Optimization of a tunable process for rapid production of calcium phosphate microparticles using a droplet-based microfluidic platform

Calcium phosphate (CaP) biomaterials are amongst the most widely used synthetic bone graft substitutes, owing to their chemical similarities to the mineral part of bone matrix and off-the-shelf availability. However, their ability to regenerate bone in critical-sized bone defects has remained inferior to the gold standard autologous bone. Hence, there is a need for methods that can be employed to efficiently produce CaPs with different properties, enabling the screening and consequent fine-tuning of the properties of CaPs towards effective bone regeneration. To this end, we propose the use of droplet microfluidics for rapid production of a variety of CaP microparticles. Particularly, this study aims to optimize the steps of a droplet microfluidic-based production process, including droplet generation, in-droplet CaP synthesis, purification and sintering, in order to obtain a library of CaP microparticles with fine-tuned properties. The results showed that size-controlled, monodisperse water-in-oil microdroplets containing calcium- and phosphate-rich solutions can be produced using a flow-focusing droplet-generator microfluidic chip. We optimized synthesis protocols based on in-droplet mineralization to obtain a range of CaP microparticles without and with inorganic additives. This was achieved by adjusting synthesis parameters, such as precursor concentration, pH value, and aging time, and applying heat treatment. In addition, our results indicated that the synthesis and fabrication parameters of CaPs in this method can alter the microstructure and the degradation behavior of CaPs. Overall, the results highlight the potential of the droplet microfluidic platform for engineering CaP microparticle biomaterials with fine-tuned properties.

Effect of minor amounts of β-calcium pyrophosphate and hydroxyapatite on the physico-chemical properties and osteoclastic resorption of β-tricalcium phosphate cylinders

β-Tricalcium Phosphate (β-TCP), one of the most used bone graft substitutes, may contain up to 5 wt% foreign phase according to standards. Typical foreign phases include β-calcium pyrophosphate (β-CPP) and hydroxyapatite (HA). Currently, the effect of small amounts of impurities on β-TCP resorption is unknown. This is surprising since pyrophosphate is a very potent osteoclast inhibitor. The main aim of this study was to assess the effect of small β-CPP fractions (<1 wt%) on the in vitro osteoclastic resorption of β-TCP. A minor aim was to examine the effect of β-CPP and HA impurities on the physico-chemical properties of β-TCP powders and sintered cylinders. Twenty-six batches of β-TCP powder were produced with a Ca/P molar ratio varying between 1.440 and 1.550. Fifteen were further processed to obtain dense and polished β-TCP cylinders. Finally, six of them, with a Ca/P molar ratio varying between 1.496 (1 wt% β-CPP) and 1.502 (1 wt% HA), were incubated in the presence of osteoclasts. Resorption was quantified by white-light interferometry. Osteoclastic resorption was significantly inhibited by β-CPP fraction in a linear manner. The presence of 1% β-CPP reduced β-TCP resorption by 40%, which underlines the importance of controlling β-CPP content when assessing β-TCP biological performance.

Extended EEG and non-convulsive status epilepticus: Benefit over routine EEG?

OBJECTIVE

EEG monitoring is increasingly used in critically ill patients, but impact on clinical outcome remains unclear. We aimed to investigate the benefit of repeated extended EEG in the prognosis of patients with non-convulsive status epilepticus (SE).

MATERIALS & METHODS

We retrospectively collected 29 consecutive patients with non-convulsive SE without coma, who underwent repeated extended EEG between 2013 and 2015. We compared these patients with an historical age-matched group of 58 patients managed between 2011 and 2013 with routine EEG only. We excluded patients treated with therapeutic coma for SE treatment. Outcome at hospital discharge was categorized as return to baseline conditions, new disability, and death.

RESULTS

Severity of SE was similar in the two groups, with similar proportion of potential fatal etiologies (58% in the extended EEG group vs 60%, P=.529), similar STESS scores (median was three in both groups, P=.714), and comparable acute hospitalization duration (median of 15 vs 11 days, P=.131). The extended EEG group received slightly more anti-epileptic drugs (median was three in both groups, P=.026). Distribution of the outcome categories at hospital discharge was similar (P=.129).

