Change in Osmotic Pressure Influences the Absorption Spectrum of Hemoglobin inside Red Blood Cells

Absorption spectra of red blood cell (RBC) suspensions are investigated in an osmolarity range in the medium from 200 mOsm to 900 mOsm. Three spectral parameters are used to characterize the process of swelling or shrinkage of RBC-the absorbance at 700 nm, the Soret peak height relative to the spectrum background, and the Soret peak wavelength. We show that with an increase in the osmolarity, the absorbance at 700 nm increases and the Soret peak relative height decreases. These changes are related to the changes in the RBC volume and the resulting increase in the hemoglobin intracellular concentration and index of refraction. Confocal microscopy and flow cytometry measurements supported these conclusions. The maximum wavelength of the Soret peak increases with increasing osmolarity due to changes in the oxygenation state of hemoglobin. Using these spectrum parameters, the process of osmosis in RBCs can be followed in real time, but it can also be applied to various processes, leading to changes in the volume and shape of RBCs. Therefore, we conclude that UV-Vis absorption spectrophotometry offers a convenient, easily accessible, and cost-effective method to monitor changes in RBC, which can find applications in the field of drug discovery and diagnostics of RBC and hemoglobin disorders.

Recognition mechanisms of hemoglobin particles by monocytes - CD163 may just be one

Hemoglobin-based oxygen carriers (HBOCs) as blood substitutes are one of the great hopes of modern transfusion and emergency medicine. After the major safety-relevant challenges of the last decades seem to be largely overcome, current developments have in common that they are affected by degradation and excretion at an early stage in test organisms. Several possible mechanisms that may be responsible for this are discussed in the literature. One of them is CD163, the receptor of the complex of haptoglobin (Hp) and hemoglobin (Hb). The receptor has been shown in various studies to have a direct affinity for Hb in the absence of Hp. Thus, it seems reasonable that CD163 could possibly also bind Hb within HBOCs and cause phagocytosis of the particles. In this work we investigated the role of CD163 in the uptake of our hemoglobin sub-micron particles (HbMPs) in monocytes and additionally screened for alternative ways of particle recognition by monocytes. In our experiments, blockade of CD163 by specific monoclonal antibodies proved to partly inhibit HbMP uptake by monocytes. It appears, however, that several other phagocytosis pathways for HbMPs might exist, independent of CD163 and also Hb.

Hemolysis by Saponin Is Accelerated at Hypertonic Conditions

Saponins are a large group of organic amphiphilic substances (surfactants) mainly extracted from herbs with biological activity, considered as one of the main ingredients in numerous remedies used in traditional medicine since ancient times. Anti-inflammatory, antifungal, antibacterial, antiviral, antiparasitic, antitumor, antioxidant and many other properties have been confirmed for some. There is increasing interest in the elucidation of the mechanisms behind the effects of saponins on different cell types at the molecular level. In this regard, erythrocytes are a very welcome model, having very simple structures with no organelles. They react to changing external conditions and substances by changing shape or volume, with damage to their membrane ultimately leading to hemolysis. Hemolysis can be followed spectrophotometrically and provides valuable information about the type and extent of membrane damage. We investigated hemolysis of erythrocytes induced by various saponin concentrations in hypotonic, isotonic and hypertonic media using measurements of real time and end-point hemolysis. The osmotic pressure was adjusted by different concentrations of NaCl, manitol or a NaCl/manitol mixture. Unexpectedly, at a fixed saponin concentration, hemolysis was accelerated at hypertonic conditions, but was much faster in NaCl compared to mannitol solutions at the same osmotic pressure. These findings confirm the colloid-osmotic mechanism behind saponin hemolysis with pore formation with increasing size in the membrane.

Poly(2-ethyl-2-oxazoline)-Conjugated Hemoglobins as a Red Blood Cell Substitute

Hemoglobin wrapped covalently with poly(2-ethyl-2-oxazoline)s (POx-Hb) is characterized physicochemically and physiologically as an artificial O2 carrier for use as a red blood cell (RBC) substitute. The POx-Hb is generated by linkage of porcine Hb surface-lysines to a sulfhydryl terminus of the POx derivative, with the average binding number of the polymers ascertained as 6. The POx-Hb shows moderately higher colloid osmotic activity and O2 affinity than the naked Hb. Human adult HbA conjugated with POx also possesses equivalent features and O2 binding properties. The POx-Hb solution exhibits good hemocompatibility, with no influence on the functions of platelets, granulocytes, and monocytes. Its circulation half-life in rats is 14 times longer than that of naked Hb. Hemorrhagic shock in rats is relieved sufficiently by infusion of the POx-Hb solution, as revealed by improvements of circulatory parameters. Serum biochemistry tests and histopathological observations indicate no acute toxicity or abnormality in the related organs. All results indicate that POx-Hb represents an attractive alternative for RBCs and a useful O2 therapeutic reagent in transfusion medicine.

