Analysis of the impact of pluronic acid on the thermal stability and infectivity of AAV6.2FF.

BACKGROUND: The advancement of AAV vectors into clinical testing has accelerated rapidly over the past two decades. While many of the AAV vectors being utilized in clinical trials are derived from natural serotypes, engineered serotypes are progressing toward clinical translation due to their enhanced tissue tropism and immune evasive properties. However, novel AAV vectors require formulation and stability testing to determine optimal storage conditions prior to their use in a clinical setting. RESULTS: Here, we evaluated the thermal stability of AAV6.2FF, a rationally engineered capsid with strong tropism for lung and muscle, in two different buffer formulations; phosphate buffered saline (PBS), or PBS supplemented with 0.001% non-ionic surfactant Pluronic F68 (PF-68). Aliquots of AAV6.2FF vector encoding the firefly luciferase reporter gene (AAV6.2FF-ffLuc) were incubated at temperatures ranging from -20°C to 55°C for varying periods of time and the impact on infectivity and particle integrity evaluated. Additionally, the impact of several rounds of freeze-thaw treatments on the infectivity of AAV6.2FF was investigated. Vector infectivity was measured by quantifying firefly luciferase expression in HEK 293 cells and AAV particle integrity was measured by qPCR quantification of encapsidated viral DNA. CONCLUSIONS: Our data demonstrate that formulating AAV6.2FF in PBS containing 0.001% PF-68 leads to increased stability and particle integrity at temperatures between -20℃ to 21℃ and protection against the destructive effects of freeze-thaw. Finally, AAV6.2FF-GFP formulated in PBS supplemented with 0.001% PF-68 displayed higher transduction efficiency in vivo in murine lung epithelial cells following intranasal administration than vector buffered in PBS alone further demonstrating the beneficial properties of PF-68.

Pluronic F127 hydrogel-loaded extracellular vesicles from adipose-derived mesenchymal stem cells promote tracheal cartilage regeneration via SCNN1B delivery.

Extracellular vesicles (EVs) derived from adipose-derived mesenchymal stem cells (AMSC-EVs) have been highlighted as a cell-free therapy due to their regenerative capability to enhance tissue and organ regeneration. Herein, we aimed to examine the mechanism of PF127-hydrogel@AMSC-EVs in promoting tracheal cartilage defect repair. Based on bioinformatics methods, SCNN1B was identified as a key gene for the osteogenic differentiation of AMSCs induced by AMSC-EVs. EVs were isolated from rat AMSCs and then loaded onto thermo-sensitive PF-127 hydrogel to develop PF127-hydrogel@AMSC-EVs. It was established that PF127-hydrogel@AMSC-EVs could effectively deliver SCNN1B into AMSCs, where SCNN1B promoted AMSC osteogenic differentiation. The promotive effect was evidenced by enhanced ALP activity, extracellular matrix mineralization, and expression of s-glycosaminoglycan, RUNX2, OCN, collagen II, PERK, and ATF4. Furthermore, the in vivo experiments revealed that PF127-hydrogel@AMSC-SCNN1B-EVs stimulated tracheal cartilage regeneration in rats through PERK/ATF4 signaling axis activation. Therefore, PF127-hydrogel@AMSC-SCNN1B-EVs may be a novel cell-free biomaterial to facilitate tracheal cartilage regeneration and cartilage injury repair.

A Novel Tendon Injury Model, Induced by Collagenase Administration Combined with a Thermo-Responsive Hydrogel in Rats, Reproduces the Pathogenesis of Human Degenerative Tendinopathy.

