Relative Centrifugal Force Research Articles

Artificial Neural Networks in Modeling of Dewaterability of Sewage Sludge

Mechanical dewatering is a key process in the management of sewage sludge. However, the drainage efficiency depends on a number of factors, from the type and dose of the conditioning agent to the parameters of the drainage device. The selection of appropriate methods and parameters of conditioning and dewatering of sewage sludge is the task of laboratory work. This work can be accelerated through the use of artificial neural network (ANNs). The paper discusses the possibilities of using ANNs in predicting the dewatering efficiency of physically conditioned sludge. The input variables were only four parameters characterizing the conditioning methods and the dewatering method by centrifugation. These were the dose of the sludge skeleton builders (cement, gypsum, fly ash, and liquid glass), sonication parameters (sonication amplitude and time), and relative centrifugal force. Dewatering efficiency parameters such as sludge hydration and separation factor were output variables. Due to the nature of the research problem, two nonlinear networks were selected: a multilayer perceptron and a radial neural network. Based on the results of the prediction of artificial neural networks, it was found that these networks can be used to forecast the effectiveness of municipal sludge dewatering. The prediction error did not exceed 1.0% of the real value. ANN can therefore be useful in optimizing the dewatering process. In the case of the conducted research, it was the optimization of the sludge dewatering efficiency as a function of the type and parameters of conditioning factors. Therefore, it is possible to predict the dewatering efficiency of sludge that has not been tested in the laboratory, for example, with the use of other doses of physical conditioner. However, the condition for correct prediction and optimization was the use of a large dataset in the neural network training process.

An important source of preanalytical error in medical laboratories: centrifugation

Abstract Centrifugation separates particles within the specimen according to their shape, dimensions, and density and basically can be defined as a separation method. The centrifuge is an essential device in medical laboratories to prepare the serum, plasma, and urine samples for analysis. It is basically an electric device composed of the stationary (motor) and the motile (rotor) part. The centrifugation depends on two main variables: relative centrifugal force (RCF) and centrifugation time. The physical impact separating the specimen into its components in the centrifuge known as RCF is expressed as the multiples of gravitational acceleration (×g). RPM, defined as the number of rotations of the centrifuge per minute, shows the speed of the centrifuge. RCF value can be calculated by using RPM, and the centrifuge radius. Because models and sizes of centrifuges vary considerably, the use of gravity (g) forces instead of RPM is suggested. The centrifuges can be classified according to their usage, speed, technical specifications, and rotor type. An accurate and precise centrifugation process is essential to prevent errors in the preanalytical phase. The purpose of this document is to ensure the standardization of a good, precise protocol for the centrifugation process among the medical laboratories.

Biologization of Pcl-Mesh Using Platelet Rich Fibrin (Prf) Enhances Its Regenerative Potential In Vitro.

Introduction: Resorbable synthetic scaffolds are promising for different indications, especially in the context of bone regeneration. However, they require additional biological components to enhance their osteogenic potential. In addition to different cell types, autologous blood-derived matrices offer many advantages to enhance the regenerative capacity of biomaterials. The present study aimed to analyze whether biologization of a PCL-mesh coated using differently centrifuged Platelet rich fibrin (PRF) matrices will have a positive influence on primary human osteoblasts activity in vitro. A polymeric resorbable scaffold (Osteomesh, OsteoporeTM (OP), Singapore) was combined with differently centrifuged PRF matrices to evaluate the additional influence of this biologization concept on bone regeneration in vitro. Peripheral blood of three healthy donors was used to gain PRF matrices centrifuged either at High (710× g, 8 min) or Low (44× g, 8 min) relative centrifugal force (RCF) according to the low speed centrifugation concept (LSCC). OP-PRF constructs were cultured with pOBs. POBs cultured on the uncoated OP served as a control. After three and seven days of cultivation, cell culture supernatants were collected to analyze the pOBs activity by determining the concentrations of VEGF, TGF-β1, PDGF, OPG, IL-8, and ALP- activity. Immunofluorescence staining was used to evaluate the Osteopontin expression of pOBs. After three days, the group of OP+PRFLow+pOBs showed significantly higher expression of IL-8, TGF-ß1, PDGF, and VEGF compared to the group of OP+PRFHigh+pOBs and OP+pOBs. Similar results were observed on day 7. Moreover, OP+PRFLow+pOBs exhibited significantly higher activity of ALP compared to OP+PRFHigh+pOBs and OP+pOBs. Immunofluorescence staining showed a higher number of pOBs adherent to OP+PRFLow+pOBs compared to the groups OP+PRFHigh+pOBs and OP+pOBs. To the best of our knowledge, this study is the first to investigate the osteoblasts activity when cultured on a PRF-coated PCL-mesh in vitro. The presented results suggest that PRFLow centrifuged according to LSCC exhibits autologous blood cells and growth factors, seem to have a significant effect on osteogenesis. Thereby, the combination of OP with PRFLow showed promising results to support bone regeneration. Further in vivo studies are required to verify the results and carry out potential results for clinical translation.