Two New Modifications of the InterCriteria Analysis

In the present work two modifications of the InterCriteria Analysis are proposed in order to extend its theoretical foundation. The results obtained from the application of these methods over real data (from patients with prostate carcinoma) have been analyzed to determine the reliability of the calculated consonance and dissonance. The similarity scores obtained by the modified versions of the InterCriteria Analysis are close to those given by the classical InterCriteria Analysis, as well as to the values of the correlation coefficients between the considered criteria. This shows the reliability of the proposed modification with respect to determining the consonance and dissonance between criteria in different problems.

Core-Shell Structured Hemoglobin Nanoparticles as Artificial O2 Carriers

This paper describes the synthesis and O₂ binding properties of core-shell structured hemoglobin (Hb) nanoparticles (NPs), artificial O₂ carriers of five types, as designed for use as red blood cell (RBC) substitutes. Human adult Hbs were polymerized using α-succinimidyl-ω-maleimide and dithiothreitol in spheroidal shapes to create parent particles. Subsequent covalent wrapping of the sphere with human serum albumin (HSA) yielded 100 nm-diameter Hb nanoparticles (HbNPs). The HbNP showed higher O₂ affinity than that of RBC, but NPs prepared under a N₂ atmosphere exhibited low O₂ affinity. Entirely synthetic particles comprising recombinant human adult Hb and recombinant HSA were also fabricated. Using a recombinant Hb (rHb) variant in which Leu-β28 of the heme pocket had been replaced with Phe, we found somewhat low O₂ affinity of rHb(βL28F)NP. Particles made of stroma-free Hb (SFHb) containing natural antioxidant enzyme catalase (SFHbNP) formed a very stable O₂ complex, even in aqueous H₂O₂ solution. The SFHbNP showed good blood compatibility and did not affect the blood cell component functionality. The circulation half-life of SFHbNP in rats was considerably longer than that of naked Hb. All results indicate these Hb-based NPs as useful alternative materials for RBC and as a useful O₂ therapeutic reagent in diverse medical scenarios.

Our Clinical Experience in the Treatment of Myasthenia Gravis Acute Exacerbations with a Novel Nanomembrane-Based Therapeutic Plasma Exchange Technology

According to the American Academy of Neurology 2011 guidelines, there is insufficient evidence to support or refute the use of therapeutic plasma exchange (TPE) for myasthenia gravis (MG). The goal of this study was to determine whether a novel nanomembrane-based TPE could be useful in the treatment of MG. Thirty-six adult patients, MGFA 4/4B and 5, with acute MG episodes were enrolled into a single-center retrospective before-and-after study to compare a conventional treatment group (n = 24) with a nanomembrane-based TPE group (n = 12). TPE or intravenous immunoglobulins (IVIG) infusions were used in impending/manifested myasthenic crises, especially in patients at high-risk for prolonged invasive ventilation (IMV) and in those tolerating non-invasive ventilation (NIV). The clinical improvement was assessed using the Myasthenia Muscle Score (0–100), with ≥20 increase for responders. The primary outcome measures included the rates of implemented TPE, IVIG, and corticosteroids immunotherapies, NIV/IMV, early tracheotomy, MMS scores, extubation time, neuro-ICU/hospital LOS, complications, and mortality rates. The univariate analysis found that IMV was lower in the nanomembrane-based group (42%) compared to the conventional treatment group (83%) (p = 0.02). The multivariate analysis using binary logistic regression revealed TPE and NIV as independent predictors for short-term (≤7 days) respiratory support (p = 0.014 for TPE; p = 0.002 for NIV). The novel TPE technology moved our clinical practice towards proactive rather than protective treatment in reducing prolonged IMV during MG acute exacerbations.

Bacterial safety study of the production process of hemoglobin-based oxygen carriers

Hemoglobin microparticles (HbMP) produced with a three-step procedure, including coprecipitation of hemoglobin with manganese carbonate, protein cross-linking, and dissolution of the carbonate template were shown to be suitable for application as artificial oxygen carriers. First preclinical safety investigations delivered promising results. Bacterial safety plays a decisive role during the production of HbMP. Therefore, the bioburden and endotoxin content of the starting materials (especially hemoglobin) and the final particle suspension are intensively tested. However, some bacteria may not be detected by standard tests due to low concentration. The aim of this study was to investigate how these bacteria would behave in the fabrication process. Biocidal effects are known for glutaraldehyde and for ethylenediaminetetraacetic acid, chemicals that are used in the fabrication process of HbMP. It was shown that both chemicals prevent bacterial growth at the concentrations used during HbMP fabrication. In addition, the particle production was carried out with hemoglobin solutions spiked with Escherichia coli or Staphylococcus epidermidis. No living bacteria could be detected in the final particle suspensions. Therefore, we conclude that the HbMP fabrication procedure is safe in respect of bacterial contamination.

