The inhibition mechanism of ϵ-polylysine against Bacillus cereus emerging in surimi gel during refrigerated storage

BACKGROUND

Refrigeration is commonly used in the processing and storage of surimi products. However, refrigerated surimi products are susceptible to microbial contamination, which leads to deterioration of the products and shortens their shelf life. The aims of the present study were therefore to evaluate the effects of ϵ-polylysine (ϵ-PL) on spoilage bacteria in surimi products, and to investigate the antibacterial mechanism of Bacillus cereus, which is the dominant spoilage bacterium.

RESULTS

ϵ-Polylysine with a high degree of polymerization (20-30K) proved able to decrease the total number of colonies in surimi products and showed an obvious antibacterial effect against B. cereus. After ϵ-PL treatments, the distinct broken areas on the bacterial surfaces and the aggregations of cells were observed by scanning electron microscope (SEM). The intracellular materials, such as small molecules, soluble proteins, and deoxyribonucleic acids in the cells were analyzed, which revealed the destructive effects of ϵ-PL on bacterial cells. Experiments with propidium iodide (PI) infiltration experiments verified that the permeability of cell membranes was enhanced by ϵ-PL treatment.

CONCLUSION

These results indicated that ϵ-PL could destroy the cell membranes and change the permeability of B. cereus, and subsequently the cell contents leaked out to achieve antibacterial effects. © 2018 Society of Chemical Industry.

Detection of DNA and poly-l-lysine using CVD graphene-channel FET biosensors

A graphene channel field-effect biosensor is demonstrated for detecting the binding of double-stranded DNA and poly-l-lysine. Sensors consist of chemical vapor deposition graphene transferred using a clean, etchant-free transfer method. The presence of DNA and poly-l-lysine are detected by the conductance change of the graphene transistor. A readily measured shift in the Dirac voltage (the voltage at which the graphene's resistance peaks) is observed after the graphene channel is exposed to solutions containing DNA or poly-l-lysine. The 'Dirac voltage shift' is attributed to the binding/unbinding of charged molecules on the graphene surface. The polarity of the response changes to positive direction with poly-l-lysine and negative direction with DNA. This response results in detection limits of 8 pM for 48.5 kbp DNA and 11 pM for poly-l-lysine. The biosensors are easy to fabricate, reusable and are promising as sensors of a wide variety of charged biomolecules.

Alginate encapsulation parameters influence the differentiation of microencapsulated embryonic stem cell aggregates

Pluripotent embryonic stem cells (ESCs) have tremendous potential as tools for regenerative medicine and drug discovery, yet the lack of processes to manufacture viable and homogenous cell populations of sufficient numbers limits the clinical translation of current and future cell therapies. Microencapsulation of ESCs within microbeads can shield cells from hydrodynamic shear forces found in bioreactor environments while allowing for sufficient diffusion of nutrients and oxygen through the encapsulation material. Despite initial studies examining alginate microbeads as a platform for stem cell expansion and directed differentiation, the impact of alginate encapsulation parameters on stem cell phenotype has not been thoroughly investigated. Therefore, the objective of this study was to systematically examine the effects of varying alginate compositions on microencapsulated ESC expansion and phenotype. Pre-formed aggregates of murine ESCs were encapsulated in alginate microbeads composed of a high or low ratio of guluronic to mannuronic acid residues (High G and High M, respectively), with and without a poly-L-lysine (PLL) coating, thereby providing four distinct alginate bead compositions for analysis. Encapsulation in all alginate compositions was found to delay differentiation, with encapsulation within High G alginate yielding the least differentiated cell population. The addition of a PLL coating to the High G alginate prevented cell escape from beads for up to 14 days. Furthermore, encapsulation within High M alginate promoted differentiation toward a primitive endoderm phenotype. Taken together, the findings of this study suggest that distinct ESC expansion capacities and differentiation trajectories emerge depending on the alginate composition employed, indicating that encapsulation material physical properties can be used to control stem cell fate.

Sensitivity of protein adsorption to architectural variations in a protein-resistant polymer brush containing engineered nanoscale adhesive sites

Patchy polymer brushes contain nanoscale (5-15 nm) adhesive elements, such as polymer coils or nanoparticles, embedded at their base at random positions on the surface. The competition between the brush's steric (protein resistant) repulsions and the attractions from the discrete adhesive elements provides a precise means to control bioadhesion. This differs from the classical approach, where functionality is placed on the brush's periphery. The current study demonstrates the impact of poly(etheylene glycol) (PEG) brush architecture and ionic strength on fibrinogen adsorption on brushes containing embedded poly-l-lysine (PLL, 20K MW) coils or "patches". The consistent appearance of a fibrinogen adsorption threshold, a minimum loading of patches on the surface, below which protein adsorption does not occur, suggests multivalent protein capture: Adsorbing proteins simultaneously engage several patches. The surface composition (patch loading) at the threshold is extremely sensitive to the brush height and ionic strength, varying up to a factor of 5 in the surface loading of the PLL patches (~50% of the range of possible surfaces). Variations in ionic strength have a similar effect, with the smallest thresholds seen for the largest Debye lengths. While trends with brush height were the clearest and most dominant, consideration of the PEG loading within the brush or its persistence length did not reveal a critical brush parameter for the onset of adsorption. The lack of straightforward correlation on brush physics was likely a result of multivalent binding, (producing an additional dependence on patch loading), and might be resolved for univalent adsorption onto more strongly binding patches. While studies with similar brushes placed uniformly on a surface revealed that the PEG loading within the brush is the best indicator of protein resistance, the current results suggest that brush height is more important for patchy brushes. Likely the interactions producing brush extension normal to the interface act similarly to drive lateral tether extension to obstruct patches.

Investigation of sensing mechanism and signal amplification in carbon nanotube based microfluidic liquid-gated transistors via pulsating gate bias

The advent of a carbon nanotube liquid-gated transistor (LGFET) for biosensing applications allows the possibility of real-time and label-free detection of biomolecular interactions. The use of an aqueous solution as dielectric, however, has traditionally restricted the operating gate bias (VG) within |VG| < 1 V, due to the electrolysis of water. Here, we propose pulsed-gating as a facile method to extend the operation window of LGFETs to |VG| > 1 V. A comparison between simulation and experimental results reveals that at voltages in excess of 1 V, the LGFET sensing mechanism has a contribution from two factors: electrostatic gating as well as capacitance modulation. Furthermore, the large IDS drop observed in the |VG| > 1 V region indicates that pulsed-gating may be readily employed as a simple method to amplify the signal in the LGFET and pushes the detection limit down to attomolar concentration levels, an order of magnitude improvement over conventionally employed DC VG biasing.

