Cryopreservant - Moreover, it is clear that cryopreservation single-cell systems has been successful, whereas cryopreservation of entire organs remains a great challenge. Presently, the duration of organ cryopreservation after procurement greatly decreases the efficiency of organ transplantation and increases cost; therefore, successful …

 
The basic principle of successful cryopreservation and resuscitation is a slow freeze and quick thaw. Although the requirements may vary amongst cell lines, as a general guide cells should be cooled at a rate of –1 °C to –3°C per minute and thawed quickly by incubation in a 37 °C water bath for 3-5 minutes.. Shelpoint

Cryopreservation is a fundamental tool of assisted reproduction and establishing long-term banking germplasm. Fertility cryopreservation is challenging because of gametes and embryos morphological, functional, and genetic changes in the cells after freeze- thawing [176,177,178,179].Nov 16, 2022 · Abstract. Organelles, cells, tissues, or any other biological construction can be preserved using a method called cryopreservation, in which samples are cooled to extremely low temperatures. The reaction of the living cell to the formation of ice is both theoretically intriguing and practically useful. Since osmotic shock, membrane damage, and ... Plant cryopreservation, specifically, is a process of cooling and storing vegetal structure as plant cells, tissues, or organs in liquid nitrogen (LN; −196 °C) or LN vapor (−160 °C). This methodology ensures the maintenance of samples’ viability after thawing, and indefinite storage is possible. The cryopreservation technique is based ...Jan 2, 2023 · Cryopreservation of tissues is a tough challenge. Cryopreservation is categorized into slow-freezing and vitrification, and vitrification has recently been recognized as a suitable method for ... Cryopreservation is a routine method for long-term storage of cell cultures. It provides a backup for active cultures and also helps prevent drift that can occur when …Cryopreserve definition: to maintain the viability of (cells, tissue, organs, etc.) by storing them at very low temperatures.. See examples of CRYOPRESERVE used in a sentence.For example, rapid cooling is associated with better cryopreservation outcomes for oocytes, pancreatic islets, and embryonic stem cells while slow cooling is recommended …Cryopreservation using DMSO resulted in high percentages of activated platelets; namely 54% of the recovered 94%. When using trehalose, 98% of the platelets had intact membranes after freezing and thawing, whereas 76% were not activated. Using Fourier transform infrared spectroscopy, subzero membrane phase behavior of platelets has … Cryopreservation is a technique for maintaining biologics at extremely low temperatures, usually at or below −80 °C, for extended periods of time (days to years). The process begins with a hypothermic exposure, as a cold cryopreservation solution is typically added to and equilibrated with the cell system. The system is then cooled through ... Core Tip: The manuscript is an overview of current cryopreservation protocols used for cold storage of hematopoietic stem cells, mesenchymal stem cells and induced pluripotent stem cells.Although dimethyl sulfoxide (DMSO) is commonly used in cryopreservation of cell lines, primary cells and stem cells, the use of DMSO has been …Nov 2, 2017 · Long-term storage of cell stocks insures that cells are available for use whenever needed. Cryopreservation of cells is the method of choice for preservation of important or rare cell stocks. There are several factors to consider when establishing a protocol for freezing, thawing, and recovery of cells after storage. These parameters may include cell concentration, cryoprotectant choice and ... Cryopreservation is a key enabling technology in regenerative medicine that provides stable and secure extended cell storage for primary tissue isolates and … Cryopreservation is a useful method for long-term storage of germplasm, especially for plant species that are difficult to conserve as seeds due to low dessication tolerance. For aquatic species, cryopreservation has limited application because female gametes and fertilized eggs usually cannot be frozen. Cryopreservation has become a central technology in many areas of clinical medicine, biotechnology, and species conservation within both plant and animal biology. …Sep 4, 2009 · More recently, cryopreservation solution formulation has moved beyond the addition of a penetrating cryoprotective agent such as DMSO (5–15%) to cell culture media, buffered saline or these media plus serum or a protein component. 