Retention Device Research Articles

Evaluation of Retention, Wear, and Maintenance of Attachment Systems for Single- or Two-Implant-Retained Mandibular Overdentures: A Systematic Review.

Attachment systems (AS) enhance retention and stability by anchoring the overdentures to implants. Since 2002, the McGill consensus statement recommends the 2-implant-retained overdentures as the standard choice for edentulous mandible (2-IRMO). Considering the large number of AS available, it remains difficult for a practitioner to make a reasoned choice. A systematic review was conducted in PubMed/Medline and carried out independently by three authors, on retention, wear, and maintenance of AS used clinically or in vitro specifically for 1- or 2-IRMO. The 45 selected studies include 14 clinical and 31 in vitro studies. The risk of bias was evaluated according to the revised Cochrane risk of bias tool for randomized trials (RoB 2). The initial retention force of the cylindrical system is higher than the ball system. The retention loss, related to the wear of the retention device, is responsible for the most common need of maintenance, requiring activation or replacement. Plastic retention devices wear out faster and more significantly than metal ones, implying a worse time behavior of cylindrical systems, but their maintenance rate is similar. Neither system appears categorically superior. Cylindrical systems provide higher initial retention than ball ones; this advantage reduces over time with wear without affecting their need for maintenance.

Assessment of Rainwater Retention Efficiency in Urban Drainage Systems—Model Studies

Around the world, there is growing interest in the use of rainwater retention, and in particular channel retention, as part of urban drainage systems. This is made possible by means of intentional damming of rainwater in the existing sewer collectors in order to maximise the use of gravitational spaces in the channels. This approach is particularly favourable for drainage types related to high levels of urban development, where construction of a building is difficult due to the low amount of space available. This article explains the results of a study concerning the efficiency assessment of three retention devices characterised by different hydraulic systems, one of which uses channel retention in its operation. The analysis conducted within the simulation study has demonstrated that the use of standard single-chamber reservoirs is the least efficient solution. A comparison of the functions of different hydraulic systems of retention reservoirs under equal conditions has shown that the necessary retention capacity of a single-chamber reservoir is many times greater in comparison to highly efficient solutions and it may constitute up to 582% of the reservoir’s capacity and works in conjunction with the channel retention system. At the same time, it has been demonstrated that the application of channel retention is not the most efficient solution for all hydraulic conditions for a drainage system or for all hydrological conditions. In addition, the article proposes a set of retention efficiency indices that may be used in the future assessment of individual rainwater storage solutions. Estimation of the necessary capacity of the retention facilities operating in specific hydraulic conditions was made on the basis of model tests—hydrodynamic modelling with the use of SWMM 5.0 software. The course of the research was planned using the theory of experiment planning (DOE) with the use of Statistica software, whereas efficiency indices were developed with the use of artificial neural networks (ANNs). The study results include practical and cognitive aspects. These may constitute guidelines for the designers and potential investors, as well as a tool with the aim of promoting the most efficient rainwater retention solutions in urban drainage systems.

Bond strength between a veneering composite resin and zirconia frameworks with attached mechanical retentive devices.

The effects of mechanical retentive devices and various surface treatments on the shear bond strength between a veneering composite resin and zirconia was investigated. Zirconia disks were classified into three surface-treatment groups: airborne-particle abrasion, overglazing, and overglazing with white alumina particles of three different grain sizes (50, 70, and 105 μm) attached onto zirconia disks (ZR-50, ZR-70, and ZR-105, respectively). They were further divided into four groups (n=44): unprimed, Clearfil Porcelain Bond Activator (CA), Clearfil Photo Bond (CB), and CA+CB. An indirect composite resin was bonded to zirconia specimens. Shear bond strengths were measured. For the ZR-70 and ZR-105 groups, the CB and CA+CB specimens exhibited higher bond strengths than the other two specimens after thermocycling. The ZR-70 and ZR-105 groups achieved micromechanical interlocking, and priming with a phosphate monomer (MDP) yielded stable bond strengths between the composite resin and zirconia with alumina particles attached as retentive devices.

A simple and innovative low cost technique for fabricating magnet retained overdentures- A case report

Various attachments have been used in overdentures to increase the retention. Application of rare earth magnets such as Sm-Co and Nd-Fe-B, for improving retention have been widely used in the field of prosthodontics, as they can be manufactured in small dimensions as retentive devices for complete dentures, removable partial dentures, obturators and maxillofacial prosthesis. However they are expensive as these attachments are not manufactured locally, so they increase the cost of treatment hence cannot be afforded by all patients. This article presents a simple and cost-efficient method of fabricating mandibular over denture retained by magnets in a patient whose mandibular residual ridge was severely resorbed with few remaining teeth and opposed by maxillary conventional removable partial denture.

