New advances in countercurrent chromatography and centrifugal partition chromatography: focus on coupling strategy.

Countercurrent chromatography (CCC) is an attractive separation method because the analytes are partitioned between two immiscible liquid phases avoiding problems related to solid stationary phase. In recent years, this technique has made great progress in separation power and detection potential. This review describes coupling strategies involving high speed CCC (HSCCC) or centrifugal partition chromatography (CPC). It includes on-line extraction-isolation, hyphenation with mass spectrometry (MS) and nuclear magnetic resonance (NMR) detectors, multidimensional CCC (MDCCC), two-dimensional CCC (2D-CCC), on-line coupling with liquid chromatography (LC), and biological tests, and innovative off-line developments. The basic principles of each method are presented and applications are summarized.

Centrifugal microfluidics for biomedical applications.

The centrifugal microfluidic platform has been a focus of academic and industrial research efforts for almost 40 years. Primarily targeting biomedical applications, a range of assays have been adapted on the system; however, the platform has found limited commercial success as a research or clinical tool. Nonetheless, new developments in centrifugal microfluidic technologies have the potential to establish wide-spread utilization of the platform. This paper presents an in-depth review of the centrifugal microfluidic platform, while highlighting recent progress in the field and outlining the potential for future applications. An overview of centrifugal microfluidic technologies is presented, including descriptions of advantages of the platform as a microfluidic handling system and the principles behind centrifugal fluidic manipulation. The paper also discusses a history of significant centrifugal microfluidic platform developments with an explanation of the evolution of the platform as it pertains to academia and industry. Lastly, we review the few centrifugal microfluidic-based sample-to-answer analysis systems shown to date and examine the challenges to be tackled before the centrifugal platform can be more broadly accepted as a new diagnostic platform. In particular, fully integrated, easy to operate, inexpensive and accurate microfluidic tools in the area of in vitro nucleic acid diagnostics are discussed.

Future of antibody purification.

Antibody purification seems to be safely ensconced in a platform, now well-established by way of multiple commercialized antibody processes. However, natural evolution compels us to peer into the future. This is driven not only by a large, projected increase in the number of antibody therapies, but also by dramatic improvements in upstream productivity, and process economics. Although disruptive technologies have yet escaped downstream processes, evolution of the so-called platform is already evident in antibody processes in late-stage development. Here we perform a wide survey of technologies that are competing to be part of that platform, and provide our [inherently dangerous] assessment of those that have the most promise.

14 years of therapeutic plasma exchange in France.

The French Registry for plasma exchange (PE) was set up in 1985. For 14 years it has allowed analysis of the techniques used along with the indications and complications. Recent analysis shows a slight fall in activity as some studies have ended, while the neurological disorders remain the most frequent indications for PE. The important changes observed over the years are the increased use of the centrifugation technique, the development of plasma and whole blood treatment and plasma substitution using a mixture of albumin and pentastarch. The French Registry for PE is the largest such database which, along with the Canadian Registry for therapeutic hemapheresis, allows both retrospective and prospective studies.

Visual symptoms and G-LOC in the operational environment and during centrifuge training of Turkish jet pilots.