Liquid whole egg fractionation: Effect of centrifugation on physicochemical attributes of quality

Pasteurized liquid whole egg was fractionated by centrifugation. Several studies showed the composition of plasma and granules that can be obtained by egg yolk centrifugation. However, few studies deal about liquid whole egg fractionation. In this work, the effect of operational conditions (relative centrifugal force—RCF, time, and temperature) on the physicochemical quality of plasma and granules was evaluated. These fractions were compared with liquid whole egg as control. The physicochemical parameters analyzed were fractionation yield and ratio, pH, water activity (aw), and color (L*, a*, b*, chroma, and hue). The plasma yield obtained ranged from 75.10% to 84.44% while the granule yield varied from 8.16% to 15.00%. Equations to forecast fractionation yield and ratio were developed. For example, the best conditions for high plasma recovery are 8,000 g for 10 min at 4°C; where the P/G ratio and plasma yield estimated are 91.08% and 84.64%, respectively. While only a granule yield of 7.88% is expected. Prediction models were also obtained for pH and color. No significant differences were detected for aw. However, significant differences were detected in color between whole egg, plasma, and granules. Practical applications This work provides a database and equations that could be used for the fractionation by centrifugation of liquid whole egg to obtain new products with improved functional properties.

Evaluation of Perioral Skin Rejuvenation with Platelet – Rich Plasma

Introduction:Using Platelet- Rich Plasma (PRP )in aesthetic dermatology has been recently considered and its safety and effectiveness have been widely reported. We conducted this study to evaluate the technique and degree of benefit. Methods: Fifteen (15) patients with different ages, sexes, and facial perioral wrinkles have participated in the current research and received a session of monthly PRP injections (three courses), targeting line and wrinkles in the perioral area. In this study, we have prepared the PRP by using a special test tube and then centrifuge it with relative centrifugal force (RCF) of 1700G for 5 minutes, followed by two minutes of soft centrifugation at room temperature. Results: Mean age ± SD was 40 ± 1.36 years. 44.7% were female. 84.5% of patients are considered adherent (≥ 95% of doses were consumed). Married patients had better adherence (p = 0.04). Age, sex, addiction, imprisonment history, intravenous drug usage were not associated with adherence (p> 0.05). We also extracted previews history of treatment cessation and regimen changes. Efavirenz containing regimens had a higher rate of failure (p =0.001). Conclusion: Wrinkles in perioral area management by PRP injection is an easy technique, with high- quality result and high patient satisfaction, no serious side effects, high patient toleration, and short downtime. Platelet- Rich Plasma can be a competitive substitute for other fillers and revitalization methods in lips and perioral rejuvenation.

