(M1330-07-37) Preparation of Polymeric Albumin Nanoparticles by a One-Step Spray Drying Process

Purpose: Spray drying is a one-step process of preparing solid particles from a slurry (solution, suspension or emulsion). Recent advancements in the spray drying technology have led to attempts at preparing solid particles in nanometer range that can further be functionalized and targeted to different parts in the body. However very few studies have been reported in the literature that demonstrate successful preparation of nanoparticles via spray drying. This study demonstrates development of solid polymeric nanoparticles using the spray drying technique via a single step. Bovine serum albumin (BSA) was chemically cross-linked to be used as polymer matrix for preparing the nanoparticles. The effect of viscosity of the cross-linked BSA on its suitability for spray drying was studied. A method for preparation of BSA nanoparticles via spray drying was developed by optimizing various spray drying parameters such as feed flow rate, inlet temperature, pressure in the drying chamber, feed viscosity, frequency of atomizer etc. The prepared nanoparticles were characterized based on their particle size and swelling characteristics.

Methods: BSA solutions of different concentrations ranging between 0.5% w/v to 5.0% w/v were prepared in deionized water and chemically cross-linked using glutaraldehyde (GA). An HPLC method was developed to estimate the time of cross-linking. This included derivatization of glutaraldehyde with 2,4-dinitrophenylhydrazine (2,4 DNPH) and quantifying the derived product. Viscosity of the cross-linked BSA solutions was determined using a portable viscometer which measured their dynamic viscosity. This helped in understanding the pumpability and sprayability of the solutions. The solutions with appropriate viscosities were spray dried using a Buchi B-90 HP spray dryer. Two sizes of nebulizers were used to carry out the spray drying process, medium and small.  Process parameters in a spray dryer, influence the formation of particles and are important because the quality of the final product is dependent upon these. After various optimizations, a spray drying method was developed using a combination of parameters, that yielded particles in the nano range. To determine the particle size, particles were dispersed in a 0.01% Tween 80 solution and subjected to analysis by a dynamic light scattering (DLS) particle size analyzer. Swelling studies were conducted by dispersing the prepared nanoparticles in 0.01% Tween 80 and determining the particle size at fixed time points up to 6 hours.

Results: HPLC analysis of the cross-linked BSA solutions indicated a minimum of 12 hours for complete cross-linking via glutaraldehyde. The viscosity studies indicated that cross-linked BSA solution of up to 5.0% w/v concentration were within the desired viscosity range of < 50 cps however spray drying studies indicated that BSA solution greater than 1.5% w/v in concentration clogged the nebulizer in the spray head. Particle size of the prepared nanoparticles was dependent on the concentration of the BSA solution. Lower concentrations produced smaller particles between 500-700 nm of range (Table 1). Higher concentrations produced particles that were in micrometer range. It was also observed that the addition of surfactants helped in obtaining particles of smaller size. Furthermore, swelling studies indicated no significant increase in particle size of the nanoparticles up to 6 hours (Figure 1).

Conclusion: The associated advantages with BSA like its biocompatibility, biodegradability, non-immunogenicity and non-toxicity make the BSA particles a better system for drug delivery than its synthetic counterparts. In this study, solid polymeric BSA nanoparticles were successfully prepared using one-step spray drying technique and characterized on the basis of their size and swelling characteristics. In future, these particles can serve as a platform technology to deliver various therapeutic agents. Facile surface modifications can be made to improve the binding of drug loaded BSA nanoparticles and the target.

References: 1. Roufegarinejad, L., et al., Molecular interactions of thymol with bovine serum albumin: Spectroscopic and molecular docking studies. Journal of Molecular Recognition, 2018. 31(7): p. e2704.

2. OSHA, OSHA Analytical Methods Manual, Glutaraldehyde, Method 64. OSHA Technical Center, , U.S.D.o. Labor, Editor. 1985, U.S. Dept. of Labor: Salt Lake City, UT. (1985).

Figure 1. Swelling of nanoparticles over 6-hour period: The nanoparticles of lower concentration of cross-linked BSA exhibit smaller size and higher concentration exhibit larger size but no significant increase is observed when particles were kept dispersed in aqueous medium.



Table 1. Results of spray drying different concentration of BSA solutions cross-linked with 0.5%w/v glutaraldehyde (with additions) using small nebulizer.