BACKGROUND: High-performance fighter aircraft produce high-sustained +Gz forces with rapid onset rates. Because of this G-producing capability, military jet pilots are subjected to physiological stress, which may lead to visual disturbances and G-induced loss of consciousness (G-LOC). Although visual disturbances are very common in jet flights, G-LOC is relatively rare but more dangerous. The frequency and causes of G-LOC need to be determined in the interest of flight safety. METHODS: Part I. A survey was conducted on Turkish jet pilots to reveal the incidence of symptoms due to +Gz acceleration. Anonymous questionnaires were given to F-16, F-4, and F-5 pilots. They consisted of inquiries about the occurrence of visual symptoms and/or G-LOC during +Gz acceleration in the operational environment. Part II. During the years 1992-1996, 486 F-16, 801 F-4, and 256 F-5 fighter pilots underwent high "G" training at Turkish Aerospace Medical Center and they were assessed in terms of G-LOC rates. RESULTS: Part I. A total of 325 pilots who flew T-37 in undergraduate pilot training (UPT) answered the questionnaire. The pilots were divided into 3 groups according to the types of aircraft, which they fly now: 116 F-16, 182 F-4, and 27 F-5 pilots. A total of 311 pilots (95.7%) reported having experienced greyouts and/or blackouts. With 25 pilots (7.7%) experiencing G-LOC, the G-LOC frequency according to the type of aircraft was: 5.2% (T-37) [in UPT]; 4.3% (F-16), 1.6% (F-4), and 0% (F-5). Part II. In centrifuge training, the incidence of G-LOC in pilots of the various types of aircraft were: 12% (F-16), 6.4% (F-4), and 8.6% (F-5). CONCLUSIONS: Centrifuge training reduces G-LOC rates of subsequent centrifuge training; and it is hoped might reduce the G-LOC rate in the operational environment. Almost all jet pilots reported having experienced +Gz related visual symptoms, but G-LOC seems to be a more common problem for pilots who fly rapid onset rate aircraft than pilots who fly high "G" capable but lower G onset rate aircraft.

Advances in primary recovery: centrifugation and membrane technology.

Significant and continual improvements in upstream processing for biologics have resulted in challenges for downstream processing, both primary recovery and purification. Given the high cell densities achievable in both microbial and mammalian cell culture processes, primary recovery can be a significant bottleneck in both clinical and commercial manufacturing. The combination of increased product titer and low viability leads to significant relative increases in the levels of process impurities such as lipids, intracellular proteins and nucleic acid versus the product. In addition, cell culture media components such as soy and yeast hydrolysates have been widely applied to achieve the cell culture densities needed for higher titers. Many of the process impurities can be negatively charged at harvest pH and can form colloids during the cell culture and harvest processes. The wide size distribution of these particles and the potential for additional particles to be generated by shear forces within a centrifuge may result in insufficient clarification to prevent fouling of subsequent filters. The other residual process impurities can lead to precipitation and increased turbidity during processing and even interference with the performance of the capturing chromatographic step. Primary recovery also poses significant challenges owing to the necessity to execute in an expedient manner to minimize both product degradation and bioburden concerns. Both microfiltration and centrifugation coupled with depth filtration have been employed successfully as primary recovery processing steps. Advances in the design and application of membrane technology for microfiltration and dead-end filtration have contributed to significant improvements in process performance and integration, in some cases allowing for a combination of multiple unit operations in a given step. Although these advances have increased productivity and reliability, the net result is that optimization of primary recovery processes has become substantially more complicated. Ironically, the application of classical chemical engineering approaches to overcome issues in primary recovery and purification (e.g., turbidity and trace impurity removal) are just recently gaining attention. Some of these techniques (e.g., membrane cascades, pretreatment, precipitation, and the use of affinity tags) are now seen almost as disruptive technologies. This paper will review the current and potential future state of research on primary recovery, including relevant papers presented at the 234th American Chemical Society (ACS) National Meeting in Boston.

Bioseparation in antibody manufacturing: the good, the bad and the ugly.

Improvements in upstream production have boosted productivity in the biomanufacturing industry, but this is leading to bottlenecks in downstream processing as current technology platforms reach their limits of throughput and scalability. Although chromatography remains an indispensible component of downstream processing due to its simplicity and high resolving power (The Good), there is virtually no economy of scale effect so more product translates almost linearly into greater production costs. Bind-and-elute processes (such as the initial capture step in antibody manufacturing) are volume-driven and therefore have knock-on effects that impact on the entire production facility since the space required for preparation, storage, and cleaning steps has to be similarly adapted (The Bad). During long-term operations with multiple cycles, thorough cleaning is necessary to prevent progressive fouling and microbial contamination (The Ugly). Innovative solutions are required, which may include revisiting simpler and less expensive separation technologies, the use of disposable modules, and the integration of improved processes that are scalable to cope with increased demands. Among the alternatives that have been put forward, membrane adsorbers are beginning to make a real impact on the industry, particularly for flow-through applications such as polishing and viral clearance.