HPMA copolymer-doxorubicin-gadolinium conjugates: synthesis, characterization, and in vitro evaluation

This study describes the synthesis, characterization, and in vitro evaluation of N-(2-hydroxypropyl)methacrylamide (HPMA) copolymer-gadolinium (Gd)-doxorubicin (Dox) conjugates. Copolymers of HPMA were derivatized to incorporate side chains for Gd chelation and Dox conjugation. The conjugates were characterized by their side chain contents, T(1) relaxivity (r(1)), stability, and in vitro cytotoxicity. High stability and relaxivity of these conjugates coupled with low toxicity show their potential for monitoring the in vivo fate of HPMA-based drug delivery systems by magnetic resonance imaging techniques.     

Nystatin—dextran conjugates: Synthesis and characterization

The coupling of nystatin (Nys), a water-insoluble antifungal agent, to dextran via an imine or amine bond was systematically investigated. Dextran was first oxidized to dialdehyde dextran using potassium periodate, purified from the oxidizing agent, and reacted with Nys to form the Schiff base. The Schiff base was reduced to the amine using borohydride. All reactions took place in water. The purification of the oxidized dextran from the oxidizing agent was essential to prevent oxidative degradation of Nys at the coupling step. The effects on the coupling yield of the following factors: dextran molecular weight, degree of oxidation (aldehyde content), Nys to dextran ratio, temperature, and reaction pH were studied. A 95% coupling yield was obtained at the optimized coupling conditions: pH 8.9 ± 0.1, 50% degree of oxidation, and initial ratio of Nys to dialdehyde dextran 1:2.5. In all experiments, dextran was decreased in molecular weight during the oxidation step. Both imine and amine forms of Nys-dextran conjugates were soluble in water and exhibited improved stability in aqueous solutions as compared to the unbound drug. The conjugates showed comparable minimum inhibitory concentration (MIC) values against Candida albicans and Cryptococcus neoformans. The conjugates were about 25 times less toxic than free Nys after a single injection in mice. © 1996 John Wiley & Sons, Inc.     

Tamoxifen-loaded polymeric micelles: preparation, physico-chemical characterization and in vitro evaluation studies

Several samples of polymeric micelles, formed by amphiphilic derivatives of PHEA, obtained by grafting into polymeric backbone of PEGs and/or hexadecylamine groups (PHEA-PEG-C(16) and PHEA-C(16)) and containing different amount of Tamoxifen, were prepared. All Tamoxifen-loaded polymeric micelles showed to increase drug water solubility. TEM studies provided evidence of the formation of supramolecular core/shell architectures containing drug, in the nanoscopic range and with spherical shape. Samples with different amount of encapsulated Tamoxifen were subjected to in vitro cytotoxic studies in order to evaluate the effect of Tamoxifen micellization on cell growth inhibition. All samples of Tamoxifen-loaded polymeric micelles showed a significantly higher antiproliferative activity in comparison with free drug, probably attributable to fluidification of cellular membranes, caused by amphiphilic copolymers, that allows a higher penetration of the drug into tumoral cells. To gain preliminary information about the potential use of prepared micelles as Tamoxifen drug delivery systems, studies evaluating drug release ability of micelle systems in media mimicking biological fluids (buffer solutions at pH 7.4 and 5.5) and in human plasma were carried out. These studies, performed evaluating the amount of Tamoxifen that remains in solution as a function of time, showed that at pH 7.4, as well as in plasma, PHEA-C(16) polymeric micelles were able to release lower drug amounts than PHEA-PEG(5000)-C(16) ones, while at pH 5.5, the behavior difference between two kind of micelles was less pronounced.     