Patellar tendinopathy is a common clinical problem, but its underlying pathophysiology remains poorly understood, primarily due to the absence of a representative experimental model. The most widely used method to generate such a model is collagenase injection, although this method possesses limitations. We developed an optimized rat model of patellar tendinopathy via the ultrasound-guided injection of collagenase mixed with a thermo-responsive Pluronic hydrogel into the patellar tendon of sixty male Wistar rats. All analyses were carried out at 3, 7, 14, 30, and 60 days post-injury. We confirmed that our rat model reproduced the pathophysiology observed in human patients through analyses of ultrasonography, histology, immunofluorescence, and biomechanical parameters. Tendons that were injured by the injection of the collagenase-Pluronic mixture exhibited a significant increase in the cross-sectional area (p < 0.01), a high degree of tissue disorganization and hypercellularity, significantly strong neovascularization (p < 0.01), important changes in the levels of types I and III collagen expression, and the organization and presence of intra-tendinous calcifications. Decreases in the maximum rupture force and stiffness were also observed. These results demonstrate that our model replicates the key features observed in human patellar tendinopathy. Collagenase is evenly distributed, as the Pluronic hydrogel prevents its leakage and thus, damage to surrounding tissues. Therefore, this model is valuable for testing new treatments for patellar tendinopathy.

An Optical Reusable 2D Radiochromic Gel-Based System for Ionising Radiation Measurements in Radiotherapy.

This work describes the development of a reusable 2D detector based on radiochromic reaction for radiotherapy dosimetric measurements. It consists of a radiochromic gel dosimeter in a cuboidal plastic container, scanning with a flatbed scanner, and data processing using a dedicated software package. This tool is assessed using the example of the application of the coincidence test of radiation and mechanical isocenters for a medical accelerator. The following were examined: scanning repeatability and image homogeneity, the impact of image processing on data processing in coincidence tests, and irradiation conditions-monitor units per radiation beam and irradiation field are selected. Optimal conditions for carrying out the test are chosen: (i) the multi-leaf collimator gap should preferably be 5 mm for 2D star shot irradiation, (ii) it is recommended to apply ≥2500-≤5000 MU per beam to obtain a strong signal enabling easy data processing, (iii) Mean filter can be applied to the images to improve calculations. An approach to dosimeter reuse with the goal of reducing costs is presented; the number of reuses is related to the MUs per beam, which, in this study, is about 5-57 for 30,000-2500 MU per beam (four fields). The proposed reusable system was successfully applied to the coincidence tests, confirming its suitability as a new potential quality assurance tool in radiotherapy.

Self-assembling Organogels Loaded with Tenoxicam for Local Intensive Pain and Inflammation Cure: In Vitro and In Vivo Correlation.

Due to tenoxicam (TX)'s poor aqueous solubility (0.072 mg/ml), it is poorly absorbable in the GIT, and the long-term oral administration of TX may cause severe GIT disturbances. Topical administration of TX can help in bypassing the GIT adverse effects. Therefore, in the present work, we constructed different pluronic/lecithin organogels (PLOs) for topical delivery of TX. PLO was constructed simply via direct mixing of an aqueous pluronic solution with lecithin solution. The prepared PLO formulations were characterized for their physicochemical properties including pH, drug content, visual inspection, viscosity, and spreadability. Also, the in vitro release and kinetic studies were carried out to investigate the mechanism of drug release. Moreover, the in vivo studies were carried out by investigating the anti-inflammatory and analgesic activities using albino male rats. The results showed that the modified PLOs have good physicochemical properties. The viscosity of the modified gels is a direct proportionality with both lecithin and pluronic concentrations. Also, subsequently, the drug release rate is directly proportional to gel viscosity. Moreover, the in vivo studies showed that the modified PLOs (F19) showed a significant ( < 0.05%) paw edema inhibition and pain analgesia compared with other investigated groups. Also, the results indicated that the increase in dose is accompanied by higher activity and a longer duration of action which extended to 12 h. Hence, the modified PLOs are promising safe candidates or vehicles for effective TX loading with sustained delivery behavior.

Modeling brain pathology to study nose-to-brain drug delivery.