Study of rs10177833 polymorphism in SLC4A5 gene and salt sensitivity in Bulgarian population

 

High sodium intake is associated with increased blood pressure and and increased risk of cardiovascular disease (CVD). Among the countries of the European Union, Bulgaria ranks first in mortality from CVD. Genetically determined salt sensitivity is present in 50% of the hypertensive and 26% of the normotensive population, posing a major public health problem. The present study was conducted within the National Program for Prevention of Chronic Non-Communicable Diseases 2014 - 2020 to assess the sodium intake of the population in Bulgaria. 36 normotensive participants are included in the study. DNA from each volunteers was isolated and genotyped for rs10177833 (A>C) in SLC4A5 gene by TaqMan SNP genotyping assay. To determine the 24-hour urinary excretion of sodium in the subjects, a random sample was taken from each participant. Sodium concentration was determined by atomic absorption spectrometry. A WHO protocol has been used to recalculate sodium excretion (Protocol for Sodium Determination in 24-hour Urine Samples). Eighteen of total of 35 participants had wild AA genotype (51.43%), thirteen were heterozygotes (37.14%) and four were carriers of two polymorphic C alleles (11.43%). The frequency of A allele of rs10177833 (A>C) in SLC4A5 gene was 70%, whereas polymorphic C allele was only 30%. The correlation analysis showed negative statistical significant relationship between rs10177833 in SLC4A5 gene and sodium concentration (in milligrams) in 24 - hours urine (r = -0.365, p = 0.031). Also the holders of CC genotype had significant lower values of Na compared to these with wild AA genotype (p = 0.01) and compared to heterozygotes (p = 0.019). In conclusion, we found a clear relationship between the polymorphic variant rs10177833 in SLC4A5 gene and the concentration of sodium in urine in Bulgarian normotensives. The tendency of association was found between the studied polymorphic variant and blood pressure values, which should be studied in a large number of participants

Key messages

Increasing the population's awareness of health risks with increased salt consumption. Regular monitoring of salt consumption.

Targeted Propolis-Loaded Poly (Butyl) Cyanoacrylate Nanoparticles: An Alternative Drug Delivery Tool for the Treatment of Cryptococcal Meningitis

In this study, we describe a nano-carrier system for propolis that is able to cross an in vitro model of the blood-brain barrier (BBB) and effectively reduce the virulence of Cryptococcus neoformans in animal models. Antimicrobial properties of propolis have been widely studied. However, propolis applications are limited by its low water solubility and poor bioavailability. Therefore, we recently formulated novel poly (n-butyl cyanoacrylate) nanoparticles (PBCA-NP) containing propolis. PBCA-NP are biocompatible, biodegradable and have been shown to effectively cross the BBB using apolipoprotein E (ApoE) as a ligand. Prepared nanoparticles were characterized for particle size, zeta potential, propolis entrapment efficiency and in vitro release. Additionally, the PBCA-NP were functionalized with polysorbate 80, which then specifically adsorbs ApoE. Using an in vitro BBB model of human brain microvascular endothelial cells hCMEC/D3, it was shown that fluorescence labelled ApoE-functionalized PBCA-NP were internalized by the cells and translocated across the cell monolayer. Propolis-loaded PBCA-NP had in vitro, antifungal activity against C. neoformans, which causes meningitis. To utilize the invertebrate model, Galleria mellonella larvae were infected with C. neoformans and treated with propolis-loaded PBCA-NP. The larvae exhibited normal behavior in toxicity testing, and treatment with propolis-loaded PBCA-NP increased survival in the C. neoformans-infected larvae group. In addition, following cryptococcal infection and then 7 days of treatment, the tissue fungal burden of mice treated with propolis-loaded PBCA-NP was significantly lower than control groups. Therefore, our ApoE-functionalized propolis-loaded PBCA-NP can be deemed as a potential targeted nanoparticle in the therapeutic treatment of cerebral cryptococcosis.

Determination of Methemoglobin in Hemoglobin Submicron Particles Using NMR Relaxometry

Methemoglobin (MetHb) is a hemoglobin (Hb) derivative with the heme iron in ferric state (Fe³⁺), unable to deliver oxygen. Quantification of methemoglobin is a very important diagnostic parameter in hypoxia. Recently, novel hemoglobin microparticles (Hb-MP) with a narrow size distribution around 700 nm, consisting of cross-linked Hb were proposed as artificial oxygen carriers. The cross-linking of Hb by glutaraldehyde (GA) generates a certain amount of MetHb. Due to the strong light scattering, quantitative determination of MetHb in Hb-MP suspensions by common spectrophotometry is not possible. Here, we demonstrate that ¹H₂O NMR relaxometry is a perfect tool for direct measurement of total Hb and MetHb concentrations in Hb-MP samples. The longitudinal relaxation rate 1/T₁ shows a linear increase with increasing MetHb concentration, whereas the transverse relaxation rate 1/T₂ linearly increases with the total Hb concentration. In both linear regressions the determination coefficient (R²) is higher than 0.99. The method does not require time-consuming pretreatment or digestion of the particles and is not impaired by light scattering. Therefore, it can be established as the method of choice for the quality control of Hb-MP and similar hemoglobin-based oxygen carriers in the future.

