If you have been reading about secondary drying and want a single page that covers the useful parts, this is it: definitions, context, how it is studied, and the questions that come up repeatedly.
Last reviewed on 2025-09-12. Where a claim depends on a specific study, the study is described rather than over-claimed.
Lyophilized products are typically hygroscopic and require protection from moisture during storage. Manufacturers seal them in glass vials, often under vacuum or an inert gas such as nitrogen. The container closure system, including the stopper and crimp seal, must prevent water vapor ingress. Storage temperature varies from controlled room temperature to refrigerated or frozen conditions, depending on the formulation. Humidity-controlled environments are essential because even brief exposure to ambient air can degrade the product.
Stability of a lyophilized product depends on its glass transition temperature, the temperature at which the amorphous cake transitions from a glassy to a rubbery state. Storage below this temperature minimizes molecular mobility and slows chemical degradation. If the storage temperature exceeds the glass transition temperature, the cake may collapse, shrink, or become sticky. Accelerated stability studies at elevated temperatures and humidity help predict shelf life, but they do not always reflect real-time behavior. Residual moisture content also plays a critical role in long-term stability.
The process usually has three stages: freezing, primary drying, and secondary drying. Freezing sets the ice crystal structure and can determine pore size in the final cake. Primary drying removes free ice by sublimation at low pressure and low shelf temperature. Secondary drying removes bound water by raising the shelf temperature, although some water may remain as part of the solid. Cycle parameters depend on formulation, fill volume, vial type, and equipment performance.
The physical chemistry of freezing influences whether a formulation forms an amorphous glass or a crystalline solid. Amorphous systems can collapse if product temperature rises above the glass transition temperature of the freeze concentrate. Crystalline systems may show eutectic melting, where ice and solute melt together at a fixed temperature. Formulators add bulking agents, lyoprotectants, and buffers to preserve structure and biological activity. The optimum cycle keeps product temperature below critical thresholds during primary drying while allowing efficient sublimation.
Lyophilization is a dehydration process that removes water from a frozen material by sublimation under low pressure. The material is first frozen so that water becomes ice; then the surrounding pressure is lowered below the vapor pressure of ice. Heat is applied gently so ice changes directly to vapor without passing through a bulk liquid phase. The vapor is collected on a cold condenser, leaving a dry porous matrix. This process differs from simple evaporation because the material remains frozen during the main drying stage.
| Property | Value | Notes |
|---|---|---|
| Appearance | White to off-white porous cake | Color depends on formulation. |
| Typical storage temperature | 2–8 °C | Refrigerated for many biologics. |
| Residual moisture | <1% to 3% | Low moisture improves stability. |
| Container | Sealed glass vial | Often with rubber stopper and aluminum crimp. |
| Reconstitution time | Seconds to minutes | Varies with cake density and diluent. |
After lyophilization, a product's quality depends on residual moisture, cake appearance, and reconstitution time. Residual moisture is often measured by Karl Fischer titration or thermogravimetric analysis. A low moisture content can slow chemical degradation, but overly dry cakes may be brittle or slow to dissolve. Stability studies track these attributes over months under defined temperature and humidity conditions. Batch records link these measurements to specific process runs and help identify trends before a product fails specification.
Storage conditions for dried products usually aim to exclude moisture and oxygen. Vials are sealed under vacuum or with an inert gas, and stoppers must maintain a barrier during transport. Temperature recommendations vary; some materials remain stable at room temperature, while others need refrigeration or frozen storage. Humidity control is critical because dried cakes can absorb water rapidly once a container is opened. Desiccant packs and moisture-barrier bags add further protection during shipping.
Quality control also examines cake structure, color, and reconstitution behavior. A collapsed or shrunken cake can indicate a thermal excursion during drying. Analytical methods such as X-ray diffraction, differential scanning calorimetry, and near-infrared spectroscopy can detect crystallinity or moisture distribution. Regulatory expectations focus on validated assays and lot-to-lot consistency. Questions remain about how well accelerated stability tests predict long-term behavior for every formulation. Visual inspection remains common but is subjective without trained reviewers and reference images.
