Insight

Biotech pharmaceuticals occupy a substantial share of the global pharmaceutical market. Developed economies in Europe and America maintain a leading position in biopharmaceutical technologies. Although China’s biopharmaceutical industry started relatively late, it has achieved remarkable progress alongside the rapid expansion of domestic biosimilars. Advancements in pharmaceutical processes and equipment have driven extensive technological adoption, among which depth filtration and its supporting facilities stand out prominently.

Filtration is a widely applied technique in biopharmaceuticals, categorized into surface filtration and depth filtration based on working mechanisms.

Surface filtration traps particles on the filter medium surface, featuring evenly distributed pore sizes throughout the material. Filter screens and membrane filters are commonly used surface filtration media in the industry.

Its working principle relies on pore size to intercept solid impurities in liquid materials. Suspended particles are retained and accumulate on the surface of screens or membranes. The filter pores can be slightly larger than target impurities. Tiny particles may penetrate pores and form a bridging effect, and the gradually built filter cake on pore openings serves as the actual functional filtering layer.

Depth filtration traditionally adopts fibrous media, with high-performance filter membranes increasingly applied in recent years. Filtration occurs within the entire porous structure of the medium. Impurities pass through intricate winding channels inside the medium and get trapped in the depth of the filter material. Driven by fluid power and thermal motion, fine particles migrate toward channel walls and adhere thereto via electrostatic force and surface tension.

Distinct disparities exist in filtration performance and operational features:

Most process liquids in biopharmaceuticals carry negative charges, including endotoxins, viruses, cells and cell debris. Depth filtration functions through electrostatic adsorption and mechanical interception. Negatively charged fine particles are adsorbed by positively charged media under low pH conditions, and oversized particles are removed mechanically.

Fermentation broth clarification represents the most common application of depth filtration. It separates substances physically after fermentation to achieve purification. Nevertheless, residual cells, colloids and other contaminants may remain in liquid and compromise filtration quality.

Secondary surface filtration is therefore adopted to eliminate residual impurities. Abundant negatively charged contaminants such as colloids, residual cells and cell fragments persist in supernatant after crude separation of fermented materials.

Pyrogens, namely endotoxins, are lipopolysaccharides derived from the outer membrane of Gram-negative bacteria with molecular weights ranging from tens of thousands to millions. Pyrogen contamination severely harms human bodies, making effective removal critical for pharmaceutical quality control.

Conventional activated carbon adsorption suffers from cumbersome operation, high labor cost and unsatisfactory purification effect. Combining electrostatic adsorption and mechanical interception, depth filtration efficiently eliminates pyrogens with lower labor intensity and superior product quality.

Small molecule refining is a specialized depth filtration technique exclusively applicable to small-molecule drugs. Traditional refining procedures are complicated and prone to operational errors, causing quality defects and high production costs.

Depth filtration simplifies technological flows and removes macromolecular contaminants including nucleic acids and proteins, boosting product yield and purity. It also eliminates invalid high-molecular-weight components such as proteins, polysaccharides and resins in traditional Chinese medicinal extracts. Compared with conventional chemical separation, this technology features easy operation, low cost and high efficiency.

The booming development of biotechnology leads to growing demand for macromolecular drugs. Such substances are thermally unstable, hence low-temperature rapid depth filtration becomes the preferred refining method. It efficiently removes impurities and concentrates active ingredients with precise filtration control.

Alternative methods have evident drawbacks: thermal denaturation damages active macromolecules due to uneven heating; solvent precipitation incurs excessive costs; chromatography requires expensive equipment and delivers low productivity.

Depth filtration enables separate extraction of bioactive macromolecular polysaccharides from Chinese herbal medicines. Different molecular weight fractions can be processed into targeted therapeutic preparations for diversified clinical applications.

Depth filtration is the core technique for purifying blood products and biological preparations. Its adsorptive property and gradient pore structure effectively eliminate viral proteins, lipids, nucleic acids and miscellaneous proteins. Characterized by reliable precision, high dirt holding capacity, low pressure difference, high flux and stable temperature, it is widely utilized in related production procedures.

Surface filtration and depth filtration are mainstream technologies in modern pharmaceutical manufacturing.

With merits of simple operation, high efficiency and outstanding purification effect, depth filtration is extensively applied to fermentation broth clarification, pyrogen removal, small and macromolecule refining, as well as purification of blood and biological products.