- Peristaltic Pumps The working principle of a peristaltic pump is very intuitive. Rollers circulate and compress the tubing, gradually “pushing” the liquid forward. The liquid only contacts the inner wall of the tubing, completely isolating it from the pump body. This structure makes peristaltic pumps the preferred choice for low-cost, disposable systems. In biopharmaceutical R&D, pilot-scale, and commercial production, whenever short-distance transport of sterile fluids and frequent batch changes are involved, peristaltic pumps are the most reliable and least prone to problems. However, peristaltic pumps are not without their drawbacks. Flow rate inherently fluctuates, resulting in limited accuracy and long-term stability; tubing fatigue is unavoidable, and shear risk gradually increases under high-speed or small-diameter conditions.
Therefore, in mRNA-LNP processes, peristaltic pumps are primarily used for material transfer before and after encapsulation, LNP dilution, and TFF feeding; in antibody production, they are well-suited for short-distance transport before and after UF/DF and fluid propulsion in disposable filling systems, but are generally not used for high-precision metering tasks.
- Gear Pumps
Gear pumps use a pair of meshing gears to rotate, creating a stable, sealed space between the teeth to continuously and uniformly propel the liquid forward. As long as the rotational speed is stable, the flow rate remains almost constant. Because of this characteristic, gear pumps are virtually irreplaceable in continuous processes and precise proportioning, especially in micro-mixing systems. Gear pumps determine the stability of the lipid-to-aqueous phase ratio, which is crucial for consistent mRNA-LNP particle size and encapsulation efficiency. However, the strength of gear pumps is also their cost. The liquid comes into direct contact with metal components, complicating cleaning and validation; the internal shear is relatively high, making them unsuitable for shear-sensitive macromolecular systems.
Therefore, in antibody processes, gear pumps are limited to metering or specific delivery nodes, rather than running throughout the entire process.
- Diaphragm Pumps
Diaphragm pumps use the reciprocating motion of a flexible diaphragm in conjunction with a check valve to deliver the liquid, completely isolating it from the driving components. Compared to gear pumps, they offer gentler shear; compared to peristaltic pumps, they can withstand higher system pressures and are more suitable for medium-scale, long-term operation. However, the requirements for diaphragm pumps are becoming increasingly stringent, with durability and corrosion resistance being the direct reasons for their high price.
Therefore, in mRNA-LNP production, diaphragm pumps are typically used for the delivery of auxiliary fluids such as buffers and solvents; while in antibody processes, they are often used in critical nodes that are shear-sensitive and require a certain back pressure.