Equipment and materials management

Equipment and materials management

Evaluation of 24 protocols for the production of platelet-rich fibrin

BackgroundThe aim of this study was to evaluate 24 protocols for the production of platelet rich fibrin (PRF) produced via horizontal centrifugation to better understand cell separation following protocols at various times and speeds.MethodsAll protocols were compared utilizing a recent method to quantify cells in PRF in 1 mL sequential layers pipetted from the upper layer downwards until all 10 mL were harvested. In total, 960 complete blood counts (CBCs) were investigated. Both solid and liquid-based PRF protocols were investigated following 24 protocols involving 6 relative centrifugal force (RCF) values (100, 200, 400, 700, 1000 and 1200g) at 4 centrifugation times (3, 5, 8 and 12 min).ResultsIn general, platelets could more easily accumulate in the upper 4 layers when compared to leukocytes owing to their lower cellular density. Protocol time seemed to have a greater impact on the final cell layer separation when compared to the effect of speed. Protocols of greater than 8 min at 400g led to no leukocyte accumulation in the upper PRF layers (found specifically within the buffy coat). Protocols at or below 200g were unable to effectively accumulate platelets/leukocytes. The optimal centrifugation speed and time for solid-PRF ranged between 400 and 700g for 8 min. It was noted that variability in patient baseline platelet/leukocyte/erythrocyte counts (hematocrit) significantly affected cell layer separation. This finding was more pronounced at lower centrifugation speeds.ConclusionsWithin the investigated ranges, a protocol of 700g for 8 min presented the highest yield of platelets/leukocytes evenly distributed throughout the upper PRF layers.

Analytical photo-centrifuge-based prediction of shelf-life and droplet packing behaviour of nanoemulsions upon removal of excess micelles

An analytical photo-centrifuge was used to develop novel experimental methods to predict the shelf-life, rheology, and inter-droplet interactions in 40 wt% canola oil-in-water nanoemulsions stabilized by 3 and 5 wt% citric acid esters of monoglyceride (Citrem). The combined influence of micellar concentration and oil droplet size on the rheology, creaming stability, and compression behaviour was studied under a series of accelerated gravitations. Nanoemulsions without excess Citrem micelles were obtained by removing them from the continuous phase using multiple cycles of ultracentrifugation. Reduction in droplet size with an increase in Citrem concentration and the removal of excess micelles resulted in a significant increase in plateau storage moduli leading to a change in phase behaviour of the nanoemulsions from liquid to viscoelastic gels. Moreover, it also showed a simultaneous drastic decrease in nanodroplets creaming velocity under accelerated gravitation. The flow behaviour of the gels was well correlated with a critical relative centrifugal force required to initiate flow under accelerated gravitation. Additionally, the colloidal forces responsible for instability was satisfactorily explained by the packing behaviour of the nanodroplets studied under a series of compression and dilatational cycles of centrifugation. We showed that the strong electrostatic repulsive force between the nanodroplets without excess micelles led to a lower packing density during compaction that did not change significantly during successive dilatational cycles. The higher packing density or compaction in the presence of excess micelles was explained by the short-range attractive depletion forces leading to weak flocculation of nanodroplets. Overall, the presence and absence of excess micelles showed a significant influence on the rheology and accelerated stability of nanoemulsions, which can be further described by the colloidal forces between the nanodroplets using the real-time advanced photo-centrifuge.

Histological characteristics of Platelet-Rich Fibrin clots obtained under various modes of blood centrifugation

Autologous products of the first and second generation, namely platelet-rich plasma and platelet-rich fibrin, are considered promising for regenerative medicine. They differ from each other in physical properties, as well as in the way they are obtained. The key procedure of all techniques is centrifugation; changing its parameters affects the biological properties of these biomaterials. The aim of the work is to determine and histologically characterize the area of concentration cells of autologous fibrin enriched with platelets, depending on the change in centrifugation parameters. The studies were carried out on rabbits. Blood was collected and platelet-rich plasma (PRP) and platelet-rich fibrin (PRF) were obtained using different values of relative centrifugal force: 100 g, 400 g, 735 g, 906 g, 1843 g. Due to the fact that it is impossible to determine the number of platelets in PRF clots, the counting was performed in platelet-rich plasma obtained by a single centrifugation with the corresponding parameters that were used to obtain PRF. The length of the formed clots was compared and a histological assessment of the cell composition in different layers (lower, middle and upper) was carried out. The highest platelet concentrations were observed in PRP obtained at 100 g and 400 g. Application of different values of centrifugal force showed obvious differences in the formation of platelet-rich fibrin clots. After preparation of I-PRF, its volume was significantly less than that of standard PRF, and the border between erythrocytes was less distinct. During the histological examination of fibrin clots, a change in the distribution of cellular elements in different parts was found with a change in the centrifugation parameters. With an increase in the parameter of relative centrifugal force, the length of the fibrin clot significantly increases, but the concentration of platelets in it significantly decreases. That is, it was found that the most optimal value of the relative centrifugal force for obtaining platelet mass is 100 g, which makes it possible to achieve the number of platelets greater than 800×109/L.

Relative Centrifugal Force (RCF; G-Force) Affects the Distribution of TGF-β in PRF Membranes Produced Using Horizontal Centrifugation.

Solid platelet-rich fibrin (PRF) is produced with centrifugation tubes designed to accelerate clotting. Thus, activated platelets may accumulate within the fibrin-rich extracellular matrix even before centrifugation is initiated. It can thus be assumed that platelets and their growth factors such as transforming growth factor-β (TGF-β) are trapped within PRF independent of their relative centrifugal force (RCF), the gravitation or g-force. To test this assumption, we prepared PRF membranes with tubes where clotting is activated by a silicone-coated interior. Tubes underwent 210 g, 650 g and 1500 g for 12 min in a horizontal centrifuge. The respective PRF membranes, either in total or separated into a platelet-poor plasma and buffy coat fraction, were subjected to repeated freeze-thawing to prepare lysates. Gingival fibroblasts were exposed to the PRF lysates to provoke the expression of TGF-β target genes. We show here that the expression of interleukin 11 (IL11) and NADPH oxidase 4 (NOX4), and Smad2/3 signaling were similarly activated by all lysates when normalized to the size of the PRF membranes. Notably, platelet-poor plasma had significantly less TGF-β activity than the buffy coat fraction at both high-speed protocols. In contrast to our original assumption, the TGF-β activity in PRF lysates produced using horizontal centrifugation follows a gradient with increasing concentration from the platelet-poor plasma towards the buffy coat layer.

Luminescence continuous flow system for monitoring the efficiency of hybrid liposomes separation using multiphase density gradient centrifugation

A method for monitoring the efficiency of the hybrid magnetoliposomes (h-MLs) separation using multiphase density gradient centrifugation (MDGC) coupled with a continuous flow system (CFS) is described. Several h-MLs suspensions containing hydrophobic magnetic gold nanoparticles (Fe3O4@AuNPs-C12SH) and different fluorophores encapsulated have been synthesized using the rapid solvent evaporation (RSE) method. The MDGC system was prepared using a non-linear multiphase density gradient formed with a bottom layer with 100% (v/v) sucrose solution and six layers containing a mixture of sucrose solution (with concentrations ranged between 10 and 55% v/v), and fixed concentrations of ficoll (30% v/v) and percoll (15% v/v) solutions. The density gradient profile was previously stabilized using a relative centrifugal force (RCF) of 4480×g for 30 min. The synthesized h-MLs were added to the density gradient profile and separated by centrifugation at 2520×g for 20 min. The efficiency of the separation procedure was tested, aspirating the separated extract into the CFS and lysing liposomes before their translation to the detector introducing surfactant solutions. The luminescence signals provided by the release of the encapsulated fluorophores and other materials provided the distribution status of the liposomes in each density gradient stage. The monitoring of the different samples revealed four different fractions (MLs, h-Ls, h-MLs, and non-encapsulated fluorophores) for each separated h-MLs. Additional information on the h-MLs has also been acquired by confocal microscopy.