53 Now recognized as essential to optimization of the cryopreservation process is the maintenance of proper cold ... Introduction. Cryopreservation is a technology employed in long-term storage of biologics achieved by cooling to cryogenic temperatures (1, 2).This preservation technique has become increasingly relevant especially in the development and commercialization of cellular therapeutic products (3, 4).Conventional cryopreservation protocols involve the …Cryopreservation. Label cryovials with the date, name of researcher, cell number, passage number and cell type (and any other useful information, for example genetic modifications). If cells are adherent, remove the cell culture media, wash in PBS, add enough trypsin to cover the cells and incubate for approximately 2 min in a 37°C incubator.1. WO2018211454 - CRYOPROTECTANT AND/OR CRYOPRESERVANT COMPOSITION, METHODS AND USES THEREOF. Publication Number WO/2018/211454. Publication Date 22.11.2018. International Application No. PCT/IB2018/053482. …Apr 15, 2010 · Practical Applications of Plant Cryopreservation. Cryopreservation of Dedifferentiated Cells and Tissues. Traditional, Simplified, and Novel Approaches for Dedifferentiated Cell Cryopreservation. Cryopreservation of Shoots and Roots. Enhancing Survival in Cryopreserved Shoot Tips using Vitrification. Cryopreservation of Seeds and Embryos Vascularized tissues and organs require perfusion for the various stages of preservation, such as preconditioning (including pre-equilibration with CPAs), preservation, and resuscita-. Fig. 1. New nature-inspired and bioengineering approaches to cryopreservation compared with classic methods. tion/recovery. Aug 10, 2023 · Cryopreservation describes methods to preserve living organisms and biological materials at very low temperatures. Central to this process is the use of liquid nitrogen, enabling successful cryogenic freezing and cryopreservation, opening possibilities for cell banking and other types of ex vivo preservation over extended periods of time. We studied the influence of sucrose applied in combination with different concentrations of penetrating cryoprotectants (DMSO, ethylene glycol, and glycerol) on the efficiency of cryopreservation of umbilical cord-derived multipotent stromal cells (MSC). The results indicate that these cells can be cryopreserved with the use of 5-10% DMSO …CRYOPRESERVATION definition: the storage of blood or living tissues at extremely cold temperatures, often –196 degrees... | Meaning, pronunciation, translations and examplesOrganelles, cells, tissues, or any other biological construction can be preserved using a method called cryopreservation, in which samples are cooled to …Improved cryopreservation of adipose tissue for the isolation of mesenchymal stem cells WO2010096821A2 (en) * 2009-02-23: 2010-08-26: Cell & Tissue Systems, Inc. Method for ice-free cryopreservation of tissue US20120190004A1 (en) * 2009-06-23: 2012-07-26: Biolex Therapeutics, Inc.We studied the influence of sucrose applied in combination with different concentrations of penetrating cryoprotectants (DMSO, ethylene glycol, and glycerol) on the efficiency of cryopreservation of umbilical cord-derived multipotent stromal cells (MSC). The results indicate that these cells can be cryopreserved with the use of 5-10% DMSO …Cryopreservation is the most prevalent method of long-term cell preservation. Effective cell cryopreservation depends on freezing, adequate storage, and correct thawing …Cellular cryopreservation is an important tool in modern biology. Here, previously reported polyampholyte cryoprotectants are studied by solid-state NMR, revealing the molecular mechanisms at play.Cryopreservation by control cooling rate is an expensive method only viable for specific cases such as prokaryote organisms 3-5. When an aqueous solution is rapidly cooled, crystallization is avoided resulting in water being in a metastable amorphous solid before becoming vitrified in a vitreous solid at temperatures below the glass transition.Dec 13, 2021 · Plant cryopreservation, specifically, is a process of cooling and storing vegetal structure as plant cells, tissues, or organs in liquid nitrogen (LN; −196 °C) or LN vapor (−160 °C). This methodology ensures the maintenance of samples’ viability after thawing, and indefinite storage is possible. The cryopreservation technique is based ... Each phytoplankton species presents a different behavior and tolerance to the cryopreservation process. Therefore, in a species-specific protocol, it is essential to ensure both growth and post-thawing cell viability. In this study, we explored the effect of cryopreservation of Scenedesmus sp. with two cryoprotectants, dimethyl sulfoxide …Abstract. Cryopreservation is the use of very low temperatures to preserve structurally intact living cells and tissues. Unprotected freezing is normally lethal and this chapter seeks to analyze some of the mechanisms involved and to show how cooling can be used to produce stable conditions that preserve life. Cryopreservation is the method of keeping the live cells, tissues and other biological samples in a deep freeze at subzero temperatures for the storage or preservation. The sample is commonly kept at −196°C. At such low temperatures, all the biological activities of the cells stop and the cell dies. Cryopreservation helps the cells to ... Cryopreservation is the use of very low temperatures to preserve structurally intact living cells and tissues. Unprotected freezing is normally lethal and this chapter seeks to analyze some of the mechanisms involved and to show how cooling can be used to produce stable conditions that preserve life. The biological effects of cooling are ... 