Towards rare earth element recovery from wastewaters: biosorption using phototrophic organisms.

Whilst the biosorption of metal ions by phototrophic (micro)organisms has been demonstrated in earlier and more recent research, the isolation of rare earth elements (REEs) from highly dilute aqueous solutions with this type of biomass remains largely unexplored. Therefore, the selective binding abilities of two microalgae (Calothrix brevissima, Chlorella kessleri) and one moss (Physcomitrella patens) were examined using Neodym and Europium as examples. The biomass of P. patens showed the highest sorption capacities for both REEs (Nd3+: 0.74 ± 0.05 mmol*g-1; Eu3+: 0.48 ± 0.05 mmol*g-1). A comparison with the sorption of precious metals (Au3+, Pt4+) and typical metal ions contained in wastewaters (Pb2+, Fe2+, Cu2+, Ni2+), which might compete for binding sites, revealed that the sorption capacities for Au3+ (1.59 ± 0.07 mmol*g-1) and Pb2+ (0.83 ± 0.02 mmol*g-1) are even higher. Although different patterns of maximum sorption capacities for the tested metal ions were observed for the microalgae, they too showed the highest affinities for Au3+, Pb2+, and Nd3+. Nd-sorption experiments in the pH range from 1 to 6 and the recorded adsorption isotherms for this element showed that the biomass of P. patens has favourable properties as biosorbent compared to the microalgae investigated here. Whilst the cultivation mode did not influence the sorption capacities for the target elements of the two algal species, it had a great impact on the properties of the moss. Thus, further studies are necessary to develop effective biosorption processes for the recovery of REEs from alternative and so far unexploited sources. KEY POINTS: • The highest binding capacity for selected REEs was registered for P. patens. • The highest biosorption was found for Au and the biomass of the examined moss. • Biosorption capacities of P. patens seem to depend on the cultivation mode.

Comparative LC-MS/MS and HPLC-UV Analyses of Meropenem and Piperacillin in Critically Ill Patients.

BACKGROUND: Therapeutic drug monitoring (TDM) of beta-lactam antibiotics has become a valuable tool to guide dosing in critically ill patients. The main goal of the study was to compare two routinely used techniques for beta-lactam TDM in intensive care unit (ICU) patient samples, namely isotope dilution liquid chromatography tandem mass spectrometry (ID-LC-MS/MS) and high-performance liquid chromatography combined with ultra-violet detection (HPLC-UV). METHODS: A set of 80 sera/plasma samples from ICU patients receiving therapeutic meropenem or piperacillin dosage was investigated. Sample duplicates and quality assessment samples were assayed in parallel with an in-house LC-MS/MS and a commercially available IVD HPLC-UV kit. A pharmacokinetic and pharmacodynamic (PK/PD) target with ≥ 22.5 mg/L for piperacillin and ≥ 8.0 mg/L for meropenem was used for medical assessment of trough sample (n = 40) antibiotic concentrations. RESULTS: There was no difference between serum and Li-heparin plasmas. Concentration deviations were found for 4% of meropenem and 17% of piperacillin samples. Eliminating the influence of the systemic bias of approximately 10% for piperacillin, measurement discrepancies ≥ 25% between LC-MS/MS and HPLC-UV analyses were only observed for ≈ 4 - 6% of all samples. In the same way, identical PK/PD target attainment rates of 50 - 60% could be obtained. CONCLUSIONS: After correction of the analytical bias for piperacillin measurements, both methods showed comparable results, also with respect to clinical decision limits. HPLC-UV analysis is an adequate TDM methodology for testing of beta-lactam antibiotics in centers where no special knowledge in LC-MS/MS based TDM is present. However, potential matrix effects, interferences, and calibration issues for both methods must be taken into account.

Radiosynthesis and Preclinical Evaluation of 18F-Fluoroglycosylated Octreotate for Somatostatin Receptor Imaging.

