Complement activation by model drug carriers for intravenous application: determination by two-dimensional electrophoresis

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.

Three Decades of Research about the Corona Around Nanoparticles: Lessons Learned and Where to Go Now

The research about how a nanoparticle (NP) interacts with a complex biological solution has been conducted, according to the literature, for almost three decades. A significant amount of data has been generated, especially in the last one and a half decade. First, it became its own research field which was later divided into many subresearch fields. This outlook does not aim to be a comprehensive review of the field or any of its subresearch fields. There is too much data published to attempt that. Instead, here it has been tried to highlight what, in the opinion, is the main step taken during these three decades. Thereafter, the weaknesses and end are pointed out with what needs to be the main focus for the future to understand the protein corona formation in the bloodstream, which is a prerequisite for the developing of true target specific drug-delivering nanoparticles.

Potassium-selective optical microsensors based on surface modified polystyrene microspheres

Ion-selective microspheres based on surface modification of polystyrene particles (0.8 and 2.4 μm, diameter) are presented here for the first time.

Protein Adsorption Patterns and Analysis on IV Nanoemulsions-The Key Factor Determining the Organ Distribution

Intravenous nanoemulsions have been on the market for parenteral nutrition since the 1950s; meanwhile, they have also been used successfully for IV drug delivery. To be well tolerable, the emulsions should avoid uptake by the MPS cells of the body; for drug delivery, they should be target-specific. The organ distribution is determined by the proteins adsorbing them after injection from the blood (protein adsorption pattern), typically analyzed by two-dimensional polyacrylamide gel electrophoresis, 2-D PAGE. The article reviews the 2-D PAGE method, the analytical problems to be faced and the knowledge available on how the composition of emulsions affects the protein adsorption patterns, e.g., the composition of the oil phase, stabilizer layer and drug incorporation into the interface or oil core. Data were re-evaluated and compared, and the implications for the in vivo distribution are discussed. Major results are that the interfacial composition of the stabilizer layer is the main determining factor and that this composition can be modulated by simple processes. Drug incorporation affects the pattern depending on the localization of the drug (oil core versus interface). The data situation regarding in vivo effects is very limited; mainly, it has to be referred to in the in vivo data of polymeric nanoparticles. As a conclusion, determination of the protein adsorption patterns can accelerate IV nanoemulsion formulation development regarding optimized organ distribution and related pharmacokinetics.

Physico-chemical parameters that govern nanoparticles fate also dictate rules for their molecular evolution

Nanoparticles are efficient to safely deliver therapeutic and imaging contrast agents to tumors for cancer diagnostic and therapy, if they can escape the reticuloendothelial system (RES) and accumulate in tumors either passively due to the enhanced permeability and retention (EPR) effect or actively via a specific ligand. The main hallmark of nanoparticles is their large surface areas, which, depending of their chemical compositions, surface coatings, electric charges, sizes and shapes, will generate complex, extremely dynamic and continuous interactions and exchanges between the nanoparticles and the different molecules present in the blood. Special attention will be paid to explain how the nanoparticles were improved step by step in order to adapt our increasing knowledge on their biophysics. In particular, we will discuss the influence of PEGylation, the difficulties to generate actively targeted particles and finally the actual trends in the manufacturing of "third-generation" smart particles.

