Propelling Minimally Invasive Tissue Regeneration With Next-Era Injectable Pre-Formed Scaffolds

The growing aging population, with its associated chronic diseases, underscores the urgency for effective tissue regeneration strategies. Biomaterials play a pivotal role in the realm of tissue reconstruction and regeneration, with a distinct shift toward minimally invasive (MI) treatments. This transition, fueled by engineered biomaterials, steers away from invasive surgical procedures to embrace approaches offering reduced trauma, accelerated recovery, and cost-effectiveness. In the realm of MI tissue repair and cargo delivery, various techniques are explored. While in situ polymerization is prominent, it is not without its challenges. This narrative review explores diverse biomaterials, fabrication methods, and biofunctionalization for injectable pre-formed scaffolds, focusing on their unique advantages. The injectable pre-formed scaffolds, exhibiting compressibility, controlled injection, and maintained mechanical integrity, emerge as promising alternative solutions to in situ polymerization challenges. The conclusion of this review emphasizes the importance of interdisciplinary design facilitated by synergizing fields of materials science, advanced 3D biomanufacturing, mechanobiological studies, and innovative approaches for effective MI tissue regeneration.

Enhanced localized therapeutic precision: A face-to-face folate-targeted Cu2+-mediated nanotherapy with thermosensitive sustained-release system

Safe and effective Cu2+ supplementation in local lesion is crucial for minimizing toxicity of DSF-based chemotherapy. Targeted delivery of Cu2+ appears more promising. Intraperitoneal chemotherapy for peritoneal carcinoma (PC) establishes "face-to-face" contact between targeted nanocarriers and tumor tissue. Herein, this study developed a biodegradable, injectable thermosensitive hydrogel that coencapsulating DSF submicroemulsion (DSF-SE) and folate-modified liposome loading glycyrrhizic acid-Cu (FCDL). FCDL acted as 'beneficial horse' to target the tumor-localized folate receptor, thus liberating Cu2+ in tumor nidus. The prepared FCDL and DSF-SE were found with uniform sizes (160.2 nm, 175.4 nm), low surface charge (-25.77 mV, -16.40 mV) and high encapsulation efficiency (97.93 %, 90.08 %). In vitro drug release profile of FCDL, DSF-SE and FCDL＆DSF-SE@G followed a sustained release pattern. And the release behavior of Cu2+ from FCDL was pH-related, i.e., Cu2+ was released faster under acidic condition. When FCDL and DSF-SE were loaded into an PLGA-PEG-PLGA-based hydrogel system, FCDL＆DSF-SE@G was formed to ensure separated delivery of Cu2+ and DSF in space but synchronized release over time. The rheology experiment showed a satisfactory gelling temperature of 32.7 °C. In vitro cytotoxicity study demonstrated that FCDL＆DSF-SE@G significantly lowered the IC50 of free Cu2+/DSF, Cu2+/DSF hydrogel and non-targeted analogue by almost 70 %, 65 % and 32 %, respectively. Accordingly, in tumor-bearing mice, FCDL＆DSF-SE@G augmented the tumor inhibition rates for the same formulations by 352 %, 145 % and 44 %, respectively. The main mechanism was attributed to higher uptake of FCDL and DSF-SE, resulting in increased Cu(DDTC)2 formation, ROS production and cell apoptosis. In conclusion, this targeted nanotherapy approach with dual-nanocarriers loaded hydrogel system, with its focus on face-to-face contact between nanocarriers and tumor tissues in the peritoneal cavity, holds significant promise for intraperitoneal chemotherapy in PC.

Recent advances on thermosensitive hydrogels-mediated precision therapy

Precision therapy has become the preferred choice attributed to the optimal drug concentration in target sites, increased therapeutic efficacy, and reduced adverse effects. Over the past few years, sprayable or injectable thermosensitive hydrogels have exhibited high therapeutic potential. These can be applied as cell-growing scaffolds or drug-releasing reservoirs by simply mixing in a free-flowing sol phase at room temperature. Inspired by their unique properties, thermosensitive hydrogels have been widely applied as drug delivery and treatment platforms for precision medicine. In this review, the state-of-the-art developments in thermosensitive hydrogels for precision therapy are investigated, which covers from the thermo-gelling mechanisms and main components to biomedical applications, including wound healing, anti-tumor activity, osteogenesis, and periodontal, sinonasal and ophthalmic diseases. The most promising applications and trends of thermosensitive hydrogels for precision therapy are also discussed in light of their unique features.

CPPs-modified chitosan as permeability-enhancing chemotherapeutic combined with gene therapy nanosystem by thermosensitive hydrogel for the treatment of osteosarcoma

BACKGROUND

Chemotherapy resistance of osteosarcoma (OS) is still the crux of poor clinical curative effect.E3 ubiquitin-protein ligase Rad18 (Rad18) contributed to doxorubicin resistance in OS, which ultimately mediated DNA damage tolerance and led to a poor prognosis and chemotherapy response in patients.

METHODS

In this study, doxorubicin was loaded in the process of Fe2+ and siRad18 forming nanoparticles(FSD) through coordination, chitosan modified with cell penetrating peptide (H6R6) was synthesized and coated on the surface of the NPs(FSD-CHR). FSD-CHR was then dispersed in thermosensitive hydrogel(PPP) for peritumoral injection of osteosarcoma in situ. Subsequently, the physicochemical properties and molecular biological characteristics of the drug delivery system were characterized. Finally, an osteosarcoma model was established to study the anti-tumor effects of multifunctional nanoparticles and the immunotherapy effect combined with αPD-L1.

RESULTS

FSD-CHR has enhanced tumor tissue permeability, siRad18 can significantly reduce Dox-mediated DNA damage tolerance and enhance anti-tumor effects, and iron-based NPs show enhanced ROS upregulation. FSD-CHR@PPP showed significant inhibition of osteosarcoma growth in vivo and a reduced incidence of lung metastasis. In addition, siRad18 was unexpectedly found to enhance Dox-mediated immunogenic cell death (ICD).FSD-CHR@PPP combined with PD-L1 blocking significantly enhanced anti-tumor effects due to decreased PD-L1 enrichment.

CONCLUSION

Hydrogel encapsulation of permeable nanoparticles provides an effective strategy for doxorubicin-resistant OS, showing that gene therapy blocking DNA damage tolerance can enhance treatment response to chemotherapy and appears to enhance the effect of ICD inducers to activate the immune system.

Liposome-integrated hydrogel hybrids: Promising platforms for cancer therapy and tissue regeneration

Drug delivery platforms have gracefully emerged as an indispensable component of novel cancer chemotherapy, bestowing targeted drug distribution, elevating therapeutic effects, and reducing the burden of unwanted side effects. In this context, hybrid delivery systems artfully harnessing the virtues of liposomes and hydrogels bring remarkable benefits, especially for localized cancer therapy, including intensified stability, excellent amenability to hydrophobic and hydrophilic medications, controlled liberation behavior, and appropriate mucoadhesion to mucopenetration shift. Moreover, three-dimensional biocompatible liposome-integrated hydrogel networks have attracted unprecedented interest in tissue regeneration, given their tunable architecture and physicochemical properties, as well as enhanced mechanical support. This review elucidates and presents cutting-edge developments in recruiting liposome-integrated hydrogel systems for cancer treatment and tissue regeneration.

Thermo-sensitive PLGA-PEG-PLGA hydrogel for sustained release of EGF to inhibit cervical cancer recurrence

Overexpression of epidermal growth factor receptor (EGFR) in cancer is a key cause of recurrence of cervical cancer (CC). Although the EGF-EGFR pathway has been studied for decades, preventing tumor growth and recurrence caused by peripheral EGF remains a great challenge. In this work, a strategy is proposed to reduce the stimulation of high concentration EGF on tumor growth by using a thermo-sensitive hydrogel. The hydrogel is a triblock copolymer composed of polyethylene glycol (PEG) and poly (lactide glycolide) (PLGA). Based on the excellent temperature sensitivity, carrier capacity, swelling property and biocompatibility, the hydrogel can absorb the liquid around the tumor by injection and release EGF continuously at low concentration. The inhibitory effect of hydrogel on tumor growth is fully confirmed by an implanted tumor mouse model with human cervical cancer cell lines (HeLa) using triple-immunodeficient NCG mice. Compared with free EGF, the EGF-loaded hydrogel can hardly induce surface plasmon resonance (SPR) response, which proves that hydrogel can effectively weaken cytoskeleton rearrangement and inhibit cell migration by continuously releasing low concentration EGF. In addition, the EGF-loaded hydrogel can reduce cell proliferation by delaying the progress of cell cycle progression. Taken together, the hydrogel can effectively protect tumor microenvironment from the stimulation of high concentration EGF, delay cancer cellular processes and tumor growth, and thus providing an approach for inhibiting tumor recurrence of CC.

