The short version of lyophilization fits in a sentence. The long version — which is the one that helps — is below.
Reviewed 2025-10-06. Anything still debated is marked as such rather than presented as settled.
Lyophilization is a dehydration technique in which a product is frozen and the solvent is removed under reduced pressure. The low pressure allows ice to sublimate directly into vapor without passing through a bulk liquid phase. This differs from conventional drying, where heat drives evaporation and can damage heat-sensitive structures. The process is used for biological materials, pharmaceutical formulations, and some foods. Its main advantage is preservation of porous structure and rapid reconstitution.
Freezing is the first stage and sets the ice structure that later becomes the pore network. The formulation is cooled below its freezing point, often with a controlled ramp, and solutes concentrate as ice forms. Primary drying then lowers chamber pressure and supplies heat to sublime the ice. The product temperature must stay below its collapse or eutectic temperature to prevent structural loss. Secondary drying raises the temperature modestly to remove bound water and achieve a low residual moisture.
Stability studies examine how temperature, humidity, and time influence a lyophilized product. Accelerated conditions provide early information about degradation pathways, while long-term studies support shelf-life claims. The glass transition temperature of the dried formulation can indicate its physical stability, and storage above this temperature may increase molecular mobility and lead to collapse or aggregation. Container closure integrity also matters because moisture or oxygen ingress can degrade the product, so vial stoppers and seals are part of the quality system.
Handling and storage practices aim to keep the cake intact and dry. Vials are typically stored upright at controlled temperatures, often between 2 °C and 8 °C or at -20 °C for longer-term use. Reconstitution involves adding a suitable diluent and gently mixing until the solid dissolves. Shaking or rapid injection of diluent can create foam or damage sensitive molecules. Once reconstituted, the product may require refrigeration and use within a defined period.
| Property | Value | Notes |
|---|---|---|
| Common synonyms | freeze-drying, lyophilisation, cryodesiccation | Lyophilization is common in pharmaceutical literature. |
| Typical chamber pressure during primary drying | 0.05–0.5 mbar (5–50 Pa) | Must remain below the triple point of water. |
| Typical shelf temperature during freezing | −40 to −20 °C | Lower temperatures may be used for eutectic systems. |
| Typical residual moisture after secondary drying | 0.5–3% w/w | Product-dependent; low moisture improves stability but can cause over-drying. |
| Typical analytical method for residual moisture | Karl Fischer titration or loss on drying | Thermogravimetric methods are also used. |
Secondary drying removes bound water that remains after ice sublimation. Shelf temperature is raised gradually while pressure remains low, reducing water content to a target range. Over-drying can cause brittleness or electrostatic issues, while under-drying affects stability. The endpoint is often judged by pressure rise tests, temperature measurements, or water content analysis. Scale-up depends on matching heat and mass transfer across equipment sizes. Small changes in shelf temperature or pressure can alter cycle length substantially.
Lyophilization, or freeze-drying, removes water from a material by freezing it and then lowering pressure so ice changes directly to vapor. The process relies on sublimation, the phase transition from solid to gas without an intervening liquid state. It is used for heat-sensitive materials that would degrade in conventional drying. The three stages are freezing, primary drying, and secondary drying, each with distinct temperature and pressure requirements. In practice, cycle design balances these variables.
Freezing determines ice crystal structure and pore size, which affect drying speed and product uniformity. Rapid freezing creates small crystals, while slow freezing creates larger crystals and often faster sublimation. During primary drying, chamber pressure is held below the vapor pressure of ice, and shelf temperature supplies heat for sublimation. The ice front recedes, leaving a porous matrix. Thermal limits such as collapse and eutectic temperatures set safe boundaries for formulation. These limits vary with solute composition and concentration.
