Your proposed strategy is unlikely to be successful, for several reasons.

You should mind that stearic acid (SA) melts at relatively high temperature (T_m = 69.3 °C). For this reason, and owing to fatty acids (FA) general tendency to form intermolecular hydrogen bonds, SA does not mix well with other lipids; it hence 'clusters out' from the typically used lipid bilayers. Due to its propensity to form H-bonds, (partially) deprotonated SA (like other FA-s and fatty alcohols), moreover, forms less well soluble (and hence non-dispersible!) complexes with its neighbouring phospholipids, such as phosphatidylcholine (which affects SA de/protonation constant that is rather high to begin with (see BBA 1994; 1196, 101-113 and 1997; 1327, 131-147) and hence detrimental to lipid and API stability). The resulting complexes have physico-chemical properties similar to phosphatidylethanolamines having similar chains, and therefore prefer non-bilayer (most often inverted hexagonal) structures (see Biochemistry (USA) 1983; 22, 1280-1289 and 1984; 23, 2634-2644) that are unsuitable for systemic drug delivery (but can require quite some time to form under unsuitable boundary conditions). Since H-bonds are more directed (and normally stronger) than ionic bonds, the relatively dilute cisPt (solubility limit in water ~0.1%!) would have to compete with more concentrated lipids to bind to SA - and in the unlikely case of success would be bound to rather than encapsulated into the produced lipidic structures, causing at least bi-functional release characteristics. cisPt (in)stability would be a challenge, too (see Cancer Res. 2014 Jul 15; 74(14): 3913–3922).

In principle, one is better served / achieves higher payload / better control over drug release by forming insoluble complexes in a liposome interior (as is being done with doxorubicin encapsulated into so-called stealth liposomes) than on a liposome surfaces. To my knowledge, this approach is not readily applicable to cisPt, however (supported by the fact thats cisPt has been tested in numerous liposomal formulations, as yet to no final avail).

Summarising advice: choose a different API and a different loading approach.

Dear Gregor, Thank you very much for addressing the problems associated with our concept of preparing Cisplatin-Stearic acid complex to improve drug loadig. Also, I cordially appreciate you for spending your valuable time in addressing the same.

We will look for the different approach to improve drug loading.

Thank you again.