Intratumoral Lactate Depletion Based on Injectable Nanoparticles-Hydrogel Composite System Synergizes with Immunotherapy against Postablative Hepatocellular Carcinoma Recurrence

Thermal ablation is a crucial therapeutic modality for hepatocellular carcinoma (HCC), but its efficacy is often hindered by the high recurrence rate attributed to insufficient ablation. Furthermore, the residual tumors following insufficient ablation exhibit a more pronounced immunosuppressive state, which accelerates the disease progression and leads to immune checkpoint blockade (ICB) resistance. Herein, evidence is presented that heightened intratumoral lactate accumulation, stemming from the augmented glycolytic activity of postablative residual HCC cells, may serve as a crucial driving force in exacerbating the immunosuppressive state of the tumor microenvironment (TME). To address this, an injectable nanoparticles-hydrogel composite system (LOX-MnO2 @Gel) is designed that gradually releases lactate oxidase (LOX)-loaded hollow mesoporous MnO2 nanoparticles at the tumor site to continuously deplete intratumoral lactate via a cascade catalytic reaction. Using subcutaneous and orthotopic HCC tumor-bearing mouse models, it is confirmed that LOX-MnO2 @Gel-mediated local lactate depletion can transform the immunosuppressive postablative TME into an immunocompetent one and synergizes with ICB therapy to significantly inhibit residual HCC growth and lung metastasis, thereby prolonging the survival of mice postablation. The work proposes an appealing strategy for synergistically combining antitumor metabolic therapy with immunotherapy to combat postablative HCC recurrence.

Complete Restoration of Hearing Loss and Cochlear Synaptopathy via Minimally Invasive, Single-Dose, and Controllable Middle Ear Delivery of Brain-Derived Neurotrophic Factor-Poly(dl-lactic acid-co-glycolic acid)-Loaded Hydrogel

Noise-induced hearing loss (NIHL) often accompanies cochlear synaptopathy, which can be potentially reversed to restore hearing. However, there has been little success in achieving complete recovery of sensorineural deafness using nearly noninvasive middle ear drug delivery before. Here, we present a study demonstrating the efficacy of a middle ear delivery system employing brain-derived neurotrophic factor (BDNF)-poly-(dl-lactic acid-co-glycolic acid) (PLGA)-loaded hydrogel in reversing synaptopathy and restoring hearing function in a mouse model with NIHL. The mouse model achieved using the single noise exposure (NE, 115 dBL, 4 h) exhibited an average 20 dBL elevation of hearing thresholds with intact cochlear hair cells but a loss of ribbon synapses as the primary cause of hearing impairment. We developed a BDNF-PLGA-loaded thermosensitive hydrogel, which was administered via a single controllable injection into the tympanic cavity of noise-exposed mice, allowing its presence in the middle ear for a duration of 2 weeks. This intervention resulted in complete restoration of NIHL at frequencies of click, 4, 8, 16, and 32 kHz. Moreover, the cochlear ribbon synapses exhibited significant recovery, whereas other cochlear components (hair cells and auditory nerves) remained unchanged. Additionally, the cochlea of NE treated mice revealed activation of tropomyosin receptor kinase B (TRKB) signaling upon exposure to BDNF. These findings demonstrate a controllable and minimally invasive therapeutic approach that utilizes a BDNF-PLGA-loaded hydrogel to restore NIHL by specifically repairing cochlear synaptopathy. This tailored middle ear delivery system holds great promise for achieving ideal clinical outcomes in the treatment of NIHL and cochlear synaptopathy.

Smart biodegradable hydrogels: Drug-delivery platforms for treatment of chronic ophthalmic diseases affecting the back of the eye

This paper aims to develop smart hydrogels based on functionalized hyaluronic acid (HA) and PLGA-PEG-PLGA (PLGA,poly-(DL-lactic-co-glycolic acid); PEG,polyethylene glycol) for use as intraocular drug-delivery platforms. Anti-inflammatory agent dexamethasone-phosphate (0.2 %w/v) was the drug selected to load on the hydrogels. Initially, different ratios of HA-aldehyde (HA-CHO) and thiolated-HA (HA-SH) were assayed, selecting as optimal concentrations 2 and 3 % (w/v), respectively. Optimized HA hydrogel formulations presented fast degradation (8 days) and drug release (91.46 ± 3.80 % in 24 h), thus being suitable for short-term intravitreal treatments. Different technology-based strategies were adopted to accelerate PLGA-PEG-PLGA water solubility, e.g. substituting PEG1500 in synthesis for higher molecular weight PEG3000 or adding cryopreserving substances to the buffer dissolution. PEG1500 was chosen to continue optimization and the final PLGA-PEG-PLGA hydrogels (PPP1500) were dissolved in trehalose or mannitol carbonate buffer. These presented more sustained release (71.77 ± 1.59 % and 73.41 ± 0.83 % in 24 h, respectively) and slower degradation (>14 days). In vitro cytotoxicity studies in the retinal-pigmented epithelial cell line (RPE-1) demonstrated good tolerance (viability values > 90 %). PLGA-PEG-PLGA hydrogels are proposed as suitable candidates for long-term intravitreal treatments. Preliminary wound healing studies with PLGA-PEG-PLGA hydrogels suggested faster proliferation at 8 h than controls.

Stimulus-Responsive Hydrogels as Drug Delivery Systems for Inflammation Targeted Therapy

Deregulated inflammations induced by various factors are one of the most common diseases in people's daily life, while severe inflammation can even lead to death. Thus, the efficient treatment of inflammation has always been the hot topic in the research of medicine. In the past decades, as a potential biomaterial, stimuli-responsive hydrogels have been a focus of attention for the inflammation treatment due to their excellent biocompatibility and design flexibility. Recently, thanks to the rapid development of nanotechnology and material science, more and more efforts have been made to develop safer, more personal and more effective hydrogels for the therapy of some frequent but tough inflammations such as sepsis, rheumatoid arthritis, osteoarthritis, periodontitis, and ulcerative colitis. Herein, from recent studies and articles, the conventional and emerging hydrogels in the delivery of anti-inflammatory drugs and the therapy for various inflammations are summarized. And their prospects of clinical translation and future development are also discussed in further detail.

Recent Advances of Multifunctional PLGA Nanocarriers in the Management of Triple-Negative Breast Cancer

Even though chemotherapy stands as a standard option in the therapy of TNBC, problems associated with it such as anemia, bone marrow suppression, immune suppression, toxic effects on healthy cells, and multi-drug resistance (MDR) can compromise their effects. Nanoparticles gained paramount importance in overcoming the limitations of conventional chemotherapy. Among the various options, nanotechnology has appeared as a promising path in preclinical and clinical studies for early diagnosis of primary tumors and metastases and destroying tumor cells. PLGA has been extensively studied amongst various materials used for the preparation of nanocarriers for anticancer drug delivery and adjuvant therapy because of their capability of higher encapsulation, easy surface functionalization, increased stability, protection of drugs from degradation versatility, biocompatibility, and biodegradability. Furthermore, this review also provides an overview of PLGA-based nanoparticles including hybrid nanoparticles such as the inorganic PLGA nanoparticles, lipid-coated PLGA nanoparticles, cell membrane-coated PLGA nanoparticles, hydrogels, exosomes, and nanofibers. The effects of all these systems in various in vitro and in vivo models of TNBC were explained thus pointing PLGA-based NPs as a strategy for the management of TNBC.

