The binding of 5-fluorouracil to native and modified human serum albumin: UV, CD, and 1H and 19F NMR investigation

In vivo and in situ monitoring of doxorubicin pharmacokinetics with an implantable bioresorbable optical sensor

Cancer treatment, particularly chemotherapy, requires balancing efficacy and toxicity. Although traditional monitoring methods can lead to suboptimal outcomes, emerging implantable chemical sensors can complement them by providing precise, real-time drug monitoring at tumor sites, although the technology remains in its early stages. Here, we introduce an ultrathin, bioresorbable implantable biosensor for real-time doxorubicin monitoring in vivo with high spatiotemporal resolution. The sensor amplifies the drug's fluorescence, enabling successful tracking of doxorubicin through the skin in live mice following intravenous injection. When paired with a reusable electronic patch, the biosensor facilitates seamless data collection and wireless transmission. A 3-month biocompatibility study, including systemic toxicity assessments, histological and blood analyses, confirms complete biodegradation with no observed toxicity. By directly measuring chemotherapeutic drug levels in tissues over time, our sensor enhances traditional monitoring methods, enabling clinicians to optimize dosing during cancer treatment and reduce the risk of locoregional recurrence following tumor removal.

Screening and assessment of molecular mechanistic actions of 5-hydroxy-1-methylpiperidin-2-one against free radicals, lung cancer cell line (A549), and binding properties on bovine serum albumin

Background

Natural products play a key role in treating different ailment including diabetes, asthma, skin diseases, and cancer. It is well known that synthetic drugs elicit significant toxicity when used in the clinic. A higher drug affinity towards carrier protein Bovine Serum Albumin (BSA) would enhance a higher drug bioavailability which in turn leads to a higher therapeutic efficacy. The focus of the present study was to investigate antioxidant and anti-cancer potential of 5-hyrdoxy1-methylpiperidin-2-one (5-HMP) isolated from leaves of Tragia involucrata.

Methods and material

In vitro free radical scavenging assays and MTT assay were employed to assess the antioxidant activity of 5-HMP and cytotoxicity of 5-HMP on lung cancer cell line, A549, respectively. In addition, attempts were made to investigate 5-HMP binding capacity on BSA by spectral studies and molecular docking.

Results

The antioxidant data revealed that 5-HMP inhibited the radicals with an IC50 value of 49.55 ± 0.75 μg/ml which was comparable with the IC50 values afforded by l-ascorbic acid. 5-HMP exhibited a dose-dependent cytotoxicity on A549 cells with an IC50 value of 30.00 ± 0.55 μg/ml. further 5-HMP induced a cell cycle arrest in A549 at S and G2/M phase. The fluorescence quenching was observed when an increasing concentration of 5-HMP, reacts with a fixed concentration of BSA (1.0 μM). The fluorescence quenching of BSA by 5-HMP indicated a binding constant of K5-HMP = 2.8 ± 1.4 × 104M−1 with corresponding binding free energy (ΔG)−6.06 K.cal/mole.

Conclusions

This paper concluded that 5-HMP possesses antioxidant properties, cytotoxic effects and also it possesses good drug binding properties on bovine serum albumin.

Optimizing circadian drug infusion schedules towards personalized cancer chronotherapy

Precision medicine requires accurate technologies for drug administration and proper systems pharmacology approaches for patient data analysis. Here, plasma pharmacokinetics (PK) data of the OPTILIV trial in which cancer patients received oxaliplatin, 5-fluorouracil and irinotecan via chronomodulated schedules delivered by an infusion pump into the hepatic artery were mathematically investigated. A pump-to-patient model was designed in order to accurately represent the drug solution dynamics from the pump to the patient blood. It was connected to semi-mechanistic PK models to analyse inter-patient variability in PK parameters. Large time delays of up to 1h41 between the actual pump start and the time of drug detection in patient blood was predicted by the model and confirmed by PK data. Sudden delivery spike in the patient artery due to glucose rinse after drug administration accounted for up to 10.7% of the total drug dose. New model-guided delivery profiles were designed to precisely lead to the drug exposure intended by clinicians. Next, the complete mathematical framework achieved a very good fit to individual time-concentration PK profiles and concluded that inter-subject differences in PK parameters was the lowest for irinotecan, intermediate for oxaliplatin and the largest for 5-fluorouracil. Clustering patients according to their PK parameter values revealed patient subgroups for each drug in which inter-patient variability was largely decreased compared to that in the total population. This study provides a complete mathematical framework to optimize drug infusion pumps and inform on inter-patient PK variability, a step towards precise and personalized cancer chronotherapy.