Short synthetic octapeptide analogs derived from the native somatostatin peptides SST-14 and SST-28, namely, octreotate (TATE) or octreotide (TOC), bind with high affinity to somatostatin receptors (sstr), mainly to subtypes 2 and 5, which are expressed in high density on neuroendocrine tumors (NET). Therefore, radiolabeled TATE or TOC derivatives represent highly valuable imaging probes for NET diagnosis by positron emission tomography (PET). The aim of our study was the development of an 18F-labeled octreotate analog as an alternative radiotracer for the clinically established 68Ga-DOTATOC and 68Ga-DOTATATE. We applied our previously developed method based on copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) to the radiosynthesis of 18F-fluoroglycosylated TATE ([18F]FGlc-TATE). [18F]FGlc-TATE was obtained in high yields of 19-22% (non-decay-corrected, referred to [18F]fluoride) and in high specific activities of 32-106 GBq/µmol. [18F]FGlc-TATE showed high affinity to sstr expressed on AR42J cells (IC50 = 4.2 nM) with fast and high internalization, and a beneficial logD7.4 of -1.8. In AR42J tumor bearing nude mice, [18F]FGlc-TATE showed high and specific tumor uptake of 5.6%ID/g at 60 min post-injection, as determined by blocking experiments using octreotide, and fast clearance from other organs, resulting in excellent tumor-to-blood ratios increasing from 9 to 17 from 30 to 60 min post-injection. Small animal PET studies revealed high uptake of [18F]FGlc-TATE in the tumor which could be blocked with octreotide by >99%. Overall, [18F]FGlc-TATE revealed excellent in vitro and in vivo properties and is therefore a viable alternative 18F-labeled radiopeptide for imaging somatostatin receptor-positive tumors by PET.

Terbium Excitation Spectroscopy as a Detection Method for Chromatographic Separation of Lanthanide-Binding Biomolecules.

Studies of biosorption and bioaccumulation of heavy metals deal mostly with challenging, inhomogeneous, and complex materials. Therefore, most reports describe only application studies, while fundamental research is limited to indirect methods and speculations on the binding mechanisms. In this study, we describe a method for detecting and isolating heavy metal-binding biomolecules directly from crude extracts. The underlying principle is terbium sensitization and fluorescence excitation spectroscopy used offline after a chromatographic run. Compounds interacting with metal ions inevitably change the coordination sphere of terbium, which is reflected in the excitation spectrum leading to metal-specific luminescence. Main advantages of our approach include simple, fast, and inexpensive experiment design, nondestructive measurements, and detection limits far below 1 mg. Here, we have applied our method for three promising biosorbents (green algae, moss, and cyanobacterium) and obtained first information on the character of active compounds isolated from each species.

Validated Nuclear-Based Transgene Expression Regulated by the Fea1 Iron-Responsive Promoter in the Green Alga Chlamydomonas reinhardtii.

Microalgae are in the focus for the production of recombinant proteins in research and potential commercial application. Inducible promoters represent important tools that potentially allow the expression of recombinant proteins at higher rates. In general, they are used to separate the culture growth phase from the production phase by initiating product formation after high cell densities have been achieved. This potentially offers a higher space-time yield, consequently improving the economics of a process. In the case of the green micro alga Chlamydomonas reinhardtii, a controlled switch between activation and deactivation of gene expression is possible by changes in cultivation parameters. In this work, parameters of induction and deactivation of the iron-responsive Fea1 promoter were analyzed over time in C. reinhardtii. The results presented for the strain CC4351 validate our previous findings presented for strain CC 400. The Fea1 promoter was successfully deactivated upon transferring the cells to medium containing 10 and 20 µM Fe3+. Within 120 h, cells showed only 1.7-6% of the initial fluorescence. Activation of the Fea1 promoter occurred promptly and prominently when cells were transferred to iron-deplete medium. In general, both strains showed a pronounced difference between the active and the inactive states of the Fea1 promoter.