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.
A freeze-dryer consists of a vacuum chamber, temperature-controlled shelves, a condenser, and a vacuum pump. Vials, ampoules, or bulk trays hold the product during the cycle. The condenser traps water vapor as ice at a temperature lower than the product. Cycle development balances shelf temperature, chamber pressure, and time. Scale-up can be difficult because heat and mass transfer change with equipment size, so process analytical tools and conservative validation are often used.
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.
After drying, a lyophilized product is usually sealed under vacuum or an inert gas to limit moisture uptake. Residual water content is measured because small changes can alter chemical stability and cake appearance. Storage temperature depends on the material; many biological products are kept at 2–8 °C, while some require −20 °C or colder. Exposure to ambient humidity during handling can cause the porous solid to absorb water and collapse. Container closures and stoppers are therefore selected for low moisture transmission and compatibility.
Quality control for lyophilized materials includes visual inspection of the cake, measurement of residual moisture, and tests for reconstitution time. An acceptable cake is typically uniform and may be slightly porous; shrinkage, meltback, or cracks can indicate process deviations. Analytical methods such as Karl Fischer titration, thermogravimetric analysis, and near-infrared spectroscopy quantify water content. Reconstitution time is recorded because a very slow or incomplete dissolution can signal collapse or aggregation. Stability studies compare samples stored under defined temperature and humidity conditions over months or years.
Regulatory expectations for lyophilized products focus on consistent manufacture and documented stability. Batches are often monitored for moisture, appearance, potency, and sterility where applicable. Process parameters such as shelf temperature, chamber pressure, and drying time are recorded and controlled within validated ranges. Open questions remain about how best to predict long-term stability from short accelerated studies, especially for complex biologics. Variations in freezing rate and ice crystal size can produce differences that are not always visible but may affect performance.
Formulation composition influences whether freeze-drying produces an intact cake or a collapsed mass. Excipients such as sugars and polymers can raise the collapse temperature and provide bulk during drying. The critical temperature for primary drying is often the collapse temperature or the glass transition temperature of the maximally concentrated phase. If the product temperature exceeds this threshold, the frozen matrix may soften and lose structure. Established practice therefore links shelf temperature and chamber pressure to the formulation's thermal properties.
The physics of freeze-drying couples heat transfer, mass transfer, and phase change. Heat supplied through the shelf must reach the sublimation front without melting the ice or degrading the product. Water vapor then travels through the already dried layer and leaves the chamber, where low pressure and cold traps keep it from returning. The dried layer acts as a resistance to vapor flow, so drying rate changes as the front recedes. Open questions remain about how pore structure and formulation heterogeneity affect drying uniformity at larger scales.
Lyophilization removes water from a frozen material by sublimation under reduced pressure. The process begins with freezing, which converts liquid water into ice and concentrates dissolved solids. Primary drying then lowers chamber pressure so ice changes directly into vapor without passing through a liquid phase. Secondary drying raises the shelf temperature to remove bound water that remains after ice sublimation. The result is a dry, porous structure that can be reconstituted later.
resting cellular-membrane potential and the propagation of action potentials in neuronal, muscular, and cardiac tissue. Due to the electrostatic and chemical properties, K+ ions are larger than Na+ ions, and ion channels and pumps in cell membranes can differentiate between the two ions, actively pumping or passively passing one of the two ions while blocking the other. hormone secretion and action vascular tone systemic blood pressure control gastrointestinal motility acid–base homeostasis glucose and insulin metabolism mineralocorticoid action renal concentrating ability fluid and electrolyte balance local cortical monoaminergic norepinephrine, serotonin, and dopamine levels, and through them, sleep/wake balance, and spontaneous activity.
