Thermosensitive sol–gel reversible hydrogels

Nitric Oxide-Photodelivering Materials with Multiple Functionalities: From Rational Design to Therapeutic Applications

The achievement of materials that are able to release therapeutic agents under the control of light stimuli to improve therapeutic efficacy is a significant challenge in health care. Nitric oxide (NO) is one of the most studied molecules in the fascinating realm of biomedical sciences, not only for its crucial role as a gaseous signaling molecule in the human body but also for its great potential as an unconventional therapeutic in a variety of diseases including cancer, bacterial and viral infections, and neurodegeneration. Handling difficulties due to its gaseous nature, reduced region of action due to its short half-life, and strict dependence of the biological effects on its concentration and generation site are critical questions to be solved for appropriate therapeutic uses of NO. Light-activatable NO precursors, namely, NO photodonors (NOPDs), address the above issues since they are stable in the dark and permit in a noninvasive fashion the remote-controlled delivery of NO on demand with great spatiotemporal precision. Engineering biocompatible materials with NOPDs and their combination with additional imaging, therapeutic, and phototherapeutic components leads to intriguing light-responsive multifunctional constructs exhibiting promising potential for biomedical applications. This contribution illustrates the most significant progress made over the last five years in achieving engineered materials including nanoparticles, gels, and thin films, sharing the common feature to deliver NO under the exclusive control of the biocompatible visible/near infrared light inputs. We will highlight the logical design behind the fabrication of these systems, illustrating the potential therapeutic applications with particular emphasis on cancer and bacterial infections.

Tricalcium phosphate-loaded injectable hydrogel as a promising osteogenic and bactericidal teicoplanin-delivery system for osteomyelitis treatment: An in vitro and in vivo investigation

Osteomyelitis is an inflammation of bone tissue usually caused by pyogenic bacteria. The most recurrent clinical approach consists of bone debridement followed by parenteral administration of antibiotics. However, systemic antibiotic treatment has limitations regarding absorption rate and bioavailability over time. The main challenge of osteomyelitis treatment consists of coupling the persistent infection treatment with the regeneration of the bone debrided. In this work, we developed an injectable drug delivery system based on poloxamer 407 hydrogel containing undoped Mg, Zn-doped tricalcium phosphate (β-TCP), and teicoplanin, a broad-spectrum antibiotic. We evaluated how the addition of teicoplanin and β-TCP affected the micellization, gelation, particle size, and surface charge of the hydrogel. Later, we studied the hydrogel degradation and drug delivery kinetics. Finally, the bactericidal, biocompatibility, and osteogenic properties were evaluated through in vitro studies and confirmed by in vivo Wistar rat models. Teicoplanin was found to be encapsulated in the corona portions of the hydrogel micelles, yielding a bigger hydrodynamics radius. The encapsulated teicoplanin showed a sustained release over the evaluated period, enough to trigger antibacterial properties against Gram-positive bacteria. Besides, the formulations were biocompatible and showed bone healing ability and osteogenic properties. Finally, in vivo studies confirmed that the proposed locally injected formulations yielded osteomyelitis treatment with superior outcomes than parenteral administration while promoting bone regeneration. In conclusion, the presented formulations are promising drug delivery systems for osteomyelitis treatment and deserve further technological improvements.

Corticosteroid-loaded chitosan-based in-situ forming gel combined with microneedle technology for improvement of burn eschar wound healing

Burn is one of the most common skin injuries and accounts for 300,000 deaths annually. Debridement and antibiotic therapy are major burn treatments, however, as debridement is not always possible and many drugs have poor penetration into necrotic tissue, permeation enhancement is acquired. Another challenge is the short duration of topically applied drugs. This study aims to address both problems by combining in-situ forming gels and microneedles. A chitosan-based in-situ forming gel of hydrocortisone was applied to human burn eschar using microneedles. The formulation was optimized using Design-Expert software. Formulation characterization was done in terms of gelling time and temperature, thermal analysis, release phenomenon, rheology, texture analysis, and stability. Finally, animal studies on mice burn wound treatment were conducted. Results showed that optimized formulation controlled the drug release, and wherever microneedle was used, drug permeation and flux increased (P-value < 0.05). In all ex-vivo and in-vivo stages, gel plus microneedle (length of 1.5 mm and application mode of 2) produced the best results concerning increased flux and faster recovery of burn eschar. In conclusion, the in-situ forming gel with appropriate texture, quality, and stability in combination with microneedle can be a good candidate for the controlled release of drugs in third-degree burn eschars.

Moxifloxacin HCl -loaded Cellulose Acetate Butylate In Situ Forming Gel for Periodontitis Treatment

Periodontitis presents significant treatment challenges due to its complexity and potential complications. In response, an in situ forming gel (ISG) loaded with moxifloxacin HCl (Mx) and cellulose acetate butyrate (CAB) was developed for targeted periodontitis therapy. Mx-loaded 10-45% CAB-based ISGs were developed, and their physicochemical properties such as rheology, viscosity, contact angle, gel morphology and gel formation, interface interaction were investigated. Moreover, the formulation performance studies including drug release and kinetics, in vitro degradation, and antimicrobial activities were also evaluated. The Mx-loaded ISGs containing 25-45% CAB demonstrated rapid matrix formation in both macroscopic and microscopic examinations and presented plastic deformation matrix. Tracking with sodium fluorescein and Nile red fluorescence probes indicated delayed solvent movement owing to CAB matrix formation. Adequate CAB content sustained Mx release for one week, following Peppas-Sahlin model and indicating a predominantly Fickian diffusion mechanism. Higher CAB content likely contributed to a denser matrix structure, leading to a slower in vitro degradation rate. Synchrotron radiation X-ray tomographic and SEM imaging provided insights into the CAB matrix structure and porous network formation. These ISG formulations effectively inhibited Staphylococcus aureus, Escherichia coli, Candida albicans, and Porphyromonas gingivalis. The Mx-loaded 40% CAB-based ISG shows promise as a dosage form for treating periodontitis. Further clinical trials are necessary to ensure the safety of this new ISG formulation, despite existing safety data for other medicinal uses of CAB. HIGHLIGHTS: Moxifloxacin HCl-loaded 10-45% cellulose acetate butyrate (CAB)-based in situ forming gels (ISG) were developed. They were evaluated for physicochemical properties, drug release, in vitro degradation, and antimicrobial activities. ISGs with 25-45% CAB showed swift matrix formation and plastic deformation Adequate CAB content sustained Mx release with Fickian diffusion mechanism They promise for periodontitis treatment because of effective inhibition of related pathogens.