A thermosensitive gel matrix for bioreactor-assisted in-cell NMR of nucleic acids and proteins

Introducing the flow through the bioreactor has revolutionized in-cell NMR spectroscopy by prolonging the measurement time available to acquire spectral information about biomacromolecules in metabolically active cells. Bioreactor technology relies on immobilizer matrices, which secure cells in the active volume of the NMR coil and enable uniform perfusion of the growth medium, supplying fresh nutrients to the cells while removing toxic byproducts of their metabolism. The main drawbacks of commonly used matrices include the inability to recover intact cells post-measurement for additional analyses and/or requirements for specific operating temperatures. Here, we report on the development and characterization of a set of thermosensitive and nontoxic triblock copolymers based on poly(D,L-lactide)-b-poly(ethylene glycol)-b-poly(D,L-lactide) (PLA-PEG-PLA). Here, we show for the first time that these copolymers are suitable as immobilizer matrices for the acquisition of in-cell NMR spectra of nucleic acids and proteins over a commonly used sample temperature range of 15-40 °C and, importantly, allow recovery of cells after completion of in-cell NMR spectra acquisition. We compared the performances of currently used matrices in terms of cell viability (dye exclusion assays), cellular metabolism (1D 31P NMR), and quality of in-cell NMR spectra of two model biomacromolecules (hybrid double-stranded/i-motif DNA and ubiquitin). Our results demonstrate the suitability and advantages of PLA-PEG-PLA copolymers for application in bioreactor-assisted in-cell NMR.

Thermo-Responsive Hydrogels Coupled with Photothermal Agents for Biomedical Applications

Intelligent hydrogels are materials with abilities to change their chemical nature or physical structure in response to external stimuli showing promising potential in multitudinous applications. Especially, photo-thermo coupled responsive hydrogels that are prepared by encapsulating photothermal agents into thermo-responsive hydrogel matrix exhibit more attractive advantages in biomedical applications owing to their spatiotemporal control and precise therapy. This work summarizes the latest progress of the photo-thermo coupled responsive hydrogel in biomedical applications. Three major elements of the photo-thermo coupled responsive hydrogel, i.e., thermo-responsive hydrogel matrix, photothermal agents, and construction methods are introduced. Furthermore, the recent developments of these hydrogels for biomedical applications are described with some selected examples. Finally, the challenges and future perspectives for photo-thermo coupled responsive hydrogels are outlined.

A disulfiram/copper gluconate co-loaded bi-layered long-term drug delivery system for intraperitoneal treatment of peritoneal carcinomatosis

To develop a long-term drug delivery system for the treatment of primary and metastatic peritoneal carcinoma (PC) by intraperitoneal (IP) injection, a disulfiram (DSF)/copper gluconate (Cu-Glu)-co-loaded bi-layered poly (lactic acid-coglycolic acid) (PLGA) microspheres (Ms) - thermosensitive hydrogel system (DSF-Ms-Cu-Glu-Gel) was established. Rate and mechanisms of drug release from DSF-Ms-Cu-Glu-Gel were explored. The anti-tumor effects of DSF-Ms-Cu-Glu-Gel by IP injection were evaluated using H22 xenograft tumor model mice. The accumulative release of DSF from Ms on the 10th day was 83.79% without burst release. When Ms were dispersed into B-Gel, burst release at 24 h decreased to 14.63%. The results showed that bis (diethyldithiocarbamate)-copper (Cu(DDC)2) was formed in DSF-Ms-Cu-Glu-Gel and slowly released from B-Gel. In a pharmacodynamic study, the mount of tumor nodes and ascitic fluid decreased in the DSF-Ms-Cu-Glu-Gel group. This was because: (1) DSF-Ms-Cu-Glu-Gel system co-loaded DSF and Cu-Glu, and physically isolated DSF and Cu-Glu before injection to protect DSF; (2) space and water were provided for the formation of Cu(DDC)2; (3) could provide an effective drug concentration in the abdominal cavity for a long time; (4) both DSF and Cu(DDC)2 were effective anti-tumor drugs, and the formation of Cu(DDC)2 occurred in the abdominal cavity, which further enhanced the anti-tumor activity. Thus, the DSF-Ms-Cu-Glu-Gel system can be potentially used for the IP treatment of PC in the future.

Macro, Micro, and Nano-Inspired Bioactive Polymeric Biomaterials in Therapeutic, and Regenerative Orofacial Applications

Introducing dental polymers has accelerated biotechnological research, advancing tissue engineering, biomaterials development, and drug delivery. Polymers have been utilized effectively in dentistry to build dentures and orthodontic equipment and are key components in the composition of numerous restorative materials. Furthermore, dental polymers have the potential to be employed for medication administration and tissue regeneration. To analyze the influence of polymer-based investigations on practical medical trials, it is required to evaluate the research undertaken in this sector. The present review aims to gather evidence on polymer applications in dental, oral, and maxillofacial reconstruction.

Gemcitabine and rapamycin-loaded mixed polymeric thermogel for metastatic pancreatic cancer therapy

Pancreatic ductal adenocarcinoma (PDAC) is the 4th leading cause of cancer-related death and has a poor 5-year overall survival. The superior therapeutic benefits of combination or co-administration of drugs as intraperitoneal chemotherapy have increased interest in developing strategies to deliver chemotherapeutic agents to patients safely. In this study, we prepared a gel comprising the thermosensitive poly(lactide-co-glycolide)-b-poly(ethylene glycol)-b-poly(lactide-co-glycolide) (PLGA-PEG-PLGA) polymer and gemcitabine (GEM), which is currently used as the primary chemotherapy for PDAC and rapamycin (RAPA), a mammalian TOR (mTOR) inhibitor, to deliver the drug through intraperitoneal injection. We performed in vitro cytotoxicity experiments to verify the synergistic effects of the two drugs at different molar ratios and characterized the physicochemical properties of the GEM, RAPA, and GEM/RAPA-loaded thermosensitive PLGA-PEG-PLGA gels, hereafter referred to as (g(G), g(R), and g(GR)), respectively. The g(GR) comprising PLGA-PEG-PLGA polymer (25% w/v) and GEM and RAPA at a molar ratio of 11:1 showed synergism and was optimized. An in vitro cytotoxicity assay was performed by treating Panc-1-luc2 tumor spheroids with g(G), g(R), or g(GR). The g(GR) treatment group showed a 2.75-fold higher inhibition rate than the non-treated (NT) and vehicle-treated groups. Furthermore, in vivo drug release assay in mice by intraperitoneal injection of g(G), g(R), or g(GR) showed a more rapid release rate of GEM than RAPA, similar to the in vitro release pattern. The drugs in the gel were released faster in vivo than in vitro and degraded in 48 h. In addition, g(GR) showed the highest anti-tumor efficacy with no toxicity to mice. These results provide evidence for the safety and efficacy of g(GR) for intraperitoneal drug delivery. This study will assist in developing and clinically administering topical anti-cancer formulations.

Current advances in nanodrug delivery systems for malaria prevention and treatment

Malaria is a life-threatening, blood-borne disease with over two hundred million cases throughout the world and is more prevalent in Sub-Saharan Africa than anywhere else in the world. Over the years, several treatment agents have been developed for malaria; however, most of these active pharmaceutical ingredients exhibit poor aqueous solubility and low bioavailability and may result in drug-resistant parasites, thus increasing malaria cases and eventually, deaths. Factors such as these in therapeutics have led to a better appreciation of nanomaterials. The ability of nanomaterials to function as drug carriers with a high loading capacity and targeted drug delivery, good biocompatibility, and low toxicity renders them an appealing alternative to conventional therapy. Nanomaterials such as dendrimers and liposomes have been demonstrated to be capable of enhancing the efficacy of antimalarial drugs. This review discusses the recent development of nanomaterials and their benefits in drug delivery for the potential treatment of malaria.

