Closed continuous-flow centrifuge

Triglyceride-filled albumin-based nanocapsules: A promising new system to avoid discarding poorly water-soluble drug candidates

Even though current drug discovery provides a variety of potential drug candidates, many of those substances are difficult to formulate due to their poor water-solubility. To overcome this obstacle a technological formulation is crucial. Albumin-based nanocarriers are a possible intravenous delivery system which is already approved and commercially available. However, no universal carrier for poorly water-soluble substances is found yet. In the present study, new preparation processes for nanocapsules consisting of a medium-chain triglyceride (MCT) core and a human serum albumin (HSA) shell were developed. The nanocarrier system exhibits desirable physicochemical properties with a hydrodynamic diameter of 150 nm and a polydispersity index of 0.1. Furthermore, the nanocapsules were stable towards the addition of electrolytes and also in basic to neutral pH range. The nanocapsules were storage stable for at least 7 months at 4 °C and could also be lyophilized to reach an even longer shelf life of at least 21 months. In addition, the nanocapsule system showed no cytotoxicity in cell culture. The developed system represents a suitable carrier for a variety of different poorly water-soluble drug substances (e.g., fenofibrate, naproxen, indomethacin) showing a high potential for a universal formulation platform for further lipophilic active pharmaceutical ingredients (APIs).

Sources of Hematopoietic Stem and Progenitor Cells and Methods to Optimize Yields for Clinical Cell Therapy

Bone marrow (BM) aspirates, mobilized peripheral blood, and umbilical cord blood (UCB) have developed as graft sources for hematopoietic stem and progenitor cells (HSPCs) for stem cell transplantation and other cellular therapeutics. Individualized techniques are necessary to enhance graft HSPC yields and cell quality from each graft source. BM aspirates yield adequate CD34⁺ cells but can result in relative delays in engraftment. Granulocyte colony-stimulating factor (G-CSF)-primed BM HSPCs may facilitate faster engraftment while minimizing graft-versus-host disease in certain patient subsets. The levels of circulating HSPCs are enhanced using mobilizing agents, such as G-CSF and/or plerixafor, which act via the stromal cell-derived factor 1/C-X-C chemokine receptor type 4 axis. Alternate niche pathway mediators, including very late antigen-4/vascular cell adhesion molecule-1, heparan sulfate proteoglycans, parathyroid hormone, and coagulation cascade intermediates, may offer promising alternatives for graft enhancement. UCB grafts have been expanded ex vivo with cytokines, notch-ligand, or mesenchymal stromal cells, and most studies demonstrated greater quantities of CD34⁺ cells ex vivo and improved short-term engraftment. No significant changes were observed in long-term repopulating potential or in patient survival. Early phase clinical trials using nicotinamide and StemReginin1 may offer improved short- and long-term repopulating ability. Breakthroughs in genome editing and stem cell reprogramming technologies may hasten the generation of pooled, third-party HSPC grafts. This review elucidates past, present, and potential future approaches to HSPC graft optimization.

The future of automated red blood cell collection

Automated red blood cell (RBC) collection is a newer but well-established form of donor apheresis. The technologies comprising and supporting apheresis have undergone significant advancements through the past 50 years, and we anticipate further improvements in devices and systems for automated RBC collection. Multiple factors must be considered in implementing automated RBC collections, but these procedures provide a way to draw additional RBC products that meet cGMP, regulatory, blood collector economic and donor objectives while maintaining or improving RBC availability. The continuing need for RBCs, accompanied by shrinking donor availability, would indicate that automated RBC collections will grow.

