A Supramolecular Gel Based on 12‐Hydroxystearic Acid/Virgin Coconut Oil for Injectable Drug Delivery

Abstract

A supramolecular organogel based on 3 wt% of 12‐hydroxystearic acid (HSA) and virgin coconut oil (oil) in the presence of a gel inhibitor, 4 wt% ethanol (EtOH), is developed and investigated for injectable implant delivery. Gel formation is observed by the test tube tilting method. The characteristic properties of the sol‐gel system are determined using rheological, thermal, and turbidity analyses. The in vitro releases of piroxicam (PX) and diclofenac acid (DFA), the models for hydrophilic and lipophilic drugs, respectively, are performed. Characterization of the blends from the three methods are comparable and indicate that the systems of HSA/oil, PX/HSA/oil, and DFA/HSA/oil gel at about 36–39 °C upon cooling and the gel turns to a sol at a temperature higher than 50 °C upon heating at a rate of 2 °C min−1. Isothermal measurements reveals that HSA/EtOH/oil, PX/HSA/EtOH/oil, and DFA/HSA/EtOH/oil remain as a sol for about 18 min at room temperature (25 °C). Both PX and DFA show a sustained release from HSA/oil and HSA/EtOH/oil.Practical Applications: The presence of ethanol which is a hydrophilic molecule can disrupt the interaction between HSA molecules and suppress gel formation at the low temperature that the system normally forms gel. This HSA/EtOH/oil system might be injectable at room temperature and become gels at the site of injection when EtOH is diffused to other tissues in the body. This system is beneficial for use as an injectable implant system for a sustained delivery of both hydrophilic and hydrophobic drugs.12‐hydroxystearic acid (HSA) and virgin coconut oil (oil) can form gels at body and lower temperatures e.g., room temperatures. The sol‐gel system is characterized using rheological, thermal, and turbidity methods. Ethanol inhibits gel formation at room temperature to facilitate injection. The mixture of HSA, ethanol, and oil might be used as an injectable implantation. Two hydrophobic (diclofenac) and hydrophilic (piroxicam) model drugs show sustained releases from HSA/oil and HSA/ethanol/oil.