Human Serum Albumin Microspheres Research Articles

Clarithromycin targeting to lung: characterization, size distribution and in vivo evaluation of the human serum albumin microspheres

Microspheres of clarithromycin have been prepared from human serum albumin using the emulsion polymerization technique. Albumin microspheres containing the active substance were injected into the tail vein of mice. Mice were sacrificed at intervals and microspheres collected from lungs and livers. The clarithromycin amount in microspheres was determined by reversed phase high performance liquid chromatographic (HPLC) method from the mice organs. Morphological and histopathological observations were also reported. The microsphere accumulation began at 10 min, and increased gradually until 6 h, then a decrease was observed. The microspheres were still present after 24 h. In the liver sample, no microsphere accumulation was observed at any time.

Immobilization of Hormones for Drug Targeting

Biological active compounds such as insulin, heparin, progesterone and labeled-LH were entrapped in glutaraldehyde cross-linked bovine serum albumin (BSA) and human serum albumin (HAS) microspheres. Studies were carried out for their binding capacity and biodegradability using new proteolytic enzymes. Effects of proteolytic enzymes such as trypsin, chymotrypsin, papain and pronase-E on microspheres were studied in order to understand the biodegradability of the cross-linked proteins. It has been observed that labeled-LG was entrapped 60% in BSA and HAS microspheres. Labelled-LH-BSA, Labelled-LH-HAS and insulin microspheres were injected into mice and rabbits. It was observed that these cross-linked microspheres were biodegradable and the process appeared to be slow one, useful for sustained release of hormones. It was also observed that these albumin microspheres exhibit fluorescence at 495 nm.

Immobilization of Hormones for Drug Targeting

Biological active compounds such as insulin, heparin, progesterone and labeled-LH were entrapped in glutaraldehyde cross-linked bovine serum albumin (BSA) and human serum albumin (HAS) microspheres. Studies were carried out for their binding capacity and biodegradability using new proteolytic enzymes. Effects of proteolytic enzymes such as trypsin, chymotrypsin, papain and pronase-E on microspheres were studied in order to understand the biodegradability of the cross-linked proteins. It has been observed that labeled-LG was entrapped 60% in BSA and HAS microspheres. Labelled-LH-BSA, Labelled-LH-HAS and insulin microspheres were injected into mice and rabbits. It was observed that these cross-linked microspheres were biodegradable and the process appeared to be slow one, useful for sustained release of hormones. It was also observed that these albumin microspheres exhibit fluorescence at 495nm.

Pulmonary Transit of Sonicated Albumin Microbubbles During Controlled Mechanical Ventilation

Air-filled human serum albumin microspheres are ultrasonic contrast tracers that pass through the right ventricle, traverse the lungs, and effectively opacify the left heart chambers in spontaneously breathing patients. In this clinical study, we assessed whether they also do so in anesthetized patients during and after mechanical ventilation. In 20 anesthetized patients undergoing intermittent positive pressure ventilation (IPPV) for elective peripheral neurosurgical procedures, a sonicated ultrasound contrast drug (0.06 mL/kg) was injected IV before inducing anesthesia in spontaneously breathing patients (baseline), during IPPV, and 5 and 30 min after tracheal extubation. Transthoracic echocardiograms were obtained in the four-chamber apical view and were recorded for off-line analysis. Time to contrast appearance in the right ventricle and pulmonary transit time were measured in cardiac cycles. The peak intensity of right and left ventricular chamber opacification were scored on a scale ranging from 1 (no contrast or traces only) to 5 (attenuation). After each injection, the time for contrast appearance in the right ventricle was similar in all patients. Pulmonary transit time increased significantly during IPPV and was normal 5 min and 30 min after extubation. Right ventricular chamber opacification achieved high-grade intensity and remained constant before, during, and after IPPV. Conversely, although the baseline contrast injection resulted in high-grade left ventricular chamber opacification, the intensity decreased significantly during IPPV, remained low 5 min after extubation, and was normalized 30 min after extubation. Implications: During intermittent positive pressure ventilation, IV sonicated albumin microbubbles pass through the lungs poorly and inefficiently opacify the left ventricle compared with the effects observed during spontaneous ventilation. (Anesth Analg 1999;89:273-7)

Pulmonary transit of sonicated albumin microbubbles during controlled mechanical ventilation: a transthoracic echocardiographic study.