Rheohaemapheresis of ophthalmological diseases and diseases of the microcirculation

Blood rheology was considered to be of limited clinical importance, until extracorporeal technologies enabling the treatment of cellular and plasmatic hyperviscosity syndromes were introduced. However, a wide range of applications, mainly referring to rheologically determined diseases of the microcirculation exists but has so far hardly been taken into consideration. The extension of indications was due to modern technical developments leading to different approaches of secondary separation such as precipitation, ad- or absorption and filtration. Based on 18 years of experience with different separation technologies the combination of some centrifugal devices applied for cell--plasma separation with secondary filtration (Rheohemapheresis) appears to be the most efficacious and economical approach for such extracorporeal treatments. The sequence and frequency of rheohaemapheresis treatments depends on the measurement of rheological measurements in combination with clinical--chemical data which are related to the distribution kinetics and synthesis rate of both blood cells and plasma proteins. Standardised treatment protocols proved the efficacy of initial therapies and were applied for controlled trials whereas long term therapies may need more flexible treatment approaches. So far an increasing experience exists for the treatment of ophthalmologic diseases, otologic disorders, diabetic complications and cardiological diseases. Rheohemapheresis was shown to be a safe treatment approach, if a careful risk assessment prior to the initiation of the therapies is performed. The treatment cannot cure diseases but enables a substantial improvement of the quality of life in patients without treatment alternatives.

Quo vadis haemapheresis. Current developments in haemapheresis

The techniques of haemapheresis originated in the development of centrifugal devices separating cells from plasma and later on plasma from cells. Subsequently membrane filtration was developed allowing for plasma-cell separation. The unspecificity of therapeutic plasma exchange led to the development of secondary plasma separation technologies being specific, semi-selective or selective such as adsorption, filtration or precipitation. In contrast on-line differential separation of cells is still under development. Whereas erythrocytapheresis, granulocytapheresis, lymphocytapheresis and stem cell apheresis are technically advanced, monocytapheresis may need further improvement. Also, indications such as erythrocytapheresis for the treatment of polycythaemia vera or photopheresis though being clinically effective and of considerable importance for an appropriate disease control are to some extent under debate as being either too costly or without sufficient understanding of the mechanism. Other forms of cell therapy are under development. Rheohaemapheresis as the most advanced technology of extracorporeal haemorheotherapy is a rapidly developing approach contributing to the treatment of microcirculatory diseases and tissue repair. Whereas the control of a considerable number of (auto-) antibody mediated diseases is beyond discussion, the indication of apheresis therapy for immune complex mediated diseases is quite often still under debate. Detoxification for artificial liver support advanced considerably during the last years, whereas conclusions on the efficacy of septicaemia treatment are debatable indeed. LDL-apheresis initiated in 1981 as immune apheresis is well established since 24 years, other semi-selective or unspecific procedures, allowing for the elimination of LDL-cholesterol among other plasma components are also being used. Correspondingly Lp(a) apheresis is available as a specific, highly efficient elimination procedure superior to techniques which also eliminate Lp(a). Quality control systems, more economical technologies as for instance by increasing automation, influencing the over-interpretation of evidence based medicine especially in patients with rare diseases without treatment alternative, more insight into the need of controlled clinical trials or alternatively improved diagnostic procedures are among others tools ways to expand the application of haemapheresis so far applied in cardiology, dermatology, haematology, immunology, nephrology, neurology, ophthalmology, otology, paediatrics, rheumatology, surgery and transfusion medicine.

The Role of Rheology in Hemapheresis

Rheological therapy attempts to favorably influence the blood flow mechanics for the treatment of diseases, mainly of the microcirculation but also of the macrocirculation. Hemapheresis, originally used only for the elimination of an excess of cellular or plasmatic components, was shown to also influence the hemorheology favorably. As extracorporeal therapy affects the rheology much more than conventional hemorheotherapy, not only cellular or plasmatic hyperviscosity syndromes but also many more diseases associated with organ perfusion problems due to diseases of the micro- and macrocirculation, especially in the elderly, were and are increasingly considered to be indicated. Technical progress led away from plasma exchange as an unspecific and unselective procedure to plasma differential separation using precipitation. adsorption, and filtration. With our recent development, we demonstrated that rheohemapheresis is the most advanced technical procedure. The mechanism of action can well be related to a synergetic consideration of rheology. However. one has to keep in mind that the elimination of blood components such as lipids, immunoglobulins, and endothelial factors may well contribute to the explanation and understanding of the positive clinical effects observed. These speculative aspects need further investigation.

