SEARCH · PubMed Health
Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Advances in biopharmaceutical technology have spawned new drug delivery devices and mechanisms. Noninvasive methods, including iontophoresis and transmucosal drug delivery, have improved treatment of certain patient population. Their use is discussed in the following paper.
The advent of matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) and electrospray ionization mass spectrometry (ESI-MS) in the last 5 years has greatly enhanced the area of protein mass spectrometry. This paper presents an overview of the applications of protein mass spectrometry in the area of analytical biotechnology, particularly as related to biopharmaceutical research and development. These applications include the determination of protein molecular mass, peptide mapping, peptide sequencing, ligand binding, determination of disulfide bonds, active site characterization of enzymes, protein self-association and protein folding/higher order structural characterization.
Residual moisture content has a significant impact on the solid-state stability of biopharmaceutical products. Protein degradation due to residual moisture is minimal at or below the monolayer level of hydration owing to low availability of water and limited dynamic activity of the protein. However, residual moisture content beyond a monolayer generally results in increased rates of decomposition due to the enhanced conformational flexibility of the protein and the ability of the less tightly bound water to mobilize reactants. In addition to moisture content, the temperature and the composition of the lyophilized plug are important variables dictating the stability of proteins in the amorphous solid state. Water can act as a plasticizer to reduce the glass transition temperature, Tg, of the amorphous polymer, thus an increase in temperature or plasticizer level can result in a phase transition from a dynamically constrained state to a dynamically relaxed state. The selection of excipients can have a large impact on water-protein interactions as small ions and/or crystallization of excipients can redistribute water available to the protein. Owing to the key role that water content plays in the conformational and/or chemical state of the protein, an accurate and precise moisture determination is essential in resolving stability issues. A wide variety of techniques for the determination of moisture content have been utilized, with special attention being placed on sample handling to minimize atmospheric moisture contamination.
The ImmunoDetection PG (protein G) cartridge which is based on perfusion chromatography has been evaluated for the quantitation of murine monoclonal antibody (IgG1) in biological fluids. The results indicate a low intra-day coefficient of variation (C.V.) < or = 5% and a sample analysis time of 5.5 min. A standard curve generated using injection of known amounts of monomeric antibody against the eluted peak area shows linearity (r2 = 0.99) over the 0.1-100 micrograms range. The minimum detectable concentration (MDC) at 280 nm is about 2 micrograms/ml which can be decreased to 200 ng/ml if the antibody elution is monitored at 214 nm. Under these conditions the C.V. is < or = 5%. Accuracy of the quantitation is independent of operator, solution composition, sample pH and the ionic strength, all of which are factors to consider in performing immunoassays. Antibody samples containing aggregated and fragmented Fc regions of the antibody will interfere with this method of quantitation. An optimized validated method for the quantitation of antibody is described. This mode of perfusion chromatography could be applied in the biopharmaceutical field due to its speed, efficiency and sensitivity.
Gene and oligonucleotide therapy are emerging as clinically viable therapeutic regimens for genetic, neoplastic, and infectious diseases. Approaches include insertion of human genes in viral vectors including recombinant retrovirus, adenovirus, adeno-associated virus, and herpes simplex virus-1, or recombinant bacterial plasmids. Viral vectors transfect cells directly; plasmid DNA is delivered with the help of cationic liposomes (lipofection), polylysine conjugates, gramicidin S, artificial viral envelopes or other such intracellular carriers. Major areas of interest include replacement of the cystic fibrosis transmembrane regulator gene and the alpha 1-antitrypsin gene; arrest of human immunodeficiency virus infection; and reversal of tumorigenicity and cancer immunization, among others. Oligonucleotide therapy is principally focusing on the same areas, although the approach is to halt DNA transcription or messenger RNA translation with code-blocking triple-helix-forming or "antisense" oligomers. Contributions from the pharmaceutical sciences are expected in pharmaceutical chemistry, drug delivery systems design, analytical chemistry, and biopharmaceutics.
