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At least 199 records · Page 11Linked to original sources
PubMed2006

Response surface designs for experiments in bioprocessing.

Many processes in the biological industries are studied using response surface methodology. The use of biological materials, however, means that run-to-run variation is typically much greater than that in many experiments in mechanical or chemical engineering and so the designs used require greater replication. The data analysis which is performed may involve some variable selection, as well as fitting polynomial response surface models. This implies that designs should allow the parameters of the model to be estimated nearly orthogonally. A class of three-level response surface designs is introduced which allows all except the quadratic parameters to be estimated orthogonally, as well as having a number of other useful properties. These subset designs are obtained by using two-level factorial designs in subsets of the factors, with the other factors being held at their middle level. This allows their properties to be easily explored. Replacing some of the two-level designs with fractional replicates broadens the class of useful designs, especially with five or more factors, and sometimes incomplete subsets can be used. It is very simple to include a few two- and four-level factors in these designs by excluding subsets with these factors at the middle level. Subset designs can be easily modified to include factors with five or more levels by allowing a different pair of levels to be used in different subsets.

Biocompatible Materials↗
PubMed1992

Noncarious cervical lesions: the decision to ignore or restore.

A variety of unusual noncarious cervical lesions (NCL) are depicted that appear to negate W.D. Miller's toothbrush/dentifrice abrasion theory and demonstrate that other factors may be involved in their etiology. Confusion exists in the designation of NCL ever since G.V. Black stated in 1908 that toothbrush/dentifrice abrasion is an erosive effect. Since abrasion and erosion are two distinct activities, it is suggested that dentistry adopt the same terminology as chemical engineering in order to foster improved communication between the sciences. The term "abfraction" has been used to supplant erosion because it seems more appropriate when describing the loss of tooth substance attributable to effects of occlusal loading forces as well as the physiochemical breaking that occurs during stress corrosion. Numerous reasons, based on accepted engineering principles, indicate that NCL should be restored. It is incumbent on dentists to become cognizant of these reasons, since this would help them inform patients of the benefits to be gained by restoring such deficient areas.

Composite Resins↗
PubMed2004

Cofilin promotes actin polymerization and defines the direction of cell motility.

A general caging method for proteins that are regulated by phosphorylation was used to study the in vivo biochemical action of cofilin and the subsequent cellular response. By acute and local activation of a chemically engineered, light-sensitive phosphocofilin mimic, we demonstrate that cofilin polymerizes actin, generates protrusions, and determines the direction of cell migration. We propose a role for cofilin that is distinct from its role as an actin-depolymerizing factor.

Actin Depolymerizing Factors↗
PubMed1968

Occupancy principle for radioactive tracers in steady-state biological systems.

Bergner's theoretical analysis of tracer dynamics has important ap plications in biology, not only for the measurement of exchangeable mass (as he demonstrated) but also for elicitation of otherwise inaccessible information on total masses of particular elements in body organs or systems-as well as in Chemical engineering and geophysics.

Biological Transport↗
PubMed2000

Amersham Pharmacia Biotech & Science Prize. Transposition and evolution of antigen-specific immunity.

Alka Agrawal grew up in Farmington Hills, near Detroit, Michigan, and earned her bachelor's degree in chemical engineering from the University of Michigan. Dr. Agrawal entered the pharmacology graduate school program at Yale University and began working in the laboratory of David Schatz, investigating the role of DNA repair proteins in V(D)J recombination. The development of an in vitro V(D)J cleavage system in the laboratory changed her focus and she began studying the cleavage mechanism as part of her doctoral research. Exposure to science policy at the National Academy of Sciences, and to science journalism through the AAAS Mass Media Science and Engineering Fellows Program, prompted Dr. Agrawal to pursue a career in science writing.

Allergens↗
PubMed2003

Antibody-mediated targeting of an adenovirus vector modified to contain a synthetic immunoglobulin g-binding domain in the capsid.

