Self-assembled oleylamine grafted alginate aggregates for hydrophobic drugs loading and controlled release

Abstract

Amphiphilic alginate derivatives obtained by hydrophobic functionalization of alginates are commonly used as the nano-bio materials for hydrophobic drugs delivery and controlled release. In this research, we proposed an optimization protocol to introduce oleylamine into the alginate backbone for the preparation of amphiphilic alginate derivative via Ugi four-component condensation reaction (Ugi-4CR), using odorless, environmental friendly, and inexpensive tosylmethyl isocyanide (TOSMIC) to replace the commonly used cyclohexyl isonitrile. The structure of the oleylamine grafted alginate (Ugi-FOlT) conjugate was confirmed by Fourier-transformed infrared spectrometry (FT-IR), 1H nuclear magnetic resonance (1H NMR), X-ray diffraction (XRD), and thermal gravimetric analysis (TGA). The degree of substitution (DS) of Ugi-FOlT determined by elemental analysis (EA) was about 40.89%, and its yield was approximately 76.4%. The self-assembled performance of Ugi-FOlT was investigated using fluorescence spectroscopy, dynamic light scattering (DLS), and transmission electron microscopy (TEM). The critical aggregation concentrations (CAC) of Ugi-FOlT was 0.043 mg/mL in 0.15 mol/L NaCl aqueous solution. Ibuprofen, a hydrophobic nonsteroidal anti-inflammatory drug (NSAIDs), was encapsulated into the self-assembled Ugi-FOlT nanoparticles by dialysis method. The drug loading content (DLC) and encapsulation efficiency (EE) determined by the UV-Vis spectrophotometer were 16.7% and 83.5%, respectively. In vitro, drug release studies revealed that almost 65.6% of ibuprofen were released from the Ugi-FOlT nanoparticles in PBS (pH = 7.4) at 37 °C. Moreover, the drug release rate was obviously dependent on the pH values of the release medium. In vitro cytotoxicity tests revealed that the blank Ugi-FOlT nanoparticles showed negligible toxicity against the murine macrophage RAW264.7 cell. Thus, the novel synthesized amphiphilic Ugi-FOlT could be used to prepare self-assembled nanoparticles for hydrophobic functional ingredients or drug delivery and sustained release.