CONCLUSIONS

Extended EEG used for the management of non-convulsive status epilepticus does not seem to improve clinical outcome, but is associated with a higher number of prescribed anti-epileptic drugs. The benefit of continuous EEG monitoring in non-convulsive SE without coma SE should be addressed through a randomized trial.

[Seizure by asystole or asystoleby seizure?]

A 75 years old man is suffering from recurrent seizures since several years. The seizures start with vegetative symptoms including tingling sensations, followed by a deep feeling of eternity and happiness. In one third of the cases he looses consciousness completely. Several workups have failed to reveal a diagnosis. An ECG loop recorder was implanted which finally revealed an asystole of 15 seconds duration. It was thought that this caused cerebral hypoxia which was triggering focal seizures. A pacemaker was inserted. The attacks of unconsciousness disappeared; however, the spells of vegetative sensations persisted. After antiepileptic treatment was initiated the symptoms improved, however it was not possible to achieve complete control. Is this patient primarily suffering from recurrent asystole or from epilepsy which causes complex seizures with disturbance of cardiac rhythm? The latter phenomenon in its most extreme presentation is better known as sudden unexplained death in epilepsy (SUDEP). The diagnostic approach and therapy of both diseases are discussed.

Mucin-like carcinoma-associated antigen defined by three monoclonal antibodies against different epitopes

Three monoclonal antibodies [MAb], b-8, b-12, and b-15, have previously been shown to react with mammary carcinomas and with a restricted set of cells in normal human tissues [C. Stähli et al., Experientia (Basel), 41: 1377-1381, 1985; H. R. Zenklusen et al., Virchows Arch. Abt. A Pathol. Anat., 413: 3-10, 1988]. They are shown here to recognize the same high molecular weight acid soluble glycoprotein antigen. Lectin binding, biolabeling, and deglycosylation experiments demonstrate that it contains O-linked carbohydrate side chains with sialic acid and hexoses including fucose, galactose, and/or galactosamine but little if any mannose. These properties, typical of mucin-like glycoproteins, agree with the antigen expression on mucin-secreting epithelial surfaces (H. R. Zenklusen et al., Virchows Arch. Abt. A Pathol. Anat., 413:3-10, 1988). The antigen is thus named mucin-like carcinoma-associated antigen (MCA). The three MAb are shown to bind to three different epitopes on MCA. Two of these epitopes (MCA-b-8 and MCA-b-15) are O-linked carbohydrates, and one (MCA-b-15) contains sialic acid. The epitope MCA-b-12 is of peptide nature. Of various two-site sandwich enzyme immunoassays composed of different combinations of the three MAb, the one with MAb b-12 in both positions is selected for a serum assay. Analyses of tumor patients' sera demonstrate that this MCA enzyme immunoassay can be of use as a tumor marker assay for mammary carcinomas. The parameter MCA enzyme immunoassay is shown to differ from other parameters described in the literature.

The immunohistochemical reactivity of a new anti-epithelial monoclonal antibody (MAb b-12) against breast carcinoma and other normal and neoplastic human tissues

A mouse monoclonal antibody, MAb b-12, has been described previously (Stähli et al. 1985) which reacts with a Mr 350 kD glycoprotein with mucin-like characteristics (Stähli et al. 1987) expressed in cytoplasm and on the surface of human breast carcinoma cell lines (MCF-7 and ZR-75-1). In the present report the immunohistochemical reactivity of this MAb with normal and malignant human tissues is analyzed. Pre-experiments showed that the epitope b-12 is resistant to formalin treatment allowing the use of tissue processed by standard paraffin embedding methods. 167 normal and 408 neoplastic tissues were tested by indirect immunofluorescence or the avidin-biotin complex method. MAb b-12 stained the apical cytoplasm of secretory epithelia and their secretions including the acinar and ductular epithelia of the breast. It reacted with all breast carcinomas independent of their histological type or stage, frequently with all but in some cases with a fraction of the tumour cells. Some other carcinomas, primarily those of adenomatous differentiation, were also reactive. In these, however, the fraction of positive tumour cells was usually lower. The b-12 epitope is thus a marker for normal and neoplastic epithelia with secretory functions, particularly for breast carcinomas of all histological types and stages, and perhaps a differentiation marker for abortive adenomatous differentiation in solid carcinomas of the gastro-intestinal, uro-genital or respiratory tract.