OBJECTIVES: To create a new mucoadhesive dosage form based on PluronicF127 followed by transformation into a gel form upon intranasal administration for targeted delivery to brain tissueMETHODS: Citicoline, cytidine diphosphocholine, designated as CDP-choline, was purchased as a white powder with the molecular weight of 510.31 g/mol. The triblock copolymers of polyethylene glycol-block-polypropylene glycol-block-polyethylene glycol (PEG-PPG-PEG), branded as Pluronic F127, was used. RESULTS: When instilled into the nasal cavity, Pluronic F127 for intranasal administration is transformed into a gel that remains retained for 45-55 minutes, which promotes better penetration of drugs into the brain tissue. CONCLUSION: The polymer's gelling and adhesive properties performed well, which is crucial for further research at the preclinical stage (Tab. 1, Fig. 5, Ref. 28).

Amphiphilic, lauric acid-coupled pluronic-based nano-micellar system for efficient glipizide delivery.

Glipizide; an insulin secretagogue belonging to the sulfonylurea class, is a widely used antidiabetic drug for managing type 2 diabetes. However, the need for life-long administration and repeated doses poses challenges in maintaining optimal blood glucose levels. In this regard, orally active sustained-release nano-formulations can be a better alternative to traditional antidiabetic formulations. The present study explored an innovative approach by formulating orally active sustained-release nano-micelles using the amphiphilic lauric acid-conjugated-F127 (LAF127) block copolymer. LAF127 block copolymer was synthesized through esterification and thoroughly characterized before being employed to develop glipizide-loaded nano-micelles (GNM) via the thin-film hydration technique. The optimized formulation exhibited mean particle size of 341.40 ± 3.21 nm and depicted homogeneous particle size distribution with a polydispersity index (PDI) < 0.2. The formulation revealed a surface charge of -17.11 ± 6.23 mV. The in vitro release studies of glipizide from developed formulation depicted a sustained release profile. Drug loaded micelles exhibited a substantial reduction in blood glucose levels in diabetic rats for a duration of up to 24 h. Notably, neither the blank nano-micelles of LAF127 nor the drug loaded micelles manifested any indications of toxicity in healthy rats. This study provides an insight on suitability of synthesized LAF127 block copolymer for development of effective oral drug delivery systems for anti-diabetic activity without any significant adverse effects.

Molecular and functional characterization of chemosensory genes from the root-knot nematode Meloidogyne graminicola.

BACKGROUND: Root-knot nematode Meloidogyne graminicola has emerged as a major threat in rice agroecosystems owing to climate change-induced changes in cultivation practices. Synthetic nematicides are continually being withdrawn from the nematode management toolbox because of their ill effects on the environment. A sustainable strategy would be to develop novel nematicides or resistant plants that would target nematode sensory perception, which is a key step in the host finding biology of plant-parasitic nematodes (PPNs). However, compared to the extensive literature on the free-living nematode Caenorhabditis elegans, negligible research has been performed on PPN chemosensory biology. RESULTS: The present study characterizes the five chemosensory genes (Mg-odr-7, Mg-tax-4, Mg-tax-4.1, Mg-osm-9, and Mg-ocr-2) from M. graminicola that are putatively associated with nematode host-finding biology. All the genes were highly transcribed in the early life stages, and RNA interference (RNAi)-induced downregulation of each candidate gene perturbed the normal behavioural phenotypes of M. graminicola, as determined by examining the tracking pattern of juveniles on Pluronic gel medium, attraction to and penetration in rice root tip, and developmental progression in rice root. In addition, a detrimental effect on nematode chemotaxis towards different volatile and nonvolatile organic compounds and host root exudates was documented. CONCLUSION: Our findings enrich the existing literature on PPN chemosensory biology and can supplement future research aimed at identifying a comprehensive chemosensory signal transduction pathway in PPNs.

An In Situ Assembled Trapping Gel Repairs Spinal Cord Injury by Capturing Glutamate and Free Calcium Ions.