Identification and characterization of in vitro and in vivo fidarestat metabolites: Toxicity and efficacy evaluation of metabolites

The progression of diabetic complications can be prevented by inhibition of aldose reductase and fidarestat considered to be highly potent. To date, metabolites of the fidarestat, toxicity, and efficacy are unknown. Therefore, the present study on characterization of hitherto unknown in vitro and in vivo metabolites of fidarestat using liquid chromatography–electrospray ionization tandem mass spectrometry (LC/ESI/MS/MS) is undertaken. In vitro and in vivo metabolites of fidarestat have been identified and characterized by using LC/ESI/MS/MS and accurate mass measurements. To identify in vivo metabolites, plasma, urine, and feces samples were collected after oral administration of fidarestat to Sprague–Dawley rats, whereas for in vitro metabolites, fidarestat was incubated in human S9 fraction, human liver microsomes, and rat liver microsomes. Furthermore, in silico toxicity and efficacy of the identified metabolites were evaluated. Eighteen metabolites have been identified. The main in vitro phase I metabolites of fidarestat are oxidative deamination, oxidative deamination and hydroxylation, reductive defluroniation, and trihydroxylation. Phase II metabolites are methylation, acetylation, glycosylation, cysteamination, and glucuronidation. Docking studies suggest that oxidative deaminated metabolite has better docking energy and conformation that keeps consensus with fidarestat whereas the rest of the metabolites do not give satisfactory results. Aldose reductase activity has been determined for oxidative deaminated metabolite (F‐1), and it shows an IC50 value of 0.44 μM. The major metabolite, oxidative deaminated, did not show any cytotoxicity in H9C2, HEK, HEPG2, and Panc1 cell lines. However, in silico toxicity, the predication result showed toxicity in skin irritation and ocular irritancy SEV/MOD versus MLD/NON (v5.1) model for fidarestat and its all metabolites. In drug discovery and development research, it is distinctly the case that the potential for pharmacologically active metabolites must be considered. Thus, the active metabolites of fidarestat may have an advantage as drug candidates as many drugs were initially observed as metabolites.     

Glucosamine-carrying temperature- and pH-sensitive microgels: preparation, characterization, and in vitro drug release studies

Glucosamine-carrying temperature- and pH-sensitive microgels with an average diameter of about 100 nm were successfully prepared by free radical precipitation polymerization. The thermo- and pH-responsive properties of the microgels were designed by the incorporation of N-isopropylacrylamide (NIPAM) and acrylic acid (AAc) to copolymerize with acrylamido-2-deoxyglucose (AADG). The stimuli sensitivity of the microgels was studied by the measurement of their sizes and volume phase transition temperature (VPTT) under different surrounding conditions. The results showed that the microgels were responsive to temperature, pH, and ionic strength, and could have a desired VPTT by modifying AADG and AAc contents. The effect of temperature and pH on insulin release from the microgels was also investigated. The release of drug at the tumor-surrounding environment is faster than that under normal physiological conditions. A preliminary in vitro cell study showed that the glucosamine-carrying microgels are more biocompatible to mouse fibroblast cells, compared to the microgels without glucosamine. These glucosamine-carrying dual-sensitive microgels may be promising carriers for targeted drug delivery to tumors.     

Facile preparation and characterization of novel oleanane-type triterpene functionalized β-cyclodextrin conjugates

Four water-soluble β-CD-pentacyclic triterpene conjugates were synthesized via ester and amide linkages. All the conjugates showed lower hydrophobicity (AlogP) than their parent.     

Gadolinium diethylenetriaminepentaacetic acid hyaluronan conjugates: preparation,properties and applications

We have prepared new hyaluronan (HA) gadolinium diethylenetriaminepentaacetic acid (DTPA) conjugates that have potential as tumor specific contrast agents for magnetic resonance imaging. Conjugates were synthesized, starting with a high molecular weight HA or with HA oligomers, by an efficient 2-step procedure involving first, reaction of ethylenediamine with HA carboxylic acid groups and, second, covalent linkage of DTPA to aminated HA. The final polymers were compared in terms of molar masses and DTPA content. Tapping mode atomic force microscopy has been used to examine the morphology of the polymers in aqueous solution.     