Handling practices aim to prevent moisture ingress and mechanical damage. Vials should remain stoppered and crimped until use, and reconstitution should follow the labeled diluent and volume. Shipping may involve temperature-controlled containers and desiccants, but direct contact between desiccant and product is avoided. Regulatory guidance expects documented storage conditions, excursion assessments, and stability commitments. Open questions remain about how best to predict long-term stability from short accelerated studies for every formulation class.
After lyophilization, the product is usually a porous cake or powder with a large internal surface area. This structure can absorb moisture quickly if exposed to humid air, so vials are sealed under vacuum or an inert gas. Moisture uptake may lower the glass transition temperature of the dried matrix and accelerate chemical or physical degradation. Storage conditions therefore depend on the formulation, container, and intended shelf life. Some products remain stable at room temperature, while others require refrigeration or freezing.
=== Salt iodization === Salt iodization is a strategy for addressing iodine deficiency, which is a cause of several physical and mental health problems. In 1990, less than 20 percent of households in developing countries had adequate iodine in their diet. By 1994, international partnerships had formed in a global campaign for Universal Salt Iodization. By 2008, it was estimated that 72 percent of households in developing countries included iodized salt in their diets, and the number of countries in which iodine deficiency disorders were a public health concern reduced by more than half from 110 to 47 countries.
=== Humans === The FPR3 gene was cloned and named based on the similarity of the amino acid sequence which it encodes to that encoded by the gene for FPR1 (see formyl peptide receptor 1 for details) The studies indicated that FPR3 is composed of 352 amino acids and its gene, similar to FPR1, has an intronless open reading frames which encodes a protein with the 7 transmembrane structure of G protein coupled receptors; FPR3 has 69% and 72% amino acid sequence identities with FPR1. All three genes localize to chromosome 19q.13.3 in the order of FPR1 (19q13.410), FPR2 (19q13.3-q13.4), and FPR3 (19q13.3-q13.4) to form a cluster which also includes the genes for another G protein-coupled chemotactic factor receptor, the C5a receptor (also termed CD88) and GPR77, and a second C5a receptor, C5a2 (C5L2), which has the structure of a G protein coupled receptor but fails to couple to G proteins and is of debated function.
Medical terminology is language used to describe the components, processes, conditions, medical procedures and treatments of the human body. In the English language, medical terminology generally has a regular morphology; the same prefixes and suffixes are used to add meanings to different roots. The root of a term often refers to an organ, tissue, or condition, and medical roots and affixes are often derived from Ancient Greek or Latin (particularly Neo-Latin). Many medical terms are examples of neoclassical compounds. Historically, all European universities used Latin as the dominant language of instruction and research, as Neo-Latin was the lingua franca of science, medicine, and education in Europe during the early modern period. Medical terminology includes a large part of anatomical terminology, which includes the anatomical terms of location, motion, muscle, bone, and histology. It also includes language from biology, chemistry, physics, and physiology, as well as vocabulary unique to the field of medicine, such as medical abbreviations. Each branch of medicine has its own clinical and scientific terminology. Medical dictionaries are specialised dictionaries for medical terminology and may be organised alphabetically or according to medical classification systems such as the Systematized Nomenclature of Medicine, International Classification of Diseases, or Unified Medical Language System. Examples of modern medical dictionaries include Mosby's Dictionary of Medicine, Nursing & Health Professions, Stedman's, Taber's, and Dorland's.
=== Legal status === MDMA is legally controlled in most of the world under the UN Convention on Psychotropic Substances and other international agreements, although exceptions exist for research and limited medical use. In general, the unlicensed use, sale or manufacture of MDMA are all criminal offences.
Sources: en.wikipedia.org
=== Hematopoietic stem cell transplant === Bronchiolitis obliterans affects up to 5.5% of people who have received HSCT. One of the biggest risk factors after HSCT is the development of GVHD with a 14% risk. Other risk factors post transplant including tobacco use, age of donor, age of recipient, lower baseline FEV1/FVC ratio, non-caucasian race, peripheral and lower circulating IgG levels. Studies have, however, shown mixed results regarding these other risk factors. There has been an association shown between the increased use of peripheral stem cells and the risk of developing bronchiolitis obliterans. Also, research has shown an increased risk for developing the disease within the first year of transplant if the person is infected with respiratory syncytial virus or parainfluenza virus within the first 100 days post transplant.