Spinal cord injury (SCI) can lead to devastating autonomic dysfunction. One of the most challenging issues for functional repair in SCI is the secondary damage caused by the increased release of glutamate and free Ca2+ from injured cells. Here, an in situ assembled trapping gel (PF-SA-GAD) is developed to sweep glutamate and Ca2+ , promoting SCI repair. The hydrogel solution is a mixture of recombinant glutamate decarboxylase 67 (rGAD67) protein, sodium alginate (SA), and pluronic F-127 (PF-127). After intrathecal administration, temperature-sensitive PF-127 promoted in situ gelation. Glutamate (Glu) is captured and decarboxylated by rGAD67 into γ-aminobutyric acid (GABA). SA reacted with the free Ca2+ to generate gellable calcium alginate. Thereby, this in situ trapping gel retarded secondary neuron injury caused by Glu and free Ca2+ during SCI. In rat models of SCI, PF-SA-GAD reduces the lesion volume and inflammatory response after SCI, restores the motor function of rats with SCI. Together, the in situ assembled trapping gel is a long-term effective and minimally invasive sweeper for the direct elimination of glutamate and Ca2+ from injury lesions and can be a novel strategy for SCI repair by preventing secondary injury.

Pluronic F127-liposome-encapsulated curcumin activates Nrf2/Keap1 signaling pathway to promote cell migration of HaCaT cells.

Curcumin (CUR) is an extract of Curcuma longa Linn., which has various pharmacological activities. The instability, low water solubility and bioavailability of CUR greatly limit its clinical application. This work prepared Pluronic F127-liposome-encapsulated curcumin (CUR-LIP-F127) and explored its functional role in wound healing. Liposome-encapsulated curcumin (CUR-LIP) and CUR-LIP-F127 were prepared. Human keratinocyte cell line (HaCaT) was treated with CUR, Pluronic F127-liposome (LIP-F127) and CUR-LIP-F127, or combined with ML385 (Nrf2 inhibitor). The expression of mRNAs and proteins was detected by quantitative real-time PCR and western blotting. MTT and wound healing assays were performed to detect cell viability and migration. CUR, LIP-F127 and CUR-LIP-F127 all had no influence on cell viability of HaCaT cells. CUR-LIP-F127 treatment significantly accelerated cell migration and enhanced the expression of nuclear factor erythroid-related factor 2 (Nrf2) and kelch-like erythroid cell-derived protein 1 (Keap1) in HaCaT cells with respect to CUR or LIP-F127 treatment. ML385 treatment impaired CUR-LIP-F127-mediated promotion of migration and up-regulation of Nrf2 and Keap1 in HaCaT cells. This work demonstrated that CUR-LIP-F127 activated Nrf2/Keap1 signaling pathway to promote migration of HaCaT cells, suggesting that CUR-LIP-F127 may contribute to wound healing.

In situ preparation of TiO2/f-MWCNT catalyst using Pluronic F127 assisted sol-gel process for sonocatalytic degradation of methylene blue.

In this study, titanium dioxide- Pluronics @F127/functionalized -multi walled carbon nanotubes (TiO2-F127f-/MWCNT) nanocatalysts were prepared, characterized, and used in methylene blue (MB) degradation under ultrasonic conditions. The characterization studies were performed using TEM, SEM, and XRD analyses to reveal the morphological and chemical properties of TiO2-F127/MWCNT nanocatalysts. To detect the optimum parameters for MB degradation using TiO2-F127/f-MWCNT nanocatalysts, several experimental parameters were conducted at various conditions such as different temperatures, pH, catalyst amount, hydrogen peroxide (H2O2) concentration, and various reaction contents. Transmission electron microscopy (TEM) analyses showed that TiO2-F127/f-MWCNT nanocatalysts consisted of a homogenous structure and have a 12.23 nm particle size. The crystalline particle size of TiO2-F127/MWCNT nanocatalysts was found to be 13.31 nm. Scanning electron microscope (SEM) analyses revealed the surface structure of TiO2-F127/f-MWCNT nanocatalysts turned to be modified after TiO2 loaded on MWCNT. Under the optimum conditions; pH: 4, MB concentration: 25 mg/L, H2O2 concentration: 30 mol/L, reaction time: and catalyst dose: 24 mg/L, chemical oxygen demand (COD) removal efficiency reached a maximum of 92%. To detect the radical effectiveness, three scavenger solvents were tested. Reuse experiments revealed that TiO2-F127/f-MWCNT nanocatalysts retained 84.2% catalytical activity after 5 cycles. Gas chromatography-mass spectrometry (GC-MS) was successfully used to identify the generated intermediates. Based on the experimental results, it has been suggested that •OH radicals are the main active species responsible for the degradation reaction in the presence of the TiO2-F127/f-MWCNT nanocatalysts.