Two noninvasive methods have been advocated for pharmacokinetic and bioavailability studies. The measurement of the salivary and urinary excretion of drugs and their metabolites may avoid sampling blood, particularly in introductory studies. The measurement of the salivary concentrations of drugs is of most value in studies on compounds which are little ionized at physiological pH values. Well studied examples where there is a good parallelism between salivary and plasma drug concentrations include the neutral drug, ethanol, the weakly acidic drugs, phenytoin and sulphapyridine, and the weakly basic drugs, carbamazepine and antipyrine. Data on the salivary secretion of more strongly acidic or basic drugs are often conflicting and further work is required to determine the usefulness of measuring the salivary secretion of such drugs in pharmacokinetic and biopharmaceutical studies. Studies on the rate of excretion or cumulative excretion of drugs and their metabolites in urine may provide good estimates of the terminal half lives of drugs. However, accurate determinations of the kinetic parameters of rapid processes are not obtainable from studies on urinary excretion. Reliable data can only be obtained if the timing of urine collections is precise and if there are no significant losses of urine.
The inability of conventional water-purification systems to meet the ultra-high purity needs of molecular biology and biopharmaceuticals reliably was attributed to their almost exclusive utilization of phase-transfer technologies. Water quality may unpredictably degrade when confronted by microorganism blooms or altered feed water characteristics. Photocatalytic point-of-use water-purification systems fed by deionized water were demonstrated to meet the most stringent water-purity needs of the molecular biologist. The reliability of the photocatalytic water-purification technology was attributed to its ability to destroy organic contaminants rather than just effect their phase transfer. Photocatalytically produced water was shown to be free of detectable microorganisms, DNA, endotoxins and RNAses. It is suitable for immunological studies involving tissue and other cell cultures because of its lack of detectable endotoxins. Because DNA was also undetectable, it is suitable for DNA and endotoxin zero-standards as well as pharmaceutical formulation. The photocatalytic water is a reliable substitute for diethyl pyrocarbonate-treated water used in RNA work, compatible with PCR and sufficiently free from other contaminants to be useful for most biochemical and enzymatic assays.
The bovine hsp70A heat-shock gene promoter was isolated and used to direct the heat-regulated synthesis of bovine herpesvirus glycoproteins gIII and gIV in transfected cultured bovine cells. Sequences encoding the viral glycoproteins incorporated mutations that deleted the transmembrane anchors. Both proteins were efficiently secreted from transfected cells in a temperature-dependent manner and the gIV so produced was found to be antigenically similar to the authentic molecule. Stable cell lines with regulated expression of these proteins were obtained and repeated thermal cycling of the cultures enabled high-yield production of these subunit vaccine antigens. The continuous production demonstrated by this system is highly relevant to the efficient and economic manufacture of vaccines and other protein biopharmaceuticals.
An assay using reversed-phase high-performance liquid chromatography with ultraviolet detection, at 278 nm, was developed to measure diclofenac in human plasma and urine at concentrations suitable for biopharmaceutical studies. Indomethacin was used as internal standard and separation was performed at 40 degrees C on a C18 Spherisorb column with acetonitrile-0.1 M sodium acetate (35:65, v/v) (pH 6.3) as mobile phase. The sample preparation is simple and rapid (extractionless), and the total run time is less than 5 min. The retention time is 2.8 min for diclofenac and 3.6 min for indomethacin. The detection limit is 0.2 microgram/ml using a 20-microliters loop.
Before the Clostridium tumour assay can be applied to the diagnosis of cancer, we sought to investigate--within the framework of a biopharmaceutical safety test--the organ persistence of test spores of Clostridium butyricum CNRZ 528. We found that non-pathogenic spores obtained in vitro, like pathogenic native spores, escape phagocytosis in various organs up until about 2 years, as tested by anaerobic cultures. The elimination of spores depended on the species of animal, the spore dose and the organs investigated. In rabbits, one week after injection, we recovered clostridial spores from blood and spleen cultures more rarely than from liver and lung. The half-life of blood clearance in patients was one day or, at half the spore dose, two days. That deep tissues of healthy animals are not normally sterile became evident in rabbits after sporadic isolation and characterization of non-administered saccharolytic and proteolytic clostridial species. During a 10-year observation period, the rate of obtainment of viable spores by in vitro cultures lessened; however, for administration of the spores in clinical phase I and phase II studies, the spore quality was acceptable.