Retrospective Study Regarding Orthodontic Retention Complications in Clinical Practice

At the end of any orthodontic treatment, retention is a necessary phase. Unfortunately, the current retention devices and the lack of proper oral hygiene on the part of patients lead to the accumulation of dental plaque, periodontal inflammation, and gingival retraction. Our retrospective study included 116 adult patients wearing various types of orthodontic retainers. To quantitatively determine the accumulation of dental plaque, we used the Quigley–Hein plaque index modified by Turesky and the Navy plaque index modified by Rustogi. Another studied parameter was related to the gingival recession associated with retention devices. We had investigated the correctness of patients’ dental hygiene, their preferences for auxiliary means of oral hygiene, the consistency with which they wear the mobile retainers, and respect the orthodontist’s instructions; we also investigated the inconveniences and the accidents that may occur during the retention period. Statistical analysis showed that plaque accumulation is significantly lower in the case of mobile retainer than fixed retainer wearers; the exception was the Hawley plate, where the interdental plaque was more than in all the other studied retainers. Periodontal recessions were more frequent in the case of fixed retainer wearing. Flossing was the most commonly used auxiliary mean for oral hygiene. The compliance of women in wearing vacuum-formed retainers was better than that of men. Patients with a class III history had more plaque accumulation, and class II/1 had the most problems related to detachment/damage of fixed retainers. Mobile retainers proved better results for oral hygiene, but fixed retainers cannot be waved.

The effect of flow partition on storm runoff and pollutant retention through raingardens with and without subsurface drainage

Green infrastructures (GIs) have been advocated worldwide to mitigate the negative impact of urbanization on regional hydrological cycle, their functions are closely related to their design features and the local environmental condition. This paper reports a field monitoring study that aimed to investigate how runoff partition in raingardens would affect flow and pollutant retention. A paired field experiment was conducted to compare runoff and pollutant retentions in two raingardens with and without subsurface drainage in a shallow water table area. Concentrations of ammonia nitrogen (NH3–N), nitrate nitrogen (NO3–N) and total phosphorus (TP) were measured at raingarden inflow, overflow and drainage paths. The results from 28 monitored storm events over two years showed that the raingarden without subsurface drainage achieved its retention mainly through ponding and infiltration, its pollutant retention rates (76% for TP, 81% for NO3–N, and 79% for NH3–N) were higher than its runoff retention rate (61%), indicating a first flush effect on pollutants retention in the raingarden during storm events, especially when the raingarden was empty and dry. The raingarden with subsurface drainage facilitated quick discharge of water, the observed runoff reduction through the raingarden was 36%; pollutant removal rates were quite variable: NH3–N was removed by 91% while the NO3–N and TP were increased by 3–47%. These results suggest that facilitating specific processes for targeted pollutants is necessary for achieving substantial pollutant removal in a stormwater retention device. Subsurface drainage pipes resulted in short circulating of runoff and lowered pollutant removal rates in the raingarden. Considering the water table fluctuation during the experimental period, we recommend to build infiltration-based GI devices to better capture first flush in intensively developed urban area, which caused deeper groundwater table. In conclusion, installations of different GI devices in urban landscape need to consider the local environmental conditions and facilitate the design features to meet specific storm runoff and pollutants mitigation requirement.

Custom fabrication of cast splint microimplant-assisted rapid palatal expansion appliances for treatment of maxillary deficiency in young adults

Background: The objective of this article was to illustrate the process in the fabrication of a custom cast splint Microimplant-Assisted Rapid Palatal Expansion (MARPE) appliance for treatment of maxillary deficiency in young adults. Findings: The fabrication of a custom-made MARPE appliance allows the casting base to design according to the shape of the patient’s palate close to the palatal mucosa. In this new design, one end consists of a casting body, inserting hole, and teeth retention device (circumferential rings) connected to the other end by a jackscrew. Connection of all parts in the integral casting unit increases the strength of the expansion appliance and avoids distortion, deformation, or damage to the palatal mucosa due to increased resistance from the oromaxillofacial area. Conclusion: This custom design can improve the clinical outcome of maxillary expansion, especially in patients with narrow and high-arched palates.