Triptolide with hepatotoxicity and nephrotoxicity used in local delivery treatment of myocardial infarction by thermosensitive hydrogel.

Myocardial infarction (MI) resulting from coronary artery occlusion is the leading global cause of cardiovascular disability and mortality. Anti-inflammatory treatment plays an important role in MI treatment. Triptolide (TPL), as a Chinese medicine monomer, has a variety of biological functions, including anti-inflammatory, anti-tumor, and immunoregulation. However, it has been proved that TPL is poorly water soluble, and has clear hepatotoxicity and nephrotoxicity, which seriously limits its clinical application. Herein, we designed a long-acting hydrogel platform (TPL@PLGA@F127) for MI treatment by intramyocardial injection. First, we found that the inflammatory response and immune regulation might be the main mechanisms of TPL against MI by network pharmacology. Subsequently, we prepared the hydrogel platform (TPL@PLGA@F127) and tested its effects and toxicity on normal organs in the early stage of MI (3 days after MI-operation). The results showed that TPL@PLGA@F127 could not only promote "repair" macrophages polarization (to M2 macrophage) by day 3 after MI, but also has a long-lasting anti-inflammatory effect in the later stage of MI (28 days after MI-operation). Additionally, we proved that TPL@PLGA@F127 could attenuate the toxicity of TPL by releasing it more slowly and stably. Finally, we observed the long-term effects of TPL@PLGA@F127 on MI and found that it could improve cardiac function, depress the myocardial fibrosis and protect the cardiomyocytes. In summary, this study indicated that TPL@PLGA@F127 could not only enhance the therapeutic effects of TPL on MI, but also attenuate the hepatotoxicity and nephrotoxicity, which established a strong foundation for the clinical application of TPL for MI.

Spray coverage analysis of topical sprays formed by cold thermoreversible hydrogels.

OBJECTIVE: Sprayable hydrogel formulations are promising topical treatments for skin wounds due to their ability to reduce application pain, prolong drug release, and provide moisture to promote skin healing. These viscoelastic materials, however, present challenges in spray ability which can be overcome using a thermoreversible hydrogels sprayed as lower viscosity liquids at cooler temperatures. The purpose of this research was to evaluate the impact of thermoreversible hydrogel formulation and device characteristics on topical spray patterns and to develop metrics to accurately describe surface coverage. METHODS: Cold solutions of Pluronic F127 were prepared at 15, 17, and 20% (w/w) and tested to determine their rheological properties. Formulations were sprayed from hand-held atomizing pump dispersers under cold conditions and two distinct areas of their spray patterns analyzed: the concentrated core and the full spray pattern. Traditional analysis of spray patterns was conducted to determine major and minor axes, ovality, and total area. In addition, new scripts were developed to evaluate the concentrated core. RESULTS: The full spray pattern analysis quantified the total area over which the spray would extend a flat surface, while the concentrated core analysis quantified the continuous region where a drug dose would be concentrated. The combination of formulation viscosity, sprayer nozzle, and spray distance produced spray patterns from highly concentrated to highly dispersed. These parameters can be controlled to generate desired hydrogel spray patterns for application on skin surfaces. CONCLUSION: The developed metrics provide a basis for topical spray analysis that can inform future product performance.