Adenovirus vectors have been targeted to different cell types by genetic modification of the capsid or by using recombinant or chemically engineered adaptor molecules. However, both genetic capsid modifications and bridging adaptors have to be specifically tailored for each particular targeting situation. Here, we present an efficient and versatile strategy allowing the direct use of monoclonal antibodies against cell surface antigens for targeting of adenovirus vectors. A synthetic 33-amino-acid immunoglobulin G (IgG)-binding domain (Z33) derived from staphylococcal protein A was inserted into the adenovirus fiber protein. The fiber retained the ability to assemble into trimers, bound IgG with high affinity (Kd = 2.4 nM), and was incorporated into vector particles. The transduction efficiency of the Z33-modified adenovirus vector in epidermal growth factor receptor (EGFR)-expressing cells was strongly and dose-dependently enhanced by combination with an EGFR-specific monoclonal antibody. The antibody-mediated increase in cellular transduction was abolished in the presence of competing protein A. In targeting experiments with differentiated primary human muscle cells, up to a 77-fold increase in reporter gene transfer was achieved by preincubation of the vector with monoclonal antibodies directed against neuronal cell adhesion molecule or integrin alpha(7), respectively. The IgG-binding adenovirus vector holds promise for directed gene transfer to a wide variety of cell types by simply changing the target-specific antibody.

Adenoviridae↗
PubMed1997

Simulated airborne spread of Aujeszky's disease and foot-and-mouth disease.

The atmospheric dispersion of virus was simulated using a computer model which had been developed for predicting the dispersion of toxic gases from chemical engineering plants. The results were compared with data from four outbreaks in which virus was believed to have been transported by air: two outbreaks of foot-and-mouth disease in the United Kingdom in 1967 and outbreaks of Aujeszky's disease in Yorkshire in 1981 to 1982 and Indiana in 1988. There was relatively good agreement with most of these data. The paper shows that the model could be useful in an emergency because the risk of virus spread could be predicted in real time.

Air Microbiology↗
PubMed1992

Tumor antigens.

This review solidifies a new concept that common and rare types of human cancers harbor a variety of tumor-specific mutant proteins that may be recognized as tumor-specific antigens. These mutant proteins are encoded by oncogenes or suppressor genes that have undergone structural mutations resulting from point mutations, chromosomal translocations, internal deletions and viral insertional mutagenesis; several of these changes result in fusion proteins. While there is no evidence that immunosurveillance against these mutant proteins can prevent the development of primary cancers without prior immunization of the host, such tumor-specific molecules might be important for diagnosis and as targets for specific immunotherapy once the cancer has developed or even as targets for preventive cancer vaccines. Evidence further supports the notion that cytolytic or helper T cells are exquisitely selective in recognizing intracellular mutant proteins, and tumor-specific T cell clones presently available may become useful for identifying previously unrecognized tumor-specific mutations. Many tumor-specific mutant proteins clearly play a causative role in the establishment of malignant behavior, whereas other carcinogen-induced changes have at least immunological relevance. In any case strong evidence in mouse and man indicates that a single malignant cell can express multiple independent antigenic target sites. Such multiplicity may allow a multi-pronged immune attack that substantially decreases the chance of tumor escape. Future work must explore whether immune responses to tumor-specific mutant proteins can lead to immunological tumor rejection and explore the possibility of chemically engineering tumor mutant peptides to be highly immunogenic, even in hosts that have previously failed to respond to the tumor.

Antigens, Neoplasm↗
PubMed2002

Nanoporous materials.

The current review article attempts to cover the field of nanoporous materials, thereby materials with voids of the order of 1 nm to 100 nm or even larger. Concepts, that have an effect on a more general basis, are introduced and the common features among the different classes of nanoporous materials are demonstrated enabling understanding their formation and stability. It is seen that the most successful method to produce nanoporous materials made by design is to imprint a template structure into a functional inorganic or even organic network. Further, the manuscript gives an introduction to state of the art overview for microporous, mesoporous and macroporous materials, while the preference lies on ordered pore structures. Further, it is demonstrated how important but also demanding the use of modern analytical techniques are. This makes the field of nanoporous materials truly interdisciplinary with aspects of inorganic chemistry, polymer science, colloid chemistry, physical chemistry, analytical chemistry and chemical engineering.

Carbon↗
PubMedDate not supplied

Supported membrane nanodevices.