Hydrogel Delivery of DNase I and Liposomal Vancomycin to Eradicate Fracture-related Methicillin-resistant Staphylococcus aureus Infection and Support Osteoporotic Fracture Healing

Fracture-related infection (FRI) is a devastating complication in orthopedic surgery. A recent study showed that FRI causes more severe infection and further delays healing in osteoporotic bone. Moreover, bacterial biofilm formed on implants cannot be eradicated by systemic antibiotics, warranting novel treatments. Here, we developed a DNase I and Vancomycin hydrogel delivery vehicle to eradicate Methicillin-resistant Staphylococcus aureus (MRSA) infection in vivo. Vancomycin was encapsulated in liposomes, and DNase I and Vancomycin/liposomal-Vancomycin was loaded on thermosensitive hydrogel. In vitro drug release test showed a burst release of DNase I (77.2%) within 72 hours and sustained release of Vancomycin (82.6%) up to day 14. The in vivo efficacy was evaluated in a clinically relevant ovariectomy (OVX) induced osteoporotic metaphyseal fracture model with MRSA infection, and a total of 120 Sprague Dawley rats were used. In the OVX with infection group, biofilm development caused a drastic inflammatory response, trabecular bone destruction, and non-union. In the DNase I and Vancomycin co-delivery hydrogel group (OVX-Inf-DVG), bacteria on bone and implant were eradicated. X-ray and micro-CT showed preservation of trabecular bone and bone union. HE staining showed the absence of inflammatory necrosis, and fracture healing was restored. The local elevation of TNF-α and IL-6 and increased number of osteoclasts were prevented in the OVX-Inf-DVG group. Our findings suggest that dual release of DNase I and Vancomycin initially followed by Vancomycin only later up to 14 days effectively eliminates MRSA infection, prevents biofilm development and provides a sterile environment to promote fracture healing in osteoporotic bone with FRI. STATEMENT OF SIGNIFICANCE: The biofilm formation on the implant is difficult to eradicate, causing recurrent infection and non-union in fracture-related infection (FRI). Here we developed a hydrogel therapy with high in vivo efficacy to eliminate MRSA biofilm infection in a clinically-relevant FRI model in osteoporotic bone. By loading DNase I and vancomycin/liposomal-vancomycin on thermosensitive poly-(DL-lactic acidco-glycolic acid) (PLGA)-polyethylene glycol (PEG)-PLGA hydrogel, a dual release of DNase I and Vancomycin was achieved whilst preserving enzyme activity. In this model, the progressive development of infection caused a drastic inflammatory response, osteoclastogenesis, trabecular bone destruction, and non-union of fracture. These pathological changes were successfully prevented by the dual delivery of DNase I and vancomycin. Our findings provide a promising strategy for FRI in osteoporotic bone.

A Physiologically Responsive Nanocomposite Hydrogel for Treatment of Head and Neck Squamous Cell Carcinoma via Proteolysis-Targeting Chimeras Enhanced Immunotherapy

Although immunotherapy has revolutionized oncotherapy, only ≈15% of head and neck squamous cell carcinoma (HNSCC) patients benefit from the current therapies. An immunosuppressive tumor microenvironment (TME) and dysregulation of the polycomb ring finger oncogene BMI1 are potential reasons for the failure. Herein, to promote immunotherapeutic efficacy against HNSCC, an injectable nanocomposite hydrogel is developed with a polymer framework (PLGA-PEG-PLGA) that is loaded with both imiquimod encapsulated CaCO₃ nanoparticles (RC) and cancer cell membrane (CCM)-coated mesoporous silica nanoparticles containing a peptide-based proteolysis-targeting chimeras (PROTAC) for BMI1 and paclitaxel (PepM@PacC). Upon injection, this nanocomposite hydrogel undergoes in situ gelation, after which it degrades in the TME over time, releasing RC and PepM@PacC nanoparticles to respectively perform immunotherapy and chemotherapy. Specifically, the RC particles selectively manipulate tumor-associated macrophages and dendritic cells to activate a T-cell immune response, while CCM-mediated homologous targeting and endocytosis delivers the PepM@PacC particles into cancer cells, where endogenous glutathione promotes disulfide bond cleavage to release the PROTAC peptide for BMI1 degradation and frees the paclitaxel from the particle pores to elicit apoptosis meanwhile enhance immunotherapy. Thus, the nanocomposite hydrogel, which is designed to exploit multiple known vulnerabilities of HNSCC, succeeds in suppressing both growth and metastasis of HNSCC.

The Role of Hydrogel in Cardiac Repair and Regeneration for Myocardial Infarction: Recent Advances and Future Perspectives

A myocardial infarction (MI) is the leading cause of morbidity and mortality, seriously threatens human health, and becomes a major health burden of our society. It is urgent to pursue effective therapeutic strategies for the regeneration and restore myocardial function after MI. This review discusses the role of hydrogel in cardiac repair and regeneration for MI. Hydrogel-based cardiac patches and injectable hydrogels are the most commonly used applications in cardiac regeneration medicine. With injectable hydrogels, bioactive compounds and cells can be delivered in situ, promoting in situ repair and regeneration, while hydrogel-based cardiac patches reduce myocardial wall stress, which passively inhibits ventricular expansion. Hydrogel-based cardiac patches work as mechanically supportive biomaterials. In cardiac regeneration medicine, clinical trials and commercial products are limited. Biomaterials, biochemistry, and biological actives, such as intelligent hydrogels and hydrogel-based exosome patches, which may serve as an effective treatment for MI in the future, are still under development. Further investigation of clinical feasibility is warranted. We can anticipate hydrogels having immense translational potential for cardiac regeneration in the near future.

The recent advancement in the PLGA-based thermo-sensitive hydrogel for smart drug delivery

To date, hydrogels have opened new prospects for potential applications for drug delivery. The thermo-sensitive hydrogels have the great potential to provide more effective and controllable release of therapeutic/bioactive agents in response to changes in temperature. PLGA is a safe FDA-approved copolymer with good biocompatibility and biodegradability. Recently, PLGA-based formulation have attracted a lot of interest for thermo-sensitive hydrogels. Thermo-sensitive PLGA-based hydrogels provide the delivery system with good spatial and temporal control, and have been widely applied in drug delivery. This review is focused on the recent progression of the thermo-sensitive and biodegradable PLGA-based hydrogels that have been reported for smart drug delivery to the different organs. Eventually, future perspectives and challenges of thermo-sensitive PLGA-based hydrogels are discussed briefly.

Research progress of hydrogels as delivery systems and scaffolds in the treatment of secondary spinal cord injury

Secondary spinal cord injury (SSCI) is the second stage of spinal cord injury (SCI) and involves vasculature derangement, immune response, inflammatory response, and glial scar formation. Bioactive additives, such as drugs and cells, have been widely used to inhibit the progression of secondary spinal cord injury. However, the delivery and long-term retention of these additives remain a problem to be solved. In recent years, hydrogels have attracted much attention as a popular delivery system for loading cells and drugs for secondary spinal cord injury therapy. After implantation into the site of spinal cord injury, hydrogels can deliver bioactive additives in situ and induce the unidirectional growth of nerve cells as scaffolds. In addition, physical and chemical methods can endow hydrogels with new functions. In this review, we summarize the current state of various hydrogel delivery systems for secondary spinal cord injury treatment. Moreover, functional modifications of these hydrogels for better therapeutic effects are also discussed to provide a comprehensive insight into the application of hydrogels in the treatment of secondary spinal cord injury.

PLGA-Based Nanomedicine: History of Advancement and Development in Clinical Applications of Multiple Diseases

Research on the use of biodegradable polymers for drug delivery has been ongoing since they were first used as bioresorbable surgical devices in the 1980s. For tissue engineering and drug delivery, biodegradable polymer poly-lactic-co-glycolic acid (PLGA) has shown enormous promise among all biomaterials. PLGA are a family of FDA-approved biodegradable polymers that are physically strong and highly biocompatible and have been extensively studied as delivery vehicles of drugs, proteins, and macromolecules such as DNA and RNA. PLGA has a wide range of erosion times and mechanical properties that can be modified. Many innovative platforms have been widely studied and created for the development of methods for the controlled delivery of PLGA. In this paper, the various manufacturing processes and characteristics that impact their breakdown and drug release are explored in depth. Besides different PLGA-based nanoparticles, preclinical and clinical applications for different diseases and the PLGA platform types and their scale-up issues will be discussed.

Silk-elastinlike protein-based hydrogels for drug delivery and embolization

Silk-Elastinlike Protein-Based Polymers (SELPs) can form thermoresponsive hydrogels that allow for the generation of in-situ drug delivery matrices. They are produced by recombinant techniques, enabling exact control of monomer sequence and polymer length. In aqueous solutions SELP strands form physical crosslinks as a function of temperature increase without the addition of crosslinking agents. Gelation kinetics, modulus of elasticity, pore size, drug release, biorecognition, and biodegradation of SELP hydrogels can be controlled by placement of amino acid residues at strategic locations in the polymer backbone. SELP hydrogels have been investigated for delivery of a variety of bioactive agents including small molecular weight drugs and fluorescent probes, oligomers of glycosaminoglycans, polymeric macromolecules, proteins, plasmid DNA, and viral gene delivery systems. In this review we provide a background for use of SELPs in matrix-mediated delivery and summarize recent investigations of SELP hydrogels for controlled delivery of bioactive agents as well as their use as liquid embolics.

