Lysozyme distribution and conformation in a biodegradable polymer matrix as determined by FTIR techniques

• Published in: Journal of controlled release Vol. 68; no. 1; pp. 31 - 40
• Main Authors: van de Weert, Marco, van ’t Hof, Ron, van der Weerd, Jaap, Heeren, Ron M.A, Posthuma, George, Hennink, Wim E, Crommelin, Daan J.A
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 31.07.2000; Elsevier
• Subjects: Analysis; Anti-Infective Agents - administration & dosage; Anti-Infective Agents - chemistry; Biodegradation, Environmental; Biological and medical sciences; Fourier-transform infrared spectroscopy; General pharmacology; Lysozyme; Medical sciences; Microspheres; Muramidase - administration & dosage; Muramidase - chemistry; Pharmaceutical technology. Pharmaceutical industry; Pharmacology. Drug treatments; Poly(lactic-co-glycolic acid); Polymers - administration & dosage; Polymers - chemistry; Protein Conformation; Protein distribution; Spectroscopy, Fourier Transform Infrared - methods; Fourier-transform infrared spectroscopy; Protein distribution; Protein conformation; Poly(lactic-co-glycolic acid); Lysozyme; Encapsulation; Glycolic acid copolymer; Fourier transformation; Pharmaceutical technology; Enzyme; Control release polymer; Drug carrier; Anhydride polymer; In vitro; Infrared spectrometry; Anhydride copolymer; Ester copolymer; Lactic acid polymer; Adsorption; Glycosidases; Water oil water emulsion; Dosage form; Hydrolases; Active ingredient; O-Glycosidases; Release; Conformation
• ISSN: 0168-3659; 1873-4995
• DOI: 10.1016/S0168-3659(00)00227-3

Lysozyme distribution and conformation in poly(lactic-co-glycolic acid)(PLGA) microspheres was determined using various infrared spectroscopic techniques. Infrared microscopy and confocal laser scanning microscopy indicated that the protein was homogeneously distributed inside the microspheres in small cavities resulting from the water-in-oil emulsification step. Part of the protein was observed at or near the cavity walls, while the rest was located within these cavities. Attenuated total reflectance (ATR) and photoacoustic spectroscopy (PAS) also showed that there is hardly any protein at the surface of the microspheres. Since this microsphere formulation gave a large burst release (ca. 50%), this burst release can not be caused by protein at the surface of the particles. Probably, the protein is rapidly released through pores in the PLGA matrix. Conformational analysis of lysozyme in the PLGA microspheres by KBr pellet transmission suffered from band shape distortion and baseline slope. Despite incomplete subtraction of the PLGA background, a characteristic band of non-covalent aggregates at 1625 cm −1 was observed in the second derivative spectrum of the protein Amide I region. The other Fourier-transform infrared (FTIR) methods yielded similar results, indicating that the sample preparation procedure did not introduce artifacts. The observed aggregation signal may correspond to the protein adsorbed to the cavity walls inside the microspheres.