Differential plasma protein binding to metal oxide nanoparticles

Nanoparticles rapidly interact with the proteins present in biological fluids, such as blood. The proteins that are adsorbed onto the surface potentially dictate the biokinetics of the nanomaterials and their fate in vivo. Using nanoparticles with different sizes and surface characteristics, studies have reported the effects of physicochemical properties on the composition of adsorbed plasma proteins. However, to date, few studies have been conducted focusing on the nanoparticles that are commonly exposed to the general public, such as the metal oxides. Using previously established ultracentrifugation approaches, two-dimensional gel electrophoresis and mass spectrometry, the current study investigated the binding of human plasma proteins to commercially available titanium dioxide, silicon dioxide and zinc oxide nanoparticles. We found that, despite these particles having similar surface charges in buffer, they bound different plasma proteins. For TiO2, the shape of the nanoparticles was also an important determinant of protein binding. Agglomeration in water was observed for all of the nanoparticles and both TiO2 and ZnO further agglomerated in biological media. This led to an increase in the amount and number of different proteins bound to these nanoparticles. Proteins with important biological functions were identified, including immunoglobulins, lipoproteins, acute-phase proteins and proteins involved in complement pathways and coagulation. These results provide important insights into which human plasma proteins bind to particular metal oxide nanoparticles. Because protein absorption to nanoparticles may determine their interaction with cells and tissues in vivo, understanding how and why plasma proteins are adsorbed to these particles may be important for understanding their biological responses.

Delivery of peptide and protein drugs over the blood-brain barrier

Peptide and protein (P/P) drugs have been identified as showing great promises for the treatment of various neurodegenerative diseases. A major challenge in this regard, however, is the delivery of P/P drugs over the blood-brain barrier (BBB). Intense research over the last 25 years has enabled a better understanding of the cellular and molecular transport mechanisms at the BBB, and several strategies for enhanced P/P drug delivery over the BBB have been developed and tested in preclinical and clinical-experimental research. Among them, technology-based approaches (comprising functionalized nanocarriers and liposomes) and pharmacological strategies (such as the use of carrier systems and chimeric peptide technology) appear to be the most promising ones. This review combines a comprehensive overview on the current understanding of the transport mechanisms at the BBB with promising selected strategies published so far that can be applied to facilitate enhanced P/P drug delivery over the BBB.

Time-dependent changes in opsonin amount associated on nanoparticles alter their hepatic uptake characteristics

The relationship between the time-dependent change in serum proteins adsorbed on nanoparticles and their disposition to the liver was investigated by employing lecithin-coated polystyrene nanosphere with a size of 50 nm (LNS-50) as a model nanoparticle in rats. The total amount of proteins adsorbed on LNS-50 increased and the qualitative profile of serum proteins adsorbed on LNS-50 changed during the incubation with serum up to 360 min. The liver perfusion study indicated that the hepatic uptake of LNS-50 incubated with serum for 360 min was significantly larger than those of LNS-50 incubated for shorter period. It was suggested that the increase in the hepatic uptake of LNS-50 with the increase in incubation time would be ascribed mainly to the increase in the opsonin-mediated uptake by Kupffer cells. Semi-quantification of major opsonins, complement C3 (C3) and immunoglobulin G (IgG), and in vitro uptake study in primary cultured Kupffer cells demonstrated that the increase in C3 and IgG amounts adsorbed on LNS-50 was directly reflected in the increased disposition of LNS-50 to Kupffer cells. These results indicate that the amounts of opsonins associated on nanoparticles would change over time and this process would be substantially reflected in the alteration of their hepatic disposition characteristics.

Proteomic analysis of protein adsorption: Serum amyloid P adsorbs to materials and promotes leukocyte adhesion

Serum and plasma protein adsorption on materials was analyzed using gel electrophoresis and ion trap mass spectrometry. Following incubation of polypropylene, polyethylene terephthalate (PET), or polydimethylsiloxane (PDMS) with 5% serum for longer than 4 h, we found unexpectedly high amounts of the pentraxin serum amyloid P. It was previously shown that serum amyloid P is constitutively expressed in humans, functions as an opsonin, and interacts with the Fcgamma receptors on leukocytes. We demonstrate that serum amyloid P adsorbed to tissue culture polystyrene, PDMS, and PET promotes the adhesion of granulocytes and monocytes in the presence of calcium. The methods developed for these studies may be useful for the large-scale study of protein adsorption and do not rely on radiolabeling or the availability of antibodies.