Nanomaterials based on thermosensitive polymer in biomedical field

The progress of nanotechnology enables us to make use of the special properties of materials on the nanoscale and open up many new fields of biomedical research. Among them, thermosensitive nanomaterials stand out in many biomedical fields because of their “intelligent” behavior in response to temperature changes. However, this article mainly reviews the research progress of thermosensitive nanomaterials, which are popular in biomedical applications in recent years. Here, we simply classify the thermally responsive nanomaterials according to the types of polymers, focusing on the mechanisms of action and their advantages and potential. Finally, we deeply investigate the applications of thermosensitive nanomaterials in drug delivery, tissue engineering, sensing analysis, cell culture, 3D printing, and other fields and probe the current challenges and future development prospects of thermosensitive nanomaterials.

Intelligent Hydrogels in Myocardial Regeneration and Engineering

Myocardial infarction (MI) causes impaired cardiac function due to the loss of cardiomyocytes following an ischemic attack. Intelligent hydrogels offer promising solutions for post-MI cardiac tissue therapy to aid in structural support, contractility, and targeted drug therapy. Hydrogels are porous hydrophilic matrices used for biological scaffolding, and upon the careful alteration of ideal functional groups, the hydrogels respond to the chemistry of the surrounding microenvironment, resulting in intelligent hydrogels. This review delves into the perspectives of various intelligent hydrogels and evidence from successful models of hydrogel-assisted treatment strategies.

Intracranial In Situ Thermosensitive Hydrogel Delivery of Temozolomide Accomplished by PLGA–PEG–PLGA Triblock Copolymer Blending for GBM Treatment

Glioblastoma (GBM) recurrence after surgical excision has grown to be a formidable obstacle to conquer. In this research, biodegradable thermosensitive triblock copolymer, poly(D, L–lactic acid–co–glycolic acid)–b–poly(ethylene glycol)–b–poly(D, L–lactic acid–co–glycolic acid (PLGA–PEG–PLGA) was utilized as the drug delivery system, loading with micronized temozolomide(micro-TMZ) to form an in situ drug–gel depot inside the resection cavity. The rheology studies revealed the viscoelastic profile of hydrogel under various conditions. To examine the molecular characteristics that affect gelation temperature, ¹H–NMR, inverse gated decoupling ¹³C–NMR, and GPC were utilized. Cryo-SEM and XRD were intended to disclose the appearance of the hydrogel and the micro-TMZ existence state. We worked out how to blend polymers to modify the gelation point (T_gel) and fit the correlation between T_gel and other dependent variables using linear regression. To simulate hydrogel dissolution in cerebrospinal fluid, a membraneless dissolution approach was used. In vitro, micro-TMZ@PLGA–PEG–PLGA hydrogel exhibited Korsmeyer–Peppas and zero–order release kinetics in response to varying drug loading, and in vivo, it suppressed GBM recurrence at an astoundingly high rate. Micro-TMZ@PLGA–PEG–PLGA demonstrates a safer and more effective form of chemotherapy than intraperitoneal TMZ injection, resulting in a spectacular survival rate (40%, n = 10) that is much more than intraperitoneal TMZ injection (22%, n = 9). By proving the viability and efficacy of micro-TMZ@PLGA–PEG–PLGA hydrogel, our research established a novel chemotherapeutic strategy for treating GBM recurrence.

Amphiphilic Crosslinked Four-Armed Poly(lactic-co-glycolide) Electrospun Membranes for Enhancing Cell Adhesion

Common poly(lactide-co-glycolide) (i-PLGA) has emerged as a biodegradable and biocompatible material in tissue engineering. However, the poor hydrophilicity and elasticity of i-PLGA lead to its limited application in tissue engineering. To this end, an amphiphilic crosslinked four-armed poly(lactic-co-glycolide) was prepared. First, four-armed PLGA (4A-PLGA) was synthesized by polymerizing l-lactide (LA) and glycolide (GA) with pentaerythritol as the initiator. Then, the hydrophilic polymer poly(glutamate propylene ester) (PGPE) was prepared through the esterification of glutamic acid and 1,2-propanediol. The hydrophilic 4A-PLGA-PGPE was finally synthesized through the condensation reaction of 4A-PLGA and PGPE with the aid of triphosgene. 4A-PLGA-PGPE was then used to prepare amphiphilic membranes by electrospinning. It was demonstrated that the mechanical properties and biocompatibility of 4A-PLGA were improved after the introduction of PGPE. Furthermore, the introduction of glutamate improved the hydrophilicity of 4A-PLGA, thus effectively promoting cell entry and adhesion, which makes the electrospun 4A-PLGA-PGPE membranes promising for tissue engineering.

Investigating a Curcumin-Loaded PLGA-PEG-PLGA Thermo-Sensitive Hydrogel for the Prevention of Alzheimer’s Disease

In Alzheimer’s disease (AD), the most common cause of dementia, patients generally forget to take pills or skip medication due to side effects, affecting the treatment efficacy. In this study, we combined a poly(lactic-co-glycolic acid), (PLGA)-poly(ethylene glycol), and (PEG)-PLGA thermo-sensitive hydrogel with curcumin (PGC) to deliver an intramuscular injection that could continuously release curcumin and maintain it at a constant level in blood to prevent AD development or progression. We evaluated the drug release profile and cytotoxicity of PGC and its effects on AD pathology through in vitro and in vivo studies and on cognitive function through an aluminum-chloride-induced AD rat model. In the in vitro study, PGC exhibited a lack of cytotoxicity, excellent anti-inflammatory and antioxidant properties, and microglial modulation. In the Morris water maze test, the PGC injection-administered AD rats presented well-focused searching behavior with the shortest swimming path and longest retention times in the quadrant where the platform was initially located. Furthermore, PGC reduced amyloid-beta aggregation and deposition and significantly increased hippocampal activity. This study demonstrated that intramuscular PGC injection can effectively prevent AD development or progression in rats without inducing toxicity; therefore, this strategy could help overcome the present challenges in AD management in humans.

Improve endothelialization of metallic cardiovascular stent via femtosecond laser induced micro/nanostructure dependent cells proliferation and drug delivery control

Regarding restenosis occurrence risk after metallic stent deployment in artery, stents with vascular smooth muscle cells antiproliferative agents sustained released from poly(lactic-co-glycolic acid) (PLGA) coating and endothelial cells proliferation favored surface textures were both attempted for endothelialization enhancement. In order to explore the interaction between the surface texture and performance of drug loaded PLGA coating, femtosecond laser surface treatment was used to change the surface characteristics of 316L stainless steel. Two different surface patterns in form of stripe (FSL100) and isolated island-like structure (FSL800) were firstly generated by femtosecond laser processing with 100 and 800 mW energy, then Rapamycin loaded PLGA coating was further deposited to polished and femtosecond laser processed 316L surfaces via a dip-coating method. The subsequent drug loading capacity and release profile studies confirmed the roles of surface texture. Morphological transition characteristics of the PLGA coating on the FLS100 sample indicate that the coating has integrity during degradation compared to the polished one. Finally, rapamycin eluting FLS100 stent was deployed to iliac arteries of New Zealand White rabbits with vascular plaques to demonstrate its endothelialization potential and resistance to restenosis.

Drug Delivery Challenges and Current Progress in Nanocarrier-Based Ocular Therapeutic System

Drug instillation via a topical route is preferred since it is desirable and convenient due to the noninvasive and easy drug access to different segments of the eye for the treatment of ocular ailments. The low dose, rapid onset of action, low or no toxicity to the local tissues, and constrained systemic outreach are more prevalent in this route. The majority of ophthalmic preparations in the market are available as conventional eye drops, which rendered <5% of a drug instilled in the eye. The poor drug availability in ocular tissue may be attributed to the physiological barriers associated with the cornea, conjunctiva, lachrymal drainage, tear turnover, blood-retinal barrier, enzymatic drug degradation, and reflex action, thus impeding deeper drug penetration in the ocular cavity, including the posterior segment. The static barriers in the eye are composed of the sclera, cornea, retina, and blood-retinal barrier, whereas the dynamic barriers, referred to as the conjunctival and choroidal blood flow, tear dilution, and lymphatic clearance, critically impact the bioavailability of drugs. To circumvent such barriers, the rational design of the ocular therapeutic system indeed required enriching the drug holding time and the deeper permeation of the drug, which overall improve the bioavailability of the drug in the ocular tissue. This review provides a brief insight into the structural components of the eye as well as the therapeutic challenges and current developments in the arena of the ocular therapeutic system, based on novel drug delivery systems such as nanomicelles, nanoparticles (NPs), nanosuspensions, liposomes, in situ gel, dendrimers, contact lenses, implants, and microneedles. These nanotechnology platforms generously evolved to overwhelm the troubles associated with the physiological barriers in the ocular route. The controlled-drug-formulation-based strategic approach has considerable potential to enrich drug concentration in a specific area of the eye.

