Pluronic F-127 hydrogel as a promising scaffold for encapsulation of dental-derived mesenchymal stem cells

Tailoring the proliferation of fibroblast cells by multiresponsive and thermosensitive stem cells composite F127 hydrogel containing folic acid.MgO:ZnO/chitosan hybrid microparticles for skin regeneration

In this study, biodegradable and thermosensitive F127 hydrogel containing folic acid.MgO:ZnO/chitosan hybrid particles (FMZC) was fabricated as a 3D mesenchymal stem cells (MSCs) delivery vehicle for regenerative medicine and wound healing purposes, in such a way to be responsive to lysozyme and UVA irradiation. The results showed that F127 hydrogel containing FMZC is a suitable and nontoxic construct for encapsulation of MSCs in the presence of lysozyme and UVA irradiation, bearing high stem cell viability and proliferation. The final hydrogel, MSC&FMZC, in response to lysozyme induced a higher proliferation rate and migration in human foreskin fibroblast cells (HFF). These phenomena were attributed to the released F.MgO:ZnO nanocomposites from chitosan microparticles and paracrine factors from MSCs within the hydrogel, resulting in synergistic biological effects. Moreover, lysozyme-treated MSC&FMZC hydrogel showed higher antibacterial and anti-biofilm activity against both Gram-positive and Gram-negative bacteria than bare hydrogel. However, a significant increase in the antibacterial activity of MSC&FMZC was observed as the treated bacteria were subjected to UVA irradiation owing to the photocatalytic activity of F.MgO:ZnO nanocomposites. Regarding the antibacterial activity and stimulating skin cell behavior of MSC&FMZC hydrogel that can promote the regenerative activities of skin, it could be considered as a promising scaffold for bacteria-accompanied wound healing.

MiR-615 Agomir Encapsulated in Pluronic F-127 Alleviates Neuron Damage and Facilitates Function Recovery After Brachial Plexus Avulsion

Brachial plexus avulsion (BPA) is a devastating traumatic peripheral nerve injury complicated with paralysis of the upper extremity. We previously reported that leucine-rich repeat and immunoglobulin-like domain-containing NOGO receptor-interacting protein 1 (LINGO-1) has a potent role in inhibiting neuron survival and axonal regeneration after the central nervous system (CNS) damage and miR-615 is a potential microRNA (miRNA) negatively regulated LINGO-1. However, the effect of miR-615 in BPA remains to be elucidated. Accumulating evidence indicates that pluronic F-127 (PF-127) hydrogel could serve as a promising vehicle for miRNA encapsulation. Thus, to further explore the potential role of hydrogel-miR-615 in BPA-reimplantation, the present study established the BPA rat model and injected miR-615 agomir encapsulated by PF-127 hydrogel into the reimplantation site using a microsyringe. In this study, results indicated that hydrogel-miR-615 agomir effectively alleviated motoneuron loss by LINGO-1 inhibition, promoted musculocutaneous nerve regeneration and myelination, reduced astrocytes activation, promoted angiogenesis and attenuated peripheral amyotrophy, leading to improved motor functional rehabilitation of the upper extremity. In conclusion, our findings demonstrate that miR-615-loaded PF-127 hydrogel may represent a novel therapeutic strategy for BPA treatment.

An Overview on Thermosensitive Oral Gel Based on Poloxamer 407

In this review, we describe the application of thermosensitive hydrogels composed of poloxamer in medicine, especially for oral cavities. Thermosensitive hydrogels remain fluid at room temperature; at body temperature, they become more viscous gels. In this manner, the gelling system can remain localized for considerable durations and control and prolong drug release. The chemical structure of the poloxamer triblock copolymer leads to an amphiphilic aqueous solution and an active surface. Moreover, the poloxamer can gel by forming micelles in an aqueous solution, depending on its critical micelle concentration and critical micelle temperature. Owing to its controlled-release effect, a thermosensitive gel based on poloxamer 407 (P407) is used to deliver drugs with different characteristics. As demonstrated in studies on poloxamer formulations, an increase in gelling viscosity decreases the drug release rate and gel dissolution time to the extent that it prolongs the drug’s duration of action in disease treatment. This property is used for drug delivery and different therapeutic applications. Its unique route of administration, for many oral diseases, is advantageous over traditional routes of administration, such as direct application and systemic treatment. In conclusion, thermosensitive gels based on poloxamers are suitable and have great potential for oral disease treatment.

Hyaluronic Acid-Functionalized Nanomicelles Enhance SAHA Efficacy in 3D Endometrial Cancer Models

Simple Summary

One of the major limitations to cancer therapies are the side effects caused by the drug interacting with any tissue in the body. There is often a balance between patient health and effectively treating the disease. To by-pass this balancing act nanoparticles are being used to deliver therapeutics straight to the tumors, acting as “Trojan Horses”. Endometrial cancers are known to have more of the cell surface protein CD44 than healthy tissues. Here, to efficiently target endometrial cancer, hyaluronic acid, which naturally binds to the CD44 protein was attached to the surface of nanoparticles and tested on microtissues or spheroids to better model a tumor and understand drug delivery performance. We show that our hyaluronic acid-nanoparticle formulations improve drug effects and interact with the cancer cells more than without this targeting agent.

Abstract

Histone Deacetylase (HDAC) enzymes are upregulated in cancer leading to the development of HDAC inhibiting compounds, several of which are currently in clinical trials. Side effects associated with toxicity and non-specific targeting indicate the need for efficient drug delivery approaches and tumor specific targeting to enhance HDAC efficacy in solid tumor cancers. SAHA encapsulation within F127 micelles functionalized with a surface hyaluronic acid moiety, was developed to target endometrial cancer cells expressing elevated levels of CD44. In vitro viability and morphology analyses was conducted in both 2D and 3D models to assess the translational potential of this approach. Encapsulation enhanced SAHA delivery and activity, demonstrating increased cytotoxic efficacy in 2D and 3D endometrial cancer models. High-content imaging showed improved nanoparticle internalization in 2D and CD44 enhanced penetration in 3D models. In addition, the nano-delivery system enhanced spheroid penetration resulting in cell growth suppression, p21 associated cell cycle arrest, as well as overcoming the formation of an EMT associated phenotype observed in free drug treated type II endometrial cancer cells. This study demonstrates that targeted nanoparticle delivery of SAHA could provide the basis for improving its efficacy in endometrial cancer. Using 3D models for endometrial cancer allows the elucidation of nanoparticle performance and CD44 targeting, likely through penetration and retention within the tumor model.

Anisotropic diffusion of Fe ions in Fricke-XO-Pluronic F-127 and Fricke-XO-gelatine 3D radiotherapy dosimeters

A new radiochromic dosimeter was examined with Raman spectroscopy and an optical approach for assessment of 3D dose distribution integrity. The acronym of the dosimeter is Fricke-XO-Pluronic F-127, where XO denotes xylenol orange; Pluronic F-127 is a copolymer matrix of poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide), and the dosimeter contains the components of a Fricke dosimetric solution. Two dosimeter samples in cuvettes were partially irradiated such that a radiation dose was absorbed at the bottom of the cuvettes. After irradiation, one sample was stored upside down such that the irradiated part was at the top and another one was stored with the irradiated part at the bottom. Two diffusion coefficients of ferric ion complexes with XO ([XO-Fe]⁺³) were calculated. They were compared with those for similar dosimeter, however with gelatine matrix instead of Pluronic F-127. The results obtained indicate an impact of the gravitational force on the diffusion of [XO-Fe]⁺³ions over time after irradiation and thus a possibility of severely undermining the integrity of a dose distribution in irradiated dosimeter. The conclusions drawn suggest the necessity of examination of different 3D Fricke dosimeter compositions for anisotropic diffusion of ferric ions.