Challenges and solutions for the delivery of biotech drugs – a review of drug nanocrystal technology and lipid nanoparticles

Biotechnology allows tailor-made production of biopharmaceuticals and biotechnological drugs; however, many of them require special formulation technologies to overcome drug-associated problems. Such potential challenges to solve are: poor solubility, limited chemical stability in vitro and in vivo after administration (i.e. short half-life), poor bioavailability and potentially strong side effects requiring drug enrichment at the site of action (targeting). This review describes the use of nanoparticulate carriers, developed in our research group, as one solution to overcome such delivery problems, i.e. drug nanocrystals, solid lipid nanoparticles (SLN), nanostructured lipid carriers (NLC) and lipid-drug conjugate (LDC) nanoparticles, examples of drugs are given. As a recently developed targeting principle, the concept of differential protein adsorption is described (PathFinder Technology) using as example delivery to the brain.

The effect of substrate molecular mobility on surface induced immune complement activation and blood plasma coagulation

Changing the length of the alkyl ester side chain in poly(alkyl methacrylates) provides a unique opportunity to systematically vary the mobility of the polymer chains, or in other words vary the glass transition temperature (T(g)), without greatly affect the solid surface energy (gamma(s)) of the polymer. A series of poly(alkyl methacrylate) coatings was therefore analysed with regard to the human immune complement (IC) activation and the surface associated blood plasma coagulation cascade (CC) properties. For the IC and CC measurements we used a quartz crystal microbalance (QCM) where we modified the chemistry of the sensor surface by applying 10-30 nm thick poly(alkyl methacrylate) coatings. The surface energy was calculated from water contact angles and small differences between the coatings were observed. The surface chemistry of the coatings, as determined with X-ray photoelectron spectroscopy (XPS), showed no deviation from expected compositions. Tapping mode atomic force microscopy (TM-AFM) measurements revealed that all coatings displayed similar morphology and the roughness was in the range of 0.7-0.9 nm. Increased polymer mobility correlated with a decrease in IC activation, measured as a decreased C3c deposition at the surface. The surface induced CC, measured as fibrin clot formation at the surface, was different between the different coatings but no correlation with molecular mobility was observed. Thus, the molecular mobility of the polymer chains had a major effect on both the IC and the CC and it seems that different aspects of the chemistry of the solid surface regulate activation of the IC and the CC.

Pegylated polystyrene particles as a model system for artificial cells

Pegylated polystyrene particles (PS-PEG) were prepared as a model system for artificial cells, by modification of carboxyl polystyrene particles (PS-COOH) with homo- and hetero-bifunctional polyethylene glycols (PEG, MW 1500, 3400, and 5000) containing an amino end group for immobilization and an amino, hydroxyl, or methoxy end group that is exposed at the surface after immobilization. Protein adsorption from human plasma dilutions (85 v %) onto PS-PEG with a PEG surface concentration higher than 40 pmol/cm2 was reduced up to 90-95% compared with protein adsorption onto PS-COOH with a final protein surface concentration of approximately 30 ng/cm2. Two-dimensional gel electrophoresis analyses showed that 30% of the total amount of adsorbed proteins onto PS-PEG are dysopsonins (i.e., nonadhesive proteins like albumin and apolipoproteins). For PS-COOH, <15% of the amount of adsorbed proteins are dysopsonins. In addition, the generation of terminal complement compound (TCC) by PS-PEG particles with a PEG surface concentration lower than approximately 55 pmol/cm2 is not significant. The low protein adsorption, the relatively high percentage of adsorbed dysopsonins, and the low level of complement activation may prevent the uptake of PS-PEG by the mononuclear phagocytic system (MPS) in vivo. Moreover, PS-PEG (PEG surface concentration > approximately 35 pmol/cm2) shows minimal interaction with cultured human umbilical vein endothelial cells (HUVEC), which mimics the endothelial lining of the blood vessel wall.

Functional groups on polystyrene model nanoparticles: influence on protein adsorption

The surface characteristics of intravenously administered particulate drug carriers decisively influence the protein adsorption that is regarded as a key factor for the in vivo fate of the carriers. Latex nanoparticles were synthesized to study the influence of different basic and acidic functional groups on particulate surfaces on the protein adsorption from human serum. The protein mass adsorbed to the particles was assessed by BCA protein assay, