Structural characterization using SAXS and rheological behaviors of pluronic F127 and methylcellulose blends

Liver bioprinting within a novel support medium with functionalized spheroids, hepatic vein structures, and enhanced post-transplantation vascularization

Cell-laden bioprinting is a promising biofabrication strategy for regenerating bioactive transplants to address organ donor shortages. However, there has been little success in reproducing transplantable artificial organs with multiple distinctive cell types and physiologically relevant architecture. In this study, an omnidirectional printing embedded network (OPEN) is presented as a support medium for embedded 3D printing. The medium is state-of-the-art due to its one-step preparation, fast removal, and versatile ink compatibility. To test the feasibility of OPEN, exceptional primary mouse hepatocytes (PMHs) and endothelial cell line-C166, were used to print hepatospheroid-encapsulated-artificial livers (HEALs) with vein structures following predesigned anatomy-based printing paths in OPEN. PMHs self-organized into hepatocyte spheroids within the ink matrix, whereas the entire cross-linked structure remained intact for a minimum of ten days of cultivation. Cultivated HEALs maintained mature hepatic functions and marker gene expression at a higher level than conventional 2D and 3D conditions in vitro. HEALs with C166-laden vein structures promoted endogenous neovascularization in vivo compared with hepatospheroid-only liver prints within two weeks of transplantation. Collectively, the proposed platform enables the manufacture of bioactive tissues or organs resembling anatomical architecture, and has broad implications for liver function replacement in clinical applications.

Sprayable ciprofloxacin-loaded poloxamer hydrogels for wound infection treatment

Topical antimicrobial treatments for severe burns and chronic wounds provide effective treatment against infections, but cause pain and discomfort with application. This study aimed to develop an antimicrobial topical formulation comprising thermoreversible poloxamers (Pluronic F127 and F68) and a broad-spectrum antimicrobial agent (ciprofloxacin hydrochloride, CH), that could be sprayed to eliminate application pain while maintaining antimicrobial activity. Formulations were characterized to determine their sprayability under cold conditions, gelation temperature, final storage modulus at skin temperature, drug release profile, ex vivo permeation through impaired porcine skin, and inhibition against common bacterial pathogens that colonize wounds. All cold formulations were sprayable from simple hand-held, pump-action sprayers due to their low viscosity. Upon heating, 17 and 20% Pluronic F127 formulations produced hydrogels eight to ten degrees below skin temperature, independent of ciprofloxacin loading. Increasing concentrations of Pluronic F127 increased the final storage modulus and viscosity of the gels, while inclusion of Pluronic F68 reduced these properties, showing that hydrogel rheological properties at skin temperature can be tuned via choice of formulation. Drug release was directly correlated to the rheological properties, with stiffer gels resulting in a decrease in drug release rate. Overall, gels released about 65-90% of their load within 12 hours. Ex vivo skin permeation demonstrated that drug was well retained in impaired porcine skin, which is desired to continuously treat bacteria localized to the wound. A well-diffusion assay indicated that the hydrogels had greater bacterial inhibition against Pseudomonas aeruginosa, Escherichia coli, and two strains of Staphylococcus aureus when compared to commercial controls. Overall, the results show the potential of CH-loaded poloxamer formulations as suitable sprayable topical dressings to deliver antimicrobials directly to wounds.

Effect of chain architecture on the structure, dynamics, and rheology of thermoresponsive poloxamer hydrogels and associated blends

Poloxamers, ABA triblock polymers composed of a poly(propylene oxide) (PPO) midblock (B) and poly(ethylene oxide) (PEO) endblocks (A), are widely studied for biomedical applications. Aqueous poloxamer 407 (P407; also referred to as F127) undergoes a solution-to-gel transition with increasing temperature, driven by the formation and ordering of micelles onto periodic lattices; however, the gel temperature and resulting modulus has limited tunability. Here, reverse P407 (RP407), a BAB polymer of the same composition and molar mass but the inverted architecture, is synthesized via anionic polymerization. The micellization and gelation temperatures of RP407 are higher than that of P407 and the PPO endblocks allow for intermicelle bridging; however, both single-component solutions favor body-centered cubic (BCC) packings. Further, aqueous RP407 displays a "soft gel" region with interesting rheological behavior, including viscoelastic aging and thermal hysteresis. Combining P407 and RP407 yields solutions with intermediate transition temperatures and alters the size and micelle packing. While the single-component solutions produce BCC packings, the blends form close-packed structures and larger micelles of higher aggregation numbers. Blends of P407 with an analogous AB diblock (E111P32) display similar behavior, whereas RP407/diblock blends form intermediate-sized BCC-packed micelles. These differences in packing and aggregation alter the local environments within the gels, which could have implications for applications such as drug delivery and protein stabilization.

Poloxamer-based nanogels as delivery systems: how structural requirements can drive their biological performance?

Poloxamers or Pluronics®-based nanogels are one of the most used matrices for developing delivery systems. Due to their thermoresponsive and flexible mechanical properties, they allowed the incorporation of several molecules including drugs, biomacromolecules, lipid-derivatives, polymers, and metallic, polymeric, or lipid nanocarriers. The thermogelling mechanism is driven by micelles formation and their self-assembly as phase organizations (lamellar, hexagonal, cubic) in response to microenvironmental conditions such as temperature, osmolarity, and additives incorporated. Then, different biophysical techniques have been used for investigating those structural transitions from the mechanisms to the preferential component's orientation and organization. Since the design of PL-based pharmaceutical formulations is driven by the choice of the polymer type, considering its physico-chemical properties, it is also relevant to highlight that factors inherent to the polymeric matrix can be strongly influenced by the presence of additives and how they are able to determine the nanogels biopharmaceuticals properties such as bioadhesion, drug loading, surface interaction behavior, dissolution, and release rate control. In this review, we discuss the general applicability of three of the main biophysical techniques used to characterize those systems, scattering techniques (small-angle X-ray and neutron scattering), rheology and Fourier transform infrared absorption spectroscopy (FTIR), connecting their supramolecular structure and insights for formulating effective therapeutic delivery systems.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12551-023-01093-2.

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.

Preparation, Structural Characterization of Anti-Cancer Drugs-Mediated Self-Assembly from the Pluronic Copolymers through Synchrotron SAXS Investigation

Chemotherapy drugs are mainly administered via intravenous injection or oral administration in a very a high dosage. If there is a targeted drug vehicle which can be deployed on the tumor, the medical treatment is specific and precise. Binary mixing of biocompatible Pluronic^® F127 and Pluronic^® L121 was used in this study for a drug carrier of pluronic biomedical hydrogels (PBHs). Based on the same PBH ingredients, the addition of fluorouracil (5-FU) was separated in three ways when it was incorporated with pluronics: F127-L121-(5-FU), F127-(5-FU), and L121-(5-FU). Small angle X-ray scattering experiments were performed to uncover the self-assembled structures of the PBHs. Meanwhile, the expected micelle and lamellar structural changes affected by the distribution of 5-FU were discussed with respect to the corresponding drug release monitoring. PBH-all with the mixing method of F127-L121-(5-FU) has the fastest drug release rate owing to the undulated amphiphilic boundary. In contrast, PBH-2 with the mixing method of L121-(5-FU) has a prolonged drug release rate at 67% for one month of the continuous drug release experiment because the flat lamellar amphiphilic boundary of PBH-2 drags the migration of 5-FU from the hydrophobic core. Therefore, the PBHs developed in the study possess great potential for targeted delivery and successfully served as a microenvironment model to elucidate the diffusion pathway of 5-FU.