Supported membrane nanodevices are based on natural or artificial ion channels embedded in a lipid membrane deposited on a chip wafer. Membrane conductance is modulated by biorecognitive events, with the use of intrinsic binding sites of the ion channel or via artificial sites fused to the channel protein. Artificial ion gates are constructed by coupling a specific ligand for the analyte near the channel entrance or a site important to triggering channel conformation. The binding event leads to the closure of the ion channel or induces a conformational change of the channel, reducing the ion flux. The signal transduced from the device is the decrease in the ion flux-induced electron current at a silver-silver chloride electrode at ultimate single-molecule sensitivity. Among the natural ion channels, gramicidin A, a transport antibiotic, was found to be most suitable, and thus was used by AMBRI, Australia, to set up prototypes of membrane biochips, using self-association of the dimer. Covalent dimerization-based devices, developed by the Vienna group, make use of the down-regulation of the permanently open membrane-spanning bisgramicidine ion channel. The reactive group at the C-terminus, a hydroxy group, allows precise coupling of the analyte-binding moiety in gramicidin as well as bisgramicidin. The device is set up with bilayer membranes deposited on apertures of a hydrophobic frame structure produced via microlithography, facing an aqueous or hydro-gel micro-environment on both sides, constructing black lipid membranes or patch-clamp devices "on chip." The setup of the device needs gel membrane supports that allow membrane formation and contribute to the stability of the bilayer by exposure of functional groups that promote electrostatic interaction and formation of hydrogen bridges and enable the introduction of covalent spacers and anchors. Photo-cross-linked polyvinylpyrrolidone and polyacrylamide, electropolymerized polydiaminobenzene and coated agarose, as well as various chemical modifications of these polymers, were employed as membrane supports. With optimized assemblies, the membrane support did allow the formation of stable bilayer membranes, proved by "gigaseal" (electrical sealing with giga-ohm resistance) to be free of any point defects in the lipid assembly. Supports with and without hydrophilic and hydrophobic anchors were studied with reference to promoting the formation of a self-assembled membrane, to their electric resistance, and to the capability to insert functional ionophores. All components, including novel chemically engineered ion channels, novel amphiphilic lipids, a microlithographically designed chip, isolating polymer frames, and a hydrogel membrane support, are combined in the new bionanodevice. Sensitivity and specificity were proved, for example, with the use of an antibody-antigen couple down-regulating the ion flux through the membrane channel. Single ion channels incorporated in the supported lipid bilayer gave stable signals at an operational stability of several hours, which is already sufficient to test and screen for membrane receptors but still insufficient to use this device as a sensor for off-site application. Further optimization to increase operational and storage stability is done by a number of groups to allow a broad application of these devices.

Biomimetic Materials↗
PubMedDate not supplied

Nanoparticles for drug delivery: review of the formulation and process difficulties illustrated by the emulsion-diffusion process.

The elaboration of nanoparticles aqueous suspensions aimed at the drug delivery and related process development appear as difficult tasks, due to specificities related to the nanometric size. Such small sizes are required for specific applications in pharmacy. The switch of micrometric to nanometric field represents an actual challenge and cannot be considered as a simple scaling-down of chemical engineers. Ideas and concepts developed first in nanosciences have been adapted to the pharmaceutical application in drug delivery. In spite of drastic constraints due to pharmaceutical application, some parameters allow the control. A brief and not exhaustive review of the state-of-the-art on polymer particles used in the drug delivery field is presented. Attention was more particularly paid on preparation processes and their constraints by describing advantages and drawbacks of each process. The adaptation to the pharmaceutical field, the difficulties and pitfalls which are shared, with most research works in nanoscience, are illustrated thanks to our own results on nanocapsules obtained by "emulsion-diffusion" process presented as a case-study. Thanks to these results, we illustrate the peculiar features and difficulties encountered regarding nanocapsules preparation and characterization. Indeed, such a process allows to prepare nanocapsules of few hundreds nanometers diameter having an oil core surrounded by a polymeric membrane. The characterization of such soft particles colloidal suspensions is often difficult and involves heavy investigation techniques in order to highlight physical mechanisms leading to the nanocapsule properties. This is a key step regarding the final properties as a drug delivery system.

Capsules↗
PubMed2002

New strategies for the prevention of radiation injury: possible implications for countering radiation hazards of long-term space travel.