Electromagnetic field-assisted cell-laden 3D printed poloxamer-407 hydrogel for enhanced osteogenesis

3D bioprinted hydrogel has gained enormous attention, especially in tissue engineering, owing to its attractive structure and excellent biocompatibility. In this study, we demonstrated that 3D bioprinted cell-laden 'thermoresponsive' poloxamer-407 (P407) gels have the potential to stimulate osteogenic differentiation of apical papilla stem cells (SCAPs) under the influence of low voltage-frequency (5 V-1 Hz, 0.62 mT) electromagnetic fields (EMFs). SCAPs were initially used for cell-laden 3D printing to biomimic the apical papilla of human teeth. The developed hydrogel exhibited higher mechanical strength as well as good printability, showing high-quality micro-architecture. Moreover, the as-printed hydrogels (5 mm × 5 mm) were loaded with plasminogen activator inhibitor-1 (PAI-1) for testing the combined effect of PAI-1 and EMFs on SCAP differentiation. Interestingly, the 3D hydrogels showed improved viability and differentiation of SCAPs under EMFs' influence as examined by live/dead assay and alizarin Red-S staining, respectively. Therefore, our results confirmed that P407 hydrogels are non-toxic for encapsulation of SCAPs, yielding high cell viability and accelerate the cell migration potential. The 3D hydrogels with PAI-1 exhibited high mRNA expression levels for osteogenic/odontogenic gene markers (ALP, Col-1, DSPP, and DMP-1) vis-à-vis control after 14 days of in vitro culture. Our findings suggest that 3D bioprinted P407 hydrogels are biocompatible for SCAP encapsulation, and the applied low voltage-frequency EMFs could effectively improve dental tissue regeneration, particularly for oral applications.

Combination Chemotherapy with Cisplatin and Chloroquine: Effect of Encapsulation in Micelles Formed by Self-Assembling Hybrid Dendritic-Linear-Dendritic Block Copolymers

Clinical outcomes of conventional drug combinations are not ideal due to high toxicity to healthy tissues. Cisplatin (CDDP) is the standard component for many cancer treatments, yet its principal dose-limiting side effect is nephrotoxicity. Thus, CDDP is commonly used in combination with other drugs, such as the autophagy inhibitor chloroquine (CQ), to enhance tumor cell killing efficacy and prevent the development of chemoresistance. In addition, nanocarrier-based drug delivery systems can overcome chemotherapy limitations, decreasing side effects and increasing tumor accumulation. The aim of this study was to evaluate the toxicity of CQ and CDDP against tumor and non-tumor cells when used in a combined treatment. For this purpose, two types of micelles based on Pluronic^® F127 hybrid dendritic–linear–dendritic block copolymers (HDLDBCs) modified with polyester or poly(esteramide) dendrons derived from 2,2′-bis(hydroxymethyl)propionic acid (HDLDBC-bMPA) or 2,2′-bis(glycyloxymethyl)propionic acid (HDLDBC-bGMPA) were explored as delivery nanocarriers. Our results indicated that the combined treatment with HDLDBC-bMPA(CQ) or HDLDBC-bGMPA(CQ) and CDDP increased cytotoxicity in tumor cells compared to the single treatment with CDDP. Encapsulations demonstrated less short-term cytotoxicity individually or when used in combination compared to the free drugs. However, and more importantly, a low degree of cytotoxicity against non-tumor cells was maintained, even when drugs were given simultaneously.

Electrohydrodynamic 3D Printing Scaffolds for Repair of Achilles Tendon Defect in Rats

Tissue engineering (TE) studies for Achilles tendon (AT) defects are a difficult and popular field in orthopedic medical practice. In this study, we applied electrohydrodynamic three-dimensional (3D) printing technology to construct scaffolds made of poly-(ɛ-ɛ-caprolactone) (PCL) and Pluronic F127 (F127) with different mass-volume ratios. The fibers and porous capabilities of the scaffolds were controlled using this technology. We found that F127 improved the hydrophilicity and degradation of PCL in vitro. The PCL scaffolds with 5% F127 were mostly favorable for cell adhesion and growth, suggesting that the scaffolds had good biocompatibility in vitro. Scaffolds with 5% F127 seeded with C3H10T1/2 cells were transplanted into AT defects in rats. A histological analysis indicated that the TE scaffolds were beneficial for the accumulation and arrangement of collagen fibers. Thus, this study provides fundamental experimental data for future clinical applications regarding TE for ATs.

Which experimental models and explorations to use in regenerative endodontics? A comprehensive review on standard practices

Since the discovery of dental pulp stem cells, a lot of teams have expressed an interest in dental pulp regeneration. Many approaches, experimental models and biological explorations have been developed, each including the use of stem cells and scaffolds with the final goal being clinical application in humans. In this review, the authors' objective was to compare the experimental models and strategies used for the development of biomaterials for tissue engineering of dental pulp with stem cells. Electronic queries were conducted on PubMed using the following terms: pulp regeneration, scaffold, stem cells, tissue engineering and biomaterial. The extracted data included the following information: the strategy envisaged, the type of stem cells, the experimental models, the exploration or analysis methods, the cytotoxicity or viability or proliferation cellular tests, the tests of scaffold antibacterial properties and take into account the vascularization of the regenerated dental pulp. From the 71 selected articles, 59% focused on the "cell-transplantation" strategy, 82% used in vitro experimentation, 58% in vivo animal models and only one described an in vivo in situ human clinical study. 87% used dental pulp stem cells. A majority of the studies reported histology (75%) and immunohistochemistry explorations (66%). 73% mentioned the use of cytotoxicity, proliferation or viability tests. 48% took vascularization into account but only 6% studied the antibacterial properties of the scaffolds. This article gives an overview of the methods used to regenerate dental pulp from stem cells and should help researchers create the best development strategies for research in this field.

Virus-like mesoporous silica-coated plasmonic Ag nanocube with strong bacteria adhesion for diabetic wound ulcer healing

The Gram-positive bacterium Staphylococcus aureus (MRSA) and the Gram-negative bacillus Escherichia coli (E. coli) can be commonly found in diabetic foot ulcers. However, the multi-drug resistant pathogenic bacteria infection is often difficult to eradicate by the conventional antibiotics and easy to spread which can lead to complications such as gangrene or sepsis. In this work, in order to pull through the low cell wall adhesion capability of typical antibacterial Ag nanoparticles, we fabricated biomimic virus-like mesoporous silica coated Ag nanocubes with gentamicin loading, and then the core-shell nanostructure was entrapped in the FDA approved hydrogel dressing. Interestingly, the Ag nanocubes with virus-like mesoporous silica coating are capable of effectively adsorbing on the rigid cell wall of both E. coli and MRSA. The intracellular H₂S in natural bacterial environment can induce generation of small Ag nanospheres, which are the ideal antibacterial nanoagents. Combined with the gentamicin delivery, the pathogenic bacteria in diabetic wound can be completely eradicated by our dressing to improve the wound healing procedure. This virus-like core-shell nanostructure sheds light for the future wound healing dressing design to promote the clinical applications on antibacterial eradication.