Accuracy and safety of infusion pumps remain a critical issue in the clinics and the development of accurate mathematical models to optimize drug administration though such devices has a key part to play in the advancement of precision medicine. Here, PK data from cancer patient receiving irinotecan, oxaliplatin and 5-fluorouracil into the hepatic artery via an infusion pump was mathematically investigated. A pump-to-patient model was designed and revealed significant inconsistencies between intended drug profiles and actual plasma concentrations. This mathematical model was then used to suggest improved profiles in order to minimise error and optimise delivery. Physiologically-based PK models of the three drugs were then linked to the pump-to-patient model. The whole framework achieved a very good fit to data and allowed quantifying inter-patient variability in PK parameters and linking them to potential clinical biomarkers via patient clustering. The developed methodology improves our understanding of patient-specific drug pharmacokinetics towards personalized drug administration.

Investigation of relaxation times in 5-fluorouracil and human serum albumin mixtures

Background

Human serum albumin (HSA) is often selected as a subject of any study because albumin is the most abundant protein in human blood plasma. NMR is recognized as a valuable method to determine the structure of proteins-ligand and protein-drug complexes.

Objective – Aim of the study

In this study, protein drug interactions were investigated using 5-Fluorouracil anti-cancer drug and human serum albumin protein.

Materials and methods

In this context 400 MHz NMR spectrometry was used and NMR relaxation rates in drug-albumin complex were investigated with respect to increase albumin concentration and increase in 5-Fluorouracil (5-FU)-albumin solution temperature.

Results

The results of this study indicated that 5-FU had a weak association with albumin, and it easily dissociated from the protein to which it was attached.

Conclusion

The obtained results also gave us useful information about molecular dynamics of drug-albumin interactions.

Lymph node effective vascular permeability and chemotherapy uptake

OBJECTIVE

Lymph node metastases are a poor prognostic factor. Additionally, responses of lymph node metastasis to therapy can be different from the primary tumor. Investigating the physiologic lymph node blood vasculature might give insight into the ability of systemic drugs to penetrate the lymph node, and thus into the differential effect of therapy between lymph node metastasis and primary tumors. Here, we measured effective vascular permeability of lymph node blood vessels and attempted to increase chemotherapy penetration by increasing effective vascular permeability.

METHODS

We developed a novel three-dimensional method to measure effective vascular permeability in murine lymph nodes in vivo. VEGF-A was systemically administered to increase effective vascular permeability. Validated high-performance liquid chromatography protocols were used to measure chemotherapeutic drug concentrations in untreated and VEGF-A-treated lymph nodes, liver, spleen, brain, and blood.

RESULTS

VEGF-A-treated lymph node blood vessel effective vascular permeability (mean 3.83 × 10^-7  cm/s) was significantly higher than untreated lymph nodes (mean 9.87 × 10^-8  cm/s). No difference was found in lymph node drug accumulation in untreated versus VEGF-A-treated mice.

CONCLUSIONS

Lymph node effective vascular permeability can be increased (~fourfold) by VEGF-A. However, no significant increase in chemotherapy uptake was measured by pretreatment with VEGF-A.

Chemotherapy, targeted agents, antiemetics and growth-factors in human milk: how should we counsel cancer patients about breastfeeding?