Doxorubicin-Loaded Human Serum Albumin Submicron Particles: Preparation, Characterization and In Vitro Cellular Uptake

Doxorubicin (DOX) is an effective anthracycline antibiotic drug which is commonly used in a broad range cancer therapy. However, due to dose depending side effects and toxicity to non-cancerous tissues, its clinical applications are restricted. To overcome these limitations, human serum albumin (HSA) has been investigated as a biocompatible drug delivery vehicle. In this study, human serum albumin submicron particles (HSA-MPs) were fabricated by using the Co-precipitation–Crosslinking–Dissolution technique (CCD technique) and DOX was loaded into the protein particles by absorption. DOX-HSA-MPs showed uniform peanut-like shape, submicron size and negative zeta-potential (−13 mV). The DOX entrapment efficiency was 25% of the initial amount. The in vitro release in phosphate buffered saline pH 7.4 was less than 1% within 5 h. In contrast, up to 40% of the entrapped DOX was released in presence of a protein digesting enzyme mixture (Pronase^®) within the same time. In addition, in vitro cytotoxicity and cellular uptake of DOX-HSA-MPs were evaluated using the lung carcinoma cell line A549. The results demonstrated that DOX-HSA-MPs reduced the cell metabolic activities after 72 h. Interestingly, DOX-HSA-MPs were taken up by A549 cells up to 98% and localized in the cell lysosomal compartment. This study suggests that DOX-HSA-MPs which was fabricated by CCD technique is seen as a promising biopolymer particle as well as a viable alternative for drug delivery application to use for cancer therapy.

Detection of CD33 expression on monocyte surface is influenced by phagocytosis and temperature

CD33 is a myeloid-associated marker and belongs to the sialic acid-binding immunoglobulin (Ig)-like lectin (Siglec) family. Such types of receptors are highly expressed in acute myeloid leukemia, which could be used in its treatment. CD33 shows high variability in its expression levels with still unknown reasons. Here, we investigated the CD33 expression of monocytes in human blood samples processed at different temperatures and in dependence on their phagocytic activity against opsonized Escherichia coli. The samples were stained by fluorescently labelled anti-human CD14 to specify the monocyte population, anti-human CD33 antibodies to evaluate CD33 expression and analyzed by flow cytometry and confocal laser scanning microscopy. In blood samples kept at 37°C or first pre-chilled at 0°C with subsequent warming up to 37°C, the percentage of CD33-positive monocytes as well as their relative fluorescence intensity was up-regulated compared to samples kept constantly at 0°C. After exposure to E. coli the CD33 relative fluorescence intensity of the monocytes activated at 37°C was 3 to 4 times higher than that of those cells kept inactive at 0°C. Microscopic analysis showed internalisation of CD33 due to its enhanced expression on the surface followed by engulfment of E. coli.

In-vitro haemocompatibility of dextran-protein submicron particles

Blood compatibility is a key requirement to fulfil for intravenous administration of drug and oxygen carrier system. Recently, we published the fabrication of oxidised-dextran (Odex)-crosslinked protein particles by one-pot formulation. In the current study we investigate the haemocompatibility of these Odex - particles including albumin particles (Odex-APs) and haemoglobin particles (Odex-HbMPs). Odex-APs and Odex-HbMPs have a submicron size ranged 800-1000 nm with peanut-like shape and a negative surface charge. In vitro haemocompatibility assays included haemolysis test, indirect phagocytosis test and platelet activation test in human blood. Odex-APs and Odex-HbMPs did not provoke any undesirable effects on the blood cells. Firstly, the ratio of haemolysis after contacted with Odex-crosslinked protein particles were less than 5% and therefore the particles may be considered non-haemolytic. Secondly, the incubation of leukocyte with Odex-APs/HbMPs did not influence the phagocytosis of leukocyte. We conclude that our particles are not recognized by monocytes or granulocytes. Finally, exposure of Odex-APs/HbMPs to platelets did not cause an activation of platelets. Additionally, Odex-HbMP/AP did not enhance or attenuate agonist-induced platelet activation. We conclude that Odex-crosslinked protein particles exhibit a very good haemocompatibility and represent highly promising carriers for drugs or oxygen.