The Antimicrobial efficacy of Elaeis guineensis: characterization, in vitro and in vivo studies

The urgent need to treat multi-drug resistant pathogenic microorganisms in chronically infected patients has given rise to the development of new antimicrobials from natural resources. We have tested Elaeis guineensis Jacq (Arecaceae) methanol extract against a variety of bacterial, fungal and yeast strains associated with infections. Our studies have demonstrated that E. guineensis exhibits excellent antimicrobial activity in vitro and in vivo against the bacterial and fungal strains tested. A marked inhibitory effect of the E. guineensis extracts was observed against C. albicans whereby E. guineensis extract at ?, 1, or 2 times the MIC significantly inhibited C. albicans growth with a noticeable drop in optical density (OD) of the bacterial culture. This finding confirmed the anticandidal activity of the extract on C. albicans. Imaging using scanning (SEM) and transmission (TEM) electron microscopy was done to determine the major alterations in the microstructure of the extract-treated C. albicans. The main abnormalities noted via SEM and TEM studies were the alteration in morphology of the yeast cells. In vivo antimicrobial activity was studies in mice that had been inoculated with C. albicans and exhibited good anticandidal activity. The authors conclude that the extract may be used as a candidate for the development of anticandidal agent.     

Antibody drug conjugates: Development,characterization, and regulatory considerations

Previously, cancer chemotherapy was often accompanied by severe side effects. Antibody drug conjugates (ADCs) were introduced to address this treatment complication. ADCs are a potent category of bioconjugates and immunoconjugates designed as targeted therapy for the treatment of cancer. ADCs are complex molecules composed of an antibody linked via linker chemistry to a cytotoxic payload or drug. Therefore, biologic properties of the cell‐surface target antigen are important in designing an effective ADC as an anticancer agent. ADCs have the ability to discriminate between the healthy and diseased tissue, so that healthy cells are less effected and get maximum therapeutic benefit. This review describes the development, characterization, and regulatory consideration of ADCs, and it summarizes the approved products in the market and in clinical trials.     

Bone-targeting melphalan prodrug with tumor-microenvironment sensitivity: Synthesis,in vitro and in vivo evaluation

The synthesis, in vitro and in vivo evaluation of novel melphalan-bisphosphonate hybrids, with a tumor microenvironment sensitive linkage were described.     

Benzylidene/2-aminobenzylidene hydrazides: Synthesis,characterization and in vitro antimicrobial evaluation

In this study a series of new mannich bases were synthesized and characterized by elemental and spectral (IR, ¹H NMR, ¹³C NMR) studies. All the synthesized compounds were evaluated for their antimicrobial activity by broth dilution method against two Gram negative strains (Escherichia coli and Pseudomonas aeruginosa), two Gram positive strains (Bacillus subtilis and Staphylococcus aureus) and fungal strain (Candida albicans and Aspergillus niger). Preliminary pharmacological evaluation revealed that the compounds (3f, 3i, 3j, and 3k) showed good activity against these strains. The result demonstrates the potential and importance of developing new mannich bases which would be effective against resistant bacterial and fungal strain.     

Magnetic nanoparticle-peptide conjugates for in vitro and in vivo targeting and extraction of cancer cells

Magnetic cobalt spinel ferrite nanoparticles coated with biocompatible polygalacturonic acid were functionalized with ligands specific for targeting expressed EphA2 receptors on ovarian cancer cells. By using such magnetic nanoparticle-peptide conjugates, targeting and extraction of malignant cells were achieved with a magnetic field. Targeting ovarian cancer cells with receptor specific peptide-modified magnetic nanoparticles resulted in cell capture from a flow stream in vitro and from the peritoneal cavity of mice in vivo. Successful removal of metastatic cancer cells from the abdominal cavity and circulation using magnetic nanoparticle conjugates indicate the feasibility of a dialysis-like treatment and may improve long-term survival rates of ovarian cancer patients. This approach can be applied for fighting other cancers, such as leukemia, once the receptors on malignant cells are identified and the efficacy of targeting ligands is established.     