== Research == With his team in the Ciulli laboratory, Ciulli's works aim to develop small molecules inducing targeted protein degradation and modulating protein-protein interactions. One example of this type of work is the discovery of proteolysis-targeting chimera or PROTAC and its therapeutic potential. Recruitment of an E3 ligase to the target protein by the PROTAC is a critical step in the mechanism of action, because it triggers the target protein to be ubiquitinated and then degraded by the proteasome. Ciulli and his colleagues were the first to produce an X-ray crystal structure of a class of PROTAC simultaneously bound to the target protein and the E3 ubiquitin ligase. Much of Ciulli's research also contributed to studies on the Von Hippel-Lindau protein E3 ligase, especially in targeting the E3 ligase with small molecules. In general, Ciulli's scientific contributions focus on targeted protein degradation (TPD) as a therapeutic modality in cancer and other diseases. His works on TPD led to the founding of Amphista Therapeutics. Amongst the other scientific accomplishments and discoveries of his laboratory, is the development of a chemical-genetic "bump and hole" approach in which Ciulli and colleagues designed an engineered mutant variant of BET bromodomains able to accommodate selectively its binding ligand, enabling the individual roles of BET proteins to be elucidated.
An accompanying study showed that the artificial WW domains were functionally similar to natural WW domains in ligand binding affinity and specificity. In de novo protein structure prediction, it has been shown that, when combined with a simple residue-residue distance metric, SCA-based scoring can fairly accurately distinguish native from non-native protein folds.
=== As NCCIH (2014–present) === In 2014, while Josephine Briggs was the director, the NCCAM was renamed the National Center for Complementary and Integrative Health (NCCIH). Briggs retired in October 2017. On August 29, 2018, the NCCIH announced Helene Langevin as the new director. She was previously the director of the Osher Center and professor-in-residence of medicine at Harvard Medical School. Her medical interests involve connective tissue. Langevin "believes that the stretching of connective tissue is how several CAM modalities 'work,' such as chiropractic, massage, and ... acupuncture". Langevin has been studying acupuncture since the 1990s. At the time of her appointment, Gorski expressed concern that the balance of power at NCCIH would "shift back towards pseudoscience" with a massive budget to fund the shift. Under Langevin, NCCIH adopted a "whole person health" research framework, investigating how different domains of health—physiology, psychology, and environment—interconnect across the continuum between health and illness. She co-led several trans-NIH initiatives, including the NIH HEAL Initiative on opioid addiction and pain management, and the funding of a Whole Person Reference Physiome and Coordination Center co-funded by 20 NIH Institutes, Centers, and Offices. The NCCIH budget grew to approximately $170 million annually under her leadership. Langevin retired from NCCIH on November 30, 2025, returning to the University of Vermont as director of research at the Osher Center for Integrative Health.
Sources: en.wikipedia.org
Two neptunium oxyselenide compounds are known, NpOSe and Np2O2Se, are formed with similar methods by replacing the neptunium hydride with neptunium dioxide. The known neptunium telluride compounds NpTe, NpTe3, Np3Te4, Np2Te3, and Np2O2Te are formed by similar procedures to the selenides and Np2O2Te is isostructural to the equivalent uranium and plutonium compounds. No neptunium−polonium compounds have been reported.
PPAR agonists are drugs which act upon the peroxisome proliferator-activated receptor. They are used for the treatment of symptoms of the metabolic syndrome, mainly for lowering triglycerides and blood sugar.
==== 2009 ==== A top-level Georgian official suspected in February 2009 that there was a connection between one German expert working for Tagliavini and Russian Gazprom-affiliated companies. In October 2009, an anonymous source told the news agency that Gazprom paid German expert. The news agency alleged that German Foreign Minister Frank-Walter Steinmeier was promised a job at Gazprom for his influence on the report. Germany was the largest trade partner of Russia as of August 2008. In September 2009, before the report was published, former Prime Minister of Estonia Mart Laar said in an interview that the commission forgot "that during the war, no Georgian soldier, no plane, no other military equipment left the legal, internationally recognized territory of Georgia. It was Georgian territory, and no Georgian soldier [left] the borders of Georgia." After the publication of the report, Laar stated that the report stated that Russian accusation of genocide was false. However, the commission did not declare Russia as aggressor, because Europe would have to hold tribunal on the Russian war crimes. Before the report was published, Russian Foreign Ministry spokesman Igor Lyakin-Frolov said Russian authorities had been "absolutely fair and honest" during investigation. He did not doubt neutrality of the report and hoped that the blame would be pinned on Ukraine for arming Georgia; however, he also stated it would be "unfair" if both Russia and Georgia were found guilty. After the report was published, Russian and South Ossetian officials mostly approved of the report.