3.2 Cryopreservation. Figure 1 depicts a flowchart showing the stages involved in the preparation of cultures prior to freezing. 1. Grow the bacteria on an appropriate nonselective, solid medium such as nutrient or blood agar under the optimum growth conditions (see Notes 2 and 3). 2. Aseptically add 2 mL of the suspending fluid to the …Cryopreservation media generally consist of a base medium, cryopreservative, and a protein source. The cryopreservative and protein protect the cells from the stress of the freeze-thaw process. A serum-free medium has generally low or no protein; but you can still use it as a base for a cryopreservative medium in the following formulations:Cryopreservation. Label cryovials with the date, name of researcher, cell number, passage number and cell type (and any other useful information, for example genetic modifications). If cells are adherent, remove the cell culture media, wash in PBS, add enough trypsin to cover the cells and incubate for approximately 2 min in a 37°C incubator. Cryopreservation is the most prevalent method of long-term cell preservation. Effective cell cryopreservation depends on freezing, adequate storage, and correct thawing techniques. Recent advances in cryopreservation techniques minimize the cellular damage which occurs while processing samples. This article focuses on the fundamentals of ... Cryopreservation is an efficient, cost-effective technique for long-term storage of plant material and different cryopreservation methods have been developed for plant cells, organs and tissues. This report reviewed a variety of cryopreservation methods in different species, as well as results of the impacts of cryopreservation on survival …The CryoDAO Mission. Interest in cryopreservation is higher than ever, but there still isn't enough research happening in the field. Even small amounts of attention could achieve significant advancements in the field, such as creating new cryoprotective agents to reduce toxicity, or creating different cryoprotection protocols based on ischemia.Cryopreservation is the most prevalent method of long-term cell preservation. Effective cell cryopreservation depends on freezing, adequate storage, and correct thawing …Kitazato, world leader in vitrification, has developed The Cryotop® Method and secured its global implementation achieving best-in-class results in cryopreservation of human specimens from gametes to blastocysts. Our objective is to provide you a method with proven evidence of success and to help you obtain the best results that only Kitazato ...Cryopreservation is a platform technology that underpins the delivery of complex therapies to patients and enables fundamental cell biology by allowing the …Cryopreservation or cryoconservation is a process where biological material - cells, tissues, or organs - are frozen to preserve the material for an extended period of time. At low temperatures (typically −80 °C (−112 °F) or −196 °C (−321 °F) using liquid nitrogen) any cell metabolism which might cause damage to the … See moreCryopreservation decreased total and progressive motility and the percentage of rapid sperm ( P < 0.01). Damage to sperm cells was confirmed by Annexin V ( P < 0.01), indicating that capacitation-like changes were induced by the cryopreservation procedures. An increase in sperm membrane fluidity was also noted in frozen/thawed …CS10 is a serum, animal component-free, defined cryopreservation medium containing 10% DMSO and it is recommended for cryopreservation of human pluripotent stem cells (hPSCs). 2.3. Cell freezing and thawing. For cryopreservation, cells were cultured under specific conditions, detached with 0,5 mM EDTA for hESCs RC17 and …This process is known as cryopreservation, and these compounds are known as cryoprotectants [12,13,14,15,16,17]. The main function of cryoprotectants is to protect cells from icing of water [9, 10]. Cryoprotectants are usually poly-hydroxy alcohols or sugars and can form strong hydrogen bond (H-bond) networks.The impact of cryopreservation on the sperm membrane is well known, and many studies agree that frozen–thawed semen is less fertile than fresh semen because of reduced sperm motility and a lower number of viable spermatozoa [ 27, 28 ]; however, it does not seem to negatively influence the live birth rate [ 29 ]. 