An increasing number of women are diagnosed with cancer during pregnancy and lactation. Women are usually advised to interrupt breastfeeding during systemic anticancer treatment for fear of serious adverse effects to the nursed infant. However, the issue is poorly addressed in the literature and very few studies have evaluated the safety of breastfeeding during or after cytotoxic drugs or target agents administration. In this review we will analyze the available evidence that addresses the issue of anticancer drugs, targeted agents, antiemetics and growth-factors excretion in human milk. This could serve as a unique resource that may aid physicians in the management of breastfeeding cancer patients interested in maintaining lactation during treatment.

The binding characteristics of the interaction between 3-(2-cyanoethyl) cytosine and human serum albumin

The binding characteristics of the interaction between 3-(2-cyanoethyl) cytosine (CECT) and human serum albumin (HSA) were investigated using fluorescence, UV absorption spectroscopic and molecular modeling techniques under simulative physiological conditions. The intrinsic fluorescence intensity of HSA was decreased with the addition of CECT. The fluorescence data handled by Stern-Volmer equation proved that the quenching mechanism of the interaction between CECT and HSA was a static quenching procedure. The binding constants evaluated utilizing the Lineweaver-Burk equation at 17, 27 and 37 °C, were 2.340 × 10(4), 2.093 × 10(4) and 1.899 × 10(4) L mol(-1), respectively. The thermodynamic parameters were calculated according to van't Hoff equations. Negative enthalpy (ΔH) and positive entropy (ΔS) values indicated that both hydrogen bond and hydrophobic force played a major role in the binding process of CECT to HSA, which was consistent with the results of the molecular modeling study. In addition, the effect of other ions on the binding constant of CECT-HSA was examined.

Interaction between phillygenin and human serum albumin based on spectroscopic and molecular docking

In this paper, the interaction of human serum albumin (HSA) with phillygenin was investigated by fluorescence, circular dichroism (CD), UV-vis spectroscopic and molecular docking methods under physiological conditions. The Stern-Volmer analysis indicated that the fluorescence quenching of HSA by phillygenin resulted from static mechanism, and the binding constants were 1.71×10(5), 1.61×10(5) and 1.47×10(4) at 300, 305 and 310K, respectively. The results of UV-vis spectra show that the secondary structure of the protein has been changed in the presence of phillygenin. The CD spectra showed that HSA conformation was altered by phillygenin with a major reduction of α-helix and an increase in β-sheet and random coil structures, indicating a partial protein unfolding. The distance between donor (HSA) and acceptor (phillygenin) was calculated to be 3.52nm and the results of synchronous fluorescence spectra showed that binding of phillygenin to HSA can induce conformational changes in HSA. Molecular docking experiments found that phillygenin binds with HSA at IIIA domain of hydrophobic pocket with hydrogen bond interactions. The ionic bonds were formed with the O (4), O (5) and O (6) of phillygenin with nitrogen of ASN109, ARG186 and LEU115, respectively. The hydrogen bonds are formed between O (2) of phillygenin and SER419. In the presence of copper (II), iron (III) and alcohol, the apparent association constant K(A) and the number of binding sites of phillygenin on HSA were both decreased in the range of 88.84-91.97% and 16.09-18.85%, respectively. In view of the evidence presented, it is expected to enrich our knowledge of the interaction dynamics of phillygenin to the important plasma protein HSA, and it is also expected to provide important information of designs of new inspired drugs.

Interaction of 3'-azido-3'-deamino daunorubicin with human serum albumin: investigation by fluorescence spectroscopy and molecular modeling methods

In this Letter, the binding of 3'-azido-3'-deamino daunorubicin (ADNR) to human serum albumin (HSA) was investigated at different temperatures by fluorescence spectroscopy at pH 7.4. The binding constant was determined according to Stern-Volmer equation based on the fluorescence quenching of HSA in the presence of ADNR. The thermodynamic parameters, ΔH and ΔS, were calculated according to the dependence of enthalpy change on the temperature to be -21.01 kJ mol(-1) and 24.71 J K(-l) mol(-l), respectively. The results revealed that ADNR had a strong ability to quench the intrinsic fluorescence of HSA through a static quenching procedure. The hydrophobic force played a major role in the interaction of ADNR with HSA, which was in good agreement with the results of molecular modeling study. The effect of various metal ions on the binding constants of ADNR with HSA was also investigated. All the experimental results and theoretical data indicated that ADNR could bind to HSA and be effectively transported and eliminated in body, which might be a useful guideline for further drug design.