Hybrid mesoporous nanostructured scaffolds as dielectric biosimilar restorative materials

BACKGROUND

The intricate structure of natural materials is in correspondence with its highly complex functional behaviour. The health of teeth depends, in a complex way, on a heterogeneous arrangement of soft and hard porous tissues that allow for an adequate flow of minerals and oxygen to provide continuous restoration. Although restorative materials, used in clinics, have been evolving from the silver amalgams to actual inorganic fillers, their structural and textural properties are scarcely biomimetic, hindering the functional recovery of the tissue.

OBJECTIVE

The objective of this work is to compare and test the hybrid mesoporous silica-based scaffolds as candidates for dentine restoration applications.

METHODS

In this work, we present the development and the physical properties study of biocompatible hybrid mesoporous nanostructured scaffolds with a chemically versatile surface and biosimilar architecture. We test their textural (BET) and dielectric permittivity (ac impedance) properties.

RESULTS

These materials, with textural and dielectric properties similar to dentine and large availability for the payload of therapeutic agents, are promising candidates as functional restorative materials, suitable for impedance characterization techniques in dental studies.

CONCLUSIONS

Structural, textural, morphological characterization and electrical properties of hybrid mesoporous show a large degree of similarity to natural dentin samples.

Thermoresponsive Hydrogel-Based Local Delivery of Simvastatin for the Treatment of Periodontitis

Except for routine scaling and root planing, there are few effective nonsurgical therapeutic interventions for periodontitis and associated alveolar bone loss. Simvastatin (SIM), one of the 3-hydroxy-3-methylglutaryl-cosenzyme A reductase inhibitors, which is known for its capacity as a lipid-lowering medication, has been proven to be an effective anti-inflammatory and bone anabolic agent that has shown promising benefits in mitigating periodontal bone loss. The local delivery of SIM into the periodontal pocket, however, has been challenging due to SIM's poor water solubility and its lack of osteotropicity. To overcome these issues, we report a novel SIM formulation of a thermoresponsive, osteotropic, injectable hydrogel (PF127) based on pyrophosphorolated pluronic F127 (F127-PPi). After mixing F127-PPi with F127 at a 1:1 ratio, the resulting PF127 was used to dissolve free SIM to generate the SIM-loaded formulation. The thermoresponsive hydrogel's rheologic behavior, erosion and SIM release kinetics, osteotropic property, and biocompatibility were evaluated in vitro. The therapeutic efficacy of SIM-loaded PF127 hydrogel on periodontal bone preservation and inflammation resolution was validated in a ligature-induced periodontitis rat model. Given that SIM is already an approved medication for hyperlipidemia, the data presented here support the translational potential of the SIM-loaded PF127 hydrogel for better clinical management of periodontitis and associated pathologies.

Bioinks-materials used in printing cells in designed 3D forms

Use of materials to activate non-functional or damaged organs and tissues goes back to early ages. The first materials used for this purpose were metals, and in time, novel materials such as ceramics, polymers and composites were introduced to the field to serve in medical applications. In the last decade, the advances in material sciences, cell biology, technology and engineering made 3D printing of living tissues or organ models in the designed structure and geometry possible by using cells alone or together with hydrogels through additive manufacturing. This review aims to give a brief information about the chemical structures and properties of bioink materials and their applications in the production of 3D tissue constructs.

A Tailored Biomimetic Hydrogel as Potential Bioink to Print a Cell Scaffold for Tissue Engineering Applications: Printability and Cell Viability Evaluation

The present study established a maximum standard for printing quality and developed a preliminary ideal index to print three-dimensional (3D) construct using the Gly-Arg-Gly-Asp (GRGD) peptide modified Pluronic-F127 hydrogel (hereafter defined as 3DG bioformer (3BE)) as bioink. In addition, the biocompatibility of 3BE for 3D printing applications was carefully investigated. For biocompatibility study and ideal printing parameter, we used the formulation of 3BE in three different concentrations (3BE-1: 25%, 3BE-2: 30%, and 3BE-3: 35%). The 3BE hydrogels were printed layer by layer as a cube-like construct with all diameters of the needle head under the same feed (100 mm/s). The printing parameters were determined using combinations of 3BE-1, 3BE-2, and 3BE-3 with three different standard needle sizes (Φ 0.13 mm, Φ 0.33 mm, and Φ 0.9 mm). The printed constructs were photographed and observed using optical microscopy. The cell viability and proliferation were evaluated using Live/Dead assay and immunofluorescence staining. Results showed that a stable of printed line and construct could be generated from the 3BE-3 combinations. Cytotoxicity assay indicated that the 3BE hydrogels possessed well biocompatibility. Bioprinting results also demonstrated that significant cell proliferation in the 3BE-3 combinations was found within three days of printing. Therefore, the study discovered the potential printing parameters of 3BE as bioink to print a stable construct that may also have high biocompatibility for cell encapsulation. This finding could serve as valuable information in creating a functional scaffold for tissue engineering applications.

Ad-Dressing Stem Cells: Hydrogels for Encapsulation

Regenerative medicine is a novel scientific field that employs the use of stem cells as cell-based therapy for the regeneration and functional restoration of damaged tissues and organs. Stem cells bear characteristics such as the capacity for self-renewal and differentiation towards specific lineages and, therefore, serve as a backup reservoir in case of tissue injuries. Therapeutically, they can be autologously or allogeneically transplanted for tissue regeneration; however, allogeneic stem cell transplantation can provoke host immune responses leading to a host-versus-transplant reaction. A probable solution to this problem is stem cell encapsulation, a technique that utilizes various biomaterials for the creation of a semi-permeable membrane that encases the stem cells. Stem cell encapsulation can be accomplished by employing a great variety of natural and/or synthetic hydrogels and offers many benefits in regenerative medicine, including protection from the host’s immune system and mechanical stress, improved cell viability, proliferation and differentiation, cryopreservation and controlled and continuous delivery of the stem-cell-secreted therapeutic agents. Here, in this review, we report and discuss almost all natural and synthetic hydrogels used in stem cell encapsulation, along with the benefits that these materials, alone or in combination, could offer to cell therapy through functional cell encapsulation.

A pure molecular drug hydrogel for post-surgical cancer treatment

Local drug delivery systems, especially hydrogels, show superior strengths in postoperative recurrence prevention. Despite great advances, clinical translation of the hydrogels has been largely restricted as these drug delivery systems generally require chemical modification or additional carrier molecules to form hydrogels, which results in side effects correlative with local inflammation and systemic toxicity. Here, we developed a pure molecular anticancer drug hydrogel that reduced post-surgical tumor recurrence. The macroscopic pure molecular hydrogel was generated via ultrasonication of anticancer drug raltitrexed in aqueous solution, which was facile and environmentally friendly without involving chemical synthesis. Molecular dynamics simulations confirmed that raltitrexed self-assembled into a nanofibrous hydrogel through hydrogen bond and π-π interaction. Delivered as a hydrogel, raltitrexed could effectively decrease tumor recurrence rate and promote the inhibition of tumor growth in vivo. This raltitrexed self-delivery hydrogel has the potential to serve as a powerful auxiliary implement for preventing postoperative local tumor recurrence.