Albumin Submicron Particles with Entrapped Riboflavin-Fabrication and Characterization

Although riboflavin (RF) belongs to the water-soluble vitamins of group B, its solubility is low. Therefore, the application of micro-formulations may help to overcome this limiting factor for the delivery of RF. In this study we immobilized RF in newly developed albumin submicron particles prepared using the Co-precipitation Crosslinking Dissolution technique (CCD-technique) of manganese chloride and sodium carbonate in the presence of human serum albumin (HSA) and RF. The resulting RF containing HSA particles (RF-HSA-MPs) showed a narrow size distribution in the range of 0.9 to 1 μm, uniform peanut-like morphology, and a zeta-potential of -15 mV. In vitro release studies represented biphasic release profiles of RF in a phosphate buffered saline (PBS) pH 7.4 and a cell culture medium (RPMI) 1640 medium over a prolonged period. Hemolysis, platelet activation, and phagocytosis assays revealed a good hemocompatibility of RF-HSA-MPs.

Drug Exchange between Albumin Nanoparticles and Erythrocyte Membranes

The effects of thioridazine (TDZ) and chlorpromazine (CPZ) and bovine serum albumin nanoparticles (BSA-NPs) on erythrocyte membranes have been investigated. Two kinds of hemolytic assays were used; hemolysis under hypotonic conditions and hemolysis in physiological conditions. Under hypotonic conditions for 50% hemolysis, both TDZ and CPZ have a biphasic effect on membranes; namely, stabilization at low concentrations and destabilization after reaching a critical concentration. In physiological conditions, there are other critical concentrations above which both drugs hemolyse the erythrocites. In each case, the critical concentrations of TDZ are lower than those of CPZ, which is consistent with the ratio of their partition coefficients. When BSA-NPs are added to the erythrocyte suspension simultaneously with the drugs, the critical concentrations increase for both drugs. The effect is due to the incorporation of a portion of drug substances into the BSA-nanoparticles, which consequently leads to the decrease of the active drug concentrations in the erythrocyte suspension medium. Similar values of the critical concentrations are found when the BSA-NPs are loaded with the drugs before their addition to the erythrocyte suspension in which case the events of the partition are: desorption of the drug from BSA-NPs, diffusion through the medium, and adsorption on erythrocyte membranes. This result suggests that the drugs are not influenced by the processes of adsorption and desorption onto and out of the BSA-NPs, and that the use of BSA-NPs as drug transporters would allow intravenous administration of higher doses of the drug without the risk of erythrocyte hemolysis.

Antioxidative protection of haemoglobin microparticles (HbMPs) by PolyDopamine

Clinically applicable haemoglobin-based oxygen carriers (HBOCs) should neither induce immunological nor toxic reactions. Additionally, Hb should be protected against oxidation. In the absence of protective enzymes (superoxide dismutase (SOD) and catalase (CAT)) Hb is oxidized to MetHb and thus losing its function of oxygen delivery. Alternatively, polydopamine (PD), a scavenger of free radicals, could be used for Hb protection against oxidation Therefore, we synthetized HbMPs modified with PD. The content of functional haemoglobin in these PD-HbMPs was twice higher than that in the control HbMPs due to the protective antioxidant effect of PD. In addition, the PD-HbMPs exhibited a high scavenging activity of free radicals including H₂O₂ and excellent biocompatibility. In contrast to monomeric dopamine, which has been shown to produce toxic effects on neurons due to formation of H₂O₂, hydroxyl radicals and superoxide during the process of auto-oxidation, PD-HbMPs are not neurotoxic. Consequently, the results presented here suggest a great potential of PD-HbMPs as HBOCs.

Inflammatory activation of human serum albumin- or ovalbumin-modified chitosan particles to macrophages and their immune response in human whole blood

Chitosan particles modified with different albumins cause immune response in human whole blood via platelet activation and phagocytosis.

Structure and properties of hybrid biopolymer particles fabricated by co-precipitation cross-linking dissolution procedure

The Co-precipitation Crosslinking Dissolution technique (CCD-technique) allows a few-steps fabrication of particles composed of different biopolymers and bioactive agents under mild conditions. Morphology and properties of the fabricated biopolymer particles depend on the fabrication conditions, the nature of the biopolymers and additives, but also on the choice of the inorganic templates for co-precipitation. Here, we investigate the influence of an acidic biopolymer, hyaluronic acid (HA), on the formation of particles from bovine hemoglobin and bovine serum albumin applying co-precipitation with CaCO₃ and MnCO₃. CaCO₃ templated biopolymer particles are almost spherical with particle size from 2 to 20 µm and protein entrapment efficiency from 13 to 77%. Presence of HA causes significant structural changes of the particles and decreasing protein entrapment efficiency. In contrast, MnCO₃ templated particles exhibit uniform peanut shape and submicron size with remarkably high protein entrapment efficiency of nearly 100%. Addition of HA has no influence on the protein entrapment efficiency or on morphology and size of the particles. These effects can be attributed to the strong interaction of Mn²⁺ with proteins and much weaker interaction with HA. Therefore, entrapment efficiency, size and structure of biopolymer particles can be optimized by varying the mineral templates and additives.