Interaction of anthracycline disaccharide with human serum albumin: investigation by fluorescence spectroscopic technique and modeling studies

Anthracyclines are considered to be some of the most effective anticancer drugs for cancer therapy. However, drug resistance and cardiotoxicity of anthracyclines limit their clinical application. An 3'-azido disaccharide analogue of daunorubicin, 7-[4-O-(2,6-dideoxy-3-O-methyl-alpha-l-arabino-hexopyranosyl)-3-azido-2,3,6-trideoxy-alpha-l-lyxo-hexopyranosyl]daunorubicinone (ADNR-3), was shown to exhibit 10-fold better activity than parent compound daunorubicin against the drug-resistant cells and completely overcomes the drug resistance with same IC(50) in both drug-resistant and drug-sensitive cells. In this paper, the interactions between ADNR-3 and human serum albumin (HSA) have been studied by spectroscopic techniques. By the analysis of fluorescence spectrum and fluorescence intensity, it was observed that the ADNR-3 has a strong ability to quench the intrinsic fluorescence of HSA through a static quenching procedure. The association constants of ADNR-3 with HSA were determined at different temperatures based on fluorescence quenching results. The negative DeltaH and positive DeltaS values in case of ADNR-3-HSA complexes showed that both hydrogen bonds and hydrophobic interactions play a role in the binding of ADNR-3 to HSA. Furthermore, synchronous fluorescence spectroscopy data and UV-vis absorbance spectra have suggested that the association between ADNR-3 and HSA changed the molecular conformation of HSA and the hydrophobic interactions play a major role in ADNR-3-HSA association. Moreover, the study of computational modeling indicated that ADNR-3 could bind to the site I of HSA and hydrophobic interaction was the major acting force for the second type of binding site, which was in agreement with the thermodynamic analysis. The distance, r, between donor (HSA) and acceptor (ADNR-3) was obtained according to the Förster's theory of non-radiation energy transfer. In addition, the effects of common ions on the binding constants of ADNR-3-HSA complexes were also investigated.

Studies on the interaction between tetraphenylporphyrin compounds and bovine serum albumin

The interaction of three porphyrin compounds with bovine serum albumin (BSA) was examined by fluorescence emission spectra at the excitation wavelength 280 nm and in UV-Vis absorption spectra. Through fluorescence quenching experiments, it was confirmed that the combination of three porphyrin compounds with BSA was a single static quenching process. The binding constant K(A), the thermodynamic parameters enthalpy change (DeltaH(0)), Gibbs free energy change (DeltaG(0)) and entropy change (DeltaS(0)) were obtained. It was found that hydrophobic interaction played a main role in tetraphenylporphyrin (TPP) or tetraparacholophenylporphyrin (TClPP) binding to BSA, while tetraparamethoxyphenylporphyrin (TMEOPP) mainly based on van der Waals' force. According to Föster energy transfer, the separate distance r, the energy transfer efficiency E and Föster radium R(0) were calculated. The results obtained from the above experiments showed that three porphyrin compounds were tightly bound to BSA.