Quantitative enzyme-linked immunosorbent assay (ELISA) is a widely used tool for analyzing biopharmaceutical and vaccine products. The superior sensitivity of the ELISA format is conferred by signal amplification through the enzymatic oxidation or hydrolysis of substrates to products with enhanced color or fluorescence. The extinction coefficient for a colored product or the quantum yield of a fluorescent product, coupled with the efficiency of the immobilized enzyme, is the determining factor for the sensitivity and precision of a given ELISA. The enhancement of precision and sensitivity using fluorogenic substrates was demonstrated in a direct-binding ELISA in a low-analyte concentration range compared with commonly used chromogenic substrates. The enhancement in precision was demonstrated quantitatively with lower coefficients of variation in measurements of signal intensities, approximately a five- to six-fold enhancement in signal-to-noise ratio at a given analyte concentration with fluorogenic substrates. Similarly, the amplitude of the enhancement in sensitivity, as reflected by relative limits of detection or quantitation, is approximately two- to five-fold when compared with commonly used chromogenic substrates. Additional advantages of a fluorescence-based ELISA format include the continuous monitoring of initial rates of enzymatic reactions, the measurement of fluorescence changes in the presence of particulate materials, the absence of a quench step, and a larger quantifiable analyte range.
Sedimentation velocity analytical ultracentrifugation (SV-AUC) has emerged in the biopharmaceutical industry as a technique to detect small quantities of protein aggregates. However, the limits of detection and quantitation of these aggregates are not yet well understood. Although diverse factors (molecule, instrument, technique, and software dependent) preclude an all-encompassing measurement of these limits for the complete system, it is possible to use simulated data to determine the quantitation limits of the data analysis software aspect. The current study examines the performance of the SEDFIT/c(s) data analysis tool with simulated antibody monomer/dimer and monomer/aggregate systems. Under completely ideal conditions (zero noise, known meniscus, and shape factor homogeneity), the software limit of quantitation was 0.01% for the monomer/aggregate system and 0.03% for the less well-resolved monomer/dimer system. Under more realistic conditions (0.005 OD root mean square [RMS] noise, shape factor variability, and long solution column), the software limits of quantitation were 0.2 and 0.6% (0.002 and 0.006 OD) for the monomer/aggregate and monomer/dimer systems, respectively. Interestingly, diminished quantitation accuracy at very low levels of oligomer was not accompanied by deterioration of fit quality (as measured by root mean square deviation [RMSD] and residuals bitmap images).
This review describes the use of nanoparticles based on solid lipids for the parenteral application of drugs. Firstly, different types of nanoparticles based on solid lipids such as "solid lipid nanoparticles" (SLN), "nanostructured lipid carriers" (NLC) and "lipid drug conjugate" (LDC) nanoparticles are introduced and structural differences are pointed out. Different production methods including the suitability for large scale production are described. Stability issues and drug incorporation mechanisms into the particles are discussed. In the second part, the biological activity of parenterally applied SLN and biopharmaceutical aspects such as pharmacokinetic profiles as well as toxicity aspects are reviewed.
