chemotherapy

Osteosarcoma (OS) is the most common malignant tumor of the bone that affects children and adolescents, and its treatment usually involves doxorubicin hydrochloride (DOX). However, the drug resistance and side effects caused by high-dose DOX infusion greatly hinder its therapeutic effects. To achieve efficient OS treatment with low toxicity, an injectable rhein (RH)-assisted crosslinked hydrogel (PVA@RH@DOX hydrogel, PRDH) was designed, which was prepared by loading DOX and RH into a polyvinyl alcohol (PVA) solution. The cytotoxicity assay and live/dead staining results showed that the combination of RH and DOX more effectively killed OS cells, producing excellent effects at low concentrations of DOX. The wound healing and transwell test results proved that PRDH could significantly inhibit the metastasis and invasion of OS cells. PRDH showed a long-lasting antitumor effect after injection of a single dose, significantly suppressing the proliferation and metastasis of OS and achieving the strategy of a single administration for long-term treatment. Excitingly, RH facilitated hydrogel formation by assisting with PVA crosslinking. This system provides an alternative regimen and broadens the horizon for the clinical treatment of OS.

CaCO3-assistant synthesis of pH/near-infrared light-responsive and injectable sodium alginate hydrogels for melanoma synergistic treatment

Melanoma is an aggressive tumor located in skin with high rates of recurrence and metastasis. Due to the limited traditional therapies, the development of novel strategies against melanoma is urgently quested. To reduce the side effects of traditional administration ways and amplify the killing effect, an injectable sodium alginate (SA)-based hydrogels were developed, in which CaCO₃/polydopamine nanoparticles (CaCO₃/PDA NPs) were embedded for the synergistic photothermal/calcium ions interference therapy of melanoma. In the study, the formation conditions and mechanical properties of CaCO₃/PDA-SA hydrogels were characterized, and their antitumor efficiency and mechanism against mouse melanoma cells were investigated. Wheninjectedintratumorally, CaCO₃/PDA-SA fluid was converted into hydrogel in situ through the interaction of pH-sensitive released Ca²⁺ and alginate chains, which increased the retention time of photothermal agents (CaCO₃/PDA NPs) at tumor sites and thereby was more conducive to produce hyperthermia via photothermal conversion to combat melanoma. Moreover, in acidic tumor microenvironment, the residual CaCO₃/PDA NPs in hydrogels continuously decomposed and released Ca²⁺ to destroy the Ca²⁺ buffering capacity and evoke the mitochondrial Ca²⁺-overloading, resulting in the inhibition of adenosine triphosphate production to accelerate cell death. Notably, besides the heat elevation, the near-infrared light (NIR) irradiation would further enhance the release of Ca²⁺ to promote the Ca²⁺-involved cell death. Therefore, a pH/NIR-responsive and injectable SA-based hydrogels were successfully established and showed enhanced treatment efficacy of melanoma through the synergism of photothermal therapy and calcium ions interference therapy.

Self-Healing Injectable Hydrogels for Tissue Regeneration

Biomaterials with the ability to self-heal and recover their structural integrity offer many advantages for applications in biomedicine. The past decade has witnessed the rapid emergence of a new class of self-healing biomaterials commonly termed injectable, or printable in the context of 3D printing. These self-healing injectable biomaterials, mostly hydrogels and other soft condensed matter based on reversible chemistry, are able to temporarily fluidize under shear stress and subsequently recover their original mechanical properties. Self-healing injectable hydrogels offer distinct advantages compared to traditional biomaterials. Most notably, they can be administered in a locally targeted and minimally invasive manner through a narrow syringe without the need for invasive surgery. Their moldability allows for a patient-specific intervention and shows great prospects for personalized medicine. Injected hydrogels can facilitate tissue regeneration in multiple ways owing to their viscoelastic and diffusive nature, ranging from simple mechanical support, spatiotemporally controlled delivery of cells or therapeutics, to local recruitment and modulation of host cells to promote tissue regeneration. Consequently, self-healing injectable hydrogels have been at the forefront of many cutting-edge tissue regeneration strategies. This study provides a critical review of the current state of self-healing injectable hydrogels for tissue regeneration. As key challenges toward further maturation of this exciting research field, we identify (i) the trade-off between the self-healing and injectability of hydrogels vs their physical stability, (ii) the lack of consensus on rheological characterization and quantitative benchmarks for self-healing injectable hydrogels, particularly regarding the capillary flow in syringes, and (iii) practical limitations regarding translation toward therapeutically effective formulations for regeneration of specific tissues. Hence, here we (i) review chemical and physical design strategies for self-healing injectable hydrogels, (ii) provide a practical guide for their rheological analysis, and (iii) showcase their applicability for regeneration of various tissues and 3D printing of complex tissues and organoids.

Light-switchable diphtherin transgene system combined with losartan for triple negtative breast cancer therapy based on nano drug delivery system

Breast cancer is a common malignancy in women. The abnormally dense collagen network in breast cancer forms a therapeutic barrier that hinders the penetration and anti-tumor effect of drugs. To overcome this hurdle, we adopted a therapeutic strategy to treat breast cancer which combined a light-switchable transgene system and losartan. The light-switchable transgene system could regulate expression of the diphtheria toxin A fragment (DTA) gene with a high on/off ratio under blue light and had great potential for spatiotemporally controllable gene expression. We developed a nanoparticle drug delivery system to achieve tumor microenvironment-responsive and targeted delivery of DTA-encoded plasmids (pDTA) to tumor sites via dual targeting to cluster of differentiation-44 and α_vβ₃ receptors. In vivo studies indicated that the combination of pDTA and losartan reduce the concentration of collagen type I from 5.9 to 1.9 µg/g and decreased the level of active transforming growth factor-β by 75.0% in tumor tissues. Moreover, deeper tumor penetration was achieved, tumor growth was inhibited, and the survival rate was increased. Our combination strategy provides a novel and practical method for clinical treatment of breast cancer.