Oxidation of 2-Mercaptobenzothiazole in Latex Gloves and Its Possible Haptenation Pathway

The rubber accelerator, 2-mercaptobenzothiazole (MBT), has been reported to cause allergic contact dermatitis from gloves and other rubber products, but its chemical fate when exposed to occupational oxidants and the mechanism of its pathogenesis are not known. It was hypothesized that the thiol group is critical to MBT's (its oxidation products or metabolites) covalent binding and/or haptenation to nucleophilic protein residues. Oxidative transformation of MBT to the disulfide 2,2'-dithiobis(benzothiazole) (MBTS) was observed within the glove matrix when hypochlorous acid, iodine, and hydrogen peroxide were used as oxidants. Cysteine reduced MBTS to MBT with subsequent formation of the mixed disulfide 2-amino-3-(benzothiazol-2-yl disulfanyl)propionic acid which was identified and characterized. Spectrophotometry and mass spectrometry experiments demonstrated the simultaneous reduction of MBTS and disulfide formation with Cys34 on bovine serum albumin, suggesting a potential route of protein haptenation through covalent bonding between protein cysteinyl residues and the MBT/MBTS thiol moiety. Metabolism of MBT using isoniazid and dexamethasone-induced rat liver microsomes, to give a protein reactive epoxide intermediate and provide an alternative protein haptenation mechanism, was not observed. The data suggest that the critical functional group on MBT is the thiol, and haptenation is via the formation of mixed disulfides between the thiol group on MBT and a protein sulfhydryl group.

Drug binding to human serum albumin: abridged review of results obtained with high-performance liquid chromatography and circular dichroism

The drug binding to plasma and tissue proteins are fundamental factors in determining the overall pharmacological activity of a drug. Human serum albumin (HSA), together with alpha1-acid glycoprotein (AGP), are the most important plasma proteins, which act as drug carriers, with drug pharmacokinetic implications, resulting in important clinical impacts for drugs that have a relatively narrow therapeutic index. This review focuses on the combination of biochromatography and circular dichroism as an effective approach for the characterization of albumin binding sites and their enantioselectivity. Furthermore, their applications to the study of changes in the binding properties of the protein arising by the reversible or covalent binding of drugs are discussed, and examples of physiological relevance reported. Perspectives of these studies reside in supporting the development of new drugs, which require miniaturization to facilitate the screening of classes of compounds for their binding to the target protein, and a deeper characterization of the mechanisms involved in the molecular recognition processes.

Investigating protein haptenation mechanisms of skin sensitisers using human serum albumin as a model protein

Covalent modification of skin proteins by electrophiles is a key event in the induction of skin sensitisation but not skin irritation although the exact nature of the binding mechanisms has not been determined empirically for the vast majority of sensitisers. It is also unknown whether immunologically relevant protein targets exist in the skin contributing to effecting skin sensitisation. To determine the haptenation mechanism(s) and spectra of amino acid reactivity in an intact protein for two sensitisers expected to react by different mechanisms, human serum albumin (HSA) was chosen as a model protein. The aim of this work was also to verify for selected non-sensitisers and irritants that no protein haptenation occurs even under forcing conditions. HSA was incubated with chemicals and the resulting complexes were digested with trypsin and analysed deploying matrix-assisted laser desorption/ionization mass spectrometry, reverse phase high performance liquid chromatography and nano-electrospray tandem mass spectrometry. The data confirmed that different residues (lysine, cysteine, histidine and tyrosine) are covalently modified in a highly selective and differential manner by the sensitisers 2,4-dinitro-1-chlorobenzene and phenyl salicylate. Additionally, non-sensitisers 2,4-dichloro-1-nitrobenzene, butyl paraben and benzaldehyde and irritants benzalkonium chloride and sodium dodecyl sulphate did not covalently modify HSA under any conditions. The data indicate that covalent haptenation is a prerequisite of skin sensitisation but not irritation. The data also suggest that protein modifications are targeted to certain amino acids residing in chemical microenvironments conducive to reactivity within an intact protein. Deriving such information is relevant to our understanding of antigen formation in the immunobiology of skin sensitisation and in the development of in vitro protein haptenation assays.

