Thermosensitive Micellar Hydrogels as Vehicles to Deliver Drugs With Different Wettability

Abstract

The design of adaptable drug delivery systems able to encapsulate and release drugs with different wettability has been attracting widespread interest. Additionally, many attempts have been made to tune hydrophobic/hydrophilic drug release kinetics over time, avoiding the so-called burst release . In this scenario, hydrogels resulting from the assembly of micellar structures showing a hydrophobic core and a hydrophilic shell could represent a promising alternative to design versatile drug vehicles. In this regard, this work aimed at designing new thermosensitive micellar hydrogels starting from a custom-made amphiphilic poly(ether urethane) (PEU). Specifically, a commercial triblock copolymer (Poloxamer ® 407), selected to ensure the temperature-driven chain arrangement into micelles, was reacted with 1,6-diisocyanatohexane and 1,4-cyclohexanedimethanol. The successful PEU synthesis was proved by size-exclusion chromatography ( w 50000 Da) and infrared spectroscopy. Subsequently, the wettability-driven drug arrangement within the micelle network as well as the influence of drug-loading on the resultant formulation thermosensitivity was investigated by selecting ibuprofen (IBU) and ibuprofen sodium salt (IBUSS) as hydrophobic and hydrophilic drugs, respectively. Specifically, growing drug amounts were loaded into PEU solutions, and the average hydrodynamic micelle diameters and the critical micellar temperatures (CMT) were measured. Systems containing IBU at the highest tested concentration (i.e., 20 mg/mL) showed a significantly higher micelle average diameter (58.2 ± 4.7 nm) and a remarkably lower CMT (8.9°C) with respect to both the control (40.1 ± 1.4 nm and 21.6°C) and IBUSS-loaded formulations (37.3 ± 2.1 nm and 22.4°C). Then, the influence of drug encapsulation on the temperature at which micelles begin to aggregate was rheologically assessed, showing that IBU-loading induced a decrease in this parameter (14.6, 8.7, and 13.7°C for virgin, IBU-loaded, and IBUSS-loaded hydrogel, respectively). Finally, IBU and IBUSS releasing mechanism was analysed using the Korsmayer–Peppas model ( n value of 0.63 ± 0.007 and 0.89 ± 0.003 for IBU- and IBUSS-loaded gels, respectively). Thanks to their micellar organisation, the here-developed hydrogel platform allowed the encapsulation of a high number of molecules with different wettability. Additionally, these systems exhibited tunable payload-releasing time without burst release and open the way toward the engineering of smart systems for the sustained co-delivery of multiple drugs in a target tissue/organ.

In Situ Nanotransformable Hydrogel for Chemo-Photothermal Therapy of Localized Tumors and Targeted Therapy of Highly Metastatic Tumors

“…Di/ Triblock copolymer based hydrogels are known to form polymeric micelles upon dissolution. 12 These micelles contain a polyethylene glycol chain on the exterior, which helps provide steric stability and prolong circulation time. 13 The transformation of hydrogels into micelles has been reported earlier; however, investigation on their metastatic tumor targeting is warranted.…”

“…Thus, fabricating nanoparticles that exhibit prolonged systemic circulation time could effectively target both primary and secondary metastatic tumors. Di/Triblock copolymer based hydrogels are known to form polymeric micelles upon dissolution . These micelles contain a polyethylene glycol chain on the exterior, which helps provide steric stability and prolong circulation time .…”

Preparation and Characterization of Vancomycin Hydrochloride-Loaded Mesoporous Silica Composite Hydrogels

“…Chitosan (250 mg) was dissolved in 10 ml of 0.1 mol/L acetic acid and then stirred for 2 h. GP-SA and a certain amount of Van/SBA-15 were added to the pre-prepared chitosan solution and then stirred for 30 min. The obtained sol was poured into a mold soaked in a 37°C water bath to produce Van/SBA-15/CS-GP-SA gel ( Laurano et al, 2020 ). The morphology of CS-GP-SA, Van/CS-GP-SA, and Van/SBA-15/CS-GP-SA were observed by SEM and TEM.…”

Responsive Nanomaterial Delivery Systems for Pancreatic Cancer Management

“…[223][224][225][226] Upon in situ injection, the hydrogels release the drug payload in a controlled and targeted manner. [227,228] A significant advantage of micellar-based thermosensitive hydrogels is their noncytotoxic gelation process, eliminating the need for potentially harmful crosslinking agents or reactions, [229] and making them particularly suitable for pancreatic cancer treatment. Furthermore, the temperature differential between the tumor site and the formulation storage temperature allows for the instant gelation of temperature-responsive polymer hydrogels, which exhibit 3D networks with the ability to absorb and retain large volumes of water in their swollen state, providing a biomimetic environment specifically tailored for administration into pancreatic tumor tissue.…”