The fluorescence intensity profile shown infiiiis measured at the ANA bottom edge. SERPINF1 recovery. Keywords:Bioseparation, lab-on-chip, BioMEMS, nanofluidics, molecular sieve == INTRODUCTION == Compared to conventional bioanalysis and diagnostic methods, direct analysis of biologically-relevant molecules (e.g., proteins and nucleic acids) can potentially enhance speed, accuracy, and sensitivity1,2. Moreover, direct biomolecule observations and manipulations help investigators probe fundamental molecular processes in biochemistry and biophysics that are often obscured in ensemble assays35. Therefore, nanofluidic systems with characteristic dimensions comparable to molecular scale can provide new opportunities for direct observation, manipulation, and analysis of biomolecules, and these nanofluidic systems can potentially provide innovative platforms to achieve ultra-sensitive and high-resolution biosensing EG00229 and detection6,7. Inspired by this concept, over the past ten years, there has been a surge of research effort from different scientific disciplines to design and fabricate different nanofluidic systems (with characteristic size scales between 10 to 100 nm) for biological and biomedical applications6,7. Among this surge, one notable research thrust is to EG00229 design efficient, regular artificial molecular sieving structures that can be a potential alternative to the conventional gel-based separation methods to improve the speed and resolution of biomolecule separation810. Development of efficient nanofluidic sieving structures is essential for optimizing biomolecule separation methods in a chip format within complete microanalysis environments810,11. These nanofluidic structures can provide flexible designs and offer precise control over the constraining geometries ideal for molecular sieving and separation. Moreover, the current research thrust in microfluidic based scaled-down analytical processes is stimulating development of different chip-based methods where bioanalysis can be carried out in a faster and lower cost fashion7,12,13. The random nanoporous gel materials that are conventionally used in routine bioseparation applications unfortunately have intrinsic difficulties being integrated into automated multistep chip-based bioanalysis systems. Therefore, EG00229 the development of a versatile regular nanofluidic sieving structure that can be monolithographically integrated within highly complex bioanalysis microsystems will have profound implications for different biological and biomedical applications. Over the past decade, there have been exciting developments in the field of artificial regular sieving structures due to the advance of micro- and nanotechnology810. So far, a myriad of regular sieve designs have been demonstrated with varying degrees of success in biomolecule separation1418. These reported artificial sieving structures have been primarily successful for the separation of large biomolecules such as viral DNA (as reviewed in Ref. [10]). Recently, we have introduced a unique regular molecular sieving structure called the anisotropic nanofluidic filter (nanofilter) array (ANA)19,20, and have demonstrated its implementation for high-resolution continuous-flow separation of a wide range of DNA fragments (between 50 to 23,000 base pairs (bp)) and proteins (between 11 to 400 kDa) EG00229 within a few minutes. In this protocol we describe the detailed fabrication of the ANA chips and how to perform continuous-flow bioseparation using these chips. == COMPARISON WITH GEL-BASED SEPARATION METHODS == Separation of EG00229 biomolecules in a biology laboratory is currently routinely achieved with gel-based separation techniques, such as gel-exclusion chromatography and slab-gel electrophoresis21,22. These gel-based separation techniques use gelatinous materials that consist of cross-linked three-dimensional nanometer-sized pore networks. Despite the popularity of both the gel-based separation methods, they still exhibit several limitations that make neither method optimal in separating complex mixtures for downstream analysis21. For example, the chief limitations of gel-exclusion chromatography are that the separation can be slow and that the resolution of the emerging peaks is limited, and additionally, relatively large amounts of samples are necessary to obtain visible and well-resolved bands. In slab-gel electrophoresis, recovery of the separated.