Cell culture\u2013based production of defective interfering influenza A virus particles in perfusion mode using an alternating tangential flow filtration system

Respiratory diseases including influenza A virus (IAV) infections represent a major threat to human health. While the development of a vaccine requires a lot of time, a fast countermeasure could be the use of defective interfering particles (DIPs) for antiviral therapy. IAV DIPs are usually characterized by a large internal deletion in one viral RNA segment. Consequentially, DIPs can only propagate in presence of infectious standard viruses (STVs), compensating the missing gene function. Here, they interfere with and suppress the STV replication and might act “universally” against many IAV subtypes. We recently reported a production system for purely clonal DIPs utilizing genetically modified cells. In the present study, we established an automated perfusion process for production of a DIP, called DI244, using an alternating tangential flow filtration (ATF) system for cell retention. Viable cell concentrations and DIP titers more than 10 times higher than for a previously reported batch cultivation were observed. Furthermore, we investigated a novel tubular cell retention device for its potential for continuous virus harvesting into the permeate. Very comparable performances to typically used hollow fiber membranes were found during the cell growth phase. During the virus replication phase, the tubular membrane, in contrast to the hollow fiber membrane, allowed 100% of the produced virus particles to pass through. To our knowledge, this is the first time a continuous virus harvest was shown for a membrane-based perfusion process. Overall, the process established offers interesting possibilities for advanced process integration strategies for next-generation virus particle and virus vector manufacturing.Key points• An automated perfusion process for production of IAV DIPs was established.• DIP titers of 7.40E + 9 plaque forming units per mL were reached.• A novel tubular cell retention device enabled continuous virus harvesting.

Use of a Novel Adhesive Suture Retention Device in Lower Leg Excisional Wound Closure: A Retrospective Review

Introduction. Lower extremity excisional wound closures are associated with complications, including infection, delayed wound healing, skin tearing after suture placement, and dehiscence. Use of a novel adhesive suture retention device (ASRD) has previously been shown to support fragile skin under high tension and improve linear closure. Objective. A retrospective analysis of lower extremity excisional wounds was performed to investigate the effect of adopting ASRD on rate of wound closure and adverse events. Materials and Methods. A retrospective chart review from 2 Mohs surgical practices was conducted. The chart review assessed the differences before and after adopting ASRD in linear closure rates, wound healing, and dehiscence rates for lower extremity post-surgical full-thickness wounds of at least 1.0 cm diameter in patients aged 18 years or older. In all cases, the authors shared the same surgical techniques, including limited undermining and use of buried dermal polyglactin sutures. In all ASRD cases, the device was used with 2-0 nylon retention sutures. Results. Adoption of ASRD was associated with a significantly faster time to healing (P < .001). Dehiscence was significantly more commonly seen in the pre-ASRD cohort (24% vs 3%, P = .03). Infection was also more common in the pre-ASRD cohort; however, the difference was not statistically significant (18% vs 3%, P = .09). Conclusions. Utilization of ASRD decreased the incidence of lower extremity wound dehiscence and resulted in faster healing times after Mohs surgery.

USE OF INVOCELL INTRAVAGINAL EMBRYO CULTURE SYSTEM FOR FIVE DAYS OF INCUBATION: A PROSPECTIVE STUDY OF SAFETY AND TOLERABILITY

The purpose of this single-center study was to prospectively evaluate the INVOcell culture device with its retention device in planned day-5 embryo transfer cycles, as to its retention, comfort, and possible vaginal mucosal irritation. INVOcell is presently approved in the US for up to 3 days. The study was prospectively approved by WCG IRB (#1295533). Women scheduled for oocyte retrieval planning blastocyst transfer at a single center (N=31) were invited to participate in the study; all gave written informed consent. Two failed screening; 29 were enrolled in the study aged 26-41 (median 36) years with body mass index of 20.1-39.5 (median 30.5) kg/m2. A vaginal speculum exam was done at the completion of each retrieval, and after INVOcell removal at 5 days; before examination of INVOcell contents, all women completed the study questionnaire. The primary endpoint of the study was device retention, determined by patient report. Secondary endpoints of patient comfort and vaginal tissue reaction to the INVOcell system were assessed after its removal by patient questionnaire and speculum exam. The INVOcell system was retained by 100% of participants. One woman felt that the system was dislodged; she was able to readjust the system to maintain it in position. A conservative analytic approach thus gives a 96% rate of successful retention. All women completed the questionnaire, which assessed overall subject comfort and satisfaction with wearing the INVOcell system. Only two subjects reported any discomfort, and that was at a tolerable level not requiring medical intervention. The overall Likert rating for discomfort of 0.17 (pain scale of 0-10 with 0 being no pain/discomfort and 10 being severe pain/discomfort) demonstrates the favorable comfort level for the INVOcell and retention device during 5-day incubation. Whereas bleeding was noted immediately after oocyte retrieval in the majority of women and considered to be a normal sequela of this procedure, at Day-5 vaginal speculum exam no lesions, ulcerations, erythema, or bleeding were noted. In conclusion, our study demonstrates that the INVOcell system can be safely used for a 5-day embryo incubation without causing vaginal irritation or mucosal injury. Our results also verify that the system is well tolerated.

