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Porous silicon (pSi) nanoparticles are loaded with Immunoglobulin A-2 (IgA2) antibodies, and the assembly is coated with pH-responsive polymers on the basis of the Eudragit family of enteric polymers (L100, S100, and L30-D55). The temporal release of the protein from the nanocomposite formulations is quantified following an in vitro protocol simulating oral delivery: incubation in simulated gastric fluid (SGF; at pH 1.2) for 2 h, followed by a fasting state simulated intestinal fluid (FasSIF; at pH 6.8) or phosphate buffer solution (PBS; at pH 7.4). The nanocomposite formulations display a negligible release in SGF, while more than 50% of the loaded IgA2 is released in solutions at a pH of 6.8 (FasSIF) or 7.4 (PBS). Between 21 and 44% of the released IgA2 retains its functional activity. A capsule-based system is also evaluated, where the IgA2-loaded particles are packed into a gelatin capsule and the capsule is coated with either EudragitL100 or EudragitS100 polymer for a targeted release in the small intestine or the colon, respectively. The capsule-based formulations outperform polymer-coated nanoparticles in vitro, preserving 45−54% of the activity of the released protein. 

Abstract Maintaining stable drug concentrations in the bloodstream is a challenge for injectable hydrophobic progestin contraceptives. This work investigates porous silicon dioxide (pSiO₂) microparticles as a delivery vehicle for progestins via melt‐infiltration of drugs into the mesopores. The pSiO₂is prepared through electrochemical anodization of single‐crystalline silicon followed by thermal oxidation, yielding vertically oriented pores (≈50 nm diameter) with porosity varied (between 35–75%) to optimize drug loading and release. Among the progestins tested, etonogestrel and levonorgestrel (LNG) decompose near their melting points, preventing melt infiltration. However, addition of 20% cholesterol by mass suppresses the melting point of LNG sufficiently to enable loading without degradation. Mass loadings exceeding 50% (drug: drug + carrier) are achieved for segesterone acetate (SEG) and LNG, retaining drug crystallinity as confirmed by X‐ray diffraction. In vitro, both SEG and LNG‐loaded pSiO₂display sustained drug release for up to 3 months, with reduced burst release, more constant steady‐state concentrations, and a substantially reduced tail compared to pure LNG or SEG, or SEG loaded into pSiO₂from a chloroform solution. In a pilot in vivo study, SEG‐loaded pSiO₂microparticles are well tolerated in 20‐week‐old female rats over a 25‐week period, with no signs of toxicity.