Spin doctors: new innovations for centrifugal apheresis

The preparation of plasma from blood has a long history dating back to the early 1900s when the concept of blood washing replaced the traditional blood letting. Over the next 57 years landmark discoveries such as centrifugal and membrane filtration systems led to different and rapid plasma, solute, and cell separation. These were not singular events but rather events influenced by the converging chemical, physiological, and engineering advances that have characterized the latter half of the 20th century. These events have led to entire new fields of biomedical research. The biotechnology for on-line plasma separation and plasma treatment has opened a new era, expanding the application of extracorporeal technology to modern therapeutic medicine. The association of biochemical or cellular abnormalities with various disease states provides the rationale for therapeutic plasma exchange (the removal of large amounts of patient's plasma, alone or with replacement with crystalloid) and therapeutic cytopheresis (removal of cellular elements). The purpose of this review is to provide a historical picture of the innovative ideas of the spin doctors and their devices, which predate the centrifugal blood and cell separators commonplace to any hospital or blood bank worldwide. The emphasis is to define the historical events and their impacts on the development of centrifugal devices and apheresis technologies.

Erythrocytapheresis. A method for rapid extracorporeal elimination of erythrocytes. Results in 65 patients

We report on the progress of a new modified method of phlebotomy, erythrocytapheresis, as a means of fast therapeutic removal of erythrocytes from the circulation. We performed erythrocytapheresis in 65 patients. In 18 patients with central venous thrombosis of the eye, the beneficial effect of this procedure proved superior to the traditional approach. In 29 patients with primary or secondary polycythemia, hemoglobin, hematocrit, and blood viscosity could be lowered drastically for up to 11 months by a single erythrocytapheresis. We performed erythrocytapheresis in an effort to deplete the iron stores in patients with hemochromatosis (14 cases) and in patients with porphyria cutanea tarda (4 cases). Several consecutive erythrocytaphereses were necessary, however, to even slightly lower the amounts of stored iron as measured by serum iron, iron-binding capacity, and serum ferritin in these patients. The intervals between treatment were 2 to 11 months, thus much longer than the intervals between blood-lettings. We did not observe any adverse side effects. There was no significant influence on the clotting system, and no reactive thrombocytosis as described after phlebotomies.

Velocities and stress levels of axisymmetric, azimuthal flow within the toroidal rotary seal of the IBM 2997 continuous flow cell separator and the implications

Continuous flow blood fraction separators are used to facilitate the removal of specific blood components for donation or for certain medical procedures. Problems with one such device, the IBM 2997 Blood Processor, have been noted in a number of independent investigations. A key feature of this particular unit is a ceramic rotary seal that allows the continuous separation by centrifugation to take place. The equation of motion for flow inside a split toroid cavity within the rotary seal has been solved numerically; velocities and shear stresses found numerically compare favorably with limiting case, analytical solutions. Predicted torque values as a function of rotation rate and fluid viscosity also served as an experimental check on the validity of the mathematical findings. Comparison of calculated shear stress levels and exposure times with known thresholds for cell damage shows that platelet and leukocyte losses may indeed be caused by the seal. Suggestions are made to improve performance of the IBM Blood Processor.

Platelet collection using the IBM 2997 cell separator

Platelets were collected using the dual-channel module on the IBM 2997 Blood Fraction Separator. We carried out 320 procedures to harvest platelets for therapeutic purposes and yielded 5.1 +/- 1.5 X 10(11) platelets (mean +/- SD). Infusion into previously unsensitized recipients with hypomegakaryocytic thrombocytopenia achieved increments at 1 hr of 19 +/- 7.3 X 10(9)/liter/m2 (mean +/- SD) and at 24 hr of 15 +/- 6.3 X 10(9)/liter/m2. The only consistent donor reaction was mild hypocalcaemia, easily corrected by calcium gluconate infusion. Changes in donor packed-cell volume and white cell count were not statistically altered (p greater than 0.05) but donor platelet counts fell from 216 +/- 43.1 X 10(9)/liter to 162.5 +2- 41.7 X 10(9)/liter (mean +/- SD) (p less than 0.01). Additional plateletphereses were carried out in seven normal volunteers, using the same technique, in order that the function of the harvested platelets could be studied. Following radiochromium labelling and reinfusion into the same donors, normal in vivo recoveries were obtained at 10 min (59.4 +/- 3.4%; mean +/- SD) and platelet mean life span was also normal (218 +/- 12 hr; mean +/- SD). Furthermore, in vitro platelet factor III availability and aggregation patterns of the harvested platelets did not differ from control values and their ultrastructural appearance was normal.