Preparation of a minocycline polymer micelle thermosensitive gel and its application in spinal cord injury

Neuroprotection is an important approach for the treatment of spinal cord injury (SCI). Minocycline (MC), a known neuroprotective agent, has been utilized for SCI treatment, but its therapeutic effect is limited by instability and low bioavailability. Herein, we developed an innovative micellar thermosensitive hydrogel (MCPP-M-gel) that encapsulates MC in polyethylene glycol (PEG)-poly(lactide-co-glycolic acid) (PLGA) micelles to enhance its therapeutic efficacy in a rat model of SCI. The micelles were synthesized via the thin-film hydration method and characterized for encapsulation efficiency, particle size, zeta potential, and polydispersity index (PDI). MCPP-M-gel demonstrated favorable physico-mechanical properties and extended MC release over 72 hours in vitro without cytotoxic effects on neural crest-derived ectoderm mesenchymal stem cells (EMSCs). Thereafter, MC, MCPP-M, MCPP-M-gel and a blank micellar thermosensitive gel were injected into the injured site of SCI rats. Histopathological evaluation demonstrated that MCPP-M-gel could promote neuronal regeneration at the injured site of the SC after 28 days. Immunofluorescence techniques revealed that MCPP-M-gel increased the expression of neuronal class III β-tubulin (Tuj1), myelin basic protein (MBP), growth-associated protein 43 (GAP43), neurofilament protein-200 (NF-200) and nestin as well as reduced glial-fibrillary acidic protein (GFAP) expression in damaged areas of the SC. In conclusion, this study innovatively developed MCPP-M-gel based on a PEG-PLGA copolymer as a biomaterial, laying a solid foundation for further research and application of MCPP-M-gel in SCI models or other neurodegenerative diseases.

Single-Component Cellulose Acetate Sulfate Hydrogels for Direct Ink Writing 3D Printing

Hydrogels, typically favored for 3D printing due to their viscoelasticity, are now trending toward ecofriendly alternatives amid growing environmental concerns. In this study, we crafted cellulose-based hydrogels, specifically employing cellulose acetate sulfate (CAS). By keeping the acetyl group substitution degree (DSacetyl = 1.8) and CAS molecular weight constant, we varied rheological properties by adjusting sulfate group substitution (DSsulfate = 0.4, 0.7, and 1.0) and CAS concentration (2-5 wt %). Rheological characterizations, including shear-thinning, yield stress, and thixotropy, were performed to identify optimal conditions for formulating CAS hydrogel ink in direct ink writing for 3D printing under selected experimental conditions. Based on rheological findings, CAS hydrogels with DSsulfate 0.7 and concentration of 4 wt % was used for 3D printing, with subsequent evaluation of printing metrics. Additionally, the effect of ionic cross-linking using Ca2+ ions on the structural integrity of 3D-printed structures was evaluated, demonstrating effective preservation through reinforced polymer networks. The shrinking and swelling behaviors of the 3D-printed structures were also significantly affected by this ionic cross-linking. Building on these findings, this work could broaden the range of cellulose derivatives available for the preparation of cellulose-based hydrogels for 3D printing.

An Injectable Thermosensitive Hydrogel with Antibacterial and Antioxidation Properties for Accelerating Wound Healing

As a new type of wound dressing, hydrogels have attracted more and more attention. However, traditional hydrogel wound dressings lack inherent antibacterial properties and are difficult to match irregular wounds, which leads to an easy wound bacterial infection. To solve the problems associated with traditional hydrogels, in this research, a thermosensitive hydrogel (PFLD) for wound dressings was developed based on Poloxamer 407 (PF127), lysine (Lys), and 3,4-dihydroxyphenylacetic acid (DOPAC). Rheological tests indicated that the PFLD hydrogel possesses injectability, adaptability to deformation, and sufficient mechanical strength for wound dressing applications. In addition, it could in situ gel at 33 °C, which indicated that the hydrogel could undergo sol-to-gel transition under body temperature. Upon using it in wound treatment, it could adapt to irregular wounds to achieve full coverage of the wound and promote the rapid hemostasis of wound bleeding. Due to the presence of DOPAC in the hydrogel, it exhibited excellent antibacterial and antioxidant properties on the wounds. The skin defect model showed that the wound shrinkage was the fastest after PFLD hydrogel treatment. On day 14, the wound shrinkage rates were 81.68 and 99.77% for the control and PFLD hydrogel groups, respectively. Therefore, the PFLD hydrogel has a broad application prospect as a dressing for the treatment of irregular wounds.

Lidocaine HCl-Loaded Polyelectrolyte Complex -Poloxamer Thermoresponsive Hydrogel: In Vitro- In Vivo Anesthetic Evaluations for Tooth Socket Wound Delivery

Local anesthesia is essential in dental practices, particularly for managing pain in tooth socket wounds, yet improving drug delivery systems remains a significant challenge. This study explored the physicochemical characteristics of lidocaine hydrochloride (LH) incorporated into a polyelectrolyte complex and poloxamer thermosensitivity hydrogel, assessing its local anesthetic efficacy in mouse models and its onset and duration of action as topical anesthetics in clinical trials. The thermoresponsive hydrogel exhibited a rapid phase transition within 1-3 minutes and demonstrated pseudo-plastic flow behavior. Its release kinetics followed Korsmeyer-Peppas, with 50% of biodegradation occurring over 48 h. In mouse models, certain thermogels showed superior anesthetic effects, with rapid onset and prolonged action, as evidenced by heat tolerance in tail-flick and hot plate models. In clinical trials, the LH-loaded thermoresponsive hydrogel provided rapid numbness onset, with anesthesia (Ton) beginning at an average of 46.5 ± 22.5 seconds and lasting effectively (Teff) for 202.5 ± 41.0 seconds, ranging from 120 to 240 seconds, indicating sustained release. These results highlight the promising properties of these formulations: rapid onset, prolonged duration, mucoadhesion, biodegradability, and high anesthesia effectiveness. This study demonstrates the potential for advancing local anesthesia across various medical fields, emphasizing the synergy between material science and clinical applications to improve patient care and safety.

Recent Advances in 3D Printing of Smart Scaffolds for Bone Tissue Engineering and Regeneration

The repair and functional reconstruction of bone defects resulting from severe trauma, surgical resection, degenerative disease, and congenital malformation pose significant clinical challenges. Bone tissue engineering (BTE) holds immense potential in treating these severe bone defects, without incurring prevalent complications associated with conventional autologous or allogeneic bone grafts. 3D printing technology enables control over architectural structures at multiple length scales and has been extensively employed to process biomimetic scaffolds for BTE. In contrast to inert and functional bone grafts, next-generation smart scaffolds possess a remarkable ability to mimic the dynamic nature of native extracellular matrix (ECM), thereby facilitating bone repair and regeneration. Additionally, they can generate tailored and controllable therapeutic effects, such as antibacterial or antitumor properties, in response to exogenous and/or endogenous stimuli. This review provides a comprehensive assessment of the progress of 3D-printed smart scaffolds for BTE applications. It begins with an introduction to bone physiology, followed by an overview of 3D printing technologies utilized for smart scaffolds. Notable advances in various stimuli-responsive strategies, therapeutic efficacy, and applications of 3D-printed smart scaffolds are discussed. Finally, the review highlights the existing challenges in the development and clinical implementation of smart scaffolds, as well as emerging technologies in this field.