Comparing ultrafiltration and equilibrium dialysis to measure unbound plasma dolutegravir concentrations based on a design of experiment approach

Dolutegravir therapeutic drug monitoring (TDM) could be improved by measuring the unbound dolutegravir plasma concentration (Cu), particularly in patients experiencing virological failure or toxicity despite achieving appropriate DTG total plasma concentrations. Equilibrium dialysis (ED) is the gold standard to measure Cu, but ED is time consuming, precluding its use in clinical practice. In contrast, ultrafiltration is applicable to TDM, but is sensitive to numerous analytical conditions. In order to evaluate measurements of Cu by ultrafiltration, ultrafiltration conditions were validated by comparison with ED. DTG concentrations were measured by LC–MS/MS. Three ultrafiltration factors (temperature, duration and relative centrifugal force [RCF]) were evaluated and compared to ED (25/37 °C), using a design of experiment strategy. Temperature was found to influence Cu results by ED (p = 0.036) and UF (p = 0.002) when results were analysed with ANOVA. Relative centrifugal force (2000 g) and time (20 min) interacted to influence Cu (p = 0.006), while individually they did not influence Cu (p = 0.88 and p = 0.42 for RCF and time). Ultrafiltration conditions which yielded the most comparable results to ED were 37 °C, 1000 g for 20 min. Ultrafiltration results greatly depended on analytical conditions, confirming the need to validate the method by comparison with ED in order to correctly interpret DTG Cu.

Correlation between the Pore Structure and Water Retention of Cemented Paste Backfill Using Centrifugal and Nuclear Magnetic Resonance Methods

This research combines a centrifugal test and nuclear magnetic resonance (NMR) technology to study the water retention capacity of the cemented paste backfill. Backfill samples with cement–tailings ratios of 1:4, 1:8, and 1:12, and solid concentrations of 71%, 74%, 77%, 80%, and 83% respectively, were prepared for the test. The relative centrifugal force ( RCF ) required for accurate testing and the T2 cutoff value that characterizes the water retention capacity were obtained through an NMR test on the backfill samples after centrifugation in saturated conditions. Based on the soil–water characteristic curve (SWCC), the NMR pore water characteristic distribution model was established, and the pore size distribution and effective water retention characteristics were analyzed. This study shows that when the rotating speed is between 1500 and 4000 rpm, the R C F of the backfill ranges from 125.8 to 894.4 g/min , and the T2 cutoff value will vary from 3 to 10 ms. With an increase in solid concentration of the backfill, both the RCF and T2 cutoff value decline. The Scanning Electron Microscope (SEM) analysis confirms that an increase in the solid concentration and cement–tailings ratio will lead to obvious bimodal characteristics of the pore size distribution curve of the backfill. In addition, the porosity will decrease, the critical pore value, which represents a value to distinguish pores with different movable fluid retention capabilities and characterizes the pore size classification, will become smaller, and the pore size distribution will become more diverse. These changes indicate that a high-concentration backfill can effectively reduce the flow of a fine-grained matrix with large pores.

Experimental study of oil mist characteristics generated from minimum quantity lubrication and flood cooling

Abstract The use of metalworking fluids during machining can generate oil mist and endanger the health of workers. In order to study the characteristics and emission laws of oil mist generated by machining, this study constructed a test bench to simulate the turning process. Parameters affecting the oil mist generated in the minimum quantity lubrication (MQL) mode and flood cooling mode were studied by means of single-factor experiments, and the formation mechanisms of oil mist were analyzed. The results show that the oil mist generated by the MQL system has two main sources, the initial escape of oil mist into the air and the evaporation/condensation of oil mist. The centrifugation has almost no effect on oil mist formation in the MQL mode. The mass concentration of oil mist generated by the MQL system is proportional to the cutting oil flow rate. When the work-piece is at room temperature, increasing the air supply pressure and nozzle distance, increases the oil mist mass concentration. For the flood cooling mode, the concentration of centrifugal aerosol is linearly and positively correlated with the relative centrifugal force generated by the work-piece, and the coefficient of determination (R2) is above 0.97. The oil mist mass concentrations in MQL mode is 8.33 mg/m3~ 305.88 mg/m3. The MMD and SMD are 0.74 µm to 4.42 µm and 0.31 µm to 2.14 µm, respectively. The oil mist mass concentrations in flood cooling mode is 0.2 mg/m3~ 22.42 mg/m3. The MMD and SMD are 1.81 µm to 6.58 µm and 0.45 µm to 5.13 µm, respectively.