Tocols represent a family of tocopherols, tocotrienols, and their derivatives, and are fundamentally derived from the simplest tocopherol, 6-hydroxy-2-methyl-2-phytylchroman, which is referred to as "tocol". The most common tocol is D-alpha-tocopherol, also known as vitamin E. Tocols can be excellent solvents for water insoluble drugs and are compatible with other cosolvents, oils and surfactants. This review highlights the major developments in the use of tocols in parenteral emulsions for drug delivery, with a focus on drug solubilization, physicochemical properties, and biopharmaceutical applications. Tocol emulsions offer an appealing alternative for the parenteral administration of poorly soluble drugs, including major chemotherapeutics such as paclitaxel. Data will be presented on solubilization of paclitaxel, a key chemotherapeutic agent, and its corresponding formulation development, toxicity, efficacy and pharmacokinetic studies in animal models and humans. The breadth of the utility of tocol-based emulsions will be discussed and examples of specific therapeutic drugs and applications will be provided. As these formulations progress further in the clinic, the therapeutic utility of tocol emulsions is anticipated to expand.
Mid-IR and Raman spectroscopy are versatile tools in pharmaceutics and biopharmaceutics, with a wide field of applications ranging from characterization of drug formulations to elucidation of kinetic processes in drug delivery. After an introduction to the basic principles of IR and Raman spectroscopy, new developments in applications of these methods for studying drug delivery systems, in particular topical drug delivery, will be reviewed. FTIR-ATR is a well-established standard method used to study drug release in semisolid formulations, drug penetration, and influence of penetration modifiers; it is also capable of in vivo studies. FTIR-PAS has been applied to measure drug content in semisolid and solid formulations, to determine drug penetration into artificial and biological membranes. The big advantage of this technique is the possibility of spectral depth profiling. However, FTIR-PAS is so far limited to in vitro investigations. Raman spectroscopy can be used to characterize the structure of colloidal drug carrier systems. Raman spectroscopy is readily applicable to in vivo studies, but such investigations must fulfill the relevant laser safety guideline. Recently, there has been tremendous technical improvement in vibrational microspectroscopy. FTIR imaging shows great promise in its ability to visualize the drug and excipient distribution in pharmaceutical formulations such as tablets and therapeutic transdermal systems, as well as to reveal the mechanism of drug release. Furthermore, this unique technique offers completely new possibilities to study the lateral diffusion of drugs.
Nasal drug delivery has now been recognized as a very promising route for delivery of therapeutic compounds including biopharmaceuticals. It has been demonstrated that low absorption of drugs can be countered by using absorption enhancers or increasing the drug residence time in the nasal cavity, and that some mucoadhesive polymers can serve both functions. This article reviews the background of nasal mucoadhesive drug delivery with special references to the biological and pharmaceutical considerations for nasal mucoadhesive drug administration. Applications of nasal mucoadhesives for the delivery of small organic molecules, antibiotics, proteins, vaccines and DNA are also discussed. Furthermore, new classes of functionalized mucoadhesive polymers, the characterization and safety aspects of nasal drug products as well as the opportunities presented by nasal drug delivery are extensively discussed.
ES cells are extraordinary cells, capable of proliferating in a pluripotent state indefinitely and of differentiating spontaneously into all cell types in vivo and many in vitro. However, the manipulation and modification of ES cells by processes such as directed differentiation and genetic modification have placed ES cells at the forefront of many biological studies and could lead to their application in biopharmaceutical areas such as cellular therapy and drug screening. Here we describe some of the ES cell based technologies that have lead to this realisation of ES cell potential.
Age-related macular degeneration, diabetic retinopathy, posterior uveitis, and retinitis due to glaucoma are leading causes of vision loss in the United States and other developed countries. Because these diseases are located in the posterior segment of the eye, topical application of ophthalmic medicines is of limited benefit, since topically applied drugs rarely reach therapeutic levels in the affected posterior tissues such as the choroid and retina. Intravitreal injections can deliver drugs to the posterior segment without the side effects associated with systemic administration. However, the repeated and long-term injections often needed may cause complications, such as vitreous hemorrhage, retinal detachment, or endophthalmitis. Recent advances in ocular drug delivery methods and the development of novel biopharmaceutical agents could lead to new regimens for the treatment of disease of the posterior retina, choroids, and macula. This review will summarize recent literature concerning ocular drug delivery of bioactive compounds to the posterior segment of the eye with emphasis on transscleral iontophoresis.