Enhanced perfusion of elliptical wound closures using a novel adhesive suture retention device.

Background and AimsThe purpose of this investigation was to test the hypothesis that a novel adhesive retention suture device (ARSD) can increase perfusion at elliptical wound closures by distributing stress away from the suture site.MethodsStress in the skin around a suture both with and without support from an ARSD was evaluated using a finite element model. A single‐center, randomized split‐scar comparison trial using laser speckle contrast analysis was used to quantify the perfusion at elliptical wound closures in human patients both with and without an ARSD.ResultsThe finite element model revealed that the ARSD promoted load transfer to the skin over a larger area, thus reducing the local stress and deformation in the skin around the suture site. Results from the split‐scar study showed a mean improvement of 25% perfusion units with the ARSD, and the improvement was statistically significant (p = 0.002).ConclusionThe reduction in local stress and enhanced perfusion around the suture site reveals the potential benefit of using an ARSD to enable more efficient healing by avoiding complications associated with both low perfusion and skin tearing, such as dehiscence, infection, and cheese wiring.

3D Printed Microfluidic Spiral Separation Device for Continuous, Pulsation-Free and Controllable CHO Cell Retention.

The development of continuous bioprocesses—which require cell retention systems in order to enable longer cultivation durations—is a primary focus in the field of modern process development. The flow environment of microfluidic systems enables the granular manipulation of particles (to allow for greater focusing in specific channel regions), which in turn facilitates the development of small continuous cell separation systems. However, previously published systems did not allow for separation control. Additionally, the focusing effect of these systems requires constant, pulsation-free flow for optimal operation, which cannot be achieved using ordinary peristaltic pumps. As described in this paper, a 3D printed cell separation spiral for CHO-K1 (Chinese hamster ovary) cells was developed and evaluated optically and with cell experiments. It demonstrated a high separation efficiency of over 95% at up to 20 × 106 cells mL−1. Control over inlet and outlet flow rates allowed the operator to adjust the separation efficiency of the device while in use—thereby enabling fine control over cell concentration in the attached bioreactors. In addition, miniaturized 3D printed buffer devices were developed that can be easily attached directly to the separation unit for usage with peristaltic pumps while simultaneously almost eradicating pump pulsations. These custom pulsation dampeners were closely integrated with the separator spiral lowering the overall dead volume of the system. The entire device can be flexibly connected directly to bioreactors, allowing continuous, pulsation-free cell retention and process operation.

Rehabilitation of severly resorbed mandibular ridge with implant supported overdenture with magnet attachment : A case report.

Magnets have been used widely in the field of dentistry for many years with some success, as they can be manufactured in small dimensions as a retentive devices in overdenture technique, maxillofacial prosthesis and obturators. These magnet attachment attached to osseointegrated implants which transfer the occlusal load to the bone, thereby prevent resorption of remaining alveolar bone and improves the retention and stability of the denture. Magnetic assembly consist of magnet and ferromagnetic metal keeper. More recently, magnets have been made from alloys of the rare earth elements samarium and neodymium, which provides stronger magnetic force per unit size. Magnets are sealed by means of the latest laser lasing techniques thus protect magnet from corrosion in oral cavity. The present article demonstrates the rehabilitation of completely edentulous patient with the help of implant supported mandibular overdenture with magnet attachment and conventional maxillary denture.

Process intensification for the production of yellow fever virus-like particles as potential recombinant vaccine antigen.