Demulsifier-Inspired Superhydrophilic/Underwater Superoleophobic Membrane Modified with Polyoxypropylene Polyoxyethylene Block Polymer for Enhanced Oil/Water Separation Properties.

Demulsifiers are considered the key materials for oil/water separation. Various works in recent years have shown that demulsifiers with polyoxypropylen epolyoxyethylene branched structures possess better demulsification effects. In this work, inspired by the chemical structure of demulsifiers, a novel superhydrophilic/underwater superoleophobic membrane modified with a polyoxypropylene polyoxyethylene block polymer was fabricated for enhanced separation of O/W emulsion. First, a typical polyoxypropylene polyoxyethylene triblock polymer (Pluronic F127) was grafted onto the poly styrene-maleic anhydride (SMA). Then, the Pluronic F127-grafted SMA (abbreviated as F127@SMA) was blended with polyvinylidene fluoride (PVDF) for the preparation of the F127@SMA/PVDF ultrafiltration membrane. The obtained F127@SMA/PVDF ultrafiltration membrane displayed superhydrophilic/underwater superoleophobic properties, with a water contact angle of 0° and an underwater oil contact angle (UOCA) higher than 150° for various oils. Moreover, it had excellent separation efficiency for SDS-stabilized emulsions, even when the oil being emulsified was crude oil. The oil removal efficiency was greater than 99.1%, and the flux was up to 272.4 L·m-2·h-1. Most importantly, the proposed F127@SMA/PVDF membrane also exhibited outstanding reusability and long-term stability. Its UOCA remained higher than 150° in harsh acidic, alkaline, and high-salt circumstances. Overall, the present work proposed an environmentally friendly and convenient approach for the development of practical oil/water separation membranes.

Design, Development, and Evaluation of SA-F127:TPGS Polymeric Mixed Micelles for Improved Delivery of Glipizide Drug: In-vitro, Ex-vivo, and In-vivo Investigations.

The anti-diabetic glipizide (GLN) drug has notable pharmaceutical advantages, but poor aqueous solubility restricts its wide applications. The present work was to develop a mixed polymeric micelle system composed of SA-F127 and TPGS to improve the water solubility and effective delivery of the GLN. First, we synthesized SA-F127 and confirmed it through FTIR, NMR, and GPC techniques. The GLN-PMM were fabricated with the thin-film technique and optimized with CCD design. The developed GLN-PMM was characterized using DLS, Zeta, TEM, Rheology, FTIR, DSC, and XRD measurements. The GLN-PMM manifested a spherical morphology with 67.86 nm particle size, a -3.85 mV zeta potential, and a 0.582±0.06 PDI value. The polymeric mixed micelles showed excellent compatibility with GLN and were amorphous in nature. NMR studies confirmed the encapsulation of GLN in the core of the mixed micelle. In addition, the GLN-PMM micelles were tested in vitro for cumulative drug release, ex vivo for permeation, and in vivo for anti-diabetic investigations. The GLN-PMM release profile in the various pH environments showed over 90% after 24 h, clearly indicating sustained release. The GLN-PMM micelles gave higher 88.86±3.39% GLN permeation from the goat intestine compared with free GLN. In-vivo anti-diabetic investigation proves the powerful anti-diabetic properties of GLN-PMM in comparison to the marketed formulation. These findings demonstrated that the polymeric mixed micelles of SA-F127 and TPGS could be a promising, effective, and environment-friendly approach for oral delivery of the GLN.

Design, Fabrication and Evaluation of Stabilized Polymeric mixed micelles for Effective Management in Cancer Therapy.

