Mesoporous Hydroxyapatite as Olanzapine Carrier Provides a Long-Acting Effect in Antidepression Treatment

An
antidepressant carrier was designed to maintain over 2 weeks
of constant medication release. The carrier was injected into muscle,
where cellular activity was employed to achieve the goal of constant
release. Mesoporous hydroxyapatite (mesoHAP) was synthesized into
an adequate size by a coprecipitation method; it then went through
a series of hydrophobic surface modifications for olanzapine (OLZ)
loading by physical absorption to produce mesoHAP–OLZ. Because
of its hydrophobic nature, OLZ was not effectively released from mesoHAP–OLZ
in an aqueous environment. However, once engulfed by macrophages,
the lysosome/endosome hybrid ruptured due to alterations in osmotic
pressure, resulting in the release of OLZ into the cytoplasm. OLZ
was then exocytosed to the extracellular space due to a high calcium
ion (Ca2+) concentration and finally reached the blood
circulation. Our findings provide a useful treatment strategy to achieve
long-term drug release with a single intramuscular (IM) injection,
helping to solve the problem of nonadherent medication intake that
often occurs in antidepressant therapy.