Effects of heat and freeze on isolated erythrocyte submembrane skeletons

In this study we heated insoluble residues, obtained after Triton-X-100 (0.1 v/v%) extraction of erythrocyte ghost membranes (EGMs). Specific heat capacity, electric capacitance and resistance, and optical transmittance (280 nm) sustained sharp changes at 49°C (TA) and 66°C (TC), the known denaturation temperatures of spectrin and band 3, respectively. The change at TA was selectively inhibited by diamide (1 mM) and taurine mustard (1 mM) while its inducing temperature was selectively decreased by formamide in full concert with the assumed involvement of spectrin denaturation. In the residues of EGMs, pretreated with 4,4'-diiso-thiocyanato stilbene-2,2'-disulfonic acid (DIDS), the change at TC was shifted from 66 to 78°C which indicated the involvement of band 3 denaturation. The freeze and rapid thaw of EGM residues resulted in a strong reduction of cooperativity of band 3 denaturation while the slow thaw completely eliminated the peak of this denaturation. These effects of freeze-thaw were prevented in residues obtained from DIDS-treated EGMs. The freeze-thaw of residues slightly affected spectrin denaturation at 49°C although an additional denaturation appeared at 55°C. The results indicate preserved molecular structure and dynamics of the membrane skeleton in Triton-X-100 extracts of EGMs. The freeze-thaw inflicted strong damage on band 3 and spectrin-actin skeleton of EGM extracts which is relevant to cryobiology, cryosurgery and cryopreservation of cells.

RBC aggregation in dextran solutions can be measured by flow cytometry

The impact of macromolecules on RBC aggregation continues to be of interest, nevertheless present measurements still have limitations and need improvement. We applied flow cytometry to measure RBC aggregation in dextran T500 (Dx500) solution. The samples were fixed in the aggregated state by glutaraldehyde. Fixed RBC exhibit auto fluorescence, which can be detected by flow cytometry. Single cells, doublets, triplets and larger aggregates can be distinguished quantitatively and quickly due to the correlation between auto fluorescence intensity and number of RBC per measured event. With the increase in concentration of Dx500, percentages of all aggregates and bigger aggregates increased significantly at concentration of 2%, 4% and 6%, while decreased when the concentration reached 8% and 10%. The percentage of bigger aggregates in concentration of 4% was higher than that in 2% and 6%. The data of flow cytometry was confirmed by microscopic observation and are in good agreement with the literature. The method provide additional advantages to the conventional measurement of RBC aggregation. It gets the distribution of single cells and aggregates as derived from the microscopic observation with hematocrit of physiological level. It uses sample volume as 1/5∼1/10 as needed in sendimentation and photometricmethods.

On the molecular interaction between albumin and ibuprofen: An AFM and QCM-D study

The adsorption of proteins on surfaces often results in a change of their structural behavior and consequently, a loss of bioactivity. One experimental method to study interactions on a molecular level is single molecular force spectroscopy that permits to measure forces down to the pico-newton range. In this work, the binding force between human serum albumin (HSA), covalently immobilized on glutaraldehyde modified gold substrates, and ibuprofen sodium salt was studied by means of single molecular force spectroscopy. First of all, a protocol was established to functionalize atomic force microscopy (AFM) tips with ibuprofen. The immobilization protocol was additionally tested by quartz crystal microbalance with dissipation (QCM-D) and contact angle measurements. AFM was used to characterize the adsorption of HSA on gold substrates, which lead to a packed monolayer of thickness slightly lower than the reported value in solution. Finally, single molecule spectroscopy results were used to characterize the binding force between albumin and ibuprofen and calculate the distance of the transition state (0.6 nm) and the dissociation rate constant (0.055 s(-1)). The results might indicate that part of the adsorbed protein still preserves its functionality upon adsorption.