PURPOSE: Cancer is one of the most common and fatal disease, chemotherapy is the major treatment against many cancer types. The anti-apoptotic BCL-2 protein's expression was increased in many cancer types and Venetoclax (VLX; BCL-2 inhibitor) is a small molecule, which selectively inhibits this specified protein. In order to increase the clinical performance of this promising inhibitor as a repurposed drug, polymeric mixed micelles formulations approach was explored. METHODS: The Venetoclax loaded polymeric mixed micelles (VPMM) were prepared by using Pluronic® F-127 and alpha tocopherol polyethylene glycol 1000 succinate (TPGS) as excipients by thin film hydration method and characteristics. The percentage drug loading capacity, entrapment efficiency and in-vitro drug release studies were performed using HPLC method. The cytotoxicity assay, cell uptake and anticancer activities were evaluated in two different cancer cells i.e. MCF-7 (breast cancer) and A-549 (lung cancer). RESULTS: Particle size, polydispersity index and zeta potential of the VPMM was found to be 72.88 ± 0.09 nm, 0.078 ± 0.009 and -4.29 ± 0.24 mV, respectively. The entrapment efficiency and %drug loading were found to be 80.12 ± 0.23% and 2.13% ± 0.14%, respectively. The IC50 of VLX was found to be 4.78, 1.30, 0.94 µg/ml at 24, 48 and 72 h, respectively in MCF-7 cells and 1.24, 0.68, and 0.314 µg/ml at 24, 48, and 72 h, respectively in A549 cells. Whereas, IC50 of VPMM was found to be 0.42, 0.29, 0.09 µg/ml at 24, 48 and 72 h, respectively in MCF-7 cells and 0.85, 0.13, 0.008 µg/ml at 24, 48 and 72 h in A549 cells, respectively, indicating VPMM showing better anti-cancer activity compared to VLX. The VPMM showed better cytotoxicity which was further proven by other assays and explained the anti-cancer activity is shown through the generation of ROS, nuclear damage,apoptotic cell death and expression of caspase-3,7, and 9 activities in apoptotic cells. CONCLUSION: The current investigation revealed that the Venetoclax loaded polymeric mixed micelles (VPMM) revealed the enhanced therapeutic efficacy against breast and lung cancer in vitro models.

High-Resolution 3D Printing of Mechanically Tough Hydrogels Prepared by Thermo-Responsive Poloxamer Ink Platform.

High-resolution 3D-printable hydrogels with high mechanical strength and biocompatibility are in great demand because of their potential applications in numerous fields. In this study, a material system comprising Pluronic F-127 dimethacrylate (FDMA) is developed to function as a direct ink writing (DIW) hydrogel for 3D printing. FDMA is a triblock copolymer that transforms into micelles at elevated temperatures. The transformation increases the viscosity of FDMA and preserves its structure during DIW 3D printing, whereupon the printed structure is solidified through photopolymerization. Because of this viscosity shift, various functionalities can be incorporated through the addition of other materials in the solution state. Acrylic acid is incorporated into the pregel solution to enhance the mechanical strength, because the carboxylate group of poly(acrylic acid) ionically crosslinks with Fe3+ , increasing the toughness of the DIW hydrogel 37 times to 2.46 MJ m-3 . Tough conductive hydrogels are also 3D printed by homogenizing poly(3,4-ethylenedioxythiophene) polystyrene sulfonate into the pregel solution. Furthermore, the FDMA platform developed herein uses DIW, which facilitates multicartridges 3D printing, and because all the materials included are biocompatible, the platform may be used to fabricate complex structures for biological applications.

Dynamic tracing using ultra-bright labeling and multi-photon microscopy identifies endothelial uptake of poloxamer 188 coated poly(lactic-co-glycolic acid) nano-carriers in vivo.