New strategies for the prevention of radiation injuries are currently being explored with the ultimate aim of developing globally radioprotective, nontoxic pharmacologics. The prophylactic treatments under review encompass such diverse pharmacologic classes as novel immunomodulators, nutritional antioxidants, and cytokines. An immunomodulator that shows promise is 5-androstenediol (AED), a well-tolerated, long-acting androstene steroid with broad-spectrum radioprotective attributes that include not only protection against acute tissue injury, but also reduced susceptibility to infectious agents, as well as reduced rates of neoplastic transformation. Other potentially useful radioprotectants currently under study include the nutraceutical vitamin E and analogs, a chemically-engineered cytokine, interleukin-1beta, and a sustained-release formulation of an aminothiol, amifostine. Results suggest that a new paradigm is evolving for the prophylaxes of radiation injuries, based on use of newly identified, nontoxic, broad-spectrum prophylactic agents whose protective action may be leveraged by subsequent postexposure use of cytokines with organ-specific reparative functions.

Animals↗
PubMed2001

Measurement of bubble size distribution in protein foam fractionation column using capillary probe with photoelectric sensors.

Bubble size is a key variable for predicting the ability to separate and concentrate proteins in a foam fractionation process. It is used to characterize not only the bubble-specific interfacial area but also coalescence of bubbles in the foam phase. This article describes the development of a photoelectric method for measuring the bubble size distribution in both bubble and foam columns for concentrating proteins. The method uses a vacuum to withdraw a stream of gas-liquid dispersion from the bubble or foam column through a capillary tube with a funnel-shaped inlet. The resulting sample bubble cylinders are detected, and their lengths are calculated by using two pairs of infrared photoelectric sensors that are connected with a high-speed data acquisition system controlled by a microcomputer. The bubble size distributions in the bubble column 12 and 1 cm below the interface and in the foam phase 1 cm above the interface are obtained in a continuous foam fractionation process for concentrating ovalbumin. The effects of certain operating conditions such as the feed protein concentration, superficial gas velocity, liquid flow rate, and solution pH are investigated. The results may prove to be helpful in understanding the mechanisms controlling the foam fractionation of proteins.

Chemical Engineering↗
PubMed2005

The Second International Workshop on Bioprinting, Biopatterning and Bioassembly.

The Second International Workshop on Bioprinting, Biopatterning and Bioassembly was held at the Medical University of South Carolina (MUSC), located in the beautiful, historic city of Charleston. The workshop attracted > 50 participants from 10 different countries, including mechanical and chemical engineers, molecular, cell and developmental biologists, biophysicists, mathematicians, clinicians, humanists and artists. Bioprinting can be defined as computer-aided, automatic, layer-by-layer deposition, transfer and patterning of biologically relevant materials. The workshop goal was to gather the world's experts and leaders, present the latest results, assess future trends, explore new applications, and promote international collaborations and academic-industrial partnerships. The workshop demonstrated the multidisciplinary and global character of ongoing efforts in the development of bioprinting technology, galvanised an evolving community of bioprintists, and demonstrated feasibility as well as strong potential for a broad spectrum of applications of bioprinting technology. The Third International Workshop on Bioprinting, Biopatterning and Bioassembly is planned for Japan in 2006.

Bioethics↗
PubMed2007

Polymeric nanogel formulations of nucleoside analogs.

Nanogels are colloidal microgel carriers that have been recently introduced as a prospective drug delivery system for nucleotide therapeutics. The crosslinked protonated polymer network of nanogels binds oppositely charged drug molecules, encapsulating them into submicron particles with a core-shell structure. The nanogel network also provides a suitable template for chemical engineering, surface modification and vectorisation. This review reveals recent attempts to develop novel drug formulations of nanogels with antiviral and antiproliferative nucleoside analogs in the active form of 5'-triphosphates, discusses structural approaches to the optimisation of nanogel properties, and discusses the development of targeted nanogel drug formulations for systemic administration. Notably, nanogels can improve the CNS penetration of nucleoside analogs that are otherwise restricted from passing across the blood-brain barrier. The latest findings reviewed here demonstrate an efficient intracellular release of nucleoside analogs, encouraging further applications of nanogel carriers for targeted drug delivery.

Animals↗