Novel nanocomposite scaffold based on gelatin/PLGA-PEG-PLGA hydrogels embedded with TGF-β1 for chondrogenic differentiation of human dental pulp stem cells in vitro

In the current study, a novel nanocomposite hydrogel scaffold comprising of natural-based gelatin and synthetic-based (poly D, L (lactide-co-glycolide) -b- poly (ethylene glycol)-b- poly D, L (lactide-co-glycolide) (PLGA-PEG-PLGA) triblock copolymer was developed and loaded with transforming growth factor- β1 (TGF-β1). Synthesized scaffolds' chemical structure was examined by ¹H NMR and ATR-FTIR. Scanning electron microscopy (SEM) confirmed particle size and morphology of the prepared nanoparticles as well as the scaffolds. The morphology analysis revealed a porous interconnected structure throughout the scaffold with a pore size dimension of about 202.05 µm. The swelling behavior, in vitro degradation, mechanical properties, density, and porosity were also evaluated. Phalloidin/DAPI staining was utilized for confirming the extended cytoskeleton of the chondrocytes. Alcian blue staining was conducted to determine cartilaginous matrix sulfated glycosaminoglycan (sGAG) synthesis. Eventually, over a period of 21 days, a real-time RT-PCR analysis was applied to measure the mRNA expression of chondrogenic marker genes, type-II collagen, SOX 9, and aggrecan, in hDPSCs cultured for up to 21 days to study the influence of gelatin/PLGA-PEG-PLGA-TGF-β1 hydrogels on hDPSCs. The findings of the cell-encapsulating hydrogels analysis suggested that the adhesion, viability, and chondrogenic differentiation of hDPSCs improved by gelatin/PLGA-PEG-PLGA-TGF-β1 nanocomposite hydrogels. These data supported the conclusion that gelatin/PLGA-PEG-PLGA-TGF-β1 nanocomposite hydrogels render the features that allow thein vitrofunctionality of encapsulated hDPSCs and hence can contribute the basis for new effective strategies for the treatment of cartilage injuries.

Light manipulation for fabrication of hydrogels and their biological applications

The development of biocompatible materials with desired functions is essential for tissue engineering and biomedical applications. Hydrogels prepared from these materials represent an important class of soft matter for mimicking extracellular environments. In particular, dynamic hydrogels with responsiveness to environments are quite appealing because they can match the dynamics of biological processes. Among the external stimuli that can trigger responsive hydrogels, light is considered as a clean stimulus with high spatiotemporal resolution, complete bioorthogonality, and fine tunability regarding its wavelength and intensity. Therefore, photoresponsiveness has been broadly encoded in hydrogels for biological applications. Moreover, light can be used to initiate gelation during the fabrication of biocompatible hydrogels. Here, we present a critical review of light manipulation tools for the fabrication of hydrogels and for the regulation of physicochemical properties and functions of photoresponsive hydrogels. The materials, photo-initiated chemical reactions, and new prospects for light-induced gelation are introduced in the former part, while mechanisms to render hydrogels photoresponsive and their biological applications are discussed in the latter part. Subsequently, the challenges and potential research directions in this area are discussed, followed by a brief conclusion. STATEMENT OF SIGNIFICANCE: Hydrogels play a vital role in the field of biomaterials owing to their water retention ability and biocompatibility. However, static hydrogels cannot meet the dynamic requirements of the biomedical field. As a stimulus with high spatiotemporal resolution, light is an ideal tool for both the fabrication and operation of hydrogels. In this review, light-induced hydrogelation and photoresponsive hydrogels are discussed in detail, and new prospects and emerging biological applications are described. To inspire more research studies in this promising area, the challenges and possible solutions are also presented.

In situ mucoadhesive hydrogel capturing tripeptide KPV: the anti-inflammatory, antibacterial and repairing effect on chemotherapy-induced oral mucositis

The self-healing of chemotherapy-induced oral mucositis is difficult in practice because of both local bacterial infection and severe inflammation. Herein, in situ mucoadhesive hydrogels (PPP_E) were successfully prepared by using temperature-sensitive PLGA-PEG-PLGA (PPP) as a matrix and epigallocatechin-3-gallate (EGCG) with inherent antibacterial activity as an adhesion enhancer. A series of PPP_E precursor solutions with various EGCG concentrations (1%, 2% and 5%) were prepared by fixing the PPP concentration at 25%. EGCG slightly decreased the sol-gel transition temperature and shortened the sol-gel transition time of the PPP hydrogel. Moreover, the incorporation of EGCG could significantly increase the tissue adhesion properties of the PPP hydrogel at 37 °C. PPP_2%E displayed a suitable gelation temperature (36.2 °C), gelation time (100 s) and storage modulus (48 Pa). Tripeptide KPV as a model drug was easily dissolved in cold PPP_2%E precursor solution to prepare KPV@PPP_2%E hydrogel. The anti-inflammatory activity and promotion of cell migration potential by KPV in PPP-2% E hydrogel were well maintained. Moreover, KPV@PPP_2%E exhibited strong antibacterial efficacy against S. aureus. PPP_2%E precursor solution rapidly transformed to a hydrogel and adhered to the wound surface for 7 hours when administrated to the gingival mucosa of rats. Treatment with KPV@PPP_2%E hydrogel greatly improved the food intake and body weight recovery of rats with chemotherapy-induced oral mucositis. Moreover, the tissue morphology of the ulcerated gingiva after application of KPV@PPP_E hydrogel was also well repaired by promoting CK10 and PCNA expression. In addition, the inflammatory cytokines including IL-1β and TNF-α were significantly inhibited by KPV@PPP_2%E hydrogel while IL-10 was up-regulated. KPV@PPP_2%E hydrogel also had an anti-bacterial effect on MRSA-infected gingival ulcer wounds, which resulted in the obvious inhibition of infiltration by inflammatory cells into submucosal tissues. Conclusively, KPV@PPP_E may be a promising practical application for cancer patients with chemotherapy-induced oral mucositis.

Combined chemotherapy for triple negative breast cancer treatment by paclitaxel and niclosamide nanocrystals loaded thermosensitive hydrogel

Triple negative breast cancer (TNBC) is the most dangerous subtype of breast cancer accompanying by unfavorable prognosis due to lack of specific therapeutic targets. Paclitaxel (PTX) is the first-line chemotherapeutic drug for TNBC and niclosamide (NLM) was identified as an inhibitor for TNBC and breast cancer stem cells (BCSCs). Intratumoral drug delivery system was a hopeful alternative for chemotherapeutic drug administration due to its targeting efficiency with lower systemic toxicity. Herein, an injectable PTX nanocrystals (PTX-NCs) and NLM nanocrystals (NLM-NCs) co-loaded PLGA-PEG-PLGA thermosensitive hydrogel (PNNCs-Ts Gel) was designed for TNBC intratumoral treatment. The final formulation realized high drug loading and appropriate particle size. PNNCs-Ts Gel displayed sustained drug release for up to 8 days in vitro. In vitro antitumor tests observed synergetic effects of combined therapy in terms of inhibiting cell proliferation and migration, inducing apoptosis. In vivo combined therapy presented a tumor growth inhibition rate about 68.8% and desired safety. Moreover, tumors after PNNCs-Ts Gel intratumoral injection possessed the lowest ratio of BCSCs, exhibiting this formulation had good ability in suppressing BCSCs and therefore could possibly prevent TNBC recurrence and metastasis. These results suggested that PNNCs-Ts Gel could be a promising strategy for TNBC treatment.