Yellow fever (YF) is a life-threatening viral disease endemic in parts of Africa and Latin America. Although there is a very efficacious vaccine since the 1930s, YF still causes 29,000-60,000 annual deaths. During recent YF outbreaks there were issues of vaccine shortage of the current egg-derived vaccine; rare but fatal vaccine adverse effects occurred; and cases were imported to Asia, where the circulating mosquito vector could potentially start local transmission. Here we investigated the production of YF virus-like particles (VLPs) using stably transfected HEK293 cells. Process intensification was achieved by combining sequential FACS (fluorescence-activated cell sorting) rounds to enrich the stable cell pool in terms of high producers and the use of perfusion processes. At shaken-tube scale, FACS enrichment of cells allowed doubling VLP production, and pseudoperfusion cultivation (with daily medium exchange) further increased VLP production by 9.3-fold as compared to batch operation mode. At perfusion bioreactor scale, the use of an inclined settler as cell retention device showed operational advantages over an ATF system. A one-step steric exclusion chromatography purification allowed significant removal of impurities and is a promising technique for future integration of upstream and downstream operations. Characterization by different techniques confirmed the identity and 3D-structure of the purified VLPs.

Design and Evaluation of a Millifluidic Insulator-Based Dielectrophoresis (DEP) Retention Device to Separate Bacteria from Tap Water

Water is a basic necessity critical to the survival of all living beings. However, many people around the world do not have consistent access to uncontaminated drinking water. Traditional water treatment methods, such as filtration and disinfection, require physical or chemical disinfectants and are prone to fouling. Dielectrophoresis (DEP) enables a system whereby polarized bioparticles exhibit lateral movement under the influence of applied, non-uniform electric fields. A single-stage, continuous flow, millimeter-sized DEP device was designed and fabricated to remove Escherichia coli K12 from contaminated tap water. Glass beads were used to alter the electric field distribution and create zones of high electric field to trap bacterial cells. The effect of varied voltages, flow rates and bead sizes on the removal efficiency was studied. The highest removal efficiency of E. coli K12 was 99.9%, with the device set at 60 V, a flow rate of 1.0 mL/min and a 200 µm bead size. Higher applied voltages, slower flow rates, and smaller bead sizes led to an increased reduction in bacteria. An optimized macro-scale system—with multiple stages of DEP—could be suitable for commercial use and would be an effective method of removing pathogens from polluted tap water.

Clinical impact of two types of mandibular retention devices - A CAD/CAM design and a traditional design - On upper airway volume in obstructive sleep apnea patients

ObjectiveThis pilot randomized crossover study evaluated the outcomes of two custom-made mandibular retention devices (MRDs), a computer-aided design (CAD)/computer-aided manufacturing (CAM) device (Narval CC™) and a non-CAD/CAM device (Narval™), on oropharyngeal airway volume in patients with obstructive sleep apnoea (OSA). Methods12 OSA patients were recruited from an University Hospital for MRD therapy with either CAD/CAM or non-CAD/CAM first. A cone-beam computed tomography evaluation (CBCT) and polysomnography assessment was performed during baseline assessment and at the end of each study period. ResultsUpper airway volume increased significantly with the CAD/CAM device (7725 +/- 6540 mm3, p = 0.008) but not with the non-CAD/CAM device (3805 +/- 7806 mm3, p = 0.13). The CAD/CAM device was also associated with a significant decrease in AHI (mean AHI after treatment 9.4±6.7 events/h, p = 0.003) and oxygen desaturation index (mean ODI of ≥ 3%/h 11.9 ± 6.8, p = 0.011). Changes in AHI (14.7 +/- 11.7 events/h, p = 0.083) and ODI (15.5 +/- 19.2, p = 0.074) were not statistically significant with the non-CAD/CAM device. The vertical dimension of occlusion increased significantly following treatment with both MRD devices (both p = 0.003), but was significantly less pronounced with the CAD/CAM device (mean difference: -2.7 +/- 1.7 mm, p = 0.003). Final mandibular protrusion after titration was the same with both devices (85%, p = 0.317). ConclusionThe CAD/CAM (Narval CCTM) device was associated with a significant increase in upper airway volume that may be caused by a lower degree of vertical separation between the jaws when compared to the non-CAD/CAM design.

Process intensification to produce a difficult-to-express therapeutic enzyme by high cell density perfusion or enhanced fed-batch.