Alginate/Pluronic F127-based encapsulation supports viability and functionality of human dental pulp stem cell-derived insulin-producing cells

BACKGROUND

Current approach for diabetes treatment remained several adverse events varied from gastrointestinal to life-threatening symptoms. Regenerative therapy regarding Edmonton protocol has been facing serious limitations involving protocol efficiency and safety. This led to the study for alternative insulin-producing cell (IPC) resource and transplantation platform. In this study, evaluation of encapsulated human dental pulp-derived stem cell (hDPSC)-derived IPCs by alginate (ALG) and pluronic F127-coated alginate (ALGPA) was performed.

RESULTS

The results showed that ALG and ALGPA preserved hDPSC viability and allowed glucose and insulin diffusion in and out. ALG and ALGPA-encapsulated hDPSC-derived IPCs maintained viability for at least 336 h and sustained pancreatic endoderm marker (NGN3), pancreatic islet markers (NKX6.1, MAF-A, ISL-1, GLUT-2 and INSULIN), and intracellular pro-insulin and insulin expressions for at least 14 days. Functional analysis revealed a glucose-responsive C-peptide secretion of ALG- and ALGPA-encapsulated hDPSC-derived IPCs at 14 days post-encapsulation.

CONCLUSION

ALG and ALGPA encapsulations efficiently preserved the viability and functionality of hDPSC-derived IPCs in vitro and could be the potential transplantation platform for further clinical application.

GSK3 inhibitor-loaded osteotropic Pluronic hydrogel effectively mitigates periodontal tissue damage associated with experimental periodontitis

Periodontitis is a chronic inflammatory disease caused by complex interactions between the host immune system and pathogens that affect the integrity of periodontium. To prevent disease progression and thus preserve alveolar bone structure, simultaneous anti-inflammatory and osteogenic intervention are essential. Hence, a glycogen synthase kinase 3 beta inhibitor (BIO) was selected as a potent inflammation modulator and osteogenic agent to achieve this treatment objective. BIO's lack of osteotropicity, poor water solubility, and potential long-term systemic side effects, however, have hampered its clinical applications. To address these limitations, pyrophosphorylated Pluronic F127 (F127-PPi) was synthesized and mixed with regular F127 to prepare an injectable and thermoresponsive hydrogel formulation (PF127) of BIO, which could adhere to hard tissue and gradually release BIO to exert its therapeutic effects locally. Comparing to F127 hydrogel, PF127 hydrogels exhibited stronger binding to hydroxyapatite (HA). Additionally, BIO's solubility in PF127 solution was dramatically improved over F127 solution and the improvement was proportional to the polymer concentration. When evaluated on a rat model of periodontitis, PF127-BIO hydrogel treatment was found to be very effective in preserving alveolar bone and ligament, and preventing periodontal inflammation, as shown by the micro-CT and histological data, respectively. Altogether, these findings suggested that the thermoresponsive PF127 hydrogel is an effective local drug delivery system for better clinical management of periodontitis and associated pathologies.

Development and Characterization of a New Endoscopic Drug-Eluting Platform With Proven Efficacy in Acute and Chronic Experimental Colitis

Background and Aims: Mucosal lesions refractory to biological treatments represent unmet needs in patients with inflammatory bowel disease (IBD) that require new treatment modalities. We developed and characterized a new endoscopic drug-eluting hydrogel (CoverGel) with proven efficacy in acute and chronic experimental colitis (EC) in rats.

Methods: CoverGel was developed based on appropriate rheological, drug release, gelation, structural, and degradation property capacities to allow endoscopic application. Experimental colitis (EC) was induced by TNBS application in rats. In acute EC 40, rats were randomized in five groups (eight each): Sham, Control, CoverGel, CoverGel + Infliximab (IFX) and CoverGel + Vedolizumab (VDZ). In chronic EC, 12 rats were randomized in two groups (six each): IFX s.c. and CoverGel + IFX. Endoscopic, histological, and blood test were performed during follow-up to evaluate clinical success. Antibodies to IFX (ATIs) were evaluated in chronic EC animal study.

Results: CoverGel is a biocompatible and bioadhesive reverse thermosensitive gelation hydrogel with a macroporous structure and drug release capacity. In acute EC animals treated with CoverGel + IFX or CoverGel + VDZ showed significantly clinical success (weight recovery, mucosal restoration, and bacterial translocation) as compared with controls and animals without a bioactive drug. In a chronic EC animal study, clinical efficacy was comparable in both groups. Levels of ATIs were significantly lower in animals treated with CoverGel + IFX vs. IFX s.c. (0.90 ± 0.06 μg/mL-c vs. 1.97 ± 0.66 μg/mL-c, p = 0.0025).

Conclusions: CoverGel is an endoscopic vehicle to locally deliver biological drugs with proven efficacy in acute and chronic EC in rats and induce less immunogenicity reaction.

Umbilical Cord-Derived Mesenchymal Stem Cell-Derived Exosomes Combined Pluronic F127 Hydrogel Promote Chronic Diabetic Wound Healing and Complete Skin Regeneration

Purpose

Chronic refractory wounds are a multifactorial comorbidity of diabetes mellitus with the characteristic of impaired vascular networks. Currently, there is a lack of effective treatments for such wounds. Various types of mesenchymal stem cell-derived exosomes (MSC-exos) have been shown to exert multiple therapeutic effects on skin regeneration. We aimed to determine whether a constructed combination of human umbilical cord MSC (hUCMSC)-derived exosomes (hUCMSC-exos) and Pluronic F-127 (PF-127) hydrogel could improve wound healing.

Materials and Methods

We topically applied human umbilical cord-derived MSC (hUCMSC)-derived exosomes (hUCMSC-exos) encapsulated in a thermosensitive PF-127 hydrogel to a full-thickness cutaneous wound in a streptozotocin-induced diabetic rat model. The material properties and wound healing ability of the hydrogel and cellular responses were analyzed.

Results

Compared with hUCMSC-exos, PF-127-only or control treatment, the combination of PF-127 and hUCMSC-exos resulted in a significantly accelerated wound closure rate, increased expression of CD31 and Ki67, enhanced regeneration of granulation tissue and upregulated expression of vascular endothelial growth factor (VEGF) and factor transforming growth factor beta-1 (TGFβ-1).

Conclusion

The efficient delivery of hUCMSC-exos in PF-127 gel and improved exosome ability could promote diabetic wound healing. Thus, this biomaterial-based exosome therapy may represent a new therapeutic approach for cutaneous regeneration of chronic wounds.

Near-infrared nerve-binding fluorophores for buried nerve tissue imaging

Nerve-binding fluorophores with near-infrared (NIR; 650 to 900 nm) emission could reduce iatrogenic nerve injury rates by providing surgeons precise, real-time visualization of the peripheral nervous system. Unfortunately, current systemically administered nerve contrast agents predominantly emit at visible wavelengths and show nonspecific uptake in surrounding tissues such as adipose, muscle, and facia, thus limiting detection to surgically exposed surface-level nerves. Here, a focused NIR fluorophore library was synthesized and screened through multi-tiered optical and pharmacological assays to identify nerve-binding fluorophore candidates for clinical translation. NIR nerve probes enabled micrometer-scale nerve visualization at the greatest reported tissue depths (~2 to 3 mm), a feat unachievable with previous visibly emissive contrast agents. Laparoscopic fluorescent surgical navigation delineated deep lumbar and iliac nerves in swine, most of which were invisible in conventional white-light endoscopy. Critically, NIR oxazines generated contrast against all key surgical tissue classes (muscle, adipose, vasculature, and fascia) with nerve signal-to-background ratios ranging from ~2 (2- to 3-mm depth) to 25 (exposed nerve). Clinical translation of NIR nerve-specific agents will substantially reduce comorbidities associated with surgical nerve damage.