Air-filled human serum albumin microspheres are ultrasonic contrast tracers that pass through the right ventricle, traverse the lungs, and effectively opacify the left heart chambers in spontaneously breathing patients. In this clinical study, we assessed whether they also do so in anesthetized patients during and after mechanical ventilation. In 20 anesthetized patients undergoing intermittent positive pressure ventilation (IPPV) for elective peripheral neurosurgical procedures, a sonicated ultrasound contrast drug (0.06 mL/kg) was injected i.v. before inducing anesthesia in spontaneously breathing patients (baseline), during IPPV, and 5 and 30 min after tracheal extubation. Transthoracic echocardiograms were obtained in the four-chamber apical view and were recorded for off-line analysis. Time to contrast appearance in the right ventricle and pulmonary transit time were measured in cardiac cycles. The peak intensity of right and left ventricular chamber opacification were scored on a scale ranging from 1 (no contrast or traces only) to 5 (attenuation). After each injection, the time for contrast appearance in the right ventricle was similar in all patients. Pulmonary transit time increased significantly during IPPV and was normal 5 min and 30 min after extubation. Right ventricular chamber opacification achieved high-grade intensity and remained constant before, during, and after IPPV. Conversely, although the baseline contrast injection resulted in high-grade left ventricular chamber opacification, the intensity decreased significantly during IPPV, remained low 5 min after extubation, and was normalized 30 min after extubation. During intermittent positive pressure ventilation, i.v. sonicated albumin microbubbles pass through the lungs poorly and inefficiently opacify the left ventricle compared with the effects observed during spontaneous ventilation.

Preparation of153Sm-particles for radiosynovectomy

This paper summarizes the development and preparation procedures for two particulate preparations of153Sm, namely the hydroxyapatite (HA) particles and human serum albumin (HSA) microspheres. Preparation of153Sm-labeled hydroxyapatite particles and153Sm-labeled albumin microspheres were done in two steps. Radiolabeling efficiency was greater than 95% for hydroxyapatite particles and greater than 80% for albumin microspheres.

Human Serum Albumin Microspheres Approximate Initial Organ-Specific Biodistributions of Transplanted Hepatocytes and Are Effective Cell Surrogates for Safety Studies

Liver repopulation with transplanted hepatocytes will generate novel cell-based therapies, although translocation of transplanted cells into lungs through portasystemic shunts has the potential for embolic complications. To facilitate safety analysis of hepatocyte transplantation, we wished to obtain effective cell surrogates and analyzed biodistributions of similarly sized 99mTc-labeled human serum albumin microspheres and rat hepatocytes. Image analysis with dual 99mTc and 111In labels indicated that cells and microspheres were similarly distributed in the liver when injected into normal rats via the spleen. Also, their distributions were similar when injected via a femoral vein or the superior mesenteric vein with cells and microspheres localizing in lungs or liver, respectively. Upon intraportal injection in rats with portal hypertension, microspheres localized in both liver and lungs, consistent with portasystemic shunting. These data demonstrate that human serum albumin microspheres are effective cell surrogates for approximating the safety of hepatocyte transplantation and should be clinically useful.

Human serum albumin microspheres approximate initial organ-specific biodistributions of transplanted hepatocytes and are effective cell surrogates for safety studies.