Fluorescence study on the interaction of human serum albumin with bromsulphalein

The binding of bromsulphalein (BSP) with human serum albumin was investigated at different temperatures, 298 and 308 K, by the fluorescence spectroscopy at pH 7.24. The binding constant was determined by Stern-Volmer equation based on the quenching of the fluorescence HSA in the presence of bromsulphalein. The effect of various metal ions on the binding constants of BSP with HSA was investigated. The thermodynamic parameters were calculated according to the dependence of enthalpy change on the temperature as follows: DeltaH and DeltaS possess small negative (9.3 kJ mol(-1)) and positive values (22.3 J K(-l)mol(-l)), respectively. The experimental results revealed that BSP has a strong ability to quench the intrinsic fluorescence of HSA through a static quenching procedure. The binding constants between BSP to HSA were remarkable and independent on temperature. The binding constants between HSA and BSP decreased in the presence of various ions, commonly decreased by 30-55%. The hydrophobic force played a major role in the interaction of BSP with HSA. All these experimental results and theoretical data clarified that BSP could bind to HSA and be effectively transported and eliminated in body, which could be a useful guideline for further drug design.

Effect of 5-fluorouracil, Optison and ultrasound on MCF-7 cell viability

The aim of this study was to analyze cell viability and expression of apoptotic-related signaling proteins in MCF-7 breast cancer cells induced by combinations of ultrasound, the anticancer drug 5-fluorouracil (5-FU) and the ultrasound contrast agent Optison. MCF-7 cells were treated with 5-FU and sonicated at the frequency of 3.0 MHz and intensity of 3.0 W/cm2 for 1 min in the presence of Optison. The cells were analyzed for lactate dehydrogenase (LDH) release (a measure of cytotoxicity) and cell proliferation (by MTT assays). The LDH/MTT ratio was used for assessment of cell death. Expression of the apoptotic-related proteins, Bax and p27kip1, as well as phosphorylated forms of ERK and Akt proteins was assessed by Western blot analysis. We demonstrate that, immediately after treatment, cell death was most dependent on Optison; however, 24 h after treatment, cell death was more dependent on 5-FU. Ultrasound duty cycle increased cell death associated with either Optison or 5-FU. Furthermore, we show that treatment with 5-FU and ultrasound increased the levels of the Bax and p27kip1 proteins, but the addition of Optison appears to suppress apoptotic protein expression.

Hapten-protein binding: from theory to practical application in the in vitro prediction of skin sensitization

In view of the forthcoming European Union ban on in vivo testing of cosmetic and toiletry ingredients, following the publication of the 7th amendment to the Cosmetics Directive, the search for practical, alternative, non-animal approaches is gathering pace. For the end-point of skin sensitization, the ultimate goal, i.e. the development and validation of alternative in vitro/in silico assays by 2013, may be achieved through a better understanding of the skin sensitization process on the cellular and molecular levels. One of the key molecular events in skin sensitization is protein haptenation, i.e. the chemical modification of self-skin protein(s) thus forming macromolecular immunogens. This concept is widely accepted and in theory can be used to explain the sensitizing capacity of many known skin sensitizers. Thus, the principle of protein or peptide haptenation could be used in in vitro assays to predict the sensitization potential of a new chemical entity. In this review, we consider some of the theoretical aspects of protein haptenation, how mechanisms of protein haptenation can be investigated experimentally and how we can use such knowledge in the development of novel, alternative approaches for predicting skin sensitization potential in the future.

Investigation of microenvironmental factors influencing the longitudinal relaxation times of drugs and other compounds

The aim of this study was to investigate the microenvironmental factors likely to influence the longitudinal relaxation time of MR visible drugs or compounds in vivo at 1.5 T. The relative influence that viscosity, albumin and paramagnetic contrast agent concentrations have on the observed longitudinal relaxation times of three 19F MR detectable drugs and compounds have been investigated. Our data show that for 5-fluorouracil, flucloxacillin and tetrafluorosuccinic acid-containing phantoms, the presence of albumin at normal physiological concentrations will have relaxation effects of the same order of magnitude as that of a commonly clinically administered contrast agent, gadolinium diethylenetriamine pentaacetic acid. The contribution of viscosity is shown, in the examples studied here, to be of minor importance, contributing less than 6.5% to the observed relaxation effects. It is also demonstrated that in the presence of competitive binding of other ligands for common binding sites on albumin, the 19F longitudinal relaxation time of 5-fluorouracil can increase by up to 340% from its value in the absence of the competing ligand. The relevance of the findings to in vivo studies is discussed.