Gene expression is the process by which the information contained within a gene is used to produce a functional gene product, such as a protein or a functional RNA molecule. This process involves multiple steps, including the transcription of the gene's sequence into RNA. For protein-coding genes, this RNA is further translated into a chain of amino acids that folds into a protein, while for non-coding genes, the resulting RNA itself serves a functional role in the cell. Gene expression enables cells to utilize the genetic information in genes to carry out a wide range of biological functions. While expression levels can be regulated in response to cellular needs and environmental changes, some genes are expressed continuously with little variation.
=== Research === A 2023 study on genetically engineered mice published in the journal PNAS found that increasing production of a particular microRNA in hair follicle stem cells, which naturally harden with age, softened the cells and stimulated hair growth. The authors of the study said the next research step is to introduce the microRNA into the stem cells using nanoparticles applied directly to the skin, to develop a similar topical application for humans.
In 1981, the PLA conducted its largest military exercise in North China since the founding of the People's Republic. In the late 1980s, the central government had increasing expenditures and limited revenue. The central government encouraged its agencies and encouraged local governments to expand their services and pursue revenues. The PLA established businesses including hotels and restaurants. The PLA gained more autonomy and permission to engage in commercial activities in exchange for a reduced role in political affairs and limited budgets; the military was downsized to free resources for economic development. The lack of oversight, ineffective self-regulation, and Jiang Zemin's and Hu Jintao's lack of close personal ties to the PLA led to systemic corruption that persisted through the late-2010s. Jiang's attempt to divest the PLA of its commercial interests was only partially successful, as many were still run by close associates of PLA officers. Corruption lowered readiness and proficiency, was a barrier to modernization and professionalization, and eroded party control. The 2010s anti-corruption campaigns and military reforms under Xi Jinping from the early-2010s were in part executed to address these problems. Following the PLA's suppression of the 1989 Tiananmen Square protests and massacre, ideological correctness was temporarily revived as the dominant theme in Chinese military affairs.
At certain times in the geological past, reef-building organisms similar to corals were very abundant. Like modern corals, these ancient organisms built reefs, some of which ended as great structures in sedimentary rocks. Fossils of fellow reef-dwellers algae, sponges, and the remains of many echinoids, brachiopods, bivalves, gastropods, and trilobites appear along with coral fossils. This makes some corals useful index fossils. Coral fossils are not restricted to reef remnants, and many solitary fossils are found elsewhere, such as Cyclocyathus, which occurs in England's Gault clay formation.
Sources: en.wikipedia.org
== Mechanisms == There is no single theory covering adhesion, and particular mechanisms are specific to particular material scenarios. Five mechanisms of adhesion have been proposed to explain why one material sticks to another:
The earliest reference to tomatoes being grown in British North America is from 1710, when herbalist William Salmon saw them in what is today South Carolina, perhaps introduced from the Caribbean. By the mid-18th century, they were cultivated on some Carolina plantations, and probably in other parts of the Southeast. Thomas Jefferson, who ate tomatoes in Paris, sent some seeds back to America. After 1860, it was often claimed that Americans believed that tomatoes were poisonous into the 1820s, but the belief was never widespread. When Alexander W. Livingston (1821–1898) began developing the tomato as a commercial crop, he had aimed to grow tomatoes smooth in contour, uniform in size, and sweet in flavor. He eventually developed over seventeen varieties. The U.S. Department of Agriculture's 1937 yearbook declared that "half of the major varieties were a result of the abilities of the Livingstons to evaluate and perpetuate superior material in the tomato". Livingston's first breed of tomato, the Paragon, was introduced in 1870. In 1875, he introduced the Acme, said to be in the parentage of most cultivars for the next twenty-five years. Other early breeders included Henry Tilden in Iowa and a Dr. Hand in Baltimore. Because of the tomato's need for heat and a long growing season, several states in the Sun Belt became major producers, particularly Florida and California. In California, tomatoes are grown under irrigation for both the fresh market and for canning and processing. The University of California, Davis's C.M.