Stem Cell-Derived Extracellular Vesicle-Bearing Injectable Hydrogel for Collagen Generation in Dermis

Despite the remarkable advances of dermal fillers that reduce wrinkles caused by dermis thickness reduction, they still lack effective hydrogel systems that stimulate collagen generation along with injection convenience. Here, we develop a stem cell-derived extracellular vesicle (EV)-bearing thermosensitive hydrogel (EVTS-Gel) for effective in vivo collagen generation. The TS-Gel undergoes sol-gel transition at 32.6 °C, as demonstrated by the storage and loss moduli crossover. Moreover, the TS-Gel and the EVTS-Gel have comparable rheological properties. Both hydrogels are injected in a sol state; hence, they require lower injection forces than conventional hydrogel-based dermal fillers. When locally administered to mouse skin, the TS-Gel extends the retention time of EVs by 2.23 times. Based on the nature of the controlled EV release, the EVTS-Gel significantly inhibits the dermis thickness reduction caused by aging compared to the bare EV treatment for 24 weeks. After a single treatment, the collagen layer thickness of the EVTS-Gel-treated dermis becomes 2.64-fold thicker than that of the bare EV-treated dermis. Notably, the collagen generation efficacy of the bare EV is poorer than that of the EVTS-Gel of a 10× lesser dose. Overall, the EVTS-Gel shows potential as an antiaging dermal filler for in vivo collagen generation.

Stimulus-Responsive Hydrogels for Targeted Cancer Therapy

Cancer is a highly heterogeneous disease and remains a global health challenge affecting millions of human lives worldwide. Despite advancements in conventional treatments like surgery, chemotherapy, and immunotherapy, the rise of multidrug resistance, tumor recurrence, and their severe side effects and the complex nature of the tumor microenvironment (TME) necessitates innovative therapeutic approaches. Recently, stimulus-responsive nanomedicines designed to target TME characteristics (e.g., pH alterations, redox conditions, enzyme secretion) have gained attention for their potential to enhance anticancer efficacy while minimizing the adverse effects of chemotherapeutics/bioactive compounds. Among the various nanocarriers, hydrogels are intriguing due to their high-water content, adjustable mechanical characteristics, and responsiveness to external and internal stimuli, making them promising candidates for cancer therapy. These properties make hydrogels an ideal nanocarrier for controlled drug release within the TME. This review comprehensively surveys the latest advancements in the area of stimulus-responsive hydrogels for cancer therapy, exploring various stimuli-responsive mechanisms, including biological (e.g., pH, redox), chemical (e.g., enzymes, glucose), and physical (e.g., temperature, light), as well as dual- or multi-stimuli responsiveness. Furthermore, this review addresses the current developments and challenges in hydrogels in cancer treatment. Our aim is to provide readers with a comprehensive understanding of stimulus-responsive hydrogels for cancer treatment, offering novel perspectives on their development for cancer therapy and other medical applications.

AS1411aptamer conjugated liposomes for targeted delivery of arsenic trioxide in mouse xenograft model of melanoma cancer

Development of AS1411aptamer-conjugated liposomes for targeted delivery of arsenic trioxide is the primary goal of this study. AS1411aptamer was used as ligand to target nucleolin, which is highly expressed on the surface of melanoma cancer cells. The targeted liposomes were constructed by the thin film method, and arsenic trioxide was loaded as cobalt (II) hydrogen arsenite (CHA) to increase the loading efficiency and stability of the liposomes. The liposomal structure was characterized by Fourier Transform Infrared Spectroscopy (FT-IR) and field emission scanning electron microscopy (FESEM). In addition, particle sizes and zeta potential of the CHA-loaded liposomes (CHAL) and aptamer-functionalized CHA-loaded liposomes (AP-CHAL) were determined. In vitro cytotoxicity of CHAL and AP-CHAL were evaluated using MTT assay in murine melanoma (B16) and mouse embryonic fibroblast (MEF) cell lines. The encapsulation efficiency of CHAL and AP-CHAL was reported as 60.2 ± 6.5% and 58.7 ± 4.2%, respectively. In vivo antitumor activity of CHAL and AP-CHAL in the B16 tumor-xenograft mouse model was dramatically observed. All mice of both groups survived until the end of treatment and showed body weight gain. The tumor protrusion completely disappeared in 50% of the mice in these groups. Furthermore, histopathology studies demonstrated that CHAL and AP-CHAL did not induce significant toxicity in healthy mice tissues. However, unlike the CHAL group, which showed an initial increase in tumor volume, a specific antitumor effect was observed in the AP-CHAL group from the beginning of treatment. The results showed that AP-CHAL can be used as an effective drug delivery system with high potential in the treatment of solid tumors.

Evaluation of the printability of agar and hydroxypropyl methylcellulose gels as gummy formulations: Insights from rheological properties

The trial-and-error method currently used to create formulations with excellent printability demands considerable time and resources, primarily due to the increasing number of variables involved. Rheology serves as a relatively rapid and highly beneficial method for assessing materials and evaluating their effectiveness as 3D constructs. However, the data obtained can be overwhelming, especially for users lacking experience in this field. This study examined the rheological properties of formulations of agar, hydroxypropyl methylcellulose, and the model drug caffeine, alongside exploring their printability as gummy formulations. The gels' rheological properties were characterized using oscillatory and rotational experiments. The correlation between these gels' rheological properties and their printability was established, and three clusters were formed based on the rheological properties and printability of the samples using principal component analysis. Furthermore, the printability was predicted using the sample's rheological property that correlated most with printability, the phase angle δ, and the regression models resulted in an accuracy of over 80%. Although these relationships merit confirmation in later studies, this study suggests a quantitative definition of the relationship between printability and one rheological property and can be used for the development of formulations destined for extrusion 3D printing.

Gelatin Methacryloyl (GelMA)-Based Biomaterial Inks: Process Science for 3D/4D Printing and Current Status

Tissue engineering for injured tissue replacement and regeneration has been a subject of investigation over the last 30 years, and there has been considerable interest in using additive manufacturing to achieve these goals. Despite such efforts, many key questions remain unanswered, particularly in the area of biomaterial selection for these applications as well as quantitative understanding of the process science. The strategic utilization of biological macromolecules provides a versatile approach to meet diverse requirements in 3D printing, such as printability, buildability, and biocompatibility. These molecules play a pivotal role in both physical and chemical cross-linking processes throughout the biofabrication, contributing significantly to the overall success of the 3D printing process. Among the several bioprintable materials, gelatin methacryloyl (GelMA) has been widely utilized for diverse tissue engineering applications, with some degree of success. In this context, this review will discuss the key bioengineering approaches to identify the gelation and cross-linking strategies that are appropriate to control the rheology, printability, and buildability of biomaterial inks. This review will focus on the GelMA as the structural (scaffold) biomaterial for different tissues and as a potential carrier vehicle for the transport of living cells as well as their maintenance and viability in the physiological system. Recognizing the importance of printability toward shape fidelity and biophysical properties, a major focus in this review has been to discuss the qualitative and quantitative impact of the key factors, including microrheological, viscoelastic, gelation, shear thinning properties of biomaterial inks, and printing parameters, in particular, reference to 3D extrusion printing of GelMA-based biomaterial inks. Specifically, we emphasize the different possibilities to regulate mechanical, swelling, biodegradation, and cellular functionalities of GelMA-based bio(material) inks, by hybridization techniques, including different synthetic and natural biopolymers, inorganic nanofillers, and microcarriers. At the close, the potential possibility of the integration of experimental data sets and artificial intelligence/machine learning approaches is emphasized to predict the printability, shape fidelity, or biophysical properties of GelMA bio(material) inks for clinically relevant tissues.