Different Re-centrifugation Conditions for Infectious Disease Screening Using the Abbott I2000.

We investigated whether an ordinary centrifuge can achieve the standard centrifugal effect required according to specifications for infectious disease screening using the Abbott i2000. Samples were collected and centrifuged following a standard operating procedure (SOP). They were then divided into three groups according to the results of the initial screening tests: a negative group, weak-positive group, and positive group. Twenty negative samples and all weak-positive and positive samples were re-analyzed. Two tubes for each re-analyzed sample were centrifuged simultaneously, one for 10 min at 10 000 × g, per recommendations, and one for 10 min at 2750 × g. No significant difference was found between the groups using different centrifugal forces. There was a strong correlation in the quantitative values between the two conditions of centrifugation. Consistency analysis showed a Cronbach's alpha > 0.8 for detection of Treponema pallidum, human immunodeficiency virus (HIV), hepatitis C virus (HCV), and hepatitis B surface antigen in the three groups (negative group, weak-positive group, and positive group) under different centrifugation conditions. Strong consistency was found under different centrifugal conditions, regardless of the initial testing results. In conclusion, we conducted centrifugation steps in duplicate, according to infectious disease screening protocols. Our study showed that all samples should be centrifuged using a recommended relative centrifugal force after a proper clotting time, as in the standard operating procedure of our laboratory. In this way, we were able to obtain the same results using an ordinary centrifuge as those obtained using a high-speed centrifuge, such as the Abbott i2000.

Distribution of particle sedimentation thickness under constant relative centrifugal force in rotating separation system using wireless electrical resistance detector

Distribution of particle sedimentation thickness under constant relative centrifugal force in rotating separation system using wireless electrical resistance detector

Analysis and estimation/prediction of the disk stack centrifuge separation performance – Scaling from benchtop fixed rotor type to disk stack centrifuges

ABSTRACT A mathematical model is proposed to calculate the total separation effectiveness in terms of GT for a disk stack centrifuge taking account of the variation of the centrifugal force with a position in the disk. In practice, the centrifuge ability/force is often referred as Relative Centrifugal Force (RCF) or G number, which is a multiple of the centrifugal acceleration over the gravitational acceleration. As the radial velocity varies it is important to integrate the relative centrifuge force, here in terms of the G number along the path taking account of the change in velocity. The separation effectiveness, GT is defined as an integrated product of local G number, G(x) and local residential time (dt), where dt is the time taken for the bulk fluid to traverse a distance from r to r+ dr. The GT value calculated for a disk type centrifuge can be compared with the GT value of others and compared with a bench top fixed rotor centrifuge. An industrial centrifuge would be expected to be able to deliver similar separation performance to a pilot or a lab scale one, if operated at the same/similar value of GT. This would allow the performance of a full-scale clarifier to be predicted. This model is, in essence, a simple alternative to the Sigma concept.

Open Source Completely 3-D Printable Centrifuge

Centrifuges are commonly required devices in medical diagnostics facilities as well as scientific laboratories. Although there are commercial and open source centrifuges, the costs of the former and the required electricity to operate the latter limit accessibility in resource-constrained settings. There is a need for low-cost, human-powered, verified, and reliable lab-scale centrifuges. This study provides the designs for a low-cost 100% 3-D printed centrifuge, which can be fabricated on any low-cost RepRap-class (self-replicating rapid prototyper) fused filament fabrication (FFF)- or fused particle fabrication (FPF)-based 3-D printer. In addition, validation procedures are provided using a web camera and free and open source software. This paper provides the complete open source plans, including instructions for the fabrication and operation of a hand-powered centrifuge. This study successfully tested and validated the instrument, which can be operated anywhere in the world with no electricity inputs, obtaining a radial velocity of over 1750 rpm and over 50 N of relative centrifugal force. Using commercial filament, the instrument costs about U.S. $25, which is less than half of all commercially available systems. However, the costs can be dropped further using recycled plastics on open source systems for over 99% savings. The results are discussed in the context of resource-constrained medical and scientific facilities.