Docosahexaenoic acid promotes micron scale liquid-ordered domains. A comparison study of docosahexaenoic versus oleic acid containing phosphatidylcholine in raft-like mixtures

The understanding of the functional role of the lipid diversity in biological membranes is a major challenge. Lipid models have been developed to address this issue by using lipid mixtures generating liquid-ordered (Lo)/liquid-disordered (Ld) immiscibility. The present study examined mixtures comprising Egg sphingomyelin (SM), cholesterol (chol) and phosphatidylcholine (PC) either containing docosahexaenoic (PDPC) or oleic acid (POPC). The mixtures were examined in terms of their capability to induce phase separation at the micron- and nano-scales. Fluorescence microscopy, electron spin resonance (ESR), X-ray diffraction (XRD) and calorimetry methods were used to analyze the lateral organization of the mixtures. Fluorescence microscopy of giant vesicles could show that the temperature of the micron-scale Lo/Ld miscibility is higher for PDPC than for POPC ternary mixtures. At 37°C, no micron-scale Lo/Ld phase separation could be identified in the POPC containing mixtures while it was evident for PDPC. In contrast, a phase separation was distinguished for both PC mixtures by ESR and XRD, indicative that PDPC and POPC mixtures differed in micron vs nano domain organization. Compared to POPC, the higher line tension of the Lo domains observed in PDPC mixtures is assumed to result from the higher difference in Lo/Ld order parameter rather than hydrophobic mismatch.

Immobilization of water-soluble HRP within poly-N-isopropylacrylamide microgel particles for use in organic media

In the present work, the immobilization of enzymes within poly-N-isopropylacrylamide (p-NIPAM) microgels using the method of solvent exchange is applied to the enzyme horseradish peroxidase (HRP). When the solvent is changed from water to isopropanol, HRP is embedded within the polymer structure. After the determination of the immobilized amount of enzyme, an enhanced specific activity of the biocatalyst in isopropanol can be observed. Karl Fischer titration is used to determine the amount of water within the microgel particles before and after solvent exchange, leading to the conclusion that an "aqueous cage" remains within the polymer structure. This represents the driving force for the immobilization due to the high affinity of HRP for water. Beside, confocal laser scanning microscopy (CLSM) images show that HRP is located within the microgel network after immobilization. This gives the best conditions for HRP to be protected against chemical and mechanical stress. We were able to transfer a water-soluble enzyme to an organic phase by reaching a high catalytic activity. Hence, the method of solvent exchange displays a general method for immobilizing enzymes within p-NIPAM microgels for use in organic solvents. With this strategy, enzymes that are not soluble in organic solvents such as HRP can be used in such polar organic solvents.

Kinetics and efficiency of a methyl-carboxylated 5-Fluorouracil-bovine serum albumin adduct for targeted delivery

5-Fluorouracil (5-FU) is a clinically well-established anti-cancer drug effectively applied in chemotherapy, mainly for the treatment of breast and colorectal cancer. Substantial disadvantages are adverse effects, arising from serious damage of healthy tissues, and shortcoming pharmacokinetics due to its low molecular weight. A promising approach for improvement of such drugs is their coupling to suitable carriers. Here, a 5-FU adduct, 5-fluorouracil acetate (FUAc) is synthesized and covalently coupled to bovine serum albumin (BSA) as model carrier molecule. On average, 12 molecules FUAc are bound to one BSA. Circular dichriosm (CD)-spectra of BSA and FUAc-BSA are identical, suggesting no significant conformational differences. FUAc-BSA is tested on T-47D and MDA-MB-231 breast cancer cells. Proliferation inhibition of membrane albumin-binding protein (mABP)-expressing T-47D cells by FUAc-BSA is similar to that of 5-FU and only moderate for MDA-MB-231 cells that lack such expression. Therefore, a crucial role of mABP expression in effective cell growth inhibition by FUAc-BSA is assumed.

Nonvasoconstrictive hemoglobin particles as oxygen carriers

Artificial oxygen carriers, favorably hemoglobin-based oxygen carriers (HBOCs), are being investigated intensively during the last 30 years with the aim to develop a universal blood substitute. However, serious side effects mainly caused by vasoconstriction triggered by nitric oxide (NO) scavenging due to penetration of nanosized HBOCs through the endothelial gaps of the capillary walls and/or oxygen oversupply in the precapillary arterioles due to their low oxygen affinity led to failure of clinical trials and FDA disapproval. To avoid these effects, HBOCs with a size between 100 and 1000 nm and high oxygen affinity are needed. Here we present for the first time unique hemoglobin particles (HbPs) of around 700 nm with high oxygen affinity and low immunogenicity using a novel, highly effective, and simple technique. The fabrication procedure provides particles with a narrow size distribution and nearly uniform morphology. The content of hemoglobin (Hb) in the particles corresponded to 80% of the Hb content in native erythrocytes. Furthermore, we demonstrate a successful perfusion of isolated mouse glomeruli with concentrated HbP suspensions in vitro. A normal, nonvasoconstrictive behavior of the afferent arterioles is observed, suggesting no oxygen oversupply and limited NO scavenging by these particles, making them a highly promising blood substitute.

