Introduction to Tangential Flow Filtration

TFF(Tangential Flow Filtration)는 신속하고 효율적으로 생체 분자를 분리하고 정제하는 방법입니다. 이는 면역학, 단백질 화학, 분자 생물학, 생화학, 미생물학 등 다양한 생물학 분야에 적용할 수 있습니다. TFF는 시료 용액(용량 범위 10mL ~ 수천 리터)을 농축하고 탈염하는 데 사용할 수 있습니다. 큰 생체 분자를 작은 생체 분자로 분획하고, 세포 부유액을 수확하고, 발효핵 및 세포 도입을 정화하는 데 사용할 수 있습니다. This report describes the basic principles that govern TFF and the use of TFF capsules and cassettes in laboratory and process development applications.

Tangential Flow Filtration 개요

Membrane filtration is a separation technique widely used in the life science laboratory. Depending on membrane porosity, it can be classified as a microfiltration or ultrafiltration process. Microfiltration membranes, with pore sizes typically between 0.1 µm and 10 µm, are generally used for clarification, sterilization, and removal of microparticulates or for cell harvesting. Ultrafiltration membranes,

with much smaller pore sizes between 0.001 and 0.1 µm, are used for concentrating and desalting dissolved molecules (proteins, peptides, nucleic acids, carbohydrates, and other biomolecules), exchanging buffers, and gross fractionation. Ultrafiltration membranes are typically classified by molecular weight cutoff (MWCO) rather than pore size.

There are two main membrane filtration modes which can use either microfiltration or ultrafiltration membranes: 1) Direct Flow Filtration (DFF), also known as ”dead-end” filtration, applies the feed stream perpendicular to the membrane face and attempts to pass 100% of the fluid through the membrane, and 2) Tangential Flow Filtration (TFF), also known as crossflow filtration, where the feed stream passes parallel to the membrane face as one portion passes through the membrane (permeate) while the remainder (retentate) is recirculated back to the feed reservoir.

TFF 배경 이론은 철망을 이용해 자갈에서 모래를 분리하는 것과 같다고 볼 수 있습니다. 철망의 구멍은 멤브레인의 공극을 의미하고 모래와 자갈은 분리될 분자를 의미합니다. In DFF, the sand and pebble mixture is forced toward the holes in the screen. The smaller sand grains fall through the pores in the screen, but the larger pebbles form a layer on the surface of the screen. This prevents sand grains at the top of the mixture from moving to and through the holes (Figure 1A). DFF의 경우 단순히 압력을 높이는 방식으로 혼합물을 압착하므로 분리 비율을 높이지 못합니다. In contrast, operating in a TFF mode prevents the formation of a restrictive layer by re-circulating the mixture. The process acts like a shaking sifter to remove the pebbles that block the holes in the screen, allowing the sand grains at the top of the mixture to fall toward and through the holes in the screen (Figure 1B).

표 1

철망으로 모래와 자갈 분리

TFF: 철망으로 모래와 자갈 분리
(A) Applying direct pressure to the mixture allows the sand grains at the bottom to fall through. A layer of pebbles builds up at the screen surface preventing sand grains at the top from moving to and through the screen.
(B) Shaking the screen breaks up the aggregated pebble layer at the bottom of the mixture and allows for complete fractionation. The crossflow dynamic of the feed stream in tangential flow filtration serves the same purpose as shaking in this example.

In solution, the same effect is encountered for DFF (Figure 2) and for TFF (Figure 3). The flow of sample solution across the membrane surface sweeps away aggregating molecules that form a membrane-clogging gel (gel polarization), allowing molecules smaller than the membrane pores to move toward and through the membrane. Thus, TFF can be faster and more efficient than DFF for size separation. 

표 2

Direct Flow Filtration Process

TFF: Direct Flow Filtration Process
(A) 피드가 멤브레인으로 직접 전달됩니다. Molecules larger than the pores accumulate at the membrane surface to form a gel, which fouls the surface, blocking the flow of liquid through the membrane.
(B) As the volume filtered increases, fouling increases and the flux rate decreases rapidly.

표 3

Tangential Flow Filtration Process

Tangential Flow Filtration Process
(A) 시료 용액이 피드 채널을 통해 흐르며 멤브레인 표면을 따라(접해) 흐를 뿐 아니라 멤브레인을 통과하기도 합니다. The crossflow prevents build up of molecules at the surface that can cause fouling.
(B) The TFF process prevents the rapid decline in flux rate seen in direct flow filtration allowing a greater volume to be processed per unit area of membrane surface.