Advances in Injectable Hydrogels Based on Diverse Gelation Methods for Biomedical Imaging

The injectable hydrogels can deliver the loads directly to the predetermined sites and form reservoirs to increase the enrichment and retention of the loads in the target areas. The preparation and injection of injectable hydrogels involve the sol-gel transformation of hydrogels, which is affected by factors such as temperature, ions, enzymes, light, mechanics (self-healing property), and pH. However, tracing the injection, degradation, and drug release from hydrogels based on different ways of gelation is a major concern. To solve this problem, contrast agents are introduced into injectable hydrogels, enabling the hydrogels to be imaged under techniques such as fluorescence imaging, photoacoustic imaging, magnetic resonance imaging, and radionuclide imaging. This review details methods for causing the gelation of imageable hydrogels; discusses the application of injectable hydrogels containing contrast agents in various imaging techniques, and finally explores the potential and challenges of imageable hydrogels based on different modes of gelation.

Fabrication of carboxymethyl cellulose-based thermo-sensitive hydrogels and inhibition of corneal neovascularization

Corneal neovascularization (CNV) is a common multifactorial sequela of anterior corneal segment inflammation, which could lead to visual impairment and even blindness. The main treatments available are surgical sutures and invasive drug injections, which could cause serious ocular complications. To solve this problem, a thermo-sensitive drug-loaded hydrogel with high transparency was prepared in this study, which could achieve the sustained-release of drugs without affecting normal vision. In briefly, the thermo-sensitive hydrogel (PFNOCMC) was prepared from oxidized carboxymethyl cellulose (OCMC) and aminated poloxamer 407 (PF127-NH2). The results proved the PFNOCMC hydrogels possess high transparency, suitable gel temperature and time. In the CNV model, the PFNOCMC hydrogel loading bone morphogenetic protein 4 (BMP4) showed significant inhibition of CNV, this is due to the hydrogel allowed the drug to stay longer in the target area. The animal experiments on the ocular surface were carried out, which proved the hydrogel had excellent biocompatibility, and could realize the sustained-release of loaded drugs, and had a significant inhibitory effect on the neovascularization after ocular surface surgery. In conclusion, PFNOCMC hydrogels have great potential as sustained-release drug carriers in the biomedical field and provide a new minimally invasive option for the treatment of neovascular ocular diseases.

Formulation development and evaluation of nasal in situ gel of promethazine hydrochloride

OBJECTIVE

The present work aims to develop mucoadhesive thermosensitive nasal in situ gel for Promethazine hydrochloride using quality by design (QbD) approach. It can reduce nasal mucociliary clearance (MCC) and increase residence of the drug on nasal mucosa. This might increase drug absorption to improve bioavailability of the drug as compared to oral dosage form.

SIGNIFICANCE

Promethazine hydrochloride is an antiemetic drug administered by oral, parenteral and rectal routes. These routes have poor patient compliance or low bioavailability. Nasal route is a better alternative as it has large surface area, high drug absorption rate and no first pass effect. Its only limitation is short drug retention time due to MCC. By formulating a mucoadhesive in situ gel, the MCC can be reduced, and drug absorption will be prolonged. Thus, improving bioavailability.

METHOD

In-situ gel was prepared by cold method having material attributes as concentration of Poloxamer 407 (X1) as gelling agent and hydroxypropyl methyl cellulose K4M (X2) as mucoadhesive agent. Critical Quality Attributes (CQA) were gelation temperature, mucoadhesive force and ex-vivo diffusion. Central composite design (CCD) was adopted for optimization.

RESULT

Optimized formulation satisfied all the CQA significant for nasal administration. Moreover, the formulation was found to be stable in accelerated stability studies for 3 months.

CONCLUSION

It can be concluded that since the drug can easily permeate through nasal mucosa and can gain access directly in the brain without undergoing first pass metabolism along with increased residence due to mucoadhesion, mucoadhesive in situ gel has potential to increase drug bioavailability.

Effects of direct addition of curdlan on the gelling characteristics of thermally induced soy protein isolate gels

In this study, the effects of the direct addition of curdlan on the physicochemical, structural, and functional properties of heat-induced soy protein isolate (SPI) gels were evaluated. Results demonstrated that the direct incorporation of curdlan enhanced the gel-forming performance, water-holding capacity, and gel strength of heat-induced SPI gels. The presence of curdlan reduced the free water molecules and α-helix content in the SPI structure and contributed to the construction of stable SPI gels with uniform and compact network structures, as visually proven by microstructure observations. Moreover, compared with the SPI gel alone, the curdlan-SPI composite gels presented a more pronounced viscoelastic property and thermal stability mainly due to the intermolecular hydrogen bonding interaction between curdlan and the SPI molecules. Our findings suggest that the direct incorporation of curdlan can effectively ameliorate the gelling characteristics of heat-induced SPI gels, indicating its potential application as a promising gel improver in the food industry.

Rheological insights on Carboxymethyl cellulose hydrogels

Hydrogels are copiously studied for tissue engineering, drug delivery, and bone regeneration owing to their water content, mechanical strength, and elastic behaviour. The preparation of stable and mechanically strengthened hydrogels without using toxic crosslinkers and expensive approaches is immensely challenging. In this study, we prepared Carboxymethyl cellulose based hydrogels with different polymer concentration via a less expensive physical crosslinking approach without using any toxic crosslinkers and evaluated their mechanical strength. In this hydrogel system, the carbopol concentration was fixed at 1 wt/v% and the Carboxymethyl cellulose concentration was varied between 1 and 5 wt/v%. In this hydrogel system, Carbopol serves as the crosslinker to bridge Carboxymethyl cellulose polymer through hydrogen bonds. Rheological analysis was employed in assessing the mechanical properties of the prepared hydrogel, in particular, the viscoelastic behaviour of the hydrogels. The viscoelastic nature and mechanical strength of the hydrogels increased with an increase in the Carboxymethyl cellulose polymer concentration. Further, our results suggested that gels with Carboxymethyl cellulose concentration between 3 wt/v % and 4 wt/v % with yield stresses of 58.83 Pa and 81.47 Pa, respectively, are potential candidates for use in transdermal drug delivery. The prepared hydrogels possessed high thermal stability and retained their gel network structure even at 50 °C. These findings are beneficial for biomedical applications in transdermal drug delivery and tissue engineering owing to the biocompatibility, stability, and mechanical strength of the prepared hydrogels.

Wound Microenvironment Self-Adjusting Hydrogels with Thermo-Sensitivity for Promoting Diabetic Wound Healing

The hard-healing chronic wounds of diabetics are still one of the most intractable problems in clinical skin injury repair. Wound microenvironments directly affect wound healing speed, but conventional dressings exhibit limited efficacy in regulating the wound microenvironment and facilitating healing. To address this serious issue, we designed a thermo-sensitive drug-controlled hydrogel with wound self-adjusting effects, consisting of a sodium alginate (SA), Antheraeapernyi silk gland protein (ASGP) and poly(N-isopropylacrylamide) (PNIPAM) for a self-adjusting microenvironment, resulting in an intelligent releasing drug which promotes skin regeneration. PNIPAM has a benign temperature-sensitive effect. The contraction, drugs and water molecules expulsion of hydrogel were generated upon surpassing lower critical solution temperatures, which made the hydrogel system have smart drug release properties. The addition of ASGP further improves the biocompatibility and endows the thermo-sensitive drug-controlled hydrogel with adhesion. Additionally, in vitro assays demonstrate that the thermo-sensitive drug-controlled hydrogels have good biocompatibility, including the ability to promote the adhesion and proliferation of human skin fibroblast cells. This work proposes an approach for smart drug-controlled hydrogels with a thermo response to promote wound healing by self-adjusting the wound microenvironment.