Matrix/analyte ratio influencing polymer molecular weight distribution in matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) has been used to characterize poly(L-lysine) polymers and unique oligomer peptides, like 10-, 15- and 25-mer [Lys]n oligolysine peptides. Several matrices have been tried in order to find optimal conditions, but only alpha-cyano-4-hydroxycinnamic acid gave analytically useful spectra. The synthetic oligomers and their mixtures gave good quality spectra, showing protonated and cationized molecules, including doubly charged species. The polymers, analogously, gave a wide distribution of single- and double-cationized peak series. The polymer distributions observed indicate the presence of significant suppression effects. The concentration (matrix/analyte ratio) was found to influence the results significantly; distributions shifting to higher masses when higher polymer concentrations were used. This effect was studied in detail using the synthetic ('monodisperse') oligolysine peptides. It was found that the relative intensities change by over an order of magnitude in the 0.1-10 pmol/microL concentration range (typical for most proteomic analyses). The results indicate that concentration effects need to be considered when MALDI-MS is used for quantitative purposes.

Non-invasive evaluation of alginate/poly-l-lysine/alginate microcapsules by magnetic resonance microscopy

In this report, we present data to demonstrate the utility of (1)H MR microscopy to non-invasively examine alginate/poly-l-lysine/alginate (APA) microcapsules. Specifically, high-resolution images were used to visualize and quantify the poly-l-lysine (PLL) layer, and monitor temporal changes in the alginate gel microstructure during a month long in vitro culture. The thickness of the alginate/PLL layer was quantified to be 40.6+/-6.2 microm regardless of the alginate composition used to generate the beads or the time of alginate/PLL interaction (2, 6, or 20 min). However, there was a notable difference in the contrast of the PLL layer that depended upon the guluronic content of the alginate and the alginate/PLL interaction time. The T(2) relaxation time and the apparent diffusion coefficient (ADC) of the alginate matrix were measured periodically throughout the month long culture period. Alginate beads generated with a high guluronic content alginate demonstrated a temporal decrease in T(2) over the duration of the experiment, while ADC was unaffected. This decrease in T(2) is attributed to a reorganization of the alginate microstructure due to periodic media exchanges that mimicked a regular feeding regiment for cultured cells. In beads coated with a PLL layer, this temporal decrease in T(2) was less pronounced suggesting that the PLL layer helped maintain the integrity of the initial alginate microstructure. Conversely, alginate beads generated with a high mannuronic content alginate (with or without a PLL layer) did not display temporal changes in either T(2) or ADC. This observation suggests that the microstructure of high mannuronic content alginate beads is less susceptible to culture conditions.

Preparation and in vitro analysis of microcapsule thalidomide formulation for targeted suppression of TNF-alpha

Recent studies have implicated the cytokine tumor necrosis factor-alpha (TNF-alpha) in the inflammation associated with Crohn's disease (CD). Thalidomide has been shown to decrease this inflammation by the suppression of TNF-alpha secretion. However, side effects associated with thalidomide have precluded its widespread usage. In the present study we investigated the efficacy of a "targeted delivery approach" for thalidomide at the site of inflammation. We observed that alginate-poly-l-lysine-alginate (APA) polymer-based microcapsule formulations that encapsulate thalidomide could be designed. These capsules could be delivered at target sites where they almost entirely suppress TNF-alpha secretion in lipopolysaccharide activated RAW 264.7 macrophage cells in vitro. These findings indicate that targeted delivery of thalidomide using APA capsules could facilitate its usage in reducing the inflammation associated with chronic conditions such as Crohn's disease and ulcerative colitis.

Modulation of the pH-responsive properties of poly(L-lysine iso-phthalamide) grafted with a poly(ethylene glycol) analogue

A pH responsive pseudopeptide, poly(L-lysine iso-phthalamide), has been modified with a hydrophilic poly(ethylene glycol) analogue, Jeffamine M-1000 and the effect of grafting ratio on the pH responsive behaviour of the grafted polymers in aqueous solution investigated using fluorescence and 1H NMR spectroscopy. It was demonstrated that at below 35.1 wt% grafting, the modified polymers retained the pH-driven conformational transition of the parent polymer from an expanded structure at high degrees of ionisation to a compact hydrophobically stabilised structure at low degrees of ionisation. The onset of pH response and the pH range over which the conformational transition occurred varied significantly with degree of grafting. At Jeffamine M-1000 ratios in excess of 48.0 wt%, the graft polymer existed in a micellular form over the whole pH studied. Potential applications in drug delivery of both the linear and micellular forms are discussed.

Physicochemical model of alginate–poly-l-lysine microcapsules defined at the micrometric/nanometric scale using ATR-FTIR, XPS, and ToF-SIMS

Alginate-poly-L-lysine-alginate (APA) microcapsules are currently being investigated as a means to immuno-isolate transplanted cells, but their biocompatibility is limited. In this study, we verified the hypothesis that poly-L-lysine (PLL), which is immunogenic when unbound, is exposed at the APA microcapsule surface. To do so, we analysed the microcapsule membrane at the micrometric/nanometric scale using attenuated total reflectance Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and time-of-flight secondary ion mass spectrometry. The results indicate that PLL and alginate molecules interact within the membrane. PLL exists in considerable amounts near the surface, contributing to the majority of the carbon within the outermost 100 Angstroms of the membrane. PLL was also detected at the true surface (the outermost monolayer) of the microcapsules. The exposure of PLL does not appear to result from defects in the outer alginate coating. This physicochemical model of APA microcapsules could explain their immunogenicity and will play an important role in the optimization of the microcapsule design.

Alginate assessment by NMR microscopy

Alginate hydrogels have long been used to encapsulate cells for the purpose of cell transplantation. However, they also have been criticized because they fail to consistently maintain their integrity for extended periods of time. Two issues of critical importance that have yet to be thoroughly addressed concerning the long-term integrity of alginate/poly-L-lysine/alginate microcapsules are: (i) are there temporal changes in the alginate/poly-L-lysine interaction and (ii) are there temporal changes in the alginate gel structure. NMR microscopy is a non-invasive analytical technique that can address these issues. in this report, we present data to demonstrate the utility of (1)H NMR microscopy to (i) visualize the poly-L-lysine layer in an effort to address the first question, and (ii) to observe temporal changes in the alginate matrix that may represent changes in the gel structure.