Liver repopulation with transplanted hepatocytes will generate novel cell-based therapies, although translocation of transplanted cells into lungs through portasystemic shunts has the potential for embolic complications. To facilitate safety analysis of hepatocyte transplantation, we wished to obtain effective cell surrogates and analyzed biodistributions of similarly sized 99mTc-labeled human serum albumin microspheres and rat hepatocytes. Image analysis with dual 99mTc and 111In labels indicated that cells and microspheres were similarly distributed in the liver when injected into normal rats via the spleen. Also, their distributions were similar when injected via a femoral vein or the superior mesenteric vein with cells and microspheres localizing in lungs or liver, respectively. Upon intraportal injection in rats with portal hypertension, microspheres localized in both liver and lungs, consistent with portasystemic shunting. These data demonstrate that human serum albumin microspheres are effective cell surrogates for approximating the safety of hepatocyte transplantation and should be clinically useful.

99m-Tc-labeled human serum albumin microspheres are effective and degradable cell surrogates for analyzing safety of hepatocyte transplantation

99m-Tc-labeled human serum albumin microspheres are effective and degradable cell surrogates for analyzing safety of hepatocyte transplantation

Preparation of human serum albumin microspheres by a novel acetone-heat denaturation method.

Human serum albumin (HSA) microspheres have been produced in the size range of 200 nm to 10 microns by the controlled addition of acetone to an aqueous solution of HSA, followed by stabilization of the formed microspheres at an elevated temperature. Microspheres produced by this acetone-heat denaturation method could be stabilized at relatively low temperatures (75 degrees C) over a short time period (15-30 min). The acetone-heat denaturation method is different from the traditional oil/water technique for preparation of HSA microspheres, both in terms of production method and the avoidance of high temperatures (> 100 degrees C) and extended heating times (> 30 min) for stabilization. This paper describes the influence of process conditions, such as volumes of acetone and HSA concentration, on the formation of the microspheres and their morphological characteristics. A loading efficiency of 8 per cent was achieved for the HSA microspheres when using rose bengal as a model compound. The release of rose bengal from the microspheres in phosphate buffered saline at 37 degrees C was dependent on the presence of the surfactant Tween 80, and varied from a 5 per cent release in 14 days in the absence of surfactant to a 50 per cent release in 8 h in the presence of surfactant.

Phagocytosis and degradation of human serum albumin microspheres and nanoparticles in human macrophages.

Nanoparticles and microspheres made from human serum albumin are biodegradable and, as a physiological material, less cytocidal than cyanoacrylates. Therefore, they should be a suitable carrier system for targeting drugs into cells of the mononuclear phagocyte system. Nevertheless, the process of phagocytic uptake and degradation of albumin particles by macrophages has so far not been documented in detail. For this reason the presented electron microscopical investigation was performed. To study both cellular particle uptake and intracellular degradation, human monocytes were isolated from the peripheral blood of healthy donors and cultivated in plastic plates. After maturation to macrophages, the cells were incubated with the particles for 2h, then washed with buffer and further cultivated for 1-7 days. After fixing with glutaraldehyde, the cells were prepared for electron microscopy. The process of incorporation was demonstrated to be phagocytosis, by scanning and transmission electron microscopy. The degradation of the microspheres was followed by transmission electron microscopy. The metabolism started some hours after particle uptake. After 3 days the process was almost terminated. After 7 days of cultivation only small numbers of intact microspheres were found in the cytoplasm.

Inhibition of HIV in vitro by antiviral drug-targeting using nanoparticles

Nanoparticles are known to accumulate in the phagocytic cells of the mononuclear phagocyte system. Therefore, the use of this carrier system for the targeting of antiviral drugs to monocytes/macrophages (MO/MAC) is an attractive concept in the treatment of diseases involving MO/MAC, e.g. infection with HIV. In this study, the ability of macrophages isolated from peripheral blood of healthy blood donors to phagocytose and metabolize human serum albumin microspheres was investigated by transmission electron microscopy. Furthermore, nanoparticles manufactured using human serum albumin or polyhexylcyanoacrylate were loaded with nucleoside analogues (AZT and ddC) and tested for their ability to prevent HIV infection in MO/MAC cultures. Our results demonstrate the effectiveness of this drug-targeting system to one of the major target cells for HIV.

Incorporation and release of chemically intact mitomycin C from albumin microspheres: a high performance liquid chromatography evaluation.