2.2.Cryopreservation is a process that preserves organelles, cells, tissues, or any other biological constructs by cooling the samples to very low temperatures. The responses of living cells to ice formation are of theoretical interest and practical relevance. Stem cells and other viable tissues, which have great potential for use in basic research ...Cryopreservation is an efficient, cost-effective technique for long-term storage of plant material and different cryopreservation methods have been developed for plant cells, organs and tissues. This report reviewed a variety of cryopreservation methods in different species, as well as results of the impacts of cryopreservation on survival …Cryopreservation: ‘I freeze people to cheat death’. 21 August 2014. By Rose Eveleth,Features correspondent. (Thinkstock) Max More will have his brain frozen after he dies, and he’s not alone ...Cryopreservation is the most prevalent method of long-term cell preservation. Effective cell cryopreservation depends on freezing, adequate storage, …Cryopreservation - Download as a PDF or view online for free. 2. Introduction Cryopreservation is the technique of freezing cells and tissues at very low temperatures (sub-zero temperatures, typically -196oC) at which the biological material remains genetically stable and metabolically inert, while minimizing ice crystal formation. …Jun 9, 2022 · Cryopreservation is performed either through programmable slow freezing, vitrification or low-CPA vitrification (ultra-rapid cooling) with vitrification being is the preferred technique in cryonics because it prevents/reduces the formation of damaging ice crystals within the cryopreserved subject . 2. INTRODUCTION. Cryopreservation is the process which refers to the “ preservation in the frozen state”. It is derived from the Greek word ‘KRYOS’ meaning ‘FROST’. The term “cryopreservation” means storage at very low temperature such as in deep freezers (-80°C) in vapour phase nitrogen (-150°C) or in liquid nitrogen (-196°C ...Cryopreservation is the most prevalent method of long-term cell preservation. Effective cell cryopreservation depends on freezing, adequate storage, …percentage of cryopreservant resulted in improved viability of MSCs post thaw up to 6 hours as evidenced by better cell recovery after 6 days of culture. Figure 1. Comparison of size and granularity immediately post -thaw from MSCs cryopreserved in BI freezing media, PLA/5% HA/10% DMSO, CryoStor 5 or CryoStor 10 .Cryopreservation decreased total and progressive motility and the percentage of rapid sperm ( P < 0.01). Damage to sperm cells was confirmed by Annexin V ( P < 0.01), indicating that capacitation-like changes were induced by the cryopreservation procedures. An increase in sperm membrane fluidity was also noted in frozen/thawed …Sep 4, 2009 · More recently, cryopreservation solution formulation has moved beyond the addition of a penetrating cryoprotective agent such as DMSO (5–15%) to cell culture media, buffered saline or these media plus serum or a protein component. 53 Now recognized as essential to optimization of the cryopreservation process is the maintenance of proper cold ... Aug 10, 2023 · Cryopreservation describes methods to preserve living organisms and biological materials at very low temperatures. Central to this process is the use of liquid nitrogen, enabling successful cryogenic freezing and cryopreservation, opening possibilities for cell banking and other types of ex vivo preservation over extended periods of time. Sucrose is known to play an important role in the cryopreservation of sperm and female gonads; however, its effect on the cryopreservation of pig spermatogonial stem cells (pSSCs) has not been tested. The aim of this work was to study the effect of sucrose during pSSC cryopreservation and to find the most effective concentration in …Plant cryopreservation, specifically, is a process of cooling and storing vegetal structure as plant cells, tissues, or organs in liquid nitrogen (LN; −196 °C) or LN vapor (−160 °C). This methodology ensures the maintenance of samples’ viability after thawing, and indefinite storage is possible. The cryopreservation technique is based ...May 25, 2023 · Cryopreservation involves maintaining the physiological function of cells, tissues, and organs at ultra-low temperatures (−80°C or −196°C), at which point cellular activities nearly cease. Cryopreservation can effectively halt biological time and overcome the limitations of existing low-temperature storage technologies, making it a ... Knowledge about fundamental cryobiology developed in parallel with in vitro embryological studies, because embryos provided good models whereby the biophysical events encountered in cryopreservation could be tested in systems which had clearly defined criteria for survival and continued development after thawing [3,4,5].This chapter …Protect your frozen cells with Gibco cryopreservation media. Freezing down cells guards against unplanned mutations, senescence, and contamination. While unprotected cell freezing is ordinarily lethal, cell freezing with cryopreservation media helps protect cells for long-term