Hierarchy of DNA immobilization and hybridization on poly-L-lysine using an atomic force microscopy study

The atomic force microscopy has been used to analyze the immobilization of single stranded DNA on poly-L-lysine-coated glass and subsequent hybridization with complimentary DNA with the Z-threshold parameter and fractal analysis methods. The poly-L-lysine layer, which has a thickness of approximately 7 nm, presents nano-defects that could be critical for DNA immobilization by acting as a nucleation sites for ssDNA and subsequently for dsDNA aggregates. The Z-threshold for the dsDNA aggregates is much larger than for ssDNA, but the statistical fractal dimension is very similar, suggesting a conformal increase of the dimensions of the dsDNA aggregates mainly in the Z-direction, due to an effective ssDNA-ccDNA molecular recognition. This study demonstrates the use of fractal analysis in conjunction with the distribution of heights to evaluate the efficiency of DNA-DNA molecular recognition on surfaces and the impact of nanodefects.

Microencapsulation of living cells in semi-permeable membranes with covalently cross-linked layers

Microencapsulation in semi-permeable membranes protects transplanted cells against immune destruction. Microcapsule strength is critical. We describe a method to microencapsulate living cells in alginate-poly-L-lysine (PLL)-alginate membranes with covalent links between adjacent layers of microcapsule membranes, while preserving the desired membrane molecular weight cut-off (MWCO) and microencapsulated cell viability. A heterobifunctional photoactivatable cross-linker, N-5-azido-2-nitrobenzoyloxysuccinimide (ANB-NOS) was used. The N-hydroxysuccinimide ester group of ANB-NOS was covalently linked to PLL. Islets of Langerhans were immobilized in alginate beads, incubated in PLL-ANB-NOS and again in alginate. Upon illumination with UVA, covalent links were created between the phenyl azide residue of ANB-NOS and alginate from both the core bead and the outer coating. Covalently linked microcapsules remained intact after 3 years in a strong alkaline buffer (pH 12), whereas standard microcapsules disappeared within 45 s in the same solution. A standardized mechanical stress broke 22-fold more standard than covalently linked microcapsules. The MWCO and microencapsulated cell viability were similar with standard and covalently linked microcapsules. These microcapsules, extremely resistant to chemical and mechanical stresses, will be useful in numerous applications.

Nanolayer characterization through wavelength multiplexing of a microsphere resonator

We optically characterize nanolayer (<150 nm) formation in situ on a silica microsphere in an aqueous environment by simultaneously following the shifts of whispering-gallery modes at two wavelengths. This approach was inspired by layer perturbation theory, which indicates that these two measurements can be used to determine independently both the thickness and the optical dielectric constant. The theory is verified for extreme cases and used to characterize a biophysically relevant hydrogel nanolayer with an extremely small excess refractive index of 0.0012.

Localization of poly-l-lysine—photosensitizer conjugate in nucleus

The cellular uptake and photocytotoxity of poly-l-lysine (pL)-chlorin e6 (Ce6) conjugate were investigated. The cellularuptake of pL-Ce6 conjugate for HeLa cells was much higher than that of Ce6, and pL-Ce6 conjugate had high binding affinityfor HeLa cells. pL-Ce6 conjugate was accumulated in the nucleus of HeLa cells, and the effective photocytotoxity wasobserved by the irradiation.

Solid-state structure of polypeptide-based rod-coil block copolymers: folding of helices

This work compares the solid-state structures of films made from a polystyrene-poly(Z-L-lysine) (1) and a polystyrene-poly(gamma-benzyl-L-glutamate) (2) block copolymer, both having virtually the same numbers of repeating units and block length ratios. Small-angle X-ray scattering (SAXS) revealed a hexagonal-in-undulated lamellar morphology for both films. The long-period and the thickness of layers obtained for 2 were by a factor of three smaller as compared to 1, indicating that PBLGlu helices were folded twice, whereas PZLLys helices were fully stretched. Another difference shows up in the packing of helices, the level of ordering being considerably lower in 2. This might be due to spatial restrictions in the proper alignment of back-folded helical segments.

Elasticity of Native and Cross-Linked Polyelectrolyte Multilayer Films

Mechanical properties of polyelectrolyte multilayer films were studied by nanoindentation using the atomic force microscope (AFM). Force-distance measurements using colloidal probe tips were systematically obtained for supported films of poly(L-lysine) and hyaluronan that are suited to bio-application. Both native and covalently cross-linked films were studied as a function of increasing layer number, which increases film thickness. The effective Young's modulus perpendicular to the film, Eperpendicular, was determined to be a function of film thickness, cross-linking, and sample age. Thick PEM films exhibited a lower Eperpendicular than thinner PEM, whereas the Young's modulus of cross-linked films was more than 10-fold larger than native films. Moduli range from approximately 20 kPa for native films up to approximately 800 kPa for cross-linked ones. Young's moduli increased slightly with sample age, plateauing after approximately 4 weeks. Spreading of smooth muscle cells on these substrates with pre-attached collagen proved to be highly dependent on film rigidity with stiffer films giving greater cell spreading.

Spatially resolved electronic detection of biopolymers

An integrated array of field-effect transistor structures is used to detect two oppositely charged biopolymers: poly(L-lysine) and DNA. Local deposition of polymer solutions on part of the array induces sizeable variations in the dc current-voltage characteristics of the transistors exposed to the molecular charge. The whole transistor array is measured in the presence of a common electrolyte. Differential signals are studied as a function of electrolyte salt and polymer concentrations. The measurements provide information on the interface electrostatic potentials of the (semiconductor/biopolymer/electrolyte) system and the experimental data are compared to an analytical model which accounts for screening of the adsorbed charge by mobile ions.