Hemoglobin-based oxygen carrier microparticles: synthesis, properties, and in vitro and in vivo investigations

Bovine hemoglobin microparticles (Hb-MPs) as suitable oxygen carriers are fabricated easily by three key steps: coprecipitation of Hb and CaCO(3) to make Hb-CaCO(3)-microparticles (Hb-CaCO(3)-MPs), cross-linking by glutaraldehyde (GA) to polymerize the Hb and dissolution of CaCO(3) template to obtain pure Hb-MPs. The Hb entrapment efficiency ranged from 8 to 50% corresponding to a hemoglobin quantity per Hb-MP of at least one-third of that in one erythrocyte. The Hb-MPs are spherical, with an average diameter of 3.2 μm and high oxygen affinity. The methemoglobin level was increased after preparation, but can be reduced to less than 7% with ascorbic acid. Phagocytosis assays showed low immunogenicity of Hb-MPs if the particles were cross-linked with low concentration of GA and treated with sodium borohydride. Magnetite-loaded Hb-MPs circulated up to 4 days after intravenous application.

Temperature Controlled Activity of Lipase B from Candida Antarctica after Immobilization within p-NIPAM Microgel Particles

The immobilization of lipase B from Candida antarctica (CalB) within micronsized poly-N-Isopropylacrylamide (p-NIPAM) microgel particles with a crosslinker content of 5% is reported. The immobilization of the enzyme was reached by an exchange from polar to organic solvents. After determining the embedded amount of CalB within the polymer network, an enhanced specific activity in n-hexane was obtained. Due to the thermoresponsibility of the polymer particles, the activity reaction was done at 25 ºC and 50 ºC. The results presented show that the reversible collapse of the microgel leads to a decreased activity with increasing temperature. Hence, p-NIPAM microgels display a good opportunity to tailor the activity of CalB. An interesting side effect is that CalB presents a suitable probe to estimate the mesh size of the polymer network, since it penetrates in the unlabeled form but not after labeling with FITC.

Nanoplasmonics for dual-molecule release through nanopores in the membrane of red blood cells

A nanoplasmonics-based opto-nanoporation method of creating nanopores upon laser illumination is applied for inducing diffusion and triggered release of small and large molecules from red blood cells (RBCs). The method is implemented using absorbing gold nanoparticle (Au-NP) aggregates on the membrane of loaded RBCs, which, upon near-IR laser light absorption, induce release of encapsulated molecules from selected cells. The binding of Au-NPs to RBCs is characterized by Raman spectroscopy. The process of release is driven by heating localized at nanoparticles, which impacts the permeability of the membrane by affecting the lipid bilayer and/or trans-membrane proteins. Localized heating and temperature rise around Au-NP aggregates is simulated and discussed. Research reported in this work is relevant for generating nanopores for biomolecule trafficking through polymeric and lipid membranes as well as cell membranes, while dual- and multi-molecule release is relevant for theragnostics and a wide range of therapies.

Antibiotic susceptibility of different lactic acid bacteria strains

Five lactic acid bacteria (LAB) strains belonging to species Lactobacillus acidophilus, Lactobacillus helveticus, Lactobacillus delbrueckii subsp. bulgaricus, Lactobacillus delbrueckii subsp. lactis and Streptococcus thermophilus were tested for their susceptibility to 27 antibiotics. The minimum inhibitory concentrations of each antimicrobial were determined using a microdilution test. Among the strains a high susceptibility was detected for most of the cell-wall synthesis inhibitors (penicillins, cefoxitin and vancomycin) and resistance toward inhibitors of DNA synthesis (trimethoprim/sulfonamides and fluoroquinolones). Generally, the Lactobacillus strains were inhibited by antibiotics such as chloramphenicol, erythromycin and tetracycline at breakpoint levels lower or equal to the levels defined by the European Food Safety Authority. Despite the very similar profile of S. thermophilus LC201 to lactobacilli, the detection of resistance toward erythromycin necessitates the performance of additional tests in order to prove the absence of transferable resistance genes.

In vitro inhibition of fungal activity by macrophage-mediated sequestration and release of encapsulated amphotericin B nanosupension in red blood cells

The efficacy of antifungal treatment has been diminished by the biodistribution limitations of amphotericin B (AmB) due to its pharmacological profile, as well as the severe side effects it causes. A cellular drug-delivery system, which incorporates human erythrocytes (RBCs) loaded with an AmB nanosuspension (AmB-NS), is developed in order to improve antifungal treatment. AmB-NS encapsulation in RBCs is achieved by using hypotonic hemolysis, leading to intracellular AmB amounts of 3.81 +/- 0.47 pg RBC(-1) and an entrapment efficacy of 15-18%. Upon phagocytosis of AmB-NS-RBCs, leukocytes show a slow AmB release over ten days, and no alteration in cell viability. This results in an immediate, permanent inhibition of intra- and extracellular fungal activity. AmB-NS-RBC-leukocyte-mediated delivery of AmB is efficient in amounts 1000 times lower than the toxic dose. This drug-delivery method is effective for the transport of water-insoluble substances, such as AmB, and this warrants consideration for further testing.