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.

Intravitreal injectable hydrogel rods with long-acting bevacizumab delivery to the retina

Retinal vascular diseases such as neovascular age-related macular degeneration (nAMD) are the leading cause of blindness worldwide. They can be treated with intravitreal injections of anti-vascular endothelial growth factor (anti-VEGF) agents by inhibiting VEGF which is a major agent of abnormal blood vessel growth. However, because of drug's short half-life, clinical treatment often requires monthly repeated intravitreal injections, causing treatment burden and undertreatment. Among various kinds of drug carriers, in situ forming hydrogels have been studied as potential intravitreal drug carriers for the high drug loading, easy injection, controlled drug release, and protection of encapsulated drugs from the environment. However, gelation time, crosslinking degree, and drug release patterns following injection of a liquid that will be subsequently gelled in situ are susceptible to be hindered by dilution of the hydrogel precursor solution with body fluids (e.g., blood or vitreous). Here, we report an injectable pre-crosslinked hydrogel rod to overcome the limitations of in situ forming hydrogels and to extend intravitreal half-life of anti-VEGF for reducing intraocular injection frequency. Hydrogel rods can be simply prepared using in situ forming hydrogels, and injectable using a designed rod injector. The adjustable crosslinking degree of hydrogel rods easily controlled bevacizumab release profiles in a sustained manner. Compared with in situ forming hydrogels, hydrogel rods effectively reduced initial burst release, and showed sustained release with long-term drug efficacy in vitro. From the 4-month in vivo pharmacokinetic analysis, following the intravitreal injection of hydrogel rods, the half-life of bevacizumab in the vitreous and retina was significantly extended, and drug elimination to aqueous humor was effectively reduced. Finally, intraocular stability, degradation, and inflammatory response of hydrogel rods were evaluated. We expect that the hydrogel rod can be a potential drug delivery system for the treatment of nAMD and other conditions that need long-term and local sustained drug administration. STATEMENT OF SIGNIFICANCE: Herein, we report an injectable pre-crosslinked hydrogel rod based on an in situ forming hydrogel to achieve intravitreal long-acting anti-VEGF delivery to reduce injection frequency and improve the long-term visual outcomes of patients with retinal vascular diseases. Hydrogel rods were readily prepared using removable molds and injected using customized injectors. Compared to the in situ forming hydrogel, hydrogel rods showed significantly reduced initial burst release, controllable release profiles for several months, physical stability, and a long-acting anti-angiogenic effect. Animal studies demonstrated that the hydrogel rods dramatically prolonged the intraocular drug half-life while significantly reducing drug elimination for up to four months. Moreover, the biodegradability and safety of the hydrogel rods suggest their suitability as an advanced intravitreal DDS for treating retinal vascular diseases.

Novel Sprayable Thermosensitive Benzydamine Hydrogels for Topical Application: Development, Characterization, and In Vitro Biological Activities

Benzydamine hydrochloride (BZD) having analgesic, anesthetic, and anti-inflammatory effects is used orally or topically in the treatment of disorders such as joint inflammation and muscle pain. Within the scope of this study, sprayable thermosensitive BZD hydrogels were developed using thermoresponsive poloxamers to avoid systemic side effects and to provide better compliance for topical administration. Also, hydroxypropyl methyl cellulose (HPMC) was employed to improve the mechanical strength and bioadhesive properties of the hydrogel. The addition of BZD generally decreased the viscosity of the formulations (p < 0.05), while increasing the gelation temperature (p < 0.05). The formulations that did not have any clogs or leaks in the nozzle of the bottle during the spraying process were considered lead formulations. To spray the formulations easily, it was found that the viscosity at RT should be less than 200 mPa·s, and their gelation temperature should be between 26 and 34°C. Increasing HPMC and poloxamer improved bioadhesion. The amount of HPMC and poloxamers did not cause a significant change in the release characteristics of the formulations (p > 0.05); the release profiles of BZD from the formulations were similar according to model-independent kinetic (f2 > 50). HPMC and poloxamers had important roles in the accumulation of BZD in the skin. In vitro biological activity studies demonstrated that the formulations presented their anti-inflammatory activity with TNF-α inhibition but did not have any effect on the inhibition of COX enzymes as expected. As a result, thermosensitive hydrogels containing BZD might be an appropriate alternative, providing an advantage in terms of easier application compared to conventional gels.

The effect of conductive aligned fibers in an injectable hydrogel on nerve tissue regeneration

Injectable hydrogels are a promising treatment option for nervous system injuries due to the difficulty to replace lost cells and nervous factors but research on injectable conductive hydrogels is limited and these scaffolds have poor electromechanical properties. This study developed a chitosan/beta-glycerophosphate/salt hydrogel and added conductive aligned nanofibers (polycaprolactone/gelatin/single-wall carbon nanotube (SWCNT)) for the first time and inspired by natural nerve tissue to improve their biochemical and biophysical properties. The results showed that the degradation rate of hydrogels is proportional to the regrowth of axons and these hydrogels' mechanical (hydrogels without nanofibers or SWCNTs and hydrogels containing these additions have the same Young's modulus as the brain and spinal cord or peripheral nerves, respectively) and electrical properties, and the interconnective structure of the scaffolds have the ability to support cells.

A Reversibly Thermoresponsive, Theranostic Nanoemulgel for Tacrolimus Delivery to Activated Macrophages: Formulation and In Vitro Validation

Despite long-term immunosuppression, organ transplant recipients face the risk of immune rejection and graft loss. Tacrolimus (TAC, FK506, Prograf®) is an FDA-approved keystone immunosuppressant for preventing transplant rejection. However, it undergoes extensive first-pass metabolism and has a narrow therapeutic window, which leads to erratic bioavailability and toxicity. Local delivery of TAC directly into the graft, instead of systemic delivery, can improve safety, efficacy, and tolerability. Macrophages have emerged as promising therapeutic targets as their increased levels correlate with an increased risk of organ rejection and a poor prognosis post-transplantation. Here, we present a locally injectable drug delivery platform for macrophages, where TAC is incorporated into a colloidally stable nanoemulsion and then formulated as a reversibly thermoresponsive, pluronic-based nanoemulgel (NEG). This novel formulation is designed to undergo a sol-to-gel transition at physiological temperature to sustain TAC release in situ at the site of local application. We also show that TAC-NEG mitigates the release of proinflammatory cytokines and nitric oxide from lipopolysaccharide (LPS)-activated macrophages. To the best of our knowledge, this is the first TAC-loaded nanoemulgel with demonstrated anti-inflammatory effects on macrophages in vitro.