Macropinocytosis of Polyplexes and Recycling of Plasmid via the Clathrin-Dependent Pathway Impair the Transfection Efficiency of Human Hepatocarcinoma Cells

Knowledge of the entry mechanism and intracellular routing of polyplexes is of major importance for designing efficient gene delivery systems. We therefore investigated the internalization and trafficking of polyplexes in HepG2 cells. pDNA encoding the luciferase was complexed with histidylated polylysine (His-pLK), a polymer that requires acidic pH for pDNA endosomal release. Fluoresceinylated polyplexes (F-His-pLK or F-pDNA) were internalized by clathrin-dependent and -independent pathways. The latter most likely occurred by macropinocytosis since it was stimulated by phorbol myristate and blocked by dimethylamiloride. Intracellular routing of the plasmid was analyzed by confocal microscopy and flow cytometry. These data revealed that: (i) one part of the plasmid was present in vesicles that were not labeled with any known organelle-specific marker, (ii) the other part was in transferrin receptor-positive vesicles, and (iii) the plasmid was not transferred to late endosomes/lysosomes. Using luciferase activity as a readout for gene expression, we found that it was strongly reduced when macropinocytosis was stimulated, whereas macropinocytosis inhibitors had no effect. However, blocking clathrin-dependent internalization by chlorpromazine completely prevented gene expression. These findings demonstrate that: (i) macropinocytosis of polyplexes and (ii) plasmid recycling impair the transfection efficiency and (iii) clathrin-dependent endocytosis is the most productive route for transfection of HepG2 cells.

Nonaqueous Capillary Zone Electrophoresis of Synthetic Organic Polypeptides

Poly(Nepsilon-trifluoroacetyl-L-lysine) was used as a model solute to investigate the potential of nonaqueous capillary electrophoresis (NACE) for the characterization of synthetic organic polymers. The information obtained by NACE was compared to that derived from size exclusion chromatography (SEC) experiments, and the two techniques were found to be complimentary for polymer characterization. On one hand, NACE permitted (i) the separation of oligomers according to their molar mass and (ii) the separation of the polymers according to the nature of the end groups. On the other hand, SEC experiments were used for the characterization of the molar mass distribution for higher molar masses. Due to the tendency of the solutes (polypeptides) to adsorb onto the fused-silica capillary wall, careful attention was paid to the rinsing procedure of the capillary between runs in order to keep the capillary surface clean. For that purpose, the use of electrophoretic desorption under denaturating conditions was very effective. Optimization of the separation was performed by studying (i) the influence of the proportion of methanol in a methanoVacetonitrile mixture and (ii) the influence of acetic acid concentration in the background electrolyte. Highly resolved separation of the oligomers (up to a degree of polymerization n of approximately 50) was obtained by adding trifluoroacetic acid to the electrolyte. Important information concerning the polymer conformations could be obtained from the mobility data. Two different plots relating the effective mobility data to the degree of polymerization were proposed for monitoring the changes in polymer conformations as a function of the number of monomers.

Analysis of glycated and ascorbylated proteins by gas chromatography-mass spectrometry

Proteins or poly-L-lysine which were incubated in the presence of ascorbic acid, dehydroascorbic acid (ascorbylation), or various sugars (glycation) were analyzed by gas chromatography-mass spectrometry (GC-MS). To also detect more labile reaction products, the Maillard modified proteins or poly-L-lysine were enzymatically hydrolyzed and reacted with N-methyl-N-(tert-butyldimethylsilyl)trifluoroacetamide to form the N(O)-tert-butyldimethylsilyl (tBDMS) derivatives prior to GC analysis. Under these conditions, the known Maillard products N (epsilon)-(carboxymethyl)lysine (1), oxalic acid mono-N (epsilon)-lysinylamide (2), and N (epsilon)-(carboxyethyl)lysine (3) could be simultaneously detected and quantified in glycated and ascorbylated proteins. Additionally, N (epsilon)-(1-carboxy-3-hydroxypropyl)-L-lysine (4) was identified for the first time as a Maillard product of proteins. Under the conditions applied here, 4 was found only in ascorbylated proteins or poly-L-lysine, but not in glycated proteins. Maillard-modified poly-L-lysine was further subjected to high-performance liquid chromatography (HPLC) analysis after enzymatic hydrolysis and formation of the phenyl isothiocyanate derivatized amino acids. Using this method, N (epsilon)-formyl-L-lysine (5), which cannot be distinguished from 2 by GC-MS analysis, was identified for the first time as a glycation product. Compound 5 is mainly formed from ribose, lactose, and fructose. The indicated Maillard products were quantified in beta-lactoglobulin (GC-MS) or poly-L-lysine (HPLC) which were glycated or ascorbylated using different precursors.

Methods for determination of milt protein and epsilon-polylysine in food additive preparations and processed foods by capillary zone electrophoresis

A simple and rapid method using capillary zone electrophoresis (CZE) for the determination of milt protein (MP), which contains mainly protamine, and polylysine (PL) in food additive preparations and processed foods was developed. CZE separation was performed on poly(vinyl alcohol)-coated capillaries at a column temperature of 20 degrees C with 120 mmol/L phosphate buffer (pH 2.5) as the running buffer. The influence of various components in food additive preparations on CZE analysis of MP and PL was examined. Egg white lysozyme, glycine, sodium acetate, glycerol, fumaric acid, calcium carbonate, dextrin, emulsifiers and sodium polyphosphate and pyrophosphate had no effect. No peak of protamine was detected in preparations containing metaphosphate. The analysis method for processed foods was composed of extraction with 4% formic acid, precipitation of macromolecular compounds with ethanol, concentration in a water bath and determination by CZE. The average recoveries were 108.4% for protamine sulfate (PS) in red bean sticky rice, and 81.3% for PL in white rice, 118% in egg sandwiches, and 115% in shiraae. The limits of detection of PS in red bean sticky rice and PL in white rice were both 50 ppm.

Ultrastructural examination of pancreatic islet containing alginate/polyaminoacidic coherent microcapsules

We ultrastructurally examined pancreatic islet containing alginate/poly-L-ornithine (AG/PLO) coherent microcapsules (CM) which we had previously developed in our laboratory. Specific issues, such as extent of CM coherency as well as morphologic integrity, and viability of the encapsulated islet subcellular organelles were addressed. We preliminarily demonstrated, both at scanning (SEM) and transmission (TEM) electron microscopy analysis, that CM seem to provide for structurally intact and functional, artificial microbarriers, enveloping each individual islet. These findings, additional to CM immunobarrier competence and biocompatibility, previously shown by our studies, might foster progress of CM into islet graft immunoisolation experimental and ultimately clinical trials.