viability as well as minimizes freezing injury for an intact cell ... Cryopreservation is an integral activity in most cell culture labs. Cryopreservation permits the storage and keeping of cells, tissues, and 3D systems like organoids, for future use. How cryopreservation is managed, the materials used and equipment employed can greatly impact its success. For instance, if cells are frozen too quickly ice ... Cryopreservation avoids it by using eggs that got extracted one time. In case of IVF treatment, doctors used to implant more than one egg in order to increase the probability of success. With cryopreservation technique, it is not required to do so. Doctors can implant one or maximum two embryos in one attempt and keep preserve the others.The PSC Cryopreservation Kit contains xeno-free PSC Cryopreservation Medium, which is a ready-to-use solution for the cryopreservation of early passage pluripotent stem cells (PSCs), and RevitaCell™ Supplement (100X), a chemically defined recovery supplement for use in the post-thaw culture media.When used in combination, these reagents help …Cryopreservation is a fundamental tool of assisted reproduction and establishing long-term banking germplasm. Fertility cryopreservation is challenging because of gametes and embryos morphological, functional, and genetic changes in the cells after freeze- thawing [176,177,178,179].Objective: We investigated the effects of freeze-thawing on the properties of articular cartilage. Design: The reproducibility of repeated biomechanical assay of the same osteochondral sample was first verified with 11 patellar plugs from 3 animals. Then, 4 osteochondral samples from 15 bovine patellae were divided into 4 groups. The …Cells were previously cryopreserved with 1M trehalose or 10% Me 2 SO + 90% FBS at short and long durations of cryopreservation. The evaluation was performed by flow cytometry of typical anti-CD61 + PE antibody on the day of thawing (day 0), and after 6 and 12 days of MK differentiation. Data are expressed as the mean ± standard …Cryopreservation, the process of storing materials at sub-zero temperatures, is an essential process for fundamental research, as well as the clinical, biomedical and food sciences 1. The ability to prolong the storage of biological materials, by reducing the temperature to slow the rate of degradation, has wide-reaching applications.Protect your frozen cells with Gibco cryopreservation media. Freezing down cells guards against unplanned mutations, senescence, and contamination. While unprotected cell freezing is ordinarily lethal, cell freezing with cryopreservation media helps protect cells for long-term viability as well as minimizes freezing injury for an intact cell ...Cryopreservation of yeast is usually achieved by growing the strain of interest in rich growth medium before adding a cryoprotective agent to cells prior to freezing. In general, yeast strains can be preserved and stored indefinitely in 25% (v/v) glycerol at temperatures of 60 C or lower [4].Abstract. As the progress of regenerative medicine places ever greater attention on cryopreservation of (stem) cells, tried and tested cryopreservation solutions deserve a second look. This article discusses the use of hydroxyethyl starch (HES) as a cryoprotectant. Charting carefully the recorded uses of HES as a cryoprotectant, in …For example, rapid cooling is associated with better cryopreservation outcomes for oocytes, pancreatic islets, and embryonic stem cells while slow cooling is recommended …Cryopreservation of oocytes, sperm, and ovarian and testicular tissues, as well as embryos, is one of the most critical procedures to preserve the reproductive capacity of …57. Advantages • Cryopreservation helps in the preservation of biological materials. • Cryopreservation is used to maintain the biosynthetic properties of plants • Sperm, gametes, embryos, tissues, bone marrow, organ can be preserved. • Helps to study the adapting nature of plants and animals under the low temperature.Oocyte cryopreservation is a reliable method for the maintenance of fertility in women undergoing treatment for medical conditions such as cancer or …Cryopreservation media generally consist of a base medium, cryopreservative, and a protein source. The cryopreservative and protein protect the cells from the stress of the freeze-thaw process. A serum-free medium has generally low or no protein; but you can still use it as a base for a cryopreservative medium in the following formulations:

Cryopreservation is an integral activity in most cell culture labs. Cryopreservation permits the storage and keeping of cells, tissues, and 3D systems like organoids, for future use. How cryopreservation is managed, the materials used and equipment employed can greatly impact its success. For instance, if cells are frozen too quickly ice ... . 123.hpcom

cryopreservant