Clinical evaluation of a flat-plate membrane plasma exchange system

A new flat-plate membrane plasma separation system specifically designed for therapeutic plasma exchange (TPE) was clinically evaluated in both research and routine clinical settings. The study included a comparison to a currently available centrifugal cell separation system employed for TPE. A total of 267 membrane procedures were performed on 39 patients over a 14-month period. Both qualitative and quantitative studies showed that membrane plasma exchange procedures were equivalent to centrifugal procedures in the removal of plasma constituents from patients. A notable difference between the two types of procedure was the effect on the peripheral blood platelet count: the plasma filtrate from the membrane system was essentially cell-free and platelet counts fell only 11% during the procedure, compared to a 53% decrease during the centrifugation runs. Patient responses to both types of procedure were similar and the frequency of side-effects was low. A sampling of patient opinion revealed a preference for the membrane system for a variety of reasons. Procedure times were shorter with the membrane system because of higher achievable blood flow rates, and thus higher plasma exchange rates, while the overall nursing time requirement was lower. The results show that this flat-plate membrane TPE system enables rapid and effective plasma exchange therapy, and offered a number of monitoring and control functions that provided a safer, more efficient therapeutic procedure in the majority of patient treatments performed in this study.

Rapid isolation of mononuclear cells from buffy coats prepared by a new blood cell separator

A newly developed cell separator for the preparation and fractionation of buffy coat cells from human peripheral blood is described. In this cell separator buffy coats (BC-1) as routinely obtained from blood banks were used for the preparation of a second buffy coat (BC-2) with a volume of only 5-6 ml. A special fractionation device allowed sterile isolation of almost pure platelets and mononuclear cells with recoveries of 75 +/- 10% and 89 +/- 4% respectively. The white blood cell contamination of the platelet suspension never exceeded 20 X 10(6) leukocytes (i.e., less than 1 leukocyte per 5000 platelets). Furthermore, the mononuclear cell suspensions were shown to be contaminated with only 3 +/- 2% granulocytes, whereas the white blood cell/red blood cell ratio was 2.6 +/- 1.6, so that they could therefore be directly used for further separation by means of centrifugal elutriation. These results indicate that this cell separator provides a rapid (+/- 1 h) isolation of both platelets and mononuclear cells without exposing the buffy coat cells to foreign substances like Ficoll or Percoll.

The historical development of automated hemapheresis

Many studies in the early twentieth century involved attempts to separate white blood cells from whole blood for further examination and experimentation as well as for the treatment of neutropenic patients. In the 1950s, the need to use blood and its derivatives efficiently produced the first apparatus to separate blood continuously in a closed system. The prototypes of present-day continuous flow blood cell separators were developed in the 1960s.

The plasma kinetics of hydroxyethyl starch 350/0.60: a potential new adjunct for centrifugal leucapheresis