Host reaction against empty alginate-polylysine microcapsules. Influence of preparation procedure

Microcapsules, prepared with alginate and polylysine, were injected intraperitoneally into mice and the number of peritoneal leucocytes as well as the cells sticking to the capsule wall were counted after 4-28 days. A significant increase in host reaction was observed when the microcapsules contained an outer layer of polylysine as compared with calcium alginate beads without polylysine or microcapsules coated with an outer layer of alginate. The alginate sources influenced the host reaction significantly. After an intraperitoneal residence of 4 days, the microcapsules were mainly surrounded by macrophages. After 28 days, several cell layers surrounded the microcapsules; macrophages, multinucleate giant cells, fibroblasts and mesothelial cells.

Glomerular epithelial cell endocytosis in puromycin-induced glomerulopathy

Glomerulopathy and nephrotic syndrome were induced in rats by intravenous puromycin aminonucleoside. Ten days after the injection of puromycin, the animals have developed heavy proteinuria. During this phase, glomerular epithelial cell endocytosis was studied by injecting a conjugate of horseradish peroxidase and poly-L-lysine. This conjugate has been shown to be endocytosed by glomerular epithelial cells. The rats were serially sacrificed from 1 min to 24 h after this injection. Peroxidase was localised cytochemically and observed at light and electron microscopy. The early events of endocytosis in glomerulopathy (namely the binding to the plasma membrane, the membrane invagination and the formation of the early vesicles) were qualitatively similar to those in the normal. The later events (the fusion of the vesicles and their movement within the cells) were inhibited. The results show that puromycin aminonucleoside damages epithelial cell endocytotic activity and affects the later processing of the conjugate within the cells.

A fluorescence method for the determination of the molecular weight cut-off of alginate-polylysine microcapsules

Several applications of microcapsules for the encapsulation of living cells or macromolecules require well defined pore sizes. The molecular weight cut-off of alginate-polylysine microcapsules has been determined using a range of fluorescent labelled dextran molecules. The diffusion of the fluorescein isothiocyanate labelled (FITC)-dextrans into the microcapsules was followed by fluorescence and confocal laser scanning microscopy. The permeability of microcapsules for FITC-dextrans with a molecular weight of 4,700 daltons and the impermeability for FITC-dextrans with a molecular weight of 40,500 daltons was confirmed with both techniques. Determination of the molecular weight cut-off, using confocal laser scanning microscopy was more reliable and required a smaller sample than fluorescence measurements.

Adsorption of bilirubin with polypeptide-coated resins

Poly-L-lysine, poly-D-lysine and poly-L-ornithine have been coated covalently onto a water-swellable polyamide resin. These sorbents, especially the polylysine coated resins, exhibit high binding affinities for bilirubin in aqueous phosphate buffer solutions at 0 degrees C. The polylysine coated resins have an improved binding affinity for bilirubin over the sorbents with lysine containing oligopeptide pendants and much higher affinity than cholestyramine. The binding capacity is directly proportional to the number of lysine residues on the resin. Replacement of poly-L-lysine with poly-D-lysine does not affect the adsorption capacity.

Glomerular epithelial-cell endocytosis of horseradish peroxidase-polylysine conjugate in immune-complex glomerulonephritis

Glomerulonephritis was induced in rats by daily intravenous cationised bovine serum albumin. The conjugate of horseradish peroxidase with poly-L-lysine was injected as a tracer of endocytosis by glomerular epithelial cells. The rats were sacrificed serially from 1 min to 24 h after the injection of the conjugate. The cytochemical localisation of peroxidase was observed by light- and electron-microscopy. Peroxidase was detectable in the GBM and immune deposits from 1 min after the injection but was cleared by 2 h. Cellular membrane staining by the conjugate and the membrane invaginations containing concentrated peroxidase were prominent adjacent to the subepithelial immune deposits. Peroxidase was initially localised intracellularly in membrane-bound vesicles adjacent to the subepithelial deposits. They subsequently moved towards the cell centre and became larger, some having the characteristics of lysosomes. Peroxidase activity significantly diminished within the cells by 16 h. The results show that glomerular epithelial-cell endocytosis in immune-complex glomerulonephritis is similar to that observed in the normal, but cellular membrane binding and invagination are more prominent adjacent to immune deposits. The trapping of the tracer in the deposits did not seem to alter its property of being taken up by the epithelial cells.

Standardization of serum fructosamine assays

We have calibrated a secondary serum protein standard by use (as primary standards) of samples of albumin and polylysine glycated with [14C]glucose in vitro, the glycation of which was assessed by radioactivity measurements and by elementary analysis for C and N. Using this standard for calibration in our improved fructosamine assay, one obtains an average fructosamine value of 247 mumol/L for nondiabetic individuals (or, in terms of total serum protein, 3.2 mumol/g)--about a tenth the value we obtained when we used the fructosamine assay of Johnson et al. (Clin Chim Acta 1983;127:87-95), standardized with desoxymorpholinofructose. In contrast, results corresponded well with the value for mean glycation of serum proteins, 3 mumol/g, determined by a furosine/HPLC method. Evidently the proposed procedure, in which a standard sharing the binding characteristics of endogenous glycated proteins is used together with our modified new fructosamine assay, leads to more realistic values for the concentrations of glycated serum proteins.

Sensitive radioimmunoassay and enzyme-linked immunosorbent assay for the simultaneous determination of chloroquine and its metabolites in biological fluids

Two new methods for the simultaneous determination of chloroquine and its two main metabolites (monodesethylchloroquine and bisdesethylchloroquine) in biological samples, radioimmunoassay (RIA) and enzyme-linked immunosorbent assay (ELISA), are described. Antiserum is produced in rabbits immunized with N-(2-carboxyethyl)desethylchloroquine:protein conjugate. Besides chloroquine, this antiserum recognizes with good affinity the two main metabolites, monodesethylchloroquine and bisdesethylchloroquine (70 and 40% of crossreaction, respectively). Amodiaquine cross reacts by 4.5%; cross reactions with monodesethylamodiaquine, bisdesethylamodiaquine, and other antimalarial drugs are less than 1%. No extraction step or sample preparation is required for either system. Sensitivity limits are, respectively, 0.70 nM (3 pg of chloroquine sulfate measured in 10 microL of plasma sample) for RIA, and 10 nM (22 pg of chloroquine sulfate measured in 5 microL of plasma sample) for ELISA. The interassay coefficients of variation are, respectively, less than 10 and less than 16% for RIA and ELISA in the range 14-410 nM (6-180 ng/mL). The results of both methods are well correlated (r = 0.97) and correlate with spectrophotometry (r = 0.98) and HPLC results (r = 0.93). Because of their high sensitivity, both methods can be used in the case of chloroquine poisoning and in the control of malaria prophylaxis and treatment.