Identification of the conserved, conformation-dependent cytokeratin epitope recognized by monoclonal antibody (lu-5)

The epitope recognized by the murine monoclonal antibody (mAB lu-5) recently described as a formaldehyde-resistant, "pan-epithelial marker" of great value in tumour diagnosis is located on the surface of cytokeratin filaments. It has been preserved during vertebrate evolution from amphibia to man. As this epitope is not reactive after SDS-polyacrylamide gel electrophoresis (SDS-PAGE), the epitope-bearing protein has been identified by a dot-blot antibody binding assay, using purified proteins in which the epitope is reconstituted. We show that the epitope is present in most cytokeratin polypeptides of both the acidic (type I) and basic (type II) subfamily but does not occur in other cytoskeletal proteins. The location of this widespread epitope is discussed with respect to homologies of amino acid sequences of cytokeratins and their conformations.

First experiments on radioimmunodetection with b-12-monoclonal antibody fragments against breast cancer antigen

In 14 patients with breast cancer the results of radioimmunoscintigraphy with 123I-labeled b-12 monoclonal antibody fragments were correct in more than two thirds of the patients.

First Experiments on Radioimmunodetection with b-12-Monoclonal Antibody Fragments against Breast Cancer Antigen

In 14 patients with breast cancer the results of radioimmunoscintigraphy with 123l-labeled b-12 monoclonal antibody fragments were correct in more than two thirds of the patients.

Monoclonal antibodies against antigens on breast cancer cells

Of 360 mAb obtained in a cell fusion experiment with the spleen cells of a mouse immunized with a mixture of different human breast carcinoma cell lines, 30 mAb were selected which reacted more strongly with tumor cells than with (noncancerous) fibroblasts. These mAb were tested for reactivity with additional types of cancerous and noncancerous tissues. Two mAb showed high tumor selectivity, but the corresponding epitopes on individual tumor cells were heterogeneously expressed. The mAb will be evaluated for in vivo applications.

Co-localization of GABA receptors and benzodiazepine receptors in the brain shown by monoclonal antibodies

The most abundant inhibitory neurotransmitter in the central nervous system, gamma-aminobutyric acid (GABA), exerts its main effects via a GABAA receptor that gates a chloride channel in the subsynaptic membrane. These receptors can contain a modulatory unit, the benzodiazepine receptor, through which ligands of different chemical classes can increase or decrease GABAA receptor function. We have now visualized a GABAA receptor in mammalian brain using monoclonal antibodies. The protein complex recognized by the antibodies contained high- and low-affinity binding sites for GABA as well as binding sites for benzodiazepines, indicative of a GABAA receptor functionally associated with benzodiazepine receptors. As the pattern of brain immunoreactivity corresponds to the autoradiographical distribution of benzodiazepine binding sites, most benzodiazepine receptors seem to be part of GABAA receptors. Two constituent proteins were identified immunologically. Because the monoclonal antibodies cross-react with human brain, they provide a means for elucidating those CNS disorders which may be linked to a dysfunction of a GABAA receptor.