Application of Bone Marrow-Derived Mesenchymal Stem Cells for Muscle Healing After Contusion Injury in Mice

BACKGROUND

Skeletal muscle injuries are very common in sports medicine. Conventional therapies have limited clinical efficacy. New treatment methods should be developed to allow athletes to return to play with better function.

PURPOSE

To evaluate the in vitro differentiation potential of bone marrow-derived mesenchymal stem cells and the in vivo histologic and physiologic effects of mesenchymal stem cell therapy on muscle healing after contusion injury.

STUDY DESIGN

Controlled laboratory study.

METHODS

Bone marrow cells were flushed from both femurs of 5-week-old C57BL/6 mice to establish immortalized mesenchymal stem cell lines. A total of 36 mice aged 8 to 10 weeks were used to develop a muscle contusion model and were divided into 6 groups (6 mice/group) on the basis of the different dosages of IM2 cells to be injected (0, 1.25 × 10⁵, and 2.5 × 10⁵ cells with/without F-127 in 100 μL of phosphate-buffered saline). Histological analysis of muscle regeneration was performed, and the fast-twitch and tetanus strength of the muscle contractions was measured 28 days after muscle contusion injury, after injections of different doses of mesenchymal stem cells with or without the F-127 scaffold beginning 14 days after contusion injury.

RESULTS

The mesenchymal stem cell-treated muscles exhibited numerous regenerating myofibers. All the groups treated with mesenchymal stem cells (1.25 × 10⁵ cells, 2.5 × 10⁵ cells, 1.25 × 10⁵ cells plus F-127, and 2.5 × 10⁵ cells plus F-127) exhibited a significantly higher number of regenerating myofibers (mean ± SD: 111.6 ± 14.77, 133.4 ± 21.44, 221.89 ± 32.65, and 241.5 ± 25.95, respectively) as compared with the control group and the control with F-127 (69 ± 18.79 and 63.2 ± 18.98). The physiologic evaluation of fast-twitch and tetanus strength did not reveal differences between the age-matched uninjured group and the groups treated with various doses of mesenchymal stem cells 28 days after contusion. Significant differences were found between the control group and the groups treated with various doses of mesenchymal stem cells after muscle contusion.

CONCLUSION

Mesenchymal stem cell therapy increased the number of regenerating myofibers and improved fast-twitch and tetanus muscle strength in a mouse model of muscle contusion. However, the rapid decay of transplanted mesenchymal stem cells suggests a paracrine effect of this action. Treatment with mesenchymal stem cells at various doses combined with the F-127 scaffold is a potential therapy for a muscle contusion.

CLINICAL RELEVANCE

Mesenchymal stem cell therapy has an effect on sports medicine because of its effects on myofiber regeneration and muscle strength after contusion injury.

Thermoresponsive Poly(ε-Caprolactone)-Poly(Ethylene/Propylene Glycol) Copolymers as Injectable Hydrogels for Cell Therapies

Injectable, thermoresponsive hydrogels are promising candidates for the delivery, maintenance and controlled release of adoptive cell therapies. Therefore, there is significant interest in the development of cytocompatible and biodegradable thermoresponsive hydrogels with appropriate gelling characteristics. Towards this end, a series of thermoresponsive copolymers consisting of poly(caprolactone) (PCL), poly(ethylene glycol) (PEG) and poly(propylene glycol) (PPG) segments, with various PEG:PPG ratios, were synthesised via ring-opening polymerisation (ROP) of ε-caprolactone and epoxy-functionalised PEG and PPG derivatives. The resultant PCL-PEG-PPG copolymers were characterised via proton nuclear magnetic resonance (1H NMR) spectroscopy, gel permeation chromatography (GPC) and differential scanning calorimetry (DSC). The thermoresponsive characteristics of the aqueous copolymer solutions at various concentrations was investigated using the inversion method. Whilst all of the copolymers displayed thermoresponsive properties, the copolymer with a ratio of 1:2 PEG:PPG exhibited an appropriate sol-gel transition (28 °C) at a relatively low concentration (10 wt%), and remained a gel at 37 °C. Furthermore, the copolymers were shown to be enzymatically degradable in the presence of lipases and could be used for the encapsulation of CD4+ T-cell lymphocytes. These results demonstrate that the thermoresponsive PCL-PEG-PPG hydrogels may be suitable for use as an adoptive cell therapy (ACT) delivery vehicle.

Three-dimensional cartilage tissue regeneration system harnessing goblet-shaped microwells containing biocompatible hydrogel

Differentiation of stem cells into chondrocytes has been studied for the engineering of cartilage tissue. However, stem cells cultured two-dimensionally have limited ability to differentiate into chondrocytes, which led to the development of three-dimensional culture systems. A recently developed microtechnological method uses microwells as a tool to form uniformly sized spheroids. In this study, we fabricated an array (10 × 10) of goblet-shaped microwells based on polydimethylsiloxane for spheroid culture. A central processing unit (CPU) was used to form holes, and metallic beads were used to form hemispherical microwell geometry. The holes were filled with Pluronic F-127 to prevent cells from sinking through the holes and allowing the cells to form spheroids. Viability and chondrogenic differentiation of human adipose-derived stem cells were assessed. The fabrication method using a micro-pin mold and metallic beads is easy and cost-effective. Our three-dimensional spheroid culture system optimizes the efficient differentiation of cells and has various applications, such as drug delivery, cell therapy, and tissue engineering.

Free thiol groups on poly(aspartamide) based hydrogels facilitate tooth-derived progenitor cell proliferation and differentiation

Cell-based tissue reconstruction is an important field of regenerative medicine. Stem and progenitor cells derived from tooth-associated tissues have strong regeneration potential. However, their in vivo application requires the development of novel scaffolds that will provide a suitable three-dimensional (3D) environment allowing not only the survival of the cells but eliciting their proliferation and differentiation. Our aim was to study the viability and differentiation capacity of periodontal ligament cells (PDLCs) cultured on recently developed biocompatible and biodegradable poly(aspartamide) (PASP)-based hydrogels. Viability and behavior of PDLCs were investigated on PASP-based hydrogels possessing different chemical, physical and mechanical properties. Based on our previous results, the effect of thiol group density in the polymer matrix on cell viability, morphology and differentiation ability is in the focus of our article. The chemical composition and 3D structures of the hydrogels were determined by FT Raman spectroscopy and Scanning Electron Microscopy. Morphology of the cells was examined by phase contrast microscopy. To visualize cell growth and migration patterns through the hydrogels, two-photon microscopy were utilized. Cell viability analysis was performed according to a standardized protocol using WST-1 reagent. PDLCs were able to attach and grow on PASP-based hydrogels. An increase in gel stiffness enhanced adhesion and proliferation of the cells. However, the highest population of viable cells was observed on the PASP gels containing free thiol groups. The presence of thiol groups does not only enhance viability but also facilitates the osteogenic direction of the differentiating cells. These cell-gel structures seem to be highly promising for cell-based tissue reconstruction purposes in the field of regenerative medicine.