Sources: en.wikipedia.org
Daniel S. Greenspan is an American biomedical scientist, academic and researcher. He is Kellett professor of Cell and Regenerative Biology at the University of Wisconsin-Madison School of Medicine and Public Health. He has authored over 120 publications. His research has mainly focused on genes encoding proteins of the extracellular space and possible links between defects in such genes and human development and disease.
The leaves are unique among seed plants, being fan-shaped with veins radiating out into the leaf blade, sometimes bifurcating (splitting), but never anastomosing to form a network. Two veins enter the leaf blade at the base and fork repeatedly in two; this is known as dichotomous venation. The leaves are usually 5–10 cm (2–4 in), but sometimes up to 15 cm (6 in) long. The old common name, maidenhair tree, derives from the leaves resembling pinnae of the maidenhair fern, Adiantum capillus-veneris. Ginkgos are prized for their autumn foliage, which is a deep saffron yellow. The species is heterophyllous (two types of leaves); those on the long shoots are thicker, have higher rates of photosynthesis, higher vein density and leaf hydraulic conductance, while those on the short shoots are better at handling drought. Leaves of long shoots are also usually notched or lobed, but only from the outer surface, between the veins. They are borne both on the more rapidly growing branch tips, where they are alternate and spaced out, and also on the short, stubby spur shoots, where they are clustered at the tips. Leaves are green both on the top and bottom and have stomata on both sides. During autumn, the leaves turn a bright yellow and then fall, sometimes within a short space of time (one to fifteen days). Leaves of the cultivar 'Tubifolia' have funnel-shaped leaves.
=== Genetics === Malignant hyperthermia's inheritance is autosomal dominant with variable penetrance. The defect is typically located on the long arm of chromosome 19 (19q13.2) involving the ryanodine receptor. More than 25 different mutations in this gene are linked with malignant hyperthermia. These mutations tend to cluster in one of three domains within the protein, designated MH1-3. MH1 and MH2 are located in the N-terminus of the protein, which interacts with L-type calcium channels and Ca2+. MH3 is located in the transmembrane forming C-terminus. This region is important for allowing Ca2+ passage through the protein following opening. Chromosome 7q and chromosome 17 have also been implicated. It has also been postulated that MH and central core disease may be allelic and thus can be co-inherited.
=== Radiology === Radiologically, the main feature required for a confident diagnosis of UIP is honeycomb change in the periphery and the lower portions (bases) of the lungs. On high-resolution computed tomography (HRCT), the following categories, depending on imaging findings, have been recommended by a collaborative effort by the American Thoracic Society, European Respiratory Society, Japanese Respiratory Society, and the Latin American Thoracic Society:
Sources: en.wikipedia.org
Lyophilized products should be stored in airtight containers, protected from moisture and light, at the temperature specified by the manufacturer. Many require refrigeration at 2–8 °C, while some need frozen storage. Always check the product label for specific conditions.
Moisture can cause the porous cake to collapse, increase molecular mobility, and accelerate chemical degradation. It may also promote microbial growth if the product lacks preservatives. Proper sealing and handling are essential to maintain stability.
Some formulations contain labile biological molecules that degrade even in the dry state at higher temperatures. Others have a low glass transition temperature, meaning the cake can soften or collapse at room temperature. Cold storage reduces molecular motion and slows degradation.
The main change is sublimation, in which ice becomes water vapor without melting into liquid water. This occurs when the chamber pressure is held below the vapor pressure of ice while mild heat is supplied. The result is a dry, porous solid that retains much of its original shape.