A rapid and highly sensitive solid-phase enzyme immunoassay specific for human fibronectin using a characterized monoclonal antibody

A solid-phase enzyme immunoassay (EIA) was developed for the quantitation of human fibronectin in body fluids and cell culture media. In the assay a human fibronectin-specific murine monoclonal IgG1 (f-33) was used as capture antibody and polyclonal rabbit anti-fibronectin as detector antibody. The antibody showed no reactivity to purified monkey, dog, rabbit, horse, sheep, mouse, bovine or chicken fibronectins. The determinant of the monoclonal antibody was mapped to the cell-binding region of the fibronectin molecule. This localization was based on the use of purified fragments of fibronectin, immunoblotting, EIA and inhibition of fibroblast adhesion and spreading by the antibody. The detection limit of the fibronectin assay was 2 ng/ml. The assay was used for the quantitation of fibronectin in human plasma, urine and cerebrospinal fluid specimens and culture media of human cells.

A GABA/benzodiazepine receptor complex from bovine brain: purification, reconstitution and immunological characterization

A GABA/benzodiazepine receptor complex was purified from bovine cerebral cortex. The receptor fraction displayed binding sites for benzodiazepines as well as high and low affinity binding sites for GABA which are characteristics of the membrane-bound receptor. Two monoclonal antibodies of which one was directed against the 50 kd and the other against the 55 kd subunit were used for immunoprecipitation studies. Both of them were shown to quantitatively precipitate the entire receptor population. These results indicate that the binding sites for benzodiazepines and GABA (high and low affinity sites) reside on the same receptor complex containing a mixture of 50 kd and 55 kd subunits. Reconstitution of the receptor in phospholipid vesicles was achieved.

The visualization of neuronal benzodiazepine receptors in the brain by autoradiography and immunohistochemistry

Recent methodological improvements in receptor autoradiography have enabled the in vitro and in vivo binding of the benzodiazepines in the brain to be visualized and pharmacologically characterized with an anatomical resolution unattainable by biochemical radioligand binding assays. This approach, combined with computerized microdensitometry, can be used not only to map the distribution of benzodiazepine receptors in the brain but also to quantify their regional densities. Furthermore, immunohistochemical studies, using monoclonal antibodies directed against the solubilized and purified GABA/benzodiazepine receptor-ionophore complex, have revealed the distribution of antigenic sites on brain neurons and their processes. The brain regions of intense immunoreactivity are known to contain a high density of GABA-ergic efferents and neuronal-type benzodiazepine receptors. Current trends and prospects in this area of receptor research are briefly reviewed.

Monoclonal antibody against the N-terminal end of human plasma fibronectin

Purified human plasma fibronectin was digested with cathepsin G and the degradation products were tested for reactivity towards a monoclonal antibody. In an immunoblotting assay, after sodium dodecyl sulphate/polyacrylamide-gel electrophoresis of the digestion products, the 85 000-Mr and 72 000-Mr gelatin- and heparin-binding fragments as well as the N-terminal 30 000-Mr heparin-binding fragment reacted with the antibody, whereas the 64 000-Mr gelatin- and heparin-binding fragment did not. In enzyme immunoassay the antibody reacted with intact fibronectin and the 30 000-Mr fragment but not with a 40 000-Mr gelatin-binding fragment. The alignment of the binding domains in these fragments and in the intact molecule [Vartio (1982) Eur. J. Biochem. 123, 223-233] localizes the antigenic determinant to the 21 000 Da N-terminal Staphylococcus aureus-binding region of fibronectin.

Monoclonal antibodies to thymosin alpha 1

Sixteen monoclonal antibodies specific for thymosin alpha 1 [Low et al., J. biol. Chem. 254, 981-986 (1979)] obtained from two fusions with the spleens of three mice [Stähli et al., Meth. Enzym. 92, 26-36 (1982b)] all react with an epitope in the C-terminal half of thymosin alpha 1. Human and foetal calf serum contain substances which cross-react with this epitope. A simple procedure to selectively remove the cross-reactive material and a sensitive RIA are described.