Advantages and Prospective Implications of Smart Materials in Tissue Engineering: Piezoelectric, Shape Memory, and Hydrogels

Conventional biomaterial is frequently used in the biomedical sector for various therapies, imaging, treatment, and theranostic functions. However, their properties are fixed to meet certain applications. Smart materials respond in a controllable and reversible way, modifying some of their properties because of external stimuli. However, protein-based smart materials allow modular protein domains with different functionalities and responsive behaviours to be easily combined. Wherein, these "smart" behaviours can be tuned by amino acid identity and sequence. This review aims to give an insight into the design of smart materials, mainly protein-based piezoelectric materials, shape-memory materials, and hydrogels, as well as highlight the current progress and challenges of protein-based smart materials in tissue engineering. These materials have demonstrated outstanding regeneration of neural, skin, cartilage, bone, and cardiac tissues with great stimuli-responsive properties, biocompatibility, biodegradability, and biofunctionality.

Free-flowing, self-crosslinking, carboxymethyl starch and carboxymethyl cellulose microgels, as smart hydrogel dressings for wound repair

Hydrogels are widely recognized and favoured as moist wound dressings due to their beneficial properties. However, their limited capacity to absorb fluids restricts their use in highly exuding wounds. Microgels are small sized hydrogels that have recently gained considerable attention in drug delivery applications due to their superior swelling behaviour and ease of application. In this study, we introduce dehydrated microgel particles (μGeld) that rapidly swell and interconnect, forming an integrated hydrogel when exposed to fluid. These free-flowing microgel particles, derived from the interaction of carboxymethylated forms of starch and cellulose, have been designed to significantly absorb fluid and release silver nanoparticles in order to effectively control infection. Studies using simulated wound models validated the microgels ability to efficiently regulate the wound exudate and create a moist environment. While the biocompatibility and hemocompatibility studies confirmed the safety of the μGel particles, its haemostatic property was established using relevant models. Furthermore, the promising results from a full-thickness wounds in rats have highlighted the enhanced healing potential of the microgel particles. These findings suggest that the dehydrated microgels can evolve as a new class of smart wound dressings.

Red Light and 5% Aminolaevulinic Acid (5%) Inhibit Proliferation and Migration of Dysplastic Oral Keratinocytes via ROS Production: An In Vitro Study

Undiagnosed and untreated oral precancerous lesions often progress into malignancies. Photodynamic therapy (PDT) might be a minimally invasive alternative to conventional treatments. 5-aminolevulinic acid (5-ALA) is one of the most commonly used photosensitizers in PDT, and it is effective on many cancer types. However, its hydrophilic characteristic limits cell membrane crossing. In the present study, the effect of a newly formulated gel containing 5% 5-ALA in combination with red light (ALAD-PDT) on a premalignant oral mucosa cell line was investigated. The dysplastic oral keratinocyte (DOK) cells were incubated with ALAD at different concentrations (0.1, 0.5, 1, and 2 mM) at two different times, 45 min or 4 h, and then irradiated for 7 min with a 630 nm LED (25 J/cm2). MTT assay, flow cytometry, wound healing assay, and quantitative PCR (qPCR) were performed. ALAD-PDT exerted inhibitory effects on the proliferation and migration of DOK cells by inducing ROS and necrosis. mRNA analysis showed modulation of apoptosis-related genes' expression (TP53, Bcl-2, survivin, caspase-3, and caspase-9). Furthermore, there was no difference between the shorter and longer incubation times. In conclusion, the inhibitory effect of the ALAD-PDT protocol observed in this study suggests that ALAD-PDT could be a promising novel treatment for oral precancerous lesions.

Poly Ethylene Glycol (PEG)-Based Hydrogels for Drug Delivery in Cancer Therapy: A Comprehensive Review

Hydrogel-based drug delivery systems (DDSs) can leverage therapeutically beneficial outcomes in cancer therapy. In this domain, polyethylene glycol (PEG) has become increasingly popular as a biomedical polymer and has found clinical use. Owing to their excellent biocompatibility, facile modifiability, and high drug encapsulation rate, PEG hydrogels have shown great promise as drug delivery platforms. Here, the progress in emerging novel designs of PEG-hydrogels as DDSs for anti-cancer therapy is reviewed and discussed, focusing on underpinning multiscale release mechanisms categorized under stimuli-responsive and non-responsive drug release. The responsive drug delivery approaches are discussed, and the underpinning release mechanisms are elucidated, covering the systems functioning based on either exogenous stimuli-response, such as photo- and magnetic-sensitive PEG hydrogels, or endogenous stimuli-response, such as enzyme-, pH-, reduction-, and temperature-sensitive PEG hydrogels. Special attention is paid to the commercial potential of PEG-based hydrogels in cancer therapy, highlighting the limitations that need to be addressed in future research for their clinical translation.

Stimuli-responsive hydrogels: smart state of-the-art platforms for cardiac tissue engineering

Biomedicine and tissue regeneration have made significant advancements recently, positively affecting the whole healthcare spectrum. This opened the way for them to develop their applications for revitalizing damaged tissues. Thus, their functionality will be restored. Cardiac tissue engineering (CTE) using curative procedures that combine biomolecules, biomimetic scaffolds, and cells plays a critical part in this path. Stimuli-responsive hydrogels (SRHs) are excellent three-dimensional (3D) biomaterials for tissue engineering (TE) and various biomedical applications. They can mimic the intrinsic tissues' physicochemical, mechanical, and biological characteristics in a variety of ways. They also provide for 3D setup, adequate aqueous conditions, and the mechanical consistency required for cell development. Furthermore, they function as competent delivery platforms for various biomolecules. Many natural and synthetic polymers were used to fabricate these intelligent platforms with innovative enhanced features and specialized capabilities that are appropriate for CTE applications. In the present review, different strategies employed for CTE were outlined. The light was shed on the limitations of the use of conventional hydrogels in CTE. Moreover, diverse types of SRHs, their characteristics, assembly and exploitation for CTE were discussed. To summarize, recent development in the construction of SRHs increases their potential to operate as intelligent, sophisticated systems in the reconstruction of degenerated cardiac tissues.

Broad-temperature-range mechanically tunable hydrogel microcapsules for controlled active release

Here, we report PNIPAm-co-PEGDA hydrogel shelled microcapsules with a thin oil layer to achieve tunable thermo-responsive release of the encapsulated small hydrophilic actives. We use a microfluidic device integrated with a temperature-controlled chamber for consistent and reliable production of the microcapsules by utilizing triple emulsion drops (W/O/W/O) with a thin oil layer as capsule templates. The interstitial oil layer between the aqueous core and the PNIPAm-co-PEGDA shell provides a diffusion barrier for the encapsulated active until the temperature reaches a critical point above which the destabilization of interstitial oil layer occurs. We find that the destabilization of the oil layer with temperature increase is caused by outward expansion of the aqueous core due to volume increase and the radial inward compression from the deswelling of the thermo-responsive hydrogel shell. The copolymerization of NIPAm with PEGDA increases the biocompatibility of the resulting microcapsule while offering the ability to alter the compressive modulus in broad ranges by simply varying crosslinker concentrations thereby to precisely tune the onset release temperature. Based on this concept, we further demonstrate that the release temperature can be enhanced up to 62 °C by adjusting the shell thickness even without varying the chemical composition of the hydrogel shell. Moreover, we incorporate gold nanorods within the hydrogel shell to spatiotemporally regulate the active release from the microcapsules by illuminating with non-invasive near infrared (NIR) light.