Intensified bioprocesses have caught industrial interest in the field of biomanufacturing in recent years. Thanks to new technology, intensified processes can support high cell densities, higher productivities and longer process times, which together can offer lower cost of goods. In this study two different intensified process modes, high cell density perfusion and enhanced fed-batch, were evaluated and compared with a conventional fed-batch process for a difficult-to-express therapeutic enzyme. The intensified process modes were cultivated with a target cell density of 100 × 106 cells/ml and with alternating tangential flow filtration, ATF, as cell retention device. The processes were designed to resemble an established optimized fed-batch process using the knowledge of this process without new dedicated optimization for the intensified modes. The design strategy included decision of the ratio of feed concentrate to base medium and glucose supplementation, which were based on target cell-specific consumption rates of key amino acids and glucose, using a targeted feeding approach (TAFE). A difficult-to-express therapeutic enzyme with multiple glycosylation sites was expressed and analyzed in the different production processes. The two new intensified processes both achieved 10 times higher volumetric productivity (mg/L/day) with retained protein quality and minor changes to the glycan profile compared to the fed-batch process. The study demonstrates the potential of using intensified processes for sensitive complex enzymes. It is shown here that it is possible to transfer a developed fed-batch process into high cell density processes either in intensified fed-batch or steady-state perfusion without new dedicated optimization. The results demonstrated as well that these intensified modes significantly increase the productivity while maintaining the desired product quality, for instance the same amount of product was obtained in 1 day during the perfusion process than in a whole fed-batch run. Without any prior optimization of the perfusion rate, the high cell density perfusion process resulted in only 1.2 times higher medium cost per gram produced protein.

Outcome after secondary alveolar bone grafting among patients with cleft lip and palate at 16 years of age: a retrospective study

To evaluate the outcome of secondary alveolar bone grafting (SABG) in patients with cleft lip and palate at 16 years of age and to identify predictors associated with surgical failure. This retrospective follow-up included 91 patients with 100 cleft palates treated with SABG at a mean age of 9.2 years. The possible predictors for surgical failure analyzed were sex, dental development stadium, type of cleft, side, tooth erupting into the graft, cortical boundary, presence of a lateral incisor, extraction, preoperative expansion, oral hygiene, retention device, and age. The outcome variable for surgical success was Bergland score I and II. Surgical outcome was analyzed at 16 years of age based on intraoral radiographs, according to the Bergland index. Statistical analyses included estimation of odds ratios for predictor variables. The post-SABG success rate was 91% (Bergland score I and II) with a mean follow-up of 7.2 years. Surgical failure was significantly associated with poor oral hygiene. This study revealed a high success rate (91%) at a mean of 7.2 years post-SABG. Poor oral hygiene significantly increased the risk of surgical failure. This suggests that increased perioperative measures to maintain good oral health could reduce surgical failure.

The influence of weirs on microplastic fate in the riverine environment (case study: Jeneberang River, Makassar City, Indonesia)

The riverine environment is known as the main pathway of microplastic entering the ocean. Recent studies show that the barricading of water flow in the riverine environment can influence the microplastic load to the ocean. The Jeneberang River, which is located in Makassar City, is prone to microplastic pollution. There are three weirs located in this river as water barricades. The aim of this study was to measure the microplastic abundance upstream and downstream of each weir flow. Microplastics in the water compartment were measured using the volume-reduce towing method and were measured in the sediment compartment using a density separator method. The results show that microplastic abundance in the water prior to passing each weir was higher (1.43 – 3.19 item/m3) compared by the flow after each weir (1.20 – 2.10 item/m3). The same pattern was also apparent in the sediment compartment where the microplastic abundance prior to the weirs tended to be higher (28.33 – 56.67 item/kg DW) compared to the compartment after the weir (30.00 – 53.33 item/kg DW). Based on microplastic shape, there is no evidence that weirs in the Jeneberang River are blocking any specific shape of microplastic. In conclusion, weirs that are commonly found in the riverine environment could act as microplastic retention devices in the riverine environment.

Continuous bleed recycling significantly increases recombinant protein production yield in perfusion cell cultures

Stable operation in mammalian perfusion cell cultures can be achieved using a waste (bleed) stream to remove excess biomass from the reactor. This stream is often considered as a necessary loss sometimes leading to consequent yield drops. In this study, an acoustic settler was used to concentrate the bleed stream in order to harvest concentrated cells and recycle the clarified portion to the bioreactor. The amount of recycled product corresponded to an equivalent increase in harvest flowrate, which led to an increased overall productivity. This equipment was chosen because it can be operated in continuous mode and there are no fouling/clogging risks as it is the case for many other cell retention devices (CRD).Two similar operating conditions (OC) were tested, one with and another without the acoustic settler working. Both conditions were compared with a strong focus on the bleed and harvest streams to evaluate the yield improvement. The separation efficiency (SE), which is the ability of the system to remove cells from the liquid phase, was calculated and was always superior to 99 %. The bleed fraction in this specific example could be decreased from 59.2 % ± 1.6–3.9 % ± 1.3 without impacting the process or the product quality and leading up to a 2.25-fold yield improvement.