Extracellular pH modulating injectable gel for enhancing immune checkpoint inhibitor therapy

Clinical data from diverse cancer types shows that the increased T cell infiltration in tumors correlates with improved patient prognosis. Acidic extracellular pH is a major attribute of the tumor microenvironment (TME) that promotes immune evasion and tumor progression. Therefore, antagonizing tumor acidity can be a powerful approach in cancer immunotherapy. Here, Pluronic F-127 is used as a NaHCO₃ releasing carrier to focally alleviate extracellular tumor acidity. In a mouse tumor model, intratumoral treatment with pH modulating injectable gel (pH_e-MIG) generates immune-favorable TME, as evidenced by the decrease of immune-suppressive cells and increase of tumor infiltrating CD8+T cells. The combination of pH_e-MIG with immune checkpoint inhibitors, anti-PD-1 and anti-TIGIT antibodies, increases intratumoral T cell function, which leads to tumor clearance. Mechanistically, extracellular acidity was shown to upregulate co-inhibitory immune checkpoint receptors and inhibit mTOR signaling pathways in memory CD8+T cells, which impaired effector functions. Furthermore, an acidic pH environment increased the expression and engagement of TIGIT and its ligand CD155, which suggested that the extracellular pH can regulate the suppressive function of TIGIT pathway. Collectively, these findings suggest that pH_e-MIG holds potential as a new TME modulator for effective immune checkpoint inhibitor therapies.

Flow induced stability of pluronic hydrogels: Injectable and unencapsulated nucleus pulposus replacement

Poloxamers, or pluronics, have been proposed as biomimetic substitutes for physiological gels. Concern regarding their ability to resist swelling under fluid flows has impeded their implementation. Using a combination of techniques including cryo-TEM and rapid X-ray imaging, we found that rapid flow rates stabilized the gels against dissolution. Energy balance calculations confirmed that disentanglement of individual micelles was not possible at time scales faster than the reptation time when the system response was that of a solid which dissipated the hydrodynamic force field via cooperative deformation. In-vivo tests were performed where the hydrogel was injected as a substitute for the nucleus pulposus following discectomy in dogs. The results indicated that the gel was still present after 3 months, and radiographs indicated that compression of the disc space was prevented despite the gel being exposed to constant perfusion. STATEMENT OF SIGNIFICANCE: This paper demonstrates a highly unexpected result and counter intuitive result, namely the inverse dependence of the dissociation rate of a physical hydrogel on the flow velocity of the liquid medium. Using cryo-electron microscopy we demonstrate that the gel responds like deformable solid in high flow rates, with minimal dissociation. Since these gels are thermoreversible, they were injected into dogs, where we show that they were a viable alternative to the nucleus pulposus, without dissolution in physiological fluid flows for at least three months.

Remineralization, Regeneration, and Repair of Natural Tooth Structure: Influences on the Future of Restorative Dentistry Practice

Currently, the principal strategy for the treatment of carious defects involves cavity preparations followed by the restoration of natural tooth structure with a synthetic material of inferior biomechanical and esthetic qualities and with questionable long-term clinical reliability of the interfacial bonds. Consequently, prevention and minimally invasive dentistry are considered basic approaches for the preservation of sound tooth structure. Moreover, conventional periodontal therapies do not always ensure predictable outcomes or completely restore the integrity of the periodontal ligament complex that has been lost due to periodontitis. Much effort and comprehensive research have been undertaken to mimic the natural development and biomineralization of teeth to regenerate and repair natural hard dental tissues and restore the integrity of the periodontium. Regeneration of the dentin-pulp tissue has faced several challenges, starting with the basic concerns of clinical applicability. Recent technologies and multidisciplinary approaches in tissue engineering and nanotechnology, as well as the use of modern strategies for stem cell recruitment, synthesis of effective biodegradable scaffolds, molecular signaling, gene therapy, and 3D bioprinting, have resulted in impressive outcomes that may revolutionize the practice of restorative dentistry. This Review covers the current approaches and technologies for remineralization, regeneration, and repair of natural tooth structure.

Injectable, thermosensitive, fast gelation, bioeliminable, and oxygen sensitive hydrogels

The decrease of tissue oxygen content due to pathological conditions leads to severe cell death and tissue damage. Restoration of tissue oxygen content is the primary treatment goal. To accurately and efficiently assess efficacy of a treatment, minimally invasive, and long-term detection of oxygen concentration in the same tissue location represents a clinically attractive strategy. Among the different oxygen concentration measurement approaches, electron paramagnetic resonance (EPR) has the potential to accomplish this. Yet there lacks injectable EPR probes that can maintain a consistent concentration at the same tissue location during treatment period to acquire a stable EPR signal, and can finally be eliminated from body without retrieval. Herein, we developed injectable and bioeliminable hydrogel-based polymeric EPR probes that exhibited fast gelation rate, slow weight loss rate, and high oxygen sensitivity. The probe was based on N-Isopropylacrylamide (NIPAAm), 2-hydroxyethyl methacrylate (HEMA), dimethyl-γ-butyrolactone acrylate (DBA), and tetrathiatriarylmethyl (TAM) radical. The injectable probes can be implanted into tissues using a minimally invasive injection approach. The high gelation rate (~10 s) allowed the probes to quickly solidify upon injection to have a high retention in tissues. The polymeric probes overcame the toxicity issue of current small molecule EPR probes. The probes can be gradually hydrolyzed. Upon complete hydrolysis, the probes became water soluble at 37 °C, thus having the potential to be removed from the body by urinary system. The probes showed slow weight loss rate so as to maintain EPR signal intensity for extended periods while retaining in a certain tissue location. The probes remained their high oxygen sensitivity after in vitro hydrolysis and in vivo implantation for 4 weeks. These hydrogel-based EPR probes have attractive properties for in vivo oxygen detection.

Bone extracts immunomodulate and enhance the regenerative performance of dicalcium phosphates bioceramics

Immunomodulation strategies are believed to improve the integration and clinical performance of synthetic bone substitutes. One potential approach is the modification of biomaterial surface chemistry to mimic bone extracellular matrix (ECM). In this sense, we hypothesized that coating synthetic dicalcium phosphate (DCP) bioceramics with bone ECM proteins would modulate the host immune reactions and improve their regenerative performance. To test this, we evaluated the in vitro proteomic surface interactions and the in vivo performance of ECM-coated bioceramic scaffolds. Our results demonstrated that coating DCP scaffolds with bone extracts, specifically those containing calcium-binding proteins, dramatically modulated their interaction with plasma proteins in vitro, especially those relating to the innate immune response. In vivo, we observed an attenuated inflammatory response against the bioceramic scaffolds and enhanced peri-scaffold new bone formation supported by the increased osteoblastogenesis and reduced osteoclastogenesis. Furthermore, the bone extract rich in calcium-binding proteins can be 3D-printed to produce customized hydrogels with improved regeneration capabilities. In summary, bone extracts containing calcium-binding proteins can enhance the integration of synthetic biomaterials and improve their ability to regenerate bone probably by modulating the host immune reaction. This finding helps understand how bone allografts regenerate bone and opens the door for new advances in tissue engineering and bone regeneration. STATEMENT OF SIGNIFICANCE: Foreign-body reaction is an important determinant of in vivo biomaterial integration, as an undesired host immune response can compromise the performance of an implanted biomaterial. For this reason, applying immunomodulation strategies to enhance biomaterial engraftment is of great interest in the field of regenerative medicine. In this article, we illustrated that coating dicalcium phosphate bioceramic scaffolds with bone-ECM extracts, especially those rich in calcium-binding proteins, is a promising approach to improve their surface proteomic interactions and modulate the immune responses towards such biomaterials in a way that improves their bone regeneration performance. Collectively, the results of this study may provide a conceivable explanation for the mechanisms involved in presenting the excellent regenerative efficacy of natural bone grafts.