Smart stimuli-responsive chitosan hydrogel for drug delivery: A review

Smart stimuli-responsive materials can respond to different signals (pH, temperature, light, electricity, etc.), and they have become a hot research topic for drug delivery. As a polysaccharide polymer with excellent biocompatibility, chitosan can be obtained from diverse natural sources. Chitosan hydrogels with different stimuli-response capabilities are widely applied in the drug delivery field. This review highlights and discusses the research progress on chitosan hydrogels concerning their stimuli-responsive capabilities. The feature of various stimuli-responsive kinds of hydrogels is outlined, and their potential use of drug delivery is summarized. Furthermore, the questions and future development chances of stimuli-responsive chitosan hydrogels are analyzed by comparing the current published literature, and the directions for the intelligent development of chitosan hydrogels are discussed.

Combining branched copolymers with additives generates stable thermoresponsive emulsions with in situ gelation upon exposure to body temperature

Branched copolymer surfactants (BCS) containing thermoresponsive polymer components, hydrophilic components, and hydrophobic termini allow the formation of emulsions which switch from liquid at room temperature to a gel state upon heating. These materials have great potential as in situ gel-forming dosage forms for administration to external and internal body sites, where the emulsion system also allows effective solubilisation of a range of drugs with different chemistries. These systems have been reported previously, however there are many challenges to translation into pharmaceutical excipients. To transition towards this application, this manuscript describes the evaluation of a range of pharmaceutically-relevant oils in the BCS system as well as evaluation of surfactants and polymeric/oligomeric additives to enhance stability. Key endpoints for this study are macroscopic stability of the emulsions and rheological response to temperature. The effect of an optimal additive (methylcellulose) on the nanoscale processes occurring in the BCS-stabilised emulsions is probed by small-angle neutron scattering (SANS) to better comprehend the system. Overall, the study reports an optimal BCS/methylcellulose system exhibiting sol-gel transition at a physiologically-relevant temperature without macroscopic evidence of instability as an in situ gelling dosage form.

Advances in buccal and oral delivery of insulin

Diabetes mellitus is a metabolic endocrine disease characterized by chronic hyperglycemia with disturbances in metabolic processes, such as those related to carbohydrates, fat, and protein. There are two main types of this disease: type 1 diabetes (T1D) and type 2 diabetes (T2D). Insulin therapy is pivotal to the management of diabetes. Over the last two decades, many routes of administration, including nasal, pulmonary, rectal, transdermal, buccal, and ocular, have been investigated. Nevertheless, subcutaneous parenteral administration is still the most common route for insulin therapy. To overcome poor bioavailability and the barriers to oral insulin absorption, novel approaches in the field of oral drug delivery and administration have been brought about by the coalescence of different branches of nanoscience and nanotechnology, such as nanomedicine, nano-biochemistry, and nano-pharmacy. Novel drug delivery systems, including nanoparticles, nano-platforms, and nanocarriers, have been suggested. The objective of this review is to provide an update on the various promising approaches that have been explored and evaluated for the safe and efficient oral and buccal administration of insulin.

Single-Step Fabrication of a Dual-Sensitive Chitosan Hydrogel by C-Mannich Reaction: Synthesis, Physicochemical Properties, and Screening of its Cu2+ Uptake

Uncovering the value of waste materials is one of the keys to sustainability. In this current work, valorization of chitosan was pursued to fabricate a novel modified chitosan functional hydrogel using a process-efficient protocol. The fabrication proceeds by a one-pot and single-step C-Mannich condensation of chitosan (3% w/v), glutaraldehyde (20 eq.), and 4-hydroxycoumarin (40 eq.) at 22 °C in 3% v/v acetic acid. The Mannich base modified chitosan hydrogel (CS-MB) exhibits a dual-responsive swelling behavior in response to pH and temperature that has not been observed in any other hydrogel systems. Combining the pre-defined optimal swelling pH (pH = 4) and temperature (T = 22 °C), the CS-MB was screened for its Cu2+ adsorption capacity at this condition. The CS-MB achieved an optimal adsorption capacity of 12.0 mg/g with 1.2 g/L adsorbent dosage after 36 h with agitation. The adsorption of Cu2+ on the surface of CS-MB was verified by EDS, and an overview of the adsorption sites was exhibited by FT-IR. The simply fabricated novel CS-MB hydrogel under investigation presents a unique response to external stimuli that exhibits a promise in heavy metal removal from aqueous media.

Visualizing Neurons Under Tension In Vivo with Optogenetic Molecular Force Sensors

The visualization of mechanical stress distribution in specific molecular networks within a living and physiologically active cell or animal remains a formidable challenge in mechanobiology. The advent of fluorescence-resonance energy transfer (FRET)-based molecular tension sensors overcame a significant hurdle that now enables us to address previously technically limited questions. Here, we describe a method that uses genetically encoded FRET tension sensors to visualize the mechanics of cytoskeletal networks in neurons of living animals with sensitized emission FRET and confocal scanning light microscopy. This method uses noninvasive immobilization of living animals to image neuronal β-spectrin cytoskeleton at the diffraction limit, and leverages multiple imaging controls to verify and underline the quality of the measurements. In combination with a semiautomated machine-vision algorithm to identify and trace individual neurites, our analysis performs simultaneous calculation of FRET efficiencies and visualizes statistical uncertainty on a pixel by pixel basis. Our approach is not limited to genetically encoded spectrin tension sensors, but can also be used for any kind of ratiometric imaging in neuronal cells both in vivo and in vitro.

The Dual Modification of PNIPAM and β-Cyclodextrin Grafted on Hyaluronic Acid as Self-Assembled Nanogel for Curcumin Delivery

Curcumin is an extract of turmeric (Curcuma longa) which possesses anti-inflammatory, anti-cancer and wound-healing effects and has been used as an active compound in biomedical research for many years. However, its poor solubility presents challenges for its use in drug delivery systems. A modified nanogel delivery system, with PNIPAM and β-cyclodextrin grafted onto hyaluronic acid (PNCDHA), was utilized to enhance the solubility. The polymer was characterized by NMR, and the inclusion complex between curcumin and β-cyclodextrin was confirmed by FTIR. The potential of this PNCDHA polymer complex as a drug delivery vehicle was supported by a curcumin encapsulation efficiency of 93.14 ± 5.6% and the release of encapsulated curcumin at 37 °C. At a concentration of 0.5% w/v in water, PNCDHA nanogels were biocompatible with fibroblast cell line (L929) up to a curcumin concentration of 50 µM. There was a direct concentration between curcumin loading and cellular internalization. A more detailed study of the cellular internalization of PNCDHA nanogel should be considered in order to clarify cellular delivery mechanisms and to assess how its viability as a carrier may be optimized.