Nucleus-specific and temporally restricted localization of proteins in Tetrahymena macronuclei and micronuclei

Labeled nuclear proteins were microinjected into the cytoplasm of Tetrahymena thermophila. Macronuclear H1, calf thymus H1, and the SV40 large T antigen nuclear localization signal linked to BSA accumulated specifically in macronuclei, even if cells were in micronuclear S phase or were nonreplicating. The way in which histone H4 localized to either the macronucleus or the micronucleus suggested that it accumulates in whichever nucleus is replicating. The inability of the micronucleus to accumulate Tetrahymena H1 or heterologous nuclear proteins, even at a period in the cell cycle when it is accumulating H4, suggests that it has a specialized transport system. These studies demonstrate that although the mechanism for localizing proteins to nuclei is highly conserved among eukaryotes, it can differ between two porecontaining nuclei lying in the same cytoplasm.

Regulation of serum glycosaminoglycan sulfotransferase activities: inhibition by sulfated glycosaminoglycans and activation by polyamines and basic peptides including a polylysine-containing segment of the c-Ki-ras 2 protein

The regulatory mechanisms for the glycosaminoglycan sulfotransferases in fetal calf serum were investigated. The enzymes examined were those which transfer sulfate from 3'-phosphoadenosine 5'-phosphosulfate to 1) position 6 of the internal N-acetylgalactosamine units of chondroitin, 2) position 6 of galactose units of keratan sulfate, and 3) position 2 (an amino group) of glucosamine units of heparan sulfate. The former two enzymes were activated by spermidine, spermine, protamine, and poly L-lysine. All the enzymes were strongly inhibited by heparin and dextran sulfate, whereas only the chondroitin 6-O-sulfotransferase was inhibited by sulfated galactosaminoglycans. The inhibition of this enzyme by the sulfated glycosaminoglycans was abolished by polylysine, indicating that the activation by polylysine is partly due to the neutralization of endogenous acidic inhibitors, including sulfated glycosaminoglycans. Affinity chromatographic studies demonstrated that heparin specifically binds to the three enzymes, which have anionic isoelectric points, and that chondroitin 6-sulfate, spermine, and polylysine bind to the former two enzymes under physiological conditions. Thus, the activation by spermine and polylysine as well as the inhibition by sulfated glycosaminoglycans also appears to occur through their binding to the enzymes. Studies with synthetic lysine oligomers and an affinity-purified (approximately 700-fold) fraction containing the former two enzymes indicated that the pentamer is the minimum unit required for the activation. A synthetic peptide, containing six consecutive lysines at the carboxy terminus of the human c-Ki-ras 2 protein, also regulated the two enzyme activities at micromolar concentrations. The possible physiological implications of the observed effects of these regulatory substances on the glycosaminoglycan sulfotransferases are discussed in relation to glycosaminoglycan synthesis during the proliferation, differentiation, and transformation of cells. The possibility of sulfated glycosaminoglycans being enzyme regulators is also discussed.

In vitro pH-dependent drug release from N4-(4-carboxybutyryl)-1-beta-D-arabinofuranosylcytosine and its conjugate with poly-L-lysine or decylenediamine-dextran T70

N4-(4-Carboxybutyryl)-1-beta-D-arabinofuranosylcytosine (glu-ara-C), the conjugate of glu-ara-C and poly-L-lysine (PLL), (PLL-glu-ara-C), and the conjugate of glu-ara-C and decylenediamine-dextran T70 (T70-C10), (T70-C10-glu-ara-C), were prepared. Drug regeneration from glu-ara-C and the conjugates was investigated in buffered solutions of pH 4,5,7,7.4 and 8. The character of the drug release from the conjugates was different from that from glu-ara-C. Namely, the release of 1-beta-D-arabinofuranosylcytosine (ara-C) from glu-ara-C was accelerated under both weakly acidic and weakly basic conditions, while it was accelerated only under weakly basic conditions from the conjugates. Overall, the drug release profiles from the conjugates showed similar patterns. However, under neutral and weakly basic conditions, ara-C was regenerated more rapidly from PLL-glu-ara-C than from T70-C10-glu-ara-C. During the incubation of glu-ara-C and the conjugates under weakly acidic conditions, 1-beta-D-arabinofuranosyluracil (ara-U) was detected and its amount increased with time to similar extents.

Sensitive detection of protein adsorption to supported lipid bilayers by frequency-dependent capacitance measurements and microelectrophoresis

In the first part, we report experiments which enable the sensitive detection of protein adsorption to lipid bilayers deposited onto chromium electrodes on glass substrates by frequency-dependent capacitance measurements. The sensitivity of the present type of sensor (better than 0.3 nm average protein layer thickness) is at least equivalent to that of ellipsometry. A high specific resistance of the supported bilayer of (1-5).10(5) omega.cm2 is achieved by deposition of a tightly packed (crystalline) cadmium arachidate monolayer in contact with the substrate, whereas the outer monolayer can be more loosely packed (fluid phase or state of fluid-solid coexistence) which is essential for the incorporation of receptors. In the present work, charged lipids are incorporated as nonspecific receptors for polylysine and cytochrome c. The capacitance measurements provide a very sensitive test of the tightness and the long-time stability of the supported bilayers and, in combination with ellipsometric thickness measurements, enable estimations of dielectric properties of protein layers (such as the permittivity). In the second part, we report first electrophoresis experiments in asymmetric bilayers on substrates which enable simultaneous measurements of lateral diffusion coefficients and frictional coefficients between monolayers. The potential application of the electrophoretic effect for the differentiation between different receptors and the amplification of signals in biosensors is discussed.