Sterilization Procedure for Temperature-Sensitive Hydrogels Loaded with Silver Nanoparticles for Clinical Applications

Hydrogels (HG) have recognized benefits as drug delivery platforms for biomedical applications. Their high sensitivity to sterilization processes is however one of the greatest challenges regarding their clinical translation. Concerning infection diseases, prevention of post-operatory related infections is crucial to ensure appropriate patient recovery and good clinical outcomes. Silver nanoparticles (AgNPs) have shown good antimicrobial properties but sustained release at the right place is required. Thus, we produced and characterized thermo-sensitive HG based on Pluronic^® F127 loaded with AgNPs (HG-AgNPs) and their integrity and functionality after sterilization by dry-heat and autoclave methods were carefully assessed. The quality attributes of HG-AgNPs were seriously affected by dry-heat methods but not by autoclaving methods, which allowed to ensure the required sterility. Also, direct sterilization of the final HG-AgNPs product proved more effective than of the raw material, allowing simpler production procedures in non-sterile conditions. The mechanical properties were assessed in post mortem rat models and the HG-AgNPs were tested for its antimicrobial properties in vitro using extremely drug-resistant (XDR) clinical strains. The produced HG-AgNPs prove to be versatile, easy produced and cost-effective products, with activity against XDR strains and an adequate gelation time and spreadability features and optimal for in situ biomedical applications.

LINGO-1 shRNA Loaded by Pluronic F-127 Promotes Functional Recovery After Ventral Root Avulsion

Spinal root avulsion typically leads to massive motoneuron death and severe functional deficits of the target muscles. Multiple pathological factors such as severe neuron loss, induction of inhibitory molecules, and insufficient regeneration are responsible for the poor functional recovery. Leucine-rich repeat and immunoglobulin-like domain-containing Nogo receptor-interacting protein 1 (LINGO-1), a central nervous system (CNS)-specific transmembrane protein that is selectively expressed on neurons and oligodendrocytes, serves as a potent negative mediator of axonal regeneration and myelination in CNS injuries and diseases. Although accumulating evidence has demonstrated improvement in axonal regeneration and neurological functions by LINGO-1 antagonism in CNS damage, the possible effects of LINGO-1 in spinal root avulsion remain undiscovered. In this study, a LINGO-1 knockdown strategy using lentiviral vectors encoding LINGO-1 short hairpin interfering RNA (shRNA) delivered by the Pluronic F-127 (PF-127) hydrogel was described after brachial plexus avulsion (BPA). We provide evidence that following BPA and immediate reimplantation, transplantation of LINGO-1 shRNA lentiviral vectors encapsulated by PF-127 rescued the injured motoneurons, enhanced axonal outgrowth and myelination, rebuilt motor endplates, facilitated the reinnervation of terminal muscles, improved angiogenesis, and promoted recovery of avulsed forelimbs. Altogether, these data suggest that delivery of LINGO-1 shRNA by a gel scaffold is a potential therapeutic approach for root avulsion. Impact Statement In this study, we attempted transplantation of lentivirus (LV)/leucine-rich repeat and immunoglobulin-like domain-containing Nogo receptor-interacting protein 1 (LINGO-1)-short hairpin interfering RNA (shRNA) encapsulated by the Pluronic F-127 (PF-127) hydrogel into a brachial plexus avulsion (BPA)-reimplantation model. We found that administration of LV/LINGO-1 shRNA facilitates neuron survival and axonal regeneration, attenuates muscle atrophy and motor endplate (MEP) loss, enhances neovascularization, and promotes functional recovery in BPA rats. Co-transplantation of LV/LINGO-1 shRNA and gel reinforces the survival-promoting effect, axonal outgrowth, and angiogenesis in comparison with LV/LINGO-1 shRNA application alone. Our research provides evidence that LV /LINGO-1 shRNA delivered by PF-127 represents a new treatment strategy for BPA repair.

Effect of lentiviral vector-mediated overexpression of hypoxia-inducible factor 1 alpha delivered by pluronic F-127 hydrogel on brachial plexus avulsion in rats

Brachial plexus avulsion often results in massive motor neuron death and severe functional deficits of target muscles. However, no satisfactory treatment is currently available. Hypoxia-inducible factor 1α is a critical molecule targeting several genes associated with ischemia-hypoxia damage and angiogenesis. In this study, a rat model of brachial plexus avulsion-reimplantation was established, in which C5–7 ventral nerve roots were avulsed and only the C6 root reimplanted. Different implants were immediately injected using a microsyringe into the avulsion-reimplantation site of the C6 root post-brachial plexus avulsion. Rats were randomly divided into five groups: phosphate-buffered saline, negative control of lentivirus, hypoxia-inducible factor 1α (hypoxia-inducible factor 1α overexpression lentivirus), gel (pluronic F-127 hydrogel), and gel + hypoxia-inducible factor 1α (pluronic F-127 hydrogel + hypoxia-inducible factor 1α overexpression lentivirus). The Terzis grooming test was performed to assess recovery of motor function. Scores were higher in the hypoxia-inducible factor 1α and gel + hypoxia-inducible factor 1α groups (in particular the gel + hypoxia-inducible factor 1α group) compared with the phosphate-buffered saline group. Electrophysiology, fluorogold retrograde tracing, and immunofluorescent staining were further performed to investigate neural pathway reconstruction and changes of neurons, motor endplates, and angiogenesis. Compared with the phosphate-buffered saline group, action potential latency of musculocutaneous nerves was markedly shortened in the hypoxia-inducible factor 1α and gel + hypoxia-inducible factor 1α groups. Meanwhile, the number of fluorogold-positive cells and ChAT-positive neurons, neovascular area (labeled by CD31 around avulsed sites in ipsilateral spinal cord segments), and the number of motor endplates in biceps brachii (identified by α-bungarotoxin) were all visibly increased, as well as the morphology of motor endplate in biceps brachil was clear in the hypoxia-inducible factor 1α and gel + hypoxia-inducible factor 1α groups. Taken together, delivery of hypoxia-inducible factor 1α overexpression lentiviral vectors mediated by pluronic F-127 effectively promotes spinal root regeneration and functional recovery post-brachial plexus avulsion. All animal procedures were approved by the Institutional Animal Care and Use Committee of Guangdong Medical University, China.

