Material selection and manufacture method of non-porous adherent cell microcarriers

Abstract

BACKGROUND: The key consumable item in stirred-tank bioreactors is non-porous microcarriers, which are suitable for adherent cell culture and play a significant role in the fabrication of viruses, recombinant proteins, and stem cells. OBJECTIVE: To summarize the material selection and manufacturing methods of non-porous microcarriers based on the favorable conditions for cell-microcarrier adhesion. METHODS: A computerized search of CNKI, PubMed, and Web of Science databases was performed with the search terms “cell cultivation, adherent cells, microcarrier, fibronectin, bioreactor, microsphere preparation” in Chinese and “cell adhesion, microcarrier, bioreactor, dextran, cell-matrix interaction, suspension culture” in English. The search time limit was from 1967 to 2025. After screening according to the inclusion and exclusion criteria, 52 articles were finally included for summary analysis. RESULTS AND CONCLUSION: Non-porous microcarriers are suitable for adherent cell culture at a density of 109-1010 cells/L. Due to the requirements for cell adhesion, non-porous microcarriers need to provide appropriate surface positive charge or integrin binding sites. Dextran, polystyrene, and collagen-based non-porous microcarriers have been commercialized and can widely support large-scale culture of various cells. Chitosan and cellulose-based non-porous microcarriers have been reported for large-scale cell culture, but these new materials have not been commercialized. Dextran and polystyrene microcarriers have been commercialized for a long time, with preparation methods of crosslinking and polymerization, respectively, and mature preparation technology. Collagen and cellulose microcarriers are mostly prepared by crosslinking, while chitosan microcarriers can be prepared by crosslinking and phase inversion.

1. Introduction

Cell culture in petri dishes with milliliter-scale medium volumes typically yields only a few million cells per dish, requiring manual operation for each dish. Due to low cell yield, high labor costs, and variability between dishes, this method is not suitable for applications such as virus production, recombinant protein extraction, or stem cell therapy.

For liter-scale cell culture, important applications include cultivating and lysing infected cells to extract viruses for vaccine manufacturing, purifying extracellular recombinant proteins and monoclonal antibodies, and producing stem cell drugs. Traditional cell factories use roller bottles with inner surface areas of 490-1,900 cm². To obtain 10^10 Vero cells (a continuous heteroploid cell line derived from African green monkey kidney epithelium, widely used in virus research and vaccine production), 100-400 roller bottles would be required, each needing inoculation, medium changes, nutrient monitoring, and passaging. This results in high labor costs and poor uniformity between bottles. In contrast, a single 5-10 L bioreactor can meet the demand for 10^10 Vero cells, offering batch processing advantages, lower labor costs, and better homogeneity of cell growth across carriers.

In 1967, Van Wezel first proposed a method to culture adherent cells on spherical microcarriers suspended by stirring, which became known as microcarrier technology. Over the years, this technology has been industrialized. Bioreactors keep microcarriers with attached cells suspended in medium via stirring or perfusion, allowing efficient nutrient access. Non-porous spherical microcarriers (referred to as microcarriers) are compatible with stirred-tank bioreactors and are used for adherent cell culture at densities of 10^9 cells/L [2-3].