The interaction of papain with polycations

An investigation has been made of the interactions of the enzyme papain with the polycations protamine, polybrene, poly(L-lysine), spermine, spermidine and the neutral polymer polyvinylpyrrolidone (PVP). At low concentrations, each behaves as an inhibitor of the enzyme. As their concentrations increased above a certain level, the activity of the systems increased, and their inhibition of the enzyme appeared to be less pronounced. When acting by themselves in the presence of the substrate haemoglobin, each of the polycations was a weak proteolytic catalyst with a ranking of catalytic effectiveness of protamine greater than polybrene greater than poly(L-lysine) greater than polyvinyl-pyrrolidone greater than spermidine greater than spermine. This effect could explain the anomalous inhibition of papain by these polycations. The interaction of papain with dansyl protamine (DNSP) and the extent of complex formation were studied using a fluorescence polarization technique and the results showed that there was a strong interaction occurred. The strength of binding was assessed by determination of the critical electrolyte concentration (0.2 M, NaNO3). The stoichiometry of the DNSP-papain complex was found to be 63 base moles of DNSP to one mole of papain.

Poly(I).poly(C), a potential drug carrier for the antitumor agent mitoxantrone: in vitro drug binding study

Coupling of mitoxantrone, a new antitumor agent, to a macromolecular carrier system may improve the drug's selectivity of action and pharmacokinetic properties. We have studied in vitro binding of mitoxantrone to poly(I).poly(C), a macromolecular, double-stranded homoribopolymer, by equilibrium dialysis and high-performance liquid chromatography (HPLC). Results showed high binding affinity for mitoxantrone to poly(I).poly(C) (Kd = 1.05 X 10(-6) M), the calculated number of mitoxantrone-binding sites is 60 per molecule poly(I).poly(C). In view of the good tolerance in clinical studies, poly(I).poly(C) may thus be a useful drug carrier for mitoxantrone. A mitoxantrone:poly(I).poly(C) ratio of 1:30 (w/w) is recommended for therapeutic studies.

Nonspecific immunocytochemical reactions with certain neurohormonal peptides and basic peptide sequences

Immunocytochemical staining experiments on filter paper or nitrocellulose models reveal that many, but not all, neurohormonal peptides, as well as poly-L-lysine, strongly bind a number of labeled reporter molecules, including colloidal gold- or peroxidase-labeled IgG, protein A, streptavidin, and albumin. Peptides displaying this type of (nonspecific) binding are basic; they include ACTH, VIP, opioid peptides, and poly-L-lysine. Pre-absorption of labeled probes with excess ACTH[1-24] or poly-L-lysine abolishes or greatly reduces binding not only to the homologous but also to the heterologous peptides tested. A number of cell types previously reported to display nonspecific immunoglobulin binding contain one or several of the basic neurohormonal peptides shown to display nonspecific absorption of labeled IgG, protein A, streptavidin, and albumin. This nonspecific absorption is reversed neither by high salt nor high pH conditions, nor by a number of detergents and blocking proteins. One dynorphin antiserum also displays nonspecific binding to the peptides as well as to pancreatic glucagon cells, and this nonspecific staining can be blocked by basic peptide pre-absorption (whether homologous or heterologous). These results suggest a need for caution when immunocytochemical studies of a number of basic polypeptides are interpreted, and also suggest the inclusion of novel control procedures in immunocytochemistry.

Influence of carbamoylation on some analytical properties of basic polypeptides

The effect of carbamoylation on the assay or identification of histones and polylysine was investigated. Incubation with sodium cyanate decreased the positive charge on these polypeptides as judged by changes in the binding of methyl orange or the electrophoretic mobility. Histones in chromatin appeared less accessible to carbamoylation than isolated histones. Carbamoylation of proteins under conditions in which there was little or no effect on the Lowry procedure could affect their assay by methods utilizing metachromasia with Coomassie Blue G. The Bradford assay has low sensitivity for Hl histone and polylysine but this can be increased by preincubation with sodium cyanate. More extensive carbamoylation of polylysine caused decreased sensitivity which was the only response seen with core nucleosomal histones and bovine serum albumin when preincubated with sodium cyanate. It was concluded that the sensitivity for Hl histone and polylysine in assays dependent on metachromasia with Coomassie Blue G may be changed by factors which decrease the positive charge on these polypeptides.

A method for probing the affinity of peptides for amphiphilic surfaces

We have developed a rapid method for probing the affinity of peptides toward an amphiphilic surface. Hydrophobic polystyrene-divinylbenzene beads of 5.7 +/- 1.5 micron diameter are coated with a monomolecular film of egg lecithin to achieve the equilibrium spreading density of the phospholipid, 6 X 10(-3) molecule/A2. The coated beads are ideally suited for assessing the affinity of peptides for phospholipid surfaces: Large quantities of lipid-coated beads of known surface area can be prepared easily and rapidly. Within the pH range 2.0 to 9.0, the adsorbed phospholipids are relatively resistant to hydrolysis and remain bound indefinitely. Following incubation with peptide ligands, beads can be separated from the reaction mixture by centrifugation. Peptides, such as melittin, which destroy or cause fusion of single bilayer phospholipid vesicles, cannot disrupt lecithin-coated beads in a comparable way, and do not displace lecithin from the surface of beads. After incubating these beads in solutions of peptides and proteins, we have determined the parameters for the binding of several ligands to the phospholipid surface. The binding of many amphiphilic peptides obeys a Langmuir adsorption isotherm, i.e., saturable reversible binding to independent and equivalent sites on the bead. That the binding is a true reversible equilibrium is shown by desorption of the ligand upon dilution. From the isotherm, the surface areas occupied by the ligand molecules were calculated, and were observed to be similar to those observed in monolayers at the air-water interface. In comparing the binding of amphiphilic peptides to that of completely hydrophilic peptides, we observed that only the former bind at levels measurable by our techniques. Thus, this method can serve as a rapid assay for detecting amphiphilicity in peptides of putative amphiphilic character.