A modified species of hydroxyethyl starch (HES 350/0.60) possessing a Mw- of 350,000 daltons combined with a molar hydroxyethyl group substitution (MS) of 0.60 (60 hydroxyethyl groups.100 glucose residues) was clinically assessed in seven normal subjects to determine the influence of these chemical modifications on intravascular clearance kinetics concomitantly with effects on the suspension stability (ESR) of blood. Following a standardised intravenous dose (30 gm.m2 BSA), the concentration of HES 350/0.60 in serum fell to half its peak value in 11.8 +/- 1.3 (SD) hours, while the ESR remained elevated for up to 12 hours post-injection. By adopting a Mw- of 350,000 daltons, the critical molecular weight (Cmw) of this colloid was surpassed, while the critical concentration (Cc), below which the suspension stability of blood is not affected, was shown to range between 0.3 and 0.5 gm.dl-1. In comparison to the present species of HES (Mw- 450,000 daltons, MS: 0.70) utilised as a sedimenting agent duirng centrifugal leucapheresis, HES 350,000/0.60 appears to affect the ESR in a similar manner, but is removed from the intravascular space approximately twice as rapidly. This more rapid clearance should be useful in avoiding cumulative build-up of HES in blood concomitant with reducing the total amount of intravascular H2O bound to this colloid, in normal and CML donors undergoing multiple cell collection procedures.

Lymphocyte depletion by continuous flow cell centrifugation in rheumatoid arthritis: clinical effects

Four patients with active, severe rheumatoid arthritis were subjected to the removal of circulating lymphocytes (lymphapheresis) for a 6-week period by use of a continuous flow cell centrifuge. Repetitive venous access was gained through forearm arteriovenous fistulae. In all patients the Ritchie-Camp articular index declined rapidly in the first week and more slowly therafter for a total mean drop of 61% below the initial value. The index continued to decline after lymphapheresis but exacerbation of disease activity developed at an average of 19 weeks. No significant untoward effects of the procedure were observed; occasional transfusions were required to compensate for the small, unavoidable erythrocyte loss.

In vitro functional capabilities of canine polymorphonuclear neutrophils collected simultaneously by continuous-flow centrifugation and continuous-flow filtration leukopheresis

Polymorphonuclear neutrophils were simultaneously collected from dogs by continuous-flow centrifugation and continuous-flow filtration leukapheresis. In vitro studies were performed on cells obtained by the two methods as well as on control cells. Studies consisted of assessment of phagocytic capacity, degranulation, chemotaxis, hexose monophosphate (HMP) shunt activity, and bacterial killing. The cells obtained from the filter were metabolically more active than those harvested by centrifugation, as evidenced by increase in resting HMP shunt activity and dimunition in total available lysozyme-secreting activity compared to centrifuged cells. Despite their impaired phagocytic capacities, the filtered cells were able to kill Staphylococcus aureus as efficiently as the centrifuged cells. Both cell populations responded to chemotactic gradients equally.

[Thrombophoresis I. Influence of centrifuge speed on thrombocyte yield, distribution of thrombocytes among centrifuge zones, and thrombocyte spreading (author's transl)]

Thrombocyte yields up to 1,4 X 10(11) per litre of separated whole blood were obtained using centrifuge speed up to 2000 RPM. With increasing speed, higher platelet concentrations in the thrombocyte zone were accompanied by a progressive decline of thrombocyte counts in the plasma zone, whereas the thrombocyte contamination in the erythrocyte zone remained unchanged. Taking into account both high extraction efficiency and good preservation of platelet function as measured by Breddin's spreading test, optimal conditions for thrombophoresis with the Aminco Celltrifuge have been obtained at 1600 RPM. Since repeated separation of the donor's blood resulted in a rising number of platelets with impaired spreading capacity, the total blood flow should be limited to the blood volume of the donor.

Time-related increase in leucocyte yields by continuous-flow centrifugation (CFC) leukopheresis

Continuous flow centrifugation leukopheresis lasting 3 to 4 h was performed 18 times on 16 normal donors. The total yield of leucocytes collected was 1.59 +/- 0.14 x 10(10) (mean +/- SE). Comparison of leucocyte yields on the first, second, third and fourth hour of leukopheresis indicated a progressive increase with time in 15 out of 18 procedures, with 3.6 times more leucocytes collected within the last hour of leukophoresis as compared to the first hour. This increase was independent of the volume of leucocytes collected per unit time, since an equally significant increase was found when calculated per 100 ml of leucocyte concentrate. Although the mechanism of this improvement in yield with time is unknown, the present data indicate, that moderate prolongation of the duration of leukopheresis may result in an increase in efficiency which is comparable to that produced by the use of hydroxyethyl starch, etiocholanolone or corticosteroids.