In situ subcutaneously injectable thermosensitive PEG-PLGA diblock and PLGA-PEG-PLGA triblock copolymer composite as sustained delivery of bispecific anti-CD3 scFv T-cell/anti-EGFR Fab Engager (BiTEE)

In this study, PEGylated poly (lactide-co-glycolide) (PLGA) thermosensitive composite hydrogels (DTgels) loaded with bispecific anti-cluster of differentiation 3 (CD3) scFv T-cell/anti-epidermal growth factor receptor (EGFR) Fab engager (BiTEE) were subcutaneously (s.c.) injected for the in situ formation of a drug deposit to resolve limitations of the clinical application of the BiTEE of a short half-life and potential side effects. Three kinds of DTgels prepared with different ratios of methoxy poly (ethylene glycol) (mPEG)-PLGA (diblock copolymer, DP) and PLGA-PEG-PLGA (triblock copolymer, TP) were designated DTgel-1, DTgel-2, and DTgel-2S. All three DTgel formulations showed thermosensitive properties with a sol-gel transition temperature at 28-34 °C, which is suitable for an injection. An in vitro release study showed that all DTgel formulations loaded with stabilized BiTEE extended the release of the BiTEE for up to 7 days. In an animal pharmacokinetics study, an s.c. injection of BiTEE/DTgel-1, BiTEE/DTgel-2, or BiTEE/DTgel-2S respectively prolonged the half-life of the BiTEE by 3.5-, 2.0-, and 2.2-fold compared to an intravenous injection of the BiTEE solution. Simultaneously, BiTEE/DTgel formulations showed almost no proinflammatory cytokine release in mice injected with T cells after s.c. administration. Results of an animal antitumor (MDA-MB-231) study indicated that an s.c. injection of the BiTEE/DTgel formulations significantly improved the antitumor efficacy compared to an intravenous (i.v.) or s.c. injection of the BiTEE solution. Moreover, BiTEE/DTgel formulations led to enhanced T-cell recruitment to solid-tumor sites. In conclusion, the in situ formation of injectable PEGylated PLGA thermosensitive hydrogels loaded with the BiTEE was successfully carried out to increase its half-life, maintain a constant blood level within therapeutic windows, and enhance T-cell recruitment to solid-tumor sites resulting in exceptional treatment efficacy.

Nano-Particulated Erlotinib Compound System in Alleviation of Lung Cancer

To produce an effective nanoparticle-loaded delivery system for the tumor drug erlotinib for non-small cell lung cancer (NSCLC) therapy, we loaded poly(lactic co glycolic acid) (PLGA) nanoparticles with erlotinib and used them to transport the drug to a target area. NCI-H1650 cells were cultured to test the permeability, efficiency, and anti-tumor capacity of PLGA and polyethyleneimine (PEI) drug delivery systems, and an NSCLC mouse model was prepared to further test the anti-tumor efficiency of PLGA. In tests using NCI-H1650 cells, we found that PLGA could effectively transport erlotinib into tumor cells, and release the loaded drug instantly. The infiltration efficiency was significantly higher than that of the PEI delivery system, and the same results were obtained in animal tests. PLGA-erlotinib could promote apoptosis and inhibit the migration of tumor cells more effectively than PEI-erlotinib. In the NSCLC mouse model, PLGA could more effectively reduce the tumor volume and the extent of tumor markers than the PEI delivery system. Immune function was also better rescued with the use of the PLGA system. We concluded that PLGA-erlotinib may be a good choice for lung cancer therapy in the future.

Hydrolysis-Driven Viscoelastic Transition in Triblock Copolyether Hydrogels with Acetal Pendants

While the hydrolytic cleavage of ester groups is widely exploited in degradable hydrogels, the scission in the midst of chain backbones can bring dramatic changes in the mechanical properties of the hydrogels. However, the predictive design of the mechanical profile of the hydrogels is a complex task, mainly due to the randomness of the location of chain scission. To overcome this challenge, we herein present degradable ABA triblock poly(ethylene oxide)-based hydrogels containing an A-block bearing acetal pendant, which provides systematically tunable mechano-temporal properties of the hydrogels. In particular, hydrophobic endocyclic tetrahydropyranyl or exocyclic 1-(cyclohexyloxy)ethyl acetal pendants are gradually cleaved by acidic hydrolysis, leading to the gel-to-sol transition at room temperature. Most importantly, a series of dynamic mechanical analyses coupled with ex situ NMR spectroscopy revealed that the hydrolysis rate can be orthogonally and precisely tuned by changing the chemical structure and hydrophobicity of acetal pendants. This study provides a platform for the development of versatile degradable hydrogels in a highly controllable manner.

Thermosensitive polymer hydrogel as a physical shield on colonic mucosa for colitis treatment

Inflammatory bowel disease (IBD), including Crohn's disease and ulcerative colitis (UC), is a chronic disease characterized by diffuse mucosal inflammation limited to the colon. Topical drug delivery systems that could be facilely performed and efficiently retained at colon sites are attractive for clinical IBD treatment. Herein, we report the exploration of an injectable thermosensitive copolymer hydrogel as a topical formulation for IBD treatment and demonstrate its feasibility in UC treatment by shielding ulcer sites from the external environment and being a drug reservoir for sustained release. Poly(aliphatic ester)-based triblock copolymer, poly(dl-lactic acid)-poly(ethylene glycol)-poly(dl-lactic acid) (PDLLA-PEG-PDLLA), adopts the solution state at room temperature yet a gel state at body temperature when the polymer concentration is more than 11%. The gel acts not only as a physical mucosal barrier for protecting ulcer sites from microorganisms like bacteria but also as a mesalazine depot for enhanced drug retention in the colon for localized, sustained drug release. In vivo UC treatment reveals that blank gel as a mucosal protector shows nearly the same treatment effect to mesalazine SR granules. Mesalazine-loaded gel significantly suppresses inflammation and has the best outcomes of indices such as colonic length, mucosal injury index, pathological tissue, and inflammatory factor. The injectable thermosensitive polymer hydrogel represents a novel, robust platform for the efficient treatment of IBD by acting as a physical shield to block out the pro-inflammatory factors as well as a drug depot for enhanced drug retention and controlled delivery.

(Macro)molecular self-assembly for hydrogel drug delivery

Hydrogels prepared via self-assembly offer scalable and tunable platforms for drug delivery applications. Molecular-scale self-assembly leverages an interplay of attractive and repulsive forces; drugs and other active molecules can be incorporated into such materials by partitioning in hydrophobic domains, affinity-mediated binding, or covalent integration. Peptides have been widely used as building blocks for self-assembly due to facile synthesis, ease of modification with bioactive molecules, and precise molecular-scale control over material properties through tunable interactions. Additional opportunities are manifest in stimuli-responsive self-assembly for more precise drug action. Hydrogels can likewise be fabricated from macromolecular self-assembly, with both synthetic polymers and biopolymers used to prepare materials with controlled mechanical properties and tunable drug release. These include clinical approaches for solubilization and delivery of hydrophobic drugs. To further enhance mechanical properties of hydrogels prepared through self-assembly, recent work has integrated self-assembly motifs with polymeric networks. For example, double-network hydrogels capture the beneficial properties of both self-assembled and covalent networks. The expanding ability to fabricate complex and precise materials, coupled with an improved understanding of biology, will lead to new classes of hydrogels specifically tailored for drug delivery applications.

Thermo-Responsive PLGA-PEG-PLGA Hydrogels as Novel Injectable Platforms for Neuroprotective Combined Therapies in the Treatment of Retinal Degenerative Diseases

The present study aims to develop a thermo-responsive-injectable hydrogel (HyG) based on PLGA-PEG-PLGA (PLGA = poly-(DL-lactic acid co-glycolic acid); PEG = polyethylene glycol) to deliver neuroprotective agents to the retina over time. Two PLGA-PEG PLGA copolymers with different PEG:LA:GA ratios (1:1.54:23.1 and 1:2.25:22.5) for HyG-1 and HyG-2 development respectively were synthetized and characterized by different techniques (gel permeation chromatography (GPC), nuclear magnetic resonance (NMR), dynamic light scattering (DLS), critical micelle concentration (CMC), gelation and rheological behaviour). According to the physicochemical characterization, HyG-1 was selected for further studies and loaded with anti-inflammatory drugs: dexamethasone (0.2%), and ketorolac (0.5%), alone or in combination with the antioxidants idebenone (1 µM) and D-α-Tocopherol polyethylene glycol 1000 succinate (TPGS) (0.002%). In vitro drug release and cytotoxicity studies were performed for the active substances and hydrogels (loaded and drug-free). A cellular model based on oxidative stress was optimized for anti-inflammatory and antioxidant screening of the formulations by using retinal-pigmented epithelial cell line hTERT (RPE-1). The copolymer 1, used to prepare thermo-responsive HyG-1, showed low polydispersity (PDI = 1.22) and a strong gel behaviour at 25% (w/v) in an isotonic buffer solution close to the vitreous temperature (31-34 °C). Sustained release of dexamethasone and ketorolac was achieved between 47 and 62 days, depending on the composition. HyG-1 was well tolerated (84.5 ± 3.2%) in retinal cells, with values near 100% when the anti-inflammatory and antioxidant agents were included. The combination of idebenone and dexamethasone promoted high oxidative protection in the cells exposed to H2O2, with viability values of 86.2 ± 14.7%. Ketorolac and dexamethasone-based formulations ameliorated the production of TNF-α, showing significant results (p ≤ 0.0001). The hydrogels developed in the present study entail a novel biodegradable tool to treat neurodegenerative processes of the retina overtime.