Preparation of mitomycin C-loaded human serum albumin (HSA) microspheres using a new technique that avoids the use of heat denaturation, which is known chemically to degrade incorporated drug, is described. This method is based on cross-linking of protein by glutaraldehyde (2.2%) during emulsification (W/O) at room temperature. The resultant particles have a mean (s.d.) diameter of 16.9 (0.34) microns (50% weight average), contain mean (s.d.) 1.15 (0.05%) mitomycin C (MMC) (w/w, n = 17) and maintain sustained release of drug over 20 h. High performance liquid chromatography (HPLC) with diode array detection was used to study the chemical integrity of the drug. Two classes of decomposition products were evaluated: chemical degradation products and drug/nucleophile covalent adducts. The HPLC separation was validated by a number of standards of proposed degradation products. To examine incorporated drug, a complete microsphere system was solubilized with 0.4% trypsin for 24 h, while to examine released drug, microspheres were immobilized on a flow-through glass wool column and fractions were collected. No evidence of significant chemical degradation or covalent coupling to protein was detected in microsphere digests. Two candidate decomposition products, representing approximately 10% of drug released from microspheres (assuming similar molar extinction coefficients to MMC), were identified in column fractions. One of these products appeared to be a covalent adduct, the other possibly an isomeric form of intact MMC. Thus, MMC is predominantly incorporated into and released (90%) chemically intact from HSA microspheres prepared by the technique described.

Hepatic tumors: signal enhancement at Doppler US after intravenous injection of a contrast agent.

Experiments were carried out to detect and establish the origin of Doppler and echo signal enhancement in small vessels of the systemic circulation and of tumors after intravenous injection of a contrast agent. Eight woodchucks (Marmota monax) were studied; each woodchuck had naturally occurring hepatocellular carcinoma. Injections of 0.1-4.0 mL of air-filled human serum albumin microspheres were administered into a hind limb or jugular vein. Ultrasound (US) examination included transabdominal duplex scanning, color Doppler imaging, placement of a Doppler transducer on the exposed tumor, and surgical implantation of pulsed Doppler cuffs. Doppler signals were assessed by recording color Doppler images and results of spectral analysis. While subjective echo level was unaffected within the tumors, dramatic Doppler signal enhancement was recorded in both normal and tumor vessels. At optimum dose levels, a signal gain of approximately 10 dB was recorded from the tumor. Analysis showed that the echo enhancement was due to the presence of the contrast agent in branches of the hepatic artery. These results suggest that tumor detection may be enhanced by intravenous administration of a US contrast agent.

Cyclophosphamide Loaded Albumin Microspheres: Liver Entrapment and Fate in Mice

AbstractMicrospheres offer the possibility of target selectivity through choice of appropriate size or surface charecteristics, slow release of drug and also minimize systemic toxicity. The active substance of this investigation, cyclophosphamide (CP), interferes with the growth of cancer cells which are eventually destroyed. Since side effects of CP are frequently dose related, by incorporating low dose of CP to human serum albumin (HSA) microspheres, the normal body cells are not affected while the tumour cells are destroyed.Cyclophosphamide microspheres were prepared by the modification of the method of Scheffel et al and Gurkan et al. 2,3-butanedione was used as a cross-linking agent. The albumin microspheres containing CP were labelled by 99mTc by incorporating SnC12.2H20 at a concentration of 5% of the matrix material. All the microspheres used in this study ranged between 1–5 μm.A suspension of 99mTc labelled cyclophosphamide microspheres was injected into swiss albino mice intravenously. At 15 min...

Preparation, characterization and performance evaluation of neomycin-HSA microspheres

Human serum albumin microspheres containing neomycin sulphate were prepared using emulsion polymerization and polymer dispersion techniques. The many variables which may affect the shape, size, stability, release of the drug from the microspheres such as internal phase to external phase volume ratio, human serum albumin content, stirring rate, polymer content and stabilizing agent concentration, were studied. Unlike the microspheres prepared by the emulsion polymerization technique, polymer dispersion stabilised microspheres were uniform in size and shape with a narrow range of size distribution. In vitro release of neomycin sulphate from albumin microspheres was studied using the dialysis cell method. The drug release from microspheres followed Q versus (t)-1/2 linear relationship. The in vivo distribution studies on prepared microspheres revealed that the localization takes place preferably in lung tissues, liver, spleen and kidney and is found to be dependent on the microsphere size. On administration of microspheres of 3-6 microns size, approximately 55 per cent of administered drug could be localized in the lungs.

