Asymmetric flow field-flow fractionation as a multifunctional technique for the characterization of polymeric nanocarriers

Abstract

The importance of polymeric nanocarriers in the field of drug delivery is ever-increasing, and the accurate characterization of their properties is paramount to understand and predict their behavior. Asymmetric flow field-flow fractionation (AF4) is a fractionation technique that has gained considerable attention for its gentle separation conditions, broad working range, and versatility. AF4 can be hyphenated to a plurality of concentration and size detectors, thus permitting the analysis of the multifunctionality of nanomaterials. Despite this potential, the practical information that can be retrieved by AF4 and its possible applications are still rather unfamiliar to the pharmaceutical scientist. This review was conceived as a primer that clearly states the “do’s and don’ts” about AF4 applied to the characterization of polymeric nanocarriers. Aside from size characterization, AF4 can be beneficial during formulation optimization, for drug loading and drug release determination and for the study of interactions among biomaterials. It will focus mainly on the advances made in the last 5 years, as well as indicating the problematics on the consensus, which have not been reached yet. Methodological recommendations for several case studies will be also included. Graphical abstract

Application of Asymmetrical Flow Field-Flow Fractionation for Characterizing the Size and Drug Release Kinetics of Theranostic Lipid Nanovesicles

“…In contrast, AF4 is more time-consuming but offers effective sample fractionation when appropriate flow/separation conditions are established. MALLS raw scattering data with associated software’s analysis provide the molar mass and the radius of gyration (root-mean-square radius) of the solutes [ 11 ]. The radius of gyration is related to the geometric radius and the distribution of mass in the particles.…”

“…In recent years, asymmetric flow field-flow fractionation (AF4) has been gaining attention as a technique, which allows thorough and detailed analysis of the size and size distribution of nanoparticle dispersions over a wide range of particle sizes irrespective of the polydispersity of the sample. It thus is suited for quality control of nanomaterials, including (phospho)lipid-based nanocarriers and innovative systems such as lipid nanoparticles [ 10 , 11 , 12 ].…”

“…The fractionation system can be coupled to different detectors, mostly comprising multi-angle laser light scattering (MALLS), differential refractive index (dRI), or UV/VIS. Such setups have been useful in determining size distribution and physical properties of nanocarriers, drug-carrier interactions (drug loading, drug release), carrier-biomolecule interactions, and evaluating the structural organization of nanocarriers [ 11 , 14 , 15 , 16 ].…”

Testing the In-Vitro Product Performance of Nanomaterial-Based Drug Products: View of the USP Expert Panel

“…This highlights the need for guidance in the identification of suitable separation methods and method validation. So far, some of the conclusions proclaiming AF4 as "one of the chosen techniques for quality control" (28) are not based on hard evidence and widely ignore the limitations outlined by other authors (31).…”

Single cell-asymmetrical flow field-flow fractionation/ICP-time of flight-mass spectrometry (sc-AF4/ICP-ToF-MS): an efficient alternative for the cleaning and multielemental analysis of individual cells

“…To this day, there are multiple applications of AF4 being reported, in various elds, like biology [34][35][36] or (nano-) medicine. 37,38 Of particular interest to this study, were the numerous applications concerning nano-and microparticle fractionation and characterization, [39][40][41][42][43] and even more so, the ones incorporating the AF4 in (single) particle analysis. 44,45 Developing a protocol for nanoparticle analysis using AF4 can be a very complicated procedure, as there are multiple aspects that need to be optimized, and issues to be addressed.…”