Abstract. Cryopreservation is the application of low temperatures to preserve the structural and functional integrity of cells and tissues. Conventional cooling protocols allow ice to form and solute concentrations to rise during the cryopreservation process. The damage caused by the rise in solute concentration can be mitigated by the …As with the cryopreservation of cell suspensions, adipose tissue cryopreservation is most frequently conducted in line with the principle of slow freezing and fast thawing. The thawing protocol usually involves the water bath thawing of samples at 37 °C and removal of the cryoprotector by washing with a buffer solution, followed by …Feb 1, 2021 · Figure 7. Ice‐inhibition performance of GO and OQCNs and their applications for cell cryopreservation. A) The honeycomb‐like structure of GO matched with ice lattice and the formation of hydrogen bonds between ice crystals and hydroxy groups. B) The influence of GO on the growth and shape of ice crystals. The cryopreservation of hematopoietic cells using dimethyl sulfoxide (DMSO) and serum is a common procedure used in transplantation. However, DMSO has clinical and biological side effects due to ...Cryopreservation: ‘I freeze people to cheat death’. 21 August 2014. By Rose Eveleth,Features correspondent. (Thinkstock) Max More will have his brain frozen after he dies, and he’s not alone ...Cryopreservation has become a central technology in many areas of clinical medicine, biotechnology, and species conservation within both plant and animal biology. Cryoprotective agents (CPAs) invariably play key roles in allowing cells to be processed for storage at deep cryogenic temperatures and to be recovered with high levels of …Sucrose is known to play an important role in the cryopreservation of sperm and female gonads; however, its effect on the cryopreservation of pig spermatogonial stem cells (pSSCs) has not been tested. The aim of this work was to study the effect of sucrose during pSSC cryopreservation and to find the most effective concentration in … Plant cryopreservation is a genetic resource conservation strategy that allows plant material, such as seeds, pollen, shoot tips or dormant buds to be stored indefinitely in liquid nitrogen. [1] After thawing, these genetic resources can be regenerated into plants and used on the field. While this cryopreservation conservation strategy can be ... Suspension cell lines can be used directly. Remove a small aliquot of cells (100-200μL) and perform a cell count. Ideally, the cell viability should be in excess of 90% in order to achieve a good recovery after freezing. Centrifuge the remaining culture at 150 x g for 5 minutes. Re-suspend cells at a concentration of 2-4x10 6 cells per mL in ...Organelles, cells, tissues, or any other biological construction can be preserved using a method called cryopreservation, in which samples are cooled to …Examples of how to use “cryopreservation” in a sentence from Cambridge Dictionary.Improved cryopreservation of adipose tissue for the isolation of mesenchymal stem cells WO2010096821A2 (en) * 2009-02-23: 2010-08-26: Cell & Tissue Systems, Inc. Method for ice-free cryopreservation of tissue US20120190004A1 (en) * 2009-06-23: 2012-07-26: Biolex Therapeutics, Inc.Abstract. There is considerable interest in the use of sugars to preserve cells. In this study, low temperature Raman spectroscopy was used to characterize the behaviors of sucrose during freezing. The hydrogen bond network between sucrose and water was investigated at −10 °C and −50 °C, and the Raman spectra showed strengthened …Cryopreservation is a key enabling technology in regenerative medicine that provides stable and secure extended cell storage for primary tissue isolates and constructs and prepared cell preparations. The essential detail of the process as it can be applied to cell-based therapies is set out in this review, covering tissue and cell isolation, …Apr 15, 2010 · Practical Applications of Plant Cryopreservation. Cryopreservation of Dedifferentiated Cells and Tissues. Traditional, Simplified, and Novel Approaches for Dedifferentiated Cell Cryopreservation. Cryopreservation of Shoots and Roots. Enhancing Survival in Cryopreserved Shoot Tips using Vitrification. Cryopreservation of Seeds and Embryos Jun 4, 2019 · Abstract. In this concept article, we outline a variety of new approaches that have been conceived to address some of the remaining challenges for developing improved methods of biopreservation. This recognizes a true renaissance and variety of complimentary, high-potential approaches leveraging inspiration by nature, nanotechnology, the thermodynamics of pressure, and several other key fields ... It is now accepted that with current methods of cryopreservation, uncontrolled ice formation in structured tissues and organs at subzero temperatures is the single most critical factor that severely restricts the extent to which tissues can survive procedures involving freezing and thawing. In recent years, this major problem has been ... .

Popular Topics