Dissolution and bioavailability improvement of bioactive apigenin using solid dispersions prepared by different techniques

Apigenin (APG) is a poorly soluble bioactive compound/nutraceutical which shows poor bioavailability upon oral administration. Hence, the objective of this research work was to develop APG solid dispersions (SDs) using different techniques with the expectation to obtain improvement in its in vitro dissolution rate and in vivo bioavailability upon oral administration. Different SDs of APG were prepared by microwave, melted and kneaded technology using pluronic-F127 (PL) as a carrier. Prepared SDs were characterized using "thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), Fourier transform infra-red (FTIR) spectrometer, powder X-ray diffraction (PXRD) and scanning electron microscopy (SEM)". After characterization, prepared SDs of APG were studied for in vitro drug release/dissolution profile and in vivo pharmacokinetic studies. The results of TGA, DSC, FTIR, PXRD and SEM indicated successful formation of APG SDs. In vitro dissolution experiments suggested significant release of APG from all SDs (67.39-84.13%) in comparison with control (32.74%). Optimized SD of APG from each technology was subjected to in vivo pharmacokinetic study in rats. The results indicated significant improvement in oral absorption of APG from SD prepared using microwave and melted technology in comparison with pure drug and commercial capsule. The enhancement in oral bioavailability of APG from microwave SD (319.19%) was 3.19 fold as compared with marketed capsule (100.00%). Significant enhancement in the dissolution rate and oral absorption of APG from SD suggested that developed SD systems can be successfully used for oral drug delivery system of APG.

Local Toxicity of Topically Administrated Thermoresponsive Systems: In Vitro Studies with In Vivo Correlation

Thermoresponsive materials have the ability to respond to a small change in temperature-a property that makes them useful in a wide range of applications and medical devices. Although very promising, there is only little conclusive data about the cytotoxicity and tissue toxicity of these materials. This work studied the biocompatibility of three Food and Drug Administration approved thermoresponsive polymers: poly( N-isopropyl acrylamide), poly(ethylene glycol)-poly(propylene glycol)-poly(ethylene glycol) tri-block copolymer, and poly(lactic acid-co-glycolic acid) and poly(ethylene glycol) tri-block copolymer. Fibroblast NIH 3T3 and HaCaT keratinocyte cells were used for the cytotoxicity testing and a mouse model for the in vivo evaluation. In vivo results generally showed similar trends as the results seen in vitro, with all tested materials presenting a satisfactory biocompatibility in vivo. pNIPAM, however, showed the highest toxicity both in vitro and in vivo, which was explained by the release of harmful monomers and impurities. More data focusing on the biocompatibility of novel thermoresponsive biomaterials will facilitate the use of existing and future medical devices.

AKT2 siRNA delivery with amphiphilic-based polymeric micelles show efficacy against cancer stem cells

Development of RNA interference-based therapies with appropriate therapeutic window remains a challenge for advanced cancers. Because cancer stem cells (CSC) are responsible of sustaining the metastatic spread of the disease to distal organs and the progressive gain of resistance of advanced cancers, new anticancer therapies should be validated specifically for this subpopulation of cells. A new amphihilic-based gene delivery system that combines Pluronic^® F127 micelles with polyplexes spontaneously formed by electrostatic interaction between anionic siRNA and cationic polyethylenimine (PEI) 10K, was designed (PM). Resultant PM gather the requirements for an efficient and safe transport of siRNA in terms of its physicochemical characteristics, internalization capacity, toxicity profile and silencing efficacy. PM were loaded with a siRNA against AKT2, an important oncogene involved in breast cancer tumorigenesis, with a special role in CSC malignancy. Efficacy of siAKT2-PM was validated in CSC isolated from two breast cancer cell lines: MCF-7 and Triple Negative MDA-MB-231 corresponding to an aggressive subtype of breast cancer. In both cases, we observed significant reduction on cell invasion capacity and strong inhibition of mammosphere formation after treatment. These results prompt AKT2 inhibition as a powerful therapeutic target against CSC and pave the way to the appearance of more effective nanomedicine-based gene therapies aimed to prevent CSC-related tumor recurrence.

Agarose-Based Hydrogels as Suitable Bioprinting Materials for Tissue Engineering

Hydrogels are useful materials as scaffolds for tissue engineering applications. Using hydrogels with additive manufacturing techniques has typically required the addition of techniques such as cross-linking or printing in sacrificial materials that negatively impact tissue growth to remedy inconsistencies in print fidelity. Thus, there is a need for bioinks that can directly print cell-laden constructs. In this study, agarose-based hydrogels commonly used for cartilage tissue engineering were compared to Pluronic, a hydrogel with established printing capabilities. Moreover, new material mixtures were developed for bioprinting by combining alginate and agarose. We compared mechanical and rheological properties, including yield stress, storage modulus, and shear thinning, as well as construct shape fidelity to assess their potential as a bioink for cell-based tissue engineering. The rheological properties and printability of agarose-alginate gels were statistically similar to those of Pluronic for all tests (p > 0.05). Alginate-agarose composites prepared with 5% w/v (3:2 agarose to alginate ratio) demonstrated excellent cell viability over a 28-day culture period (>∼70% cell survival at day 28) as well matrix production over the same period. Therefore, agarose-alginate mixtures showed the greatest potential as an effective bioink for additive manufacturing of biological materials for cartilage tissue engineering.

Substituting gelatine with Pluronic F-127 matrix in 3D polymer gel dosimeters can improve nuclear magnetic resonance, thermal and optical properties

This work discusses the substitution of a gelatine physical gel matrix with a matrix made of poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) (Pluronic F-127) in five 3D radiotherapy polymer gel dosimeters: MAGAT, PAGAT, NIPAM, VIPAR^nd (VIP) and VIPAR^CT (VIC). The current research outcomes showed that not each polymer gel dosimeter could be manufactured with Pluronic F-127. Two of the polymer gel dosimeters (PAGAT and VIP) containing the Pluronic F-127 matrix allowed for some proper dose response for radiotherapy dosimetry (a response to a dose range of e.g. 0‒50 Gy). The new best performing Pluronic-based polymer gel dosimeters were characterised by improved nuclear magnetic resonance properties, when being compared to gels with gelatine matrix at the same monomer content. These are: (i) a ~33% higher dose sensitivity; (ii) a comparable or slightly higher linear and dynamic dose range and (iii) a lower (new VIP composition, VIP3) or equivocal (new PAGAT composition, PAGAT2-Pluronic) dose threshold. However, there might be optimised gelatine based polymer dosimeters demonstrating even better sensitivity. UV-vis spectrophotometry measurements revealed that Pluronic matrices ensure six-times lower (VIP3-Pluronic) and eight-times lower (PAGAT2-Pluronic) absorbance (at 400 nm) of non-irradiated gels compared to gelatine matrices, which makes the new polymer gel dosimeters optically improved in comparison to their corresponding gelatine-based compositions. The differences in absorption reduce for higher wavelengths. Differential scanning calorimetry measurements revealed the following temperature stability ranges for the gels: (i) VIP with gelatine matrix: 0 °C‒26 °C, (ii) VIP3 with Pluronic matrix: 13.8 °C-55.2 °C, (iii) PAGAT2 with gelatine matrix: 0 °C-80 °C and (iv) PAGAT2 with Pluronic matrix: 21.4 °C-55.2 °C. In conclusion, Pluronic F-127 is an attractive co-polymer to serve as a substitute for the gelatine matrix in some 3D polymer gel dosimeters.