Cyclophosphamide loaded albumin microspheres II. Release characteristics

The purpose of this investigation was to evaluate the release characteristics of cyclophosphamide (CP) from glutaraldehyde stabilized human serum albumin microspheres, and to study the effect of the extent of cross-linking, the amount of the stabilizing agent and the size of the microspheres on the in vitro release of CP. Microspheres were prepared by emulsion polymerization method using two different volumes (0.1 and 0.7 ml) of glutaraldehyde solution (25 per cent) and two different crosslinking durations (15 min and 1 h). The resulting mean particle size of the microspheres also varied between 2.5 microns and 3.7 microns. The total CP content in microspheres was analysed from the surface drug and the entrapped drug.

Chromatographic studies of mitomycin C degradation in albumin microspheres

Serum albumins and polylactic acid (PLA) have been used as bioerodable polymers in the preparation of drug-containing microspheres for parenteral drug delivery. The albumin microsphere may be prepared via either chemical cross-linking or heat denaturation of the protein. Heat-denatured albumin microspheres containing mitomycin C (MMC) have been used in pre-clinical and clinical investigations. Due to the high reactivity of MMC as a bifunctional alkylating agent, a study on the stability of MMC in the albumin and PLA microspheres has been carried out using a high-performance liquid chromatographic (HPLC) method. Human serum albumin (HSA) microspheres were prepared using an emulsion method via either heat denaturation at 120 or 170°C or the use of 0.5 M biacetyl as a cross-linking agent. The PLA microspheres were prepared by an emulsion method at 55°C. HPLC analysis of the HSA microspheres showed that about 37% of MMC was converted to 2,7-diaminomitosene derivatives in microspheres prepared by heat denaturation at 120°C. The degradation increased to 82% when the microspheres were prepared with a denaturation temperature of 170°C. The use of biacetyl as a cross-linking agent in the preparation of HSA microspheres resulted in a complete degradation of the incorporated MMC. Biacetyl was found to interact with MMC leading to the formation of 7-aminomitosene derivatives. In contrast to the albumin system, MMC may be incorporated into PLA microspheres without degradation.

Magnetite albumin microspheres: a new MR contrast material.

A superparamagnetic MR contrast agent was synthesized by incorporating 150-250-A particles of magnetite (Fe3O4, Fe2O3) in 1-5 microns human serum albumin microspheres. Magnetite albumin microspheres (MAM) target almost exclusively to the reticuloendothelial system after IV administration, are stable in vitro and in vivo, and possess a long shelf life. The agent has a large magnetic susceptibility effect that selectively reduces T2 with little effect on T1. Biodistribution studies that use a dose of 20 mg MAM/kg show prompt clearance from the blood pool with marked decrease in T2 for rat liver (40%) and spleen (45%) with a small decrease in liver (5%) and spleen (10%) T1 values. Pulmonary T1 and T2 decrease transiently over the first 24 hr, while no significant changes were observed in other tissues. Imaging of a rabbit VX2 tumor model resulted in a 200% increase in the contrast ratio of VX2 tumor to normal liver on T2-weighted and mixed T1-/T2-weighted pulse sequences after administration of contrast agent. The extreme potency, excellent targeting, and apparent lack of toxicity of this agent suggest that MAM probably will have a clinical application in detecting focal hepatic and splenic lesions.

Labelling of human serum albumin millimicrospheres (hamm) with99mTc

Human serum albumin microspheres were labelled with99mTc as a single step kit with radiochemical yields higher than 95%. With respect to the organ distribution in mice, the per cent of injected dose in liver was 78%.