Effect of heating temperature and time on pharmaceutical characteristics of albumin microspheres containing 5-fluorouracil

In this study, we found that both heating temperature and heating time affect mean particle size, particle size distribution, and drug entrapment efficiency of albumin microspheres. The change in heating temperature may affect the particle size of the product, especially when heating is carried out at a lower temperature (90°C–120°C). Hence the temperature should be selected on the basis of desired size range. Given that it is desirable for a maximum amount of the drug used in the preparation to become entrapped in microspheres, heating temperature and heating time for denaturation of albumin should be selected cautiously, as both have a significant effect on drug entrapment efficiency. In the present case, the highest entrapment was found in batches prepared by heating at 90°C for 5 minutes. However, the extent of stabilization at the selected temperature and the time of heating should also be taken into consideration, as they may affect the release of drugs to target tissue.

Spectrophotometric and spectrofluorimetric determination of fluorouracil in the presence of its degradation products

Three reliable spectrophotometric and spectrofluorimetric procedures are described for the determination of fluorouracil in bulk powder and ampoules in the presence of its degradation products. One spectrophotometric procedure, based on measurement at 555 nm of the violet-coloured complex formed by fluorouracil with cobalt(II), has a detection limit of 0.03 mg mL(-1). Two sensitive spectrofluorimetric procedures are also proposed. One is based on measurement of the intrinsic fluorescence of the liberated fluorouracil at 375 nm, after precipitation as its cobalt(II) complex, decomposition of the precipitate with sulphuric acid and excitation at 295 nm. The second depends on excitation of the fluorouracil-cobalt(II) complex at 395 nm and measuring its fluorescence at 483 nm. The limits of detection of the two spectrofluorimetric procedures are 0.5 and 2 microg mL(-1), respectively. The three procedures have been used successfully for the determination of fluorouracil ampoules. The validity of the methods has been assessed by applying the standard addition technique.

Determination of the binding of a beta 2-blocker drug, frusemide and ceftriaxone to serum proteins by capillary zone electrophoresis

A modified Hummel-Dreyer method was used to study the binding of drugs with serum proteins by high performance capillary electrophoresis. The study was carried out to check the possible interaction between serum proteins and a highly selective beta 2-blocker, ICI 118551 (ICI). To prove the suitability of the method the protein binding of frusemide and ceftriaxone, drugs previously investigated, was also studied. The analyses were carried out by injecting a solution of s alpha(1)-acidic glycoprotein (alpha(1)-AGP) or human serum albumin in 70 mM NaH2PO4/Na2HPO4(pH 7.4) buffer into an uncoated fused silica capillary filled with the same buffer. In the capillary, maintained at a working temperature of 35 degrees C, a known amount of the ICI, frusemide or ceftriaxone was added. The method allows the bound drug to be determined directly.

Determination of 5-fluorouracil in human plasma by a simple and sensitive reversed-phase HPLC method

A simple and sensitive reversed-phase HPLC method with UV detection was developed and validated for the quantitation of 5-fluorouracil (5-FC) in human plasma. After acidification and salting out, 5-FU was extracted into ethyl acetate and back-extracted into a basic buffer. The extract was adjusted to neutral pH before being injected onto the HPLC column. 5-FU was separated from the matrix components on a YMC ODS-AQ column at 40 degrees C using an aqueous mobile phase of 10 mM potassium phosphate at pH 5.5. A linear gradient of 0-25% methanol wash eluted late peaks, maintained column performance, and increased column stability. The run time was 20 min. The linear range was 25-300 ng ml-1 (r2 > 0.999). The limit of quantitation was 25 ng ml-1, with a signal-to-noise ratio of 23:1. Interday precision and accuracy of quality control samples were 6.2-8.4% relative standard deviation and -0.1(-)+1.9% relative error.