Biophysics of cell separations

To the Chemist, it has long been second nature to work with separate, purified substances. Biochemists and molecular biologists have now largely achieved the same working position, with their powerful separation techniques of ultracentrifugation, electrophoresis, chromatography and the like. For the cell biologists, it is a much more recent phenomenon that widespread attention is being directed towards quantitative measurement of properties in isolated, homogeneous cell types. The richness and diversity of cell systems beg for cleverness on the part of the experimenter.

Granulocyte harvest for transfusion: donor response to repeated leukapheresis

Leukapheresis of normal donors with the NCI-IBM Continuous Flow Blood Cell Separator was compared with the method of filtration leukapheresis. An average of 5.7 times 10-9 (range 1.4 to 10.9 times 10-9) granulocytes were collected on 25 occasions with the blood cell separator compared with an average of 36.6 times 10-9 (range 20.1 to 61.3 times 10-9) obtained by filtration leukapheresis on 85 occasions. Donor platelet counts decreased following donation by an average of 29,000/mul (14%) with continuous flow centrifugation (CFC) and an average of 40,000/mul (17%) with filtration leukapheresis (FL). Estimated donor packed red blood cell loss, including blood obtained for investigative purposes, was 80 ml per donation with CFC and 67 ml per donation when FL was used. FL resulted in at least a 25 per cent increase in the granulocyte count of donors by donation completion in 61 per cent of donors, although postdonation granulocytosis did not correlate with increased cell harvest. CFC donors generally displayed a postdonation decrease in granulocyte count. Normal numbers of granulocytes were maintained in donors undergoing frequent leukapheresis and no donor's health was compromised by the removal of large numbers of granulocytes. Repeated donations were possible with both systems. Although platelet counts dropped more with FL, the procedure was performed as frequently as eight times in a ten-day period without development of severe donor thrombocytopenia. Donor red blood cell loss appears to be the limiting factor in the repeated use of either system. Blood loss could be significantly decreased under routine conditions if fewer samples were obtained for investigational purposes. Filtration leukapheresis offers the advantage of significantly greater granulocyte yields than is possible with CFC unless modifications such as arterio-venous shunts or the use of steroids and/or rouleaux-inducing agents are employed.

Cells capable of colony formation in the peripheral blood of man

Colony-forming cells have been found in the peripheral blood of man and have been grown in vitro by use of a soft agar gel technique. It has been possible to collect these cells with a blood-cell separator in numbers similar to those found in the peripheral circulation. Repeat leukapheresis of the same donor does not reduce the number of circulating colony-forming cells.

Infusion of long-chain fatty acid anions by continuous-flow centrifugation

We have developed a method for the rapid infusion into plasma of large amounts of long-chain free fatty acids (FFA). Unanesthetized dogs were connected by a peripheral artery to a closed, continuousflow centrifuge from which cells and plasma emerged in separate lines. Sodium oleate was infused directly into the plasma line before cells and plasma were recombined and returned to the animal through a peripheral vein.The centrifugation procedure itself produced only small changes in circulating levels of glucose, FFA, and electrolytes. Plasma flow rates as high as 100 ml/min could be maintained, and centrifugations of 12 hr were accomplished without complications. During centrifugation, sodium oleate was infused at rates up to 80 muEq/kg per min for 2.5 hr; the maximum molar ratio of FFA to albumin without hemolysis was 10:1. Plasma FFA levels rose rapidly after infusions were started and reached constant elevated levels within 15-20 min. Oleate infusion at 10-50 muEq/kg per min produced a rise in plasma FFA proportional to the infusion rate. The maximum increment in plasma FFA above control values was 1.66 muEq/ml. When infusions ended, plasma FFA declined rapidly to control levels. Oleate infusion at rates below 30 muEq/kg per min did not reduce levels of other plasma FFA. Infusion at high rates was accompanied by a marked fall in blood glucose. This method permits adminsitration of long-chain fatty acids in sufficient quantities to study their individual metabolic effects, and provides a new way to supply lipid calories parenterally.