Effect of hydrophilically modified ibuprofen on thermoresponsive gelation of pluronic copolymer

Pluronic F68 Micelles as Carriers for an Anti-Inflammatory Drug: A Rheological and Scattering Investigation

Age-long ambition of medical scientists has always been advancement in healthcare and therapeutic medicine. Biomedical research indeed claims paramount importance in nanomedicine and drug delivery, and the development of biocompatible storage structures for delivering drugs stands at the heart of emerging scientific works. The delivery of drugs into the human body is nevertheless a nontrivial and challenging task, and it is often addressed by using amphiphilic compounds as nanosized delivery vehicles. Pluronics belong to a peculiar class of biocompatible and thermosensitive nonionic amphiphilic copolymers, and their self-assemblies are employed as drug delivery excipients because of their unique properties. We herein report on the encapsulation of diclofenac sodium within Pluronic F68 self-assemblies in water, underpinning the impact of the drug on the rheological and microstructural evolution of pluronic-based systems. The self-assembly and thermoresponsive micellization were studied through isothermal steady rheological experiments at different temperatures on samples containing 45 wt % Pluronic F68 and different amounts of diclofenac sodium. The adoption of scattering techniques, small-angle X-ray scattering (SAXS) and small-angle neutron scattering (SANS), allowed for the description of the system features at the nanometer length scale, providing information about the characteristic size of each part of the micellar structures as a function of temperature and drug concentration. Diclofenac sodium is not a good fellow for Pluronic F68. The triblock copolymer aids the encapsulation of the drug, highly improving its water solubility, whereas diclofenac sodium somehow hinders Pluronic self-assembly. By using a simple empirical model and no fitting parameters, the steady viscosity can be predicted, although qualitatively, through the volume fraction of the micelles extracted through scattering techniques and compared to the rheological one. A tunable control of the viscous behavior of such biomedical systems may be achieved through the suitable choice of their composition.

Role of Bovine Serum Albumin Addition in Micellization and Gel Formation of Poloxamer 407

The combination of the thermoresponsive polymer and protein has demonstrated great promise in its applications in drug delivery and tissue engineering fields. This study described the impact of bovine serum albumin (BSA) on the micellization and sol-gel transition behaviors of poloxamer 407 (PX). The micellization of aqueous PX solutions with and without BSA was examined using isothermal titration calorimetry. In the calorimetric titration curves, the pre-micellar region, the transition concentration region, and the post-micellar region were observed. The presence of BSA had no noticeable impact on critical micellization concentration, but the inclusion of BSA caused the pre-micellar region to expand. In addition to studying the self-organization of PX at a particular temperature, the temperature-induced micellization and gelation of PX were also explored using differential scanning calorimetry and rheology. The incorporation of BSA had no discernible effect on critical micellization temperature (CMT), but it did affect gelation temperature (T_gel) and gel integrity of PX-based systems. The response surface approach illustrated the linear relation between the compositions and the CMT. The major factor affecting the CMT of the mixtures was the concentration of PX. The alteration of the T_gel and the gel integrity were discovered to be a consequence of the intricate interaction between PX and BSA. BSA mitigated the inter-micellar entanglements. Hence, the addition of BSA demonstrated a modulating influence on T_gel and a softening effect on gel integrity. Understanding the influence of serum albumin on the self-assembly and gelation of PX will enable the creation of thermoresponsive drug delivery and tissue engineering systems with controlled gelation temperatures and gel strength.

Intranasally administered thermosensitive gel for brain-targeted delivery of rhynchophylline to treat Parkinson's disease

The aim of this study is to overcome the obstacle of the blood-brain barrier (BBB) in therapeutic drugs of Parkinson's disease (PD), like rhynchophylline (RIN) entry by intranasal administration and to solve the problem of short residence time of drugs in the nasal cavity by the dosage form design of thermosensitive gel. We first conducted a study of the screening of absorption enhancers and 3% hydroxypropyl-β-cyclodextrin (HP-β-CD) was effective to improve the nasal mucosal permeability of RIN. By adjusting the ratio of different components in order to make the gel with adhesion and rapid gelation which were determined to be Poloxamer 407 (P407) 20%, Poloxamer 188 (P188) 1%, polyethylene glycol 6000 (PEG-6000) 1% and HP-β-CD 3%. In addition, the characterization showed that the thermosensitive gel was network cross-linked, rapidly gelation upon entry into the nasal cavity and was stable as semi-solid state with adhesion as well as sustained release properties. Moreover, pharmacokinetic study was performed to evaluate the bioavailability and brain targeting of RIN thermosensitive gel and which were 1.6 times and 2.1 times higher than those of oral administration. We also evaluated the anti-PD effects of RIN thermosensitive gel in-vitro as well as in-vivo. The results showed that RIN thermosensitive gel was effective in repairing the motor function impairment, dysregulated expression levels of oxidative stress factors, and positive neuronal damage within the substantia nigra and dopamine caused by PD. The constructed intranasal drug administration strategy through thermosensitive gel provided a new choice for targeted treatment of PD together with other central nervous system diseases.