Detection of an advanced glycosylation product bound to protein in situ

Protein amino groups can react with glucose without the aid of enzymes to form stable Amadori products containing 1-amino-1-deoxyketose residues. These adducts can undergo subsequent rearrangements and dehydrations to form various brown and fluorescent pigments. Recently, a chromophore, 2-(2-furoyl)-4(5)-(2-furanyl)-1H-imidazole (FFI), was isolated from acid hydrolysates of bovine serum albumin (BSA) and poly-L-lysine which had been incubated with glucose. To confirm the presence of FFI in situ, a radioimmunoassay was developed. A derivative of FFI, 4-furanyl-2-furoyl-1H-imidazole-1-hexanoic acid, was coupled to BSA and used to immunize rabbits. A radioactive FFI derivative was synthesized by reaction of 2-furyl-glyoxal with gamma-amino-[2,3-3H]butyric acid to form FFI-[3H]butyric acid. The resultant antiserum showed binding affinity to FFI and cross-reactivity for related compounds. FFI bound to proteins was liberated by acid hydrolysis or digestion by proteinase K prior to measurement. A linear relationship was seen between the amount of FFI equivalent detected and the amount of acid hydrolysate or enzymatic digest assayed. Poly-L-lysine and BSA incubated with glucose showed a time-dependent increase in the amounts of fluorescence and FFI equivalence. The detection of a time-related increase in the amount of FFI or a closely related structure in enzymatically digested proteins implicates it as an in situ product on proteins which have undergone the Maillard reaction with glucose. Of physiological significance is that FFI could also be detected in human globin and serum albumin from normal individuals. Thus, proteins exposed to glucose in vitro and in vivo form FFI as an in situ glycosylation product.

Colorimetric determination of microgram quantities of polylysine by trypan blue precipitation

A simple and sensitive method for the determination of polylysine in solution is described. Polylysine is quantitatively precipitated with trypan blue. The absorbance of unbound dye in the supernatant is inversely proportional to the concentration of this polyamino acid. The precipitation is identical for all sizes of polylysine of molecular weight 13,000 or higher, and is prevented by the addition of either polyanions or serum. The measurable range of polylysine hydrobromide is between 1 and 10 micrograms/ml, which is about 10-fold lower than that by the published methyl orange precipitation method.

Factors affecting the assay of histone H1 and polylysine by binding of Coomassie blue G

Although a mixture of calf thymus histones or the H2B and H4 fractions gave values in the Bradford assay that were similar to those for bovine serum albumin, low values were obtained with histone H1 and polylysine. The assay was found to be more sensitive for histone H1 and polylysine if the phosphoric acid concentration in the reagent was decreased or the polypeptide solutions contained low concentrations of nonionic detergents. Substitution of perchloric acid or hydrochloric acid for phosphoric acid and alcohol in the Coomassie blue G reagent provided an assay that was similar in sensitivity for histone H1 and a total histone mixture. It was suggested that the degree of metachromasia with Coomassie blue G may serve as a probe of conformational changes in histone H1.

Mechanism of binding of mouse interferon to controlled pore glass

Many proteins bind to controlled pore glass; they are either acid elutable or alkali elutable. Mouse interferon is an acid-elutable protein. Since poly(L-lysine) and, to some extent, poly(L-arginine) are also eluted from controlled pore glass under acidic conditions, one may postulate that mouse interferon binds to controlled pore glass via some of the protein's epsilon-amino groups (of lysine) and/or guanidinium groups (of arginine) and the beads' silanol (hydroxyl groups). The necessity of lysine in the binding of interferon to controlled pore glass is further substantiated by the fact that citraconylated interferon does not bind to controlled pore glass. A requirement for Lewis acid-base interaction between the beads' B2O3 groups and the amide groups of arginine is unlikely in view of the results obtained with the alternative system, ZrOH, which, being devoid of B2O3, did bind interferon. Since a substantial amount of interferon could be eluted from controlled pore glass with ethylene glycol and high salt, one may assume that some hydrophobicity is involved in the binding of interferon to controlled pore glass.

Model system studies of staining procedures for lysine and arginine residues

Using polyacrylamide films containg poly-lysine, polyarginine and DNA as test models, a variety of reportedly specific staining procedures have been examine. Contrary to published observations, mixtures of fast green and eosin Y show no specific staining of either lysine or arginine. Both amino-acids bind eosin from the mixture more strongly than fast green. Arginine apparently has a greater affinity for this eosin than has lysine which contradicts previous reports that lysine will be stained by eosin arginine will stain with fast green, if proteins containing both amino-acids are stained with dye mixture. In films containing lysine and/or arginine picric acid is shown to bind specifically to the arginine. The picric acidarginine complex resists disruption in 0.004 M borate buffer which is a solvent used for subsequent staining of lysine residues with bromophenol blue. Picric acid may also be used as a hydrolysant and substitute for hydrocholoric acid in a Feulgen-like procedure which stains DNA to the same level as the classiclal hydrochloric acid based procedure while also staining arginine present.

The molecular organization of asymmetric lipid bilayers and lipid-peptide complexes

Oriented fatty acid bilayers with asymmetric distributions of lipid head group types, hydrocarbon chain lengths, and associated polypeptides have been analyzed by a combined use of high resolution electron microscopy and X-ray diffraction techniques. The exclusion of fixatives, stains, and embedding materials has made it possible to relate unequivocally microscopic images to molecular composition. The ultrastructure of asymmetric bilayers has been determined by a novel analysis in which one half of the bilayer serves as a structural reference for the entire bilayer. Absolute electron density profiles at 7 A resolution have been computed for bilayers formed from long and short chain length lipids either segregated to opposite sides or mixed together in both sides of the bilayer. The data indicate that the two lipids self organize in a specific paired configuration. Detailed analysis of bilayers associated with poly-L-lysine shows that although this hydrophilic peptide resides near the lipid head group region, its presence alters the arrangement of the bilayer hydrocarbon chains.

[Synthesis of conjugates of heptalysine and penicillins (author's transl)]

Heptalysine was synthesized as a non-immunogenic carrier for artificial antigens with penicilloyl-group specificity. The synthesis was carried out by conventional techniques via different routes by condensation of appropriately protected intermediates. Best results were obtained with the use of the benzyloxycarbonyl group for intermediate protection of the alpha-amino-groups and the tert.-butyloxycarbonyl-group together with the tert.-butylester for permanent blockage of the terminal alpha-amino group, the epsilon-amino groups and the terminal carboxyl group. Heptalysine and also lysine were reacted with benzylpenicillin, alpha-aminobenzylpenicillin and tert.-butyloxycarbonyl-alpha aminobenzylpenicillin--to prevent the alpha-amino groups of penicillin from reacting--in aqueous solutions at pH 10.6-11.6 according to Levine and Redmond. The products were isolated after precipitation with acid or dialysation against water by lyophilisation. The penicilloyl group content of the conjugates as estimated from elemental analysis, penamaldate tests and the NMR spectra proved to be rather high: 5-7 residues/mol.