Evidence for preferential proteolytic cleavage of one of the two fibronectin subunits and for immunological localization of a site distinguishing them

Purified plasma fibronectin was digested sequentially by thrombin and cathepsin G or by cathepsin G alone and the degradation products and their gelatin-binding and heparin-binding fractions were analyzed in NaDodSO4-polyacrylamide gel electrophoresis followed by immunoblotting with a defined monoclonal anti-fibronectin antibody. In early cathepsin G digests, several gelatin-binding fragments were detected: a few large (Mr greater than or equal to 150 000) polypeptides and fragments of Mr = 85 000, 72 000, 64 000 and 40 000. The 85 000-Mr and 64 000-Mr fragments appeared as closely spaced doublets and reacted with the antibody while the 72 000-Mr and 40 000-Mr fragments did not. Therefore the 64 000-Mr fragments are likely to be derived from the 85 000-Mr fragments. Three large fragments that bound to heparin, but not to gelatin were detected: Mr = 145 000, 135 000 and 120 000. Of these only the 135 000-Mr peptide reacted with the antibody. When fibronectin was digested with thrombin, polypeptides of Mr = 180 000-200 000 and a 30 000-Mr NH2-terminal fragment were produced. Cathepsin G added to this mixture further cleaved the fragments to a digestion pattern resembling that obtained from intact fibronectin except that the 85 000-Mr and 64 000-Mr fragments appeared as single bands and the amount of the 72 000-Mr fragment was reduced. The results suggest that thrombin cleaves the 30 000-Mr fragment preferentially from the NH2-terminal end of one of the two subunits of fibronectin and that the 85 000-Mr, 72 000-Mr and 64 000-Mr fragments obtained by the additional cathepsin G digestion were derived from the other chain. The results are consistent with the model that the antigenic determinant resides 72 000-85 000 Da from the NH2-terminus and is cleaved by cathepsin G alternatively at one of its sides. Thus, the components of the 85 000-Mr and 64 000-Mr doublets are derived from different subunits and the region located by the antibody may be responsible for the difference in their migration in the polyacrylamide gel.

Association of a Mr 50,000 cap-binding protein with the cytoskeleton in baby hamster kidney cells

A monoclonal antibody directed against eukaryotic mRNA 5'-cap-binding protein (anti-CBP antibody) was used to localize cap-binding protein (CBP) in BHK-21 baby hamster kidney cells by immunofluorescence microscopy. It was found that the antibody reacts with a fibrous network extending through the cytoplasm in a radial arrangement. The network behaves like intermediate filaments in colchicine-treated cells, suggesting a direct or indirect linkage of CBP with intermediate filaments. The association of CBP with a cytoskeletal element was further confirmed by isolation of proteins from Triton X-100-extracted cells and identification of CBP in the cytoskeletal fraction with anti-CBP antibody. The major polypeptide reacting with anti-CBP antibody is a Mr 50,000 component. Tryptic peptide mapping showed that this polypeptide is related to a Mr 24,000 polypeptide identified as CBP in earlier experiments [Sonenberg, N., Morgan, M. A., Testa, D., Colonna, R. J. & Shatkin, A. J. (1978) Proc. Natl. Acad. Sci. USA 75, 4843-4847].

Production of hybridomas secreting monoclonal antibodies to the human leukocyte interferons

Thirteen monoclonal antibodies to human leukocyte interferon have been obtained. They exhibit different patterns of binding to purified leukocyte interferon species that are consistent with the structural multiplicity of the human leukocyte interferons. These antibodies will be useful as probes into the structure of the human leukocyte interferons, for their purification, and for rapid assay of leukocyte interferon.

High frequencies of antigen-specific hybridomas: dependence on immunization parameters and prediction by spleen cell analysis

Hybridomas producing antibodies against soluble antigens have in most cases been difficult to establish. After fusion of myeloma cells with spleen cells obtained from mice immunized with a soluble protein, hybridomas secreting specific antibodies have been observed to occur very rarely among non-specific hybridomas. We found that the frequency of specific hybridomas correlates directly with the increase over background of the frequency of blast and/or plasma cells in the spleen (measured by cell size analysis) after antigenic stimulation. High yields of specific hybridomas were obtained simply by following a novel immunization technique consisting of several conventional preimmunization courses followed by 4 very high doses of antigen in saline on each of the last 4 days before fusion.