Hyperthermia-Induced In Situ Drug Amorphization by Superparamagnetic Nanoparticles in Oral Dosage Forms

Superparamagnetic iron oxide nanoparticles (SPIONs) generate heat upon exposure to an alternating magnetic field (AMF), which has been studied for hyperthermia treatment and triggered drug release. This study introduces a novel application of magnetic hyperthermia to induce amorphization of a poorly aqueous soluble drug, celecoxib, in situ in tablets for oral administration. Poor aqueous solubility of many drug candidates is a major hurdle in oral drug development. A novel approach to overcome this challenge is in situ amorphization of crystalline drugs.

This method facilitates amorphization by molecular dispersion of the drug in a polymeric network inside a tablet, circumventing the physical instability encountered during the manufacturing and storage of conventional amorphous solid dispersions. However, the current shortcomings of this approach include low drug loading, toxicity of excipients, and drug degradation. Here, doped SPIONs produced by flame spray pyrolysis are compacted with polyvinylpyrrolidone and celecoxib and exposed to an AMF in solid state. A design of experiments approach was used to investigate the effects of SPION composition (Zn_0.5Fe_2.5O₄ and Mn_0.5Fe_2.5O₄), doped SPION content (10–20 wt %), drug load (30–50 wt %), and duration of AMF (3–15 min) on the degree of drug amorphization.

The degree of amorphization is strongly linked to the maximum tablet temperature achieved during the AMF exposure (r = 0.96), which depends on the SPION composition and content in the tablets. Complete amorphization is achieved with 20 wt % Mn_0.5Fe_2.5O₄ and 30 wt % celecoxib in the tablets that reached the maximum temperature of 165.2 °C after 15 min of AMF exposure. Furthermore, manganese ferrite exhibits no toxicity in human intestinal Caco-2 cell lines. The resulting maximum solubility of in situ amorphized celecoxib is 5 times higher than that of crystalline celecoxib in biorelevant intestinal fluid. This demonstrates the promising capability of SPIONs as enabling excipients to magnetically induce amorphization in situ in oral dosage forms.

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Tablet Preparation

The tablets were prepared based on the experimental design. Physical mixtures of doped SPIONs, celecoxib (M_w = 381.4 g mol^–1), PVP (M_w = 2000–3000 g mol^–1), and magnesium stearate (0.5 wt %) (M_w = 591.3 g mol^–1) were prepared using a mortar and pestle. Celecoxib and magnesium stearate were purchased from Fagron Nordic A/S (Denmark). Kollidon 12PF (PVP) was a kind gift from BASF (Germany). From the physical mixtures, 50 ± 2 mg flat faced tablets (Ø 6 mm) were prepared using an instrumented single punch tablet press GTP-1 (Gamlen Instruments, UK). The tablet press was fitted with a 500 mg load cell (CT6-500-022) and used at a compression pressure of 160 MPa. The tablets and the mixtures were stored in airtight containers until further use.

DOI: 10.1021/acsami.2c03556