Controlled release of baricitinib from a thermos-responsive hydrogel system inhibits inflammation by suppressing JAK2/STAT3 pathway in acute spinal cord injury

Aggressive inflammation is an important pathological process of secondary injury in acute spinal cord injury (SCI). However, traditional treatments of secondary injury in acute SCI have achieved little success. Novel biomaterials combined with small molecule drugs are considered as a potential treatment for SCI. Baricitinib, a highly selective JAK1/JAK2 inhibitor, can effectively inhibit the JAK2/STAT3 pathway involved in the modulation of inflammation. However, to evaluate Baricitinib's therapeutic effect on SCI remains to be confirmed. In this study, we designed an injectable PLGA-PEG-PLGA thermos-sensitive hydrogel with baricitinib (Bari-P hydrogel) and measured its efficacy, physical and biological properties in vitro. In the SCI rat, Bari-P hydrogel was injected into the injured spinal cord. Neuronal regeneration was evaluated at 3 days and 4 weeks after surgery by determining the inflammatory cytokine levels, behavioral tests, and histological analysis. The hydrogel can gel in the body, disintegrate almost within 72 h and achieve drug release. Baricitinib can effectively inhibit the JAK2/STAT3 pathway of microglia in vitro; while in vivo experiments show that Bari-P hydrogel treatment can inhibit the phosphorylation of JAK2, STAT3 and suppress the production of inflammatory cytokines, and reduces neuronal apoptosis. Histopathological analysis and behavioral tests showed that Bari-P hydrogel reduced neuronal apoptosis in the early stage of injury and later promoted functional recovery. In summary, Bari-P hydrogel reduced neuronal apoptosis and promoted functional recovery in spinal cord injured rats by inhibiting the JAK2-STAT3 pathway and controlling the expression of inflammatory cytokines in the early stages of injury.

Synthesis and characterization of PLGA-PEG-PLGA based thermosensitive polyurethane micelles for potential drug delivery

Polyurethane nanomicelle is a promising functional drug delivery system. In this work, the polyurethane (P3-PU) was synthesized from PLGA₁₂₀₀-PEG₁₄₅₀-PLGA₁₂₀₀ (P3, a thermosensitive and biodegradable triblock copolymer) and L-lysine ester diisocyanate (LDI). Then, reactive benzaldehyde was further imported to terminate P3-PU to obtain benzaldehyde modified polyurethane (P3-PUDA). The micelles, temperature-sensitive P3-PU nanomicelle and P3-PUDA nanomicelle, were systematically investigated, including the size, stability, temperature sensitivity, drug loading and release behavior, cytotoxic on human hepatocytes (L02), and inhibitory effect on human hepatocellular carcinoma cells (HepG2). The results show the thermosensitive behavior of the micelles can be adjusted by the terminal group. The polyurethane micelles with a uniform size between 20 nm and 30 nm showed excellent stability and good biocompatibility to L02 cells. Besides, in vitro experiments showed that Dox-loaded P3-PUDA micelles exhibited faster and higher release rate at 37 °C and better inhibitory effect on HepG2 than the Dox-loaded P3-PU micelles. Moreover, the achieved benzaldehyde modified polyurethanes also provides various possibilities to adjust further to enlarge its applications. Therefore, the polyurethane micelles will have great potential in the field of drug carriers.

Supramolecular thermogels from branched PCL-containing polyurethanes

Thermogels are temperature-responsive hydrogels which are most commonly formed by supramolecular self-assembly of polymer amphiphiles comprising of both hydrophobic and hydrophilic segments. Although polyurethane thermogels have shown great promise as biomaterials, their synthesis by step-growth polymerisation of diols and diisocyanates can also result in formation of allophanate branches, which arise from the reaction between free isocyanate groups and urethane linkages along the polymer backbone. In this paper, we investigate the effects of different synthetic conditions on the degree of allophanate branching on polyurethane amphiphiles, and explore the influences of these branches on the polymers' critical micelle concentration (CMC), thermodynamics of micellization and subsequent thermogel properties. Our findings offer new insights into the relationship between polymer structure, micelle and gel properties. These results highlight the importance of taking polymer branching into account for understanding the hierarchical self-assembly of polymer amphiphiles and the resulting thermogel properties and behaviour.

In vivo biocompatibility and efficacy of dexamethasone-loaded PLGA-PEG-PLGA thermogel in an alkali-burn induced corneal neovascularization disease model

Challenges of ophthalmic drug delivery arise not only from the limited solubility of hydrophobic therapeutics, but also the restricted permeability and fast clearance of drugs due to the complex anatomy and physiology of eyes. Excellent biocompatibility of a thermosensitive polymer, PLGA-PEG-PLGA (1800-1500-1800, LA:GA ratio = 3:1), as an ophthalmic delivery system was demonstrated in our previous work. In this study, delivery of dexamethasone using this thermogel via a single subconjunctival injection for prolonged treatment was evaluated with corneal neovascularization using an alkali-burn diseased model in rat. Solubility of dexamethasone in the polymeric solution was increased by 5.2-fold and the resulting drug-loaded solution formed in situ rigid gel at body temperature. Prolonged in vitro release of dexamethasone from the gel structure was noted. Dexamethasone gel formulation was demonstrated to be more effective in reducing the burn stimulus and neovascularization in the rat diseased model. The findings suggest the PLGA-PEG-PLGA in situ gelling system can be applied for ophthalmic drug delivery to achieve sustained drug release and improved efficacy.

In Situ Forming Injectable Thermoresponsive Hydrogels for Controlled Delivery of Biomacromolecules

Due to their relatively large molecular sizes and delicate nature, biologic drugs such as peptides, proteins, and antibodies often require high and repeated dosing, which can cause undesired side effects and physical discomfort in patients and render many therapies inordinately expensive. To enhance the efficacy of biologic drugs, they could be encapsulated into polymeric hydrogel formulations to preserve their stability and help tune their release in the body to their most favorable profile of action for a given therapy. In this study, a series of injectable, thermoresponsive hydrogel formulations were evaluated as controlled delivery systems for various peptides and proteins, including insulin, Merck proprietary peptides (glucagon-like peptide analogue and modified insulin analogue), bovine serum albumin, and immunoglobulin G. These hydrogels were prepared using concentrated solutions of poly(lactide-co-glycolide)-block-poly(ethylene glycol)-block-poly(lactide-co-glycolide) (PLGA-PEG-PLGA), which can undergo temperature-induced sol-gel transitions and spontaneously solidify into hydrogels near the body temperature, serving as an in situ depot for sustained drug release. The thermoresponsiveness and gelation properties of these triblock copolymers were characterized by dynamic light scattering (DLS) and oscillatory rheology, respectively. The impact of different hydrogel-forming polymers on release kinetics was systematically investigated based on their hydrophobicity (LA/GA ratios), polymer concentrations (20, 25, and 30%), and phase stability. These hydrogels were able to release active peptides and proteins in a controlled manner from 4 to 35 days, depending on the polymer concentration, solubility nature, and molecular sizes of the cargoes. Biophysical studies via size exclusion chromatography (SEC) and circular dichroism (CD) indicated that the encapsulation and release did not adversely affect the protein conformation and stability. Finally, a selected PLGA-PEG-PLGA hydrogel system was further investigated by the encapsulation of a therapeutic glucagon-like peptide analogue and a modified insulin peptide analogue in diabetic mouse and minipig models for studies of glucose-lowering efficacy and pharmacokinetics, where superior sustained peptide release profiles and long-lasting glucose-lowering effects were observed in vivo without any significant tolerability issues compared to peptide solution controls. These results suggest the promise of developing injectable thermoresponsive hydrogel formulations for the tunable release of protein therapeutics to improve patient's comfort, convenience, and compliance.