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.

Chiral Supramolecular Polymers Assembled by Amphiphilic Oligopeptide-Perylene Diimides and High Electrochemical Sensing

Various secondary structures, for example, β-sheet hydrogen bonds formed by oligopeptides exhibiting high directionality and selectivity provide a new avenue to regulate optoelectronic performances of supramolecular assemblies constructed by π-conjugated chromophores. In this work, oligopeptide-perylene diimides (AUPDIs) are synthesized to generate β-sheet strands which guide the formation of chiral supramolecular polymers with a diversity of morphologies in combination with the π-π stacking even in aqueous media. Complex morphology transitions are successfully controlled by simply adjusting the water volume fraction in the binary solvent of water and tetrahydrofuran from spherical hollow aggregates to long helical nanowires and to short nanofibers. The mechanism of the assembly changes from cooperative to the isodesmic model relying on AUPDI concentrations. This originates from the transformation in the β-sheet that regulates profoundly the arrangement of the AUPDI molecules. Prominently efficient and positive electronic sensing to triethylamine for highly helical nanowires engenders due to the highly ordered helical arrangement within the nanowires, fourfold of the short nanofibers.

Poloxamer: A versatile tri-block copolymer for biomedical applications

Poloxamers, also called Pluronic, belong to a unique class of synthetic tri-block copolymers containing central hydrophobic chains of poly(propylene oxide) sandwiched between two hydrophilic chains of poly(ethylene oxide). Some chemical characteristics of poloxamers such as temperature-dependent self-assembly and thermo-reversible behavior along with biocompatibility and physiochemical properties make poloxamer-based biomaterials promising candidates for biomedical application such as tissue engineering and drug delivery. The microstructure, bioactivity, and mechanical properties of poloxamers can be tailored to mimic the behavior of various types of tissues. Moreover, their amphiphilic nature and the potential to self-assemble into the micelles make them promising drug carriers with the ability to improve the drug availability to make cancer cells more vulnerable to drugs. Poloxamers are also used for the modification of hydrophobic tissue-engineered constructs. This article collects the recent advances in design and application of poloxamer-based biomaterials in tissue engineering, drug/gene delivery, theranostic devices, and bioinks for 3D printing. STATEMENT OF SIGNIFICANCE: Poloxamers, also called Pluronic, belong to a unique class of synthetic tri-block copolymers containing central hydrophobic chains of poly(propylene oxide) sandwiched between two hydrophilic chains of poly(ethylene oxide). The microstructure, bioactivity, and mechanical properties of poloxamers can be tailored to mimic the behavior of various types of tissues. Moreover, their amphiphilic nature and the potential to self-assemble into the micelles make them promising drug carriers with the ability to improve the drug availability to make cancer cells more vulnerable to drugs. However, no reports have systematically reviewed the critical role of poloxamer for biomedical applications. Research on poloxamers is growing today opening new scenarios that expand the potential of these biomaterials from "traditional" treatments to a new era of tissue engineering. To the best of our knowledge, this is the first review article in which such issue is systematically reviewed and critically discussed in the light of the existing literature.

Self-Assembled Dual Helical Nanofibers of Amphiphilic Perylene Diimides with Oligopeptide Substitution

We designed an asymmetric amphiphilic perylene diimide (PDI) with the oligopeptide substituting one of the imides. The self-assembly mechanism of this PDI in different solvents was investigated. Right-handed "dual" helical nanofibers/nanowires with a uniform lateral dimension of ∼8 nm are constructively self-assembled. The long-term ordered degree within the nanofibers stems from the delicate balance between π-π stacking of the PDI rings and β-sheet-like hydrogen bond formed by the oligopeptide. The synergistic interplay between the hydrogen bond and π-π stacking rather than competition endows the nanofibers with the controllable longitudinal dimensions by different factors such as the concentration and solvents. The transition from the nanofibers to the small aggregates is also achieved by the addition of trifluoroacetic acid because of breakup of the hydrogen bonds, which is reversed by further addition of trimethylamine. The acid-base stimulation can be extended to different solvents as long as the existence of the unique hydrogen bonds.