A Review on Thermal Properties of Hydrogels for Electronic Devices Applications

Hydrogels, as a series of three-dimensional, crosslinked, hydrophilic network polymers, exhibit extraordinary properties in softness, mechanical robustness and biocompatibility, which have been extensively utilized in various fields, especially for electronic devices. However, since hydrogels contain plenty of water, the mechanical and electrochemical properties are susceptible to temperature. The thermal characteristics of hydrogels can significantly affect the performance of flexible electronic devices. In this review, recent research on the thermal characteristics of hydrogels and their applications in electronic devices is summarized. The focus of future work is also proposed. The thermal stability, thermoresponsiveness and thermal conductivity of hydrogels are discussed in detail. Anti-freezing and anti-drying properties are the critical points for the thermal stability of hydrogels. Methods such as introducing soluble ions and organic solvents into hydrogels, forming ionogels, modifying polymer chains and incorporating nanomaterials can improve the thermal stability of hydrogels under extreme environments. In addition, the critical solution temperature is crucial for thermoresponsive hydrogels. The thermoresponsive capacity of hydrogels is usually affected by the composition, concentration, crosslinking degree and hydrophilic/hydrophobic characteristics of copolymers. In addition, the thermal conductivity of hydrogels plays a vital role in the electronics applications. Adding nanocomposites into hydrogels is an effective way to enhance the thermal conductivity of hydrogels.

Antibacterial smart hydrogels: New hope for infectious wound management

Millions of people die annually due to uncured wound infections. Healthcare systems incur high costs to treat wound infections. Tt is predicted to become more challenging due to the rise of multidrug-resistant conditions. During the last decades, smart antibacterial hydrogels could attract attention as a promising solution, especially for skin wound infections. These antibacterial hydrogels are termed 'smart' due to their response to specific physical and chemical environmental stimuli. To deliver different drugs to particular sites in a controlled manner, various types of crosslinking strategies are used in the manufacturing process. Smart hydrogels are designed to provide antimicrobial agents to the infected sites or are built from polymers with inherent disinfectant properties. This paper aims to critically review recent pre-clinical and clinical advances in using smart hydrogels against skin wound infections and propose the next best thing for future trends. For this purpose, an introduction to skin wound healing and disease is presented and intelligent hydrogels responding to different stimuli are introduced. Finally, the most promising investigations are discussed in their related sections. These studies can pave the way for producing new biomaterials with clinical applications.

Gold-Nanoparticle Hybrid Nanostructures for Multimodal Cancer Therapy

With the urgent need for bio-nanomaterials to improve the currently available cancer treatments, gold nanoparticle (GNP) hybrid nanostructures are rapidly rising as promising multimodal candidates for cancer therapy. Gold nanoparticles (GNPs) have been hybridized with several nanocarriers, including liposomes and polymers, to achieve chemotherapy, photothermal therapy, radiotherapy, and imaging using a single composite. The GNP nanohybrids used for targeted chemotherapy can be designed to respond to external stimuli such as heat or internal stimuli such as intratumoral pH. Despite their promise for multimodal cancer therapy, there are currently no reviews summarizing the current status of GNP nanohybrid use for cancer theragnostics. Therefore, this review fulfills this gap in the literature by providing a critical analysis of the data available on the use of GNP nanohybrids for cancer treatment with a specific focus on synergistic approaches (i.e., triggered drug release, photothermal therapy, and radiotherapy). It also highlights some of the challenges that hinder the clinical translation of GNP hybrid nanostructures from bench to bedside. Future studies that could expedite the clinical progress of GNPs, as well as the future possibility of improving GNP nanohybrids for cancer theragnostics, are also summarized.

Nano-Formulation Based Intravesical Drug Delivery Systems: An Overview of Versatile Approaches to Improve Urinary Bladder Diseases

Intravesical drug delivery is a direct drug delivery approach for the treatment of various bladder diseases. The human urinary bladder has distinctive anatomy, making it an effective barrier against any toxic agent seeking entry into the bloodstream. This screening function of the bladder derives from the structure of the urothelium, which acts as a semi-permeable barrier. However, various diseases related to the urinary bladder, such as hyperactive bladder syndrome, interstitial cystitis, cancer, urinary obstructions, or urinary tract infections, can alter the bladder’s natural function. Consequently, the intravesical route of drug delivery can effectively treat such diseases as it offers site-specific drug action with minimum side effects. Intravesical drug delivery is the direct instillation of medicinal drugs into the urinary bladder via a urethral catheter. However, there are some limitations to this method of drug delivery, including the risk of washout of the therapeutic agents with frequent urination. Moreover, due to the limited permeability of the urinary bladder walls, the therapeutic agents are diluted before the process of permeation, and consequently, their efficiency is compromised. Therefore, various types of nanomaterial-based delivery systems are being employed in intravesical drug delivery to enhance the drug penetration and retention at the targeted site. This review article covers the various nanomaterials used for intravesical drug delivery and future aspects of these nanomaterials for intravesical drug delivery.

Multiresponsive Polymer Nanocomposite Liquid Crystals Having Heterogeneous Phase Transitions for Battery-Free Temperature Maintenance Indicators

Multiresponsive functional materials that respond to more than one external stimulus are promising for novel photonic, electronic, and biomedical applications. However, the design or synthesis of new multiresponsive materials is challenging. Here, this work reports a facile method to prepare a multiresponsive colloidal material by mixing a liquid-crystalline 2D nanocolloid and a functional polymer colloid. For this purpose, electrically sensitive exfoliated α-ZrP 2D nanocolloids and thermosensitive block copolymer colloids that are dispersed well in water are mixed. In the liquid-crystalline nanocomposite, nematic, antinematic, or isotropic assemblies of α-ZrP, nanoparticles can be electrically and selectively obtained by applying electric fields with different frequencies; furthermore, their rheology is thermally and reversibly controlled through thesol-gel-sol transition. The nanocomposite exhibits a solid gel phase within a predesigned gel temperature range and a liquid sol phase outside this range. These properties facilitate the design of a simple display device in which information can be electrically written and thermally stabilized or erased, and using the device, a battery-free temperature maintenance indication function is demonstrated. The proposed polymer nanocomposite method can enrich the physical properties of 2D nanocolloidal liquid crystals and create new opportunities for eco-friendly, reusable, battery-free electro-optical devices.

Dually-Thermoresponsive Hydrogel with Shape Adaptability and Synergetic Bacterial Elimination in the Full Course of Wound Healing

Incomplete contact between a pre-formed hydrogel and irregular wound limits the therapeutic effect of the dressing and increases the risk of infection; while great concerns have remained regarding the potential toxicity of the residual additives of chemical crosslinking for in situ forming hydrogels. Therefore, it is desirable to develop a self-adaptive hydrogel in response to skin temperature with shape adaptability and efficient antibacterial properties to prevent microbial invasion. Herein, a dually-thermoresponsive hydrogel composed of poly(N-isopropylacrylamide) (PNIPAm) and methacrylated κ-carrageenan (MA-κ-CA) is designed with compliance at physiological temperature to realize shape adaptability for completely covering irregular wounds. Furthermore, the hydrogel with near-infrared (NIR)-responsive polypyrrole-polydopamine nanoparticles (PPy-PDA NPs) and Zn²⁺ -derived zeolitic imidazolate framework (ZIF-8) can generate localized heat and gradually release Zn²⁺ to realize safe, effective synergetic photothermal-chemical bactericidal capability. In addition, the release rate of Zn²⁺ can be accelerated by NIR-induced heating, and thus a more efficient sterilization can be provided to severely infected wounds. Therefore, the proposed hydrogel would serve as a promising wound dressing for the full course of wound healing, with the abilities of perfectly covering the wound and adapting to regenerating tissue, and controllable photothermal-chemical antibacterial capability to reach high bactericidal efficiency and long-term release of antibacterial agents.