Muscle cells work by detecting a flow of electrical impulses from the brain which signals them to contract through the release of calcium by the sarcoplasmic reticulum. Fatigue (reduced ability to generate force) may occur due to the nerve, or within the muscle cells themselves.
This was an increase from the 228,834 reports submitted in the previous year). Most of these reports are submitted by banks and similar financial institutions (there were 186,897 reports from the banking sector in the year ended 30 September 2010). Although 5,108 different organisations submitted suspicious activity reports to the authorities in the year ended 30 September 2010, just four organisations submitted approximately half of all reports, and the top 20 reporting organisations accounted for three-quarters of all reports. The offence of failing to report a suspicion of money laundering by another person carries a maximum penalty of five years' imprisonment. The Criminal Finances Act 2017 introduced unexplained wealth orders, another tool to combat money laundering, whereby the owner of an asset greater than £50,000 may be required to show how the purchase was financed. On 1 May 2018, the UK House of Commons, without opposition, passed the Sanctions and Anti–Money Laundering Bill, which will set out the UK government's intended approach to exceptions and licenses when the nation becomes responsible for implementing its own sanctions and will also require notorious overseas British territory tax havens such as the Cayman Islands and the British Virgin Islands to establish public registers of the beneficial ownership of firms in their jurisdictions by the end of 2020. The legislation was passed by the House of Lords on 21 May and received Royal Asset on 23 May.
During 1986, Syed Zaki Salahuddin, Dharam Ablashi, and Robert Gallo cultivated peripheral blood mononuclear cells from patients with AIDS and lymphoproliferative illnesses. Short-lived, large, refractile cells that frequently contained intranuclear and/or intracytoplasmic inclusion bodies were documented. Electron microscopy revealed a novel virus that they named human B-lymphotropic virus (HBLV). Shortly after its discovery, Ablashi et al. described five cell lines that can be infected by the newly discovered HBLV. They published that HSB-2, a particular T-cell line, is highly susceptible to infection. Ablashi's pioneering research concluded by suggesting that the virus name be changed from HBLV to HHV-6, in accord with the published provisional classification of herpes viruses. Years later, HHV-6 was divided into subtypes. Early research (1992) described two very similar, yet unique variants: HHV-6A and HHV-6B. The distinction was warranted due to unique restriction endonuclease cleavages, monoclonal antibody reactions, and growth patterns. HHV-6A includes several adult-derived strains and its disease spectrum is not well defined, although it is thought by some to be more neurovirulent. HHV-6B is commonly detected in children with roseola infantum, as it is the etiologic agent for this condition. Within these two viruses is a sequence homology of 95%. In 2012, HHV-6A and HHV-6B were officially recognized as distinct species.
Sources: en.wikipedia.org
Yes, the terms are generally interchangeable. Lyophilization is more common in pharmaceutical and laboratory contexts, while freeze-drying appears widely in food science and general writing. Both describe removal of solvent by sublimation under vacuum after freezing.
Reduced pressure keeps the process below the triple point of water, so ice can sublimate directly to vapor. It also lowers the temperature needed for drying, which helps preserve heat-sensitive materials. Without vacuum, melting or boiling could occur instead of controlled sublimation.
The rate depends on heat transfer to the product and mass transfer of vapor through the dried layer. A cold condenser, adequate vacuum, and suitable shelf temperature all influence speed. Formulation properties such as solid content and collapse temperature also set practical limits.
Residual moisture can influence chemical degradation, cake collapse, and long-term stability. Low moisture levels usually improve stability, but each product has an optimal range.