Effect of CaCl₂ Concentration As Crosslinker to the Physical Characteristics of  Bovine Serum Albumin (BSA)-Alginate Microspheres

Esti Hendradi¹⁾, Elisa Dwianita¹⁾ , Dewi Melani Hariyadi¹⁾

¹Departement of Pharmaceutics,  Faculty of Pharmacy, Universitas Airlangga, Gedung Nanizar Zaman Joenoes, Kampus C UNAIR, Jl. Mulyorejo Surabaya 60115, Indonesia.

Corresponding author: esti-h@ff.unair.ac.id; estihendradi@yahoo.com

Background: Bovine Serum Albumin (BSA) is a material used as vaccine antigen.  BSA was chosen as a model because it can induce the formation of immunoglobulin G (IgG) antibodies and induce helper T cells 1 and 2. BSA is formulated into microspheres to increase the effectiveness and stability of the active agents. Objective:The aim of this research was to investigate  the effect of crosslinker concentration on the characteristics BSA– loaded alginate microspheres. Materials and Methods: Microspheres were prepared using ionotropic gelation with aerosolization technique. In the formulas, CaCl₂ concentration  as crosslinker (0.5M, 1.0M, 1.5M) and sodium alginate as polymer (2.5 %) were used.  Microspheres were resuspended in 5% maltodextrin solution as lyoprotectant and were freeze-dried for 24 hours. The characteristics of microspheres were evaluated such as FT-IR, particle size, morphology, drug loading (DL), entrapment efficiency (EE), and yield value.  Interaction between polymer and CaCl₂ in microspheres was characterized by FT-IR and thermal analysis used DTA. Results: The FT-IR spectra interactions between drug, polymer, and crosslinked was confirmed by the shift of carbonyl group and the loss of guluronic wave number in the fingerprint area. In DTA termogram, it was shown a decrease of melting point of the formula at the temperature 166 – 163 °C. All mircospheres were spherical, smooth and had particle size below 5µm. Particle size decreased by increasing concentration of CaCl₂. Spherical microspheres were shown with average sizes from 2.39 to 3.46 µm, and moisture content was < 5% . Drug loading increased by increasing CaCl₂ concentration. Entrapment efficiency and Yield increased by increasing CaCl₂ concentration. Yield value was between 64.37% – 77.44%. Conclusion: Increased CaCl₂ concentration decreased particle size, formed spherical microspheres and smooth surfaces, increased drug loading, increased entrapment efficiency and increased yield. The particle size produced was quite suitable for the use of the inhalation route (alveolus) which was 1 to 5 μm.