Binary and ternary inclusion complexes of dapsone in cyclodextrins and polymers: preparation, characterization and evaluation

Dapsone (DAP) is a synthetic sulfone drug with bacteriostatic activity, mainly against Mycobacterium leprae. In this study we have investigated the interactions of DAP with cyclodextrins, 2-hydroxypropyl-β-cyclodextrin (HPβCD) and β-cyclodextrin (βCD), in the presence and absence of water-soluble polymers, in order to improve its solubility and bioavailability. Solid systems DAP/HPβCD and DAP/βCD, in the presence or absence of polyvinylpyrrolidone (PVP K30) or hydroxypropyl methylcellulose (HPMC), were prepared. The binary and ternary systems were evaluated and characterized by SEM, DSC, XRD and NMR analysis as well as phase solubility assays, in order to investigate the interactions between DAP and the excipients in aqueous solution. This study revealed that inclusion complexes of DAP and cyclodextrins (HPβCD and βCD) can be produced in order to improve DAP solubility and bioavailability in the presence or absence of polymers (PVP K30 and HPMC). The more stable inclusion complex was obtained with HPβCD, and consequently HPβCD was more efficient in improving DAP solubility than βCD, and the addition of polymers had no influence on DAP solubility or on the stability of the DAP/CDs complexes.     

Microrough cobalt-chromium alloy surfaces for Paclitaxel delivery: preparation, characterization, and in vitro drug release studies

Cobalt-chromium (Co-Cr) alloys have extensive biomedical applications including drug-eluting stents (DES). This study investigates the use of eight different microrough Co-Cr alloy surfaces for delivering paclitaxel (PAT) for potential use in DES. The eight different surfaces include four bare microrough and four self-assembled monolayer (SAM) coated microrough surfaces. The bare microrough surfaces were prepared by grit blasting Co-Cr with glass beads (50 and 100 μm in size) and Al(2)O(3) (50 and 110 μm). The SAM coated surfaces were prepared by depositing a -COOH terminated phosphonic acid monolayer on the different microrough surfaces. PAT was then deposited on all the bare and SAM coated microrough surfaces. The surfaces were characterized using scanning electron microscopy (SEM), 3D optical profilometry, and Fourier transform infrared spectroscopy (FTIR). SEM showed the different morphologies of microrough surfaces without and with PAT coating. An optical profiler showed the 3D topography of the different surfaces and the changes in surface roughness and surface area after SAM and PAT deposition. FTIR showed ordered SAMs were formed on glass bead grit blasted surfaces, while the molecules were disordered on Al(2)O(3) grit blasted surfaces. Also, FTIR showed the successful deposition of PAT on these surfaces. The PAT release was investigated for up to two weeks using high performance liquid chromatography. Al(2)O(3) grit blasted bare microrough surfaces showed sustained release profiles, while the glass bead grit blasted surfaces showed burst release profiles. All SAM coated surfaces showed biphasic drug release profiles, which is an initial burst release followed by a slow and sustained release. SAM coated Al(2)O(3) grit blasted surfaces prolonged the sustained release of PAT in a significant amount during the second week of drug elution studies, while this behavior was not observed for any other surfaces used in this study. Thus, this study demonstrates the use of different microrough Co-Cr alloy surfaces for delivering PAT for potential applications in DES and other medical devices.     

Synthesis,characterisation and chromatographic evaluation of polyether dendrimer stationary phases

Supercritical carbon dioxide has attracted attention as a potential replacement for traditional organic solvents due to its simplified workup procedures and reduced environmental impact—providing a green chemistry approach for organic solvent-free functionalisation. In addition to the environmental benefits, the enhanced diffusivity observed in supercritical solvents can often enhance reaction rates. We have applied these valuable features to the preparation of silica-bonded stationary phases and examined their potential in liquid chromatography. We report the successful preparation and characterisation of polyether silica based on Frechet dendrimers—this significantly enhances the range of stationary-phase chemistries that can be prepared in supercritical fluids. First- and second-generation polyether silicas were prepared, characterised, end-capped and evaluated for use as stationary phases for liquid chromatography. Figure SRM1649 on 2nd generation polyether silica Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.