Establishing a protocol for water sample processing for the detection of Blastocystis sp.

This study was aimed at establishing a protocol for water sample processing for the detection of Blastocystis sp. using distilled water spiked with Blastocystis sp. cysts.The study established a protocol involving eight technical aspects, namely, storage temperature, storage duration, minimum water sample volume, optimum relative centrifugal force, centrifugation duration, minimum number of cyst for inoculation in Jones' medium and turn-around-time for the detection of vacuolar forms of Blastocystis sp. Results showed a minimum of 1.0 L water sample should be collected and processed on the same day. Otherwise, it should be stored at 4 °C and processed within 3 days. Water sample should be centrifuged at 1400×g for 10 min. For the isolation of Blastocystis sp. cysts, parasite pellet could be layered on top of Ficoll-Paque™ PLUS, centrifuged at 1400×g for 20 min and washed twice using 0.9% saline with centrifugation at 1400×g for 10 min. A minimum of 1 × 105 cysts could then be inoculated in Jones’ medium supplement with 10% horse serum, incubated at 37 °C and examined for any presence of vacuolar forms of Blastocystis sp. after 3 days of inoculation. A protocol for water sample processing for the detection of Blastocystis sp. has successfully been established. The protocol was validated using 106 various water samples. This protocol will be very useful in determining the extent of Blastocystis sp. contamination in water sources in order to identify the seriousness of contamination.

The role of centrifugation process in the preparation of therapeutic blood concentrates: Standardization of the protocols to improve reproducibility

Investigations of endogenous blood-derived growth factors have increased in the past two decades. The initial protocols for blood concentrates, such as platelet-rich-plasma, utilized anticoagulants followed by bovine thrombin to catalyze fibrin polymerization. Subsequently, platelet-rich-fibrin (PRF) protocol was developed to eliminate anticoagulants and thrombin. The PRF production was described in a vertical rotor centrifuge with an angle of ~33°. Many commercial enterprises have attempted to replicate this protocol with a multitude of different centrifuges. These attempts have utilized revolutions per minute (RPM) to develop their protocol to generate PRF. However, RPM is a variable parameter, as it depends on the design and radius of the centrifuge. The separation of blood components is highly dependent on the relative centrifugal force (RCF) generated, which is based on the applied centrifugal force, expressed as multiples of earth's gravitation (g) field. RCF is a function of the acceleration due to the gravity of the earth, g = 9.81 m/s2 RCF, not RPM, is the key factor for the sedimentation of the cells and proteins within blood concentrates. RCF is determined using the maximum centrifuge radius for calculation. The initial PRF was generated by applying an RCF of 700 ×g. Accordingly, so far, a large number of studies existing about PRF are not comparable, as they were technically prepared with different RCFs. In addition, due to the nonstandardized measurement methods, in some published studies, incorrect RCF values are published as the authors did not know how to calculate the RCF correctly. This is the case for a widespread blood concentrate called leukocyte-PRF, which is commercially available. Recently, we introduced the low-speed centrifugation concept (LSCC) for the production for solid and liquid PRF matrices. This concept is based on the above-mentioned initial PRF protocols, which represents a relatively high RCF. It shows that a systematic reduction of 700 ×g to 44 ×g can significantly increase the cells and growth factors within the same blood concentrates. The LSCC concept was established initially for a fixed rotor centrifuge with a radius of ~110 mm. The present narrative review highlights the necessity of standardization in the generation of blood concentrates, which utilizes RCF, rather than commercial protocols.