The potential of poly(lactic-co-glycolic acid) (PLGA) to design nanoparticles (NPs) and target the central nervous system remains to be exploited. In the current study we designed fluorescent 70-nm PLGA NPs, loaded with bulky fluorophores, thereby making them significantly brighter than quantum dots in single-particle fluorescence measurements. The high brightness of NPs enabled their visualization by intravital real-time 2-photon microscopy. Subsequently, we found that PLGA NPs coated with pluronic F-68 circulated in the blood substantially longer than uncoated NPs and were taken up by cerebro-vascular endothelial cells. Additionally, confocal microscopy revealed that coated PLGA NPs were present in late endothelial endosomes of cerebral vessels within 1 h after systemic injection and were more readily taken up by endothelial cells in peripheral organs. The combination of ultra-bright NPs and in vivo imaging may thus represent a promising approach to reduce the gap between development and clinical application of nanoparticle-based drug carriers.

Impact of small molecule and reverse poloxamer addition on the micellization and gelation mechanisms of poloxamer hydrogels.

Poloxamer 407 (P407) is widely used for targeted drug-delivery because it exhibits thermoresponsive gelation behavior near body temperature, stemming from a disorder-to-order transition. Hydrophobic small molecules can be encapsulated within P407; however, these additives often negatively impact the rheological properties and lower the gelation temperatures of the hydrogels, limiting their clinical utility. Here we investigate the impact of adding two BAB reverse poloxamers (RPs), 25R4 and 31R1, on the thermal transitions, rheological properties, and assembled structures of P407 both with and without incorporated small molecules. By employing a combination of differential scanning calorimetry (DSC), rheology, and small-angle x-ray scattering (SAXS), we determine distinct mechanisms for RP incorporation. While 25R4 addition promotes inter-micelle bridge formation, the highly hydrophobic 31R1 co-micellizes with P407. Small molecule addition lowers thermal transition temperatures and increases the micelle size, while RP addition mitigates the decreases in modulus traditionally associated with small molecule incorporation. This fundamental understanding yields new strategies for tuning the mechanical and structural properties of the hydrogels, enabling design of drug-loaded formulations with ideal thermal transitions for a range of clinical applications.

Non-Ionic Surfactant Effects on Innate Pluronic 188 Behavior: Interactions, and Physicochemical and Biocompatibility Studies.

The aim of this research was to prepare novel block copolymer-surfactant hybrid nanosystems using the triblock copolymer Pluronic 188, along with surfactants of different hydrophilic to lipophilic balance (HLB ratio-which indicates the degree to which a surfactant is hydrophilic or hydrophobic) and thermotropic behavior. The surfactants used were of non-ionic nature, of which Tween 80® and Brij 58® were more hydrophilic, while Span 40® and Span 60® were more hydrophobic. Each surfactant has unique innate thermal properties and an affinity towards Pluronic 188. The nanosystems were formulated through mixing the pluronic with the surfactants at three different ratios, namely 90:10, 80:20, and 50:50, using the thin-film hydration technique and keeping the pluronic concentration constant. The physicochemical characteristics of the prepared nanosystems were evaluated using various light scattering techniques, while their thermotropic behavior was characterized via microDSC and high-resolution ultrasound spectroscopy. Microenvironmental parameters were attained through the use of fluorescence spectroscopy, while the cytotoxicity of the nanocarriers was studied in vitro. The results indicate that the combination of Pluronic 188 with the above surfactants was able to produce hybrid homogeneous nanoparticle populations of adequately small diameters. The different surfactants had a clear effect on physicochemical parameters such as the size, hydrodynamic diameter, and polydispersity index of the final formulation. The mixing of surfactants with the pluronic clearly changed its thermotropic behavior and thermal transition temperature (Tm) and highlighted the specific interactions that occurred between the different materials, as well as the effect of increasing the surfactant concentration on inherent polymer characteristics and behavior. The formulated nanosystems were found to be mostly of minimal toxicity. The obtained results demonstrate that the thin-film hydration method can be used for the formulation of pluronic-surfactant hybrid nanoparticles, which in turn exhibit favorable characteristics in terms of their possible use in drug delivery applications. This investigation can be used as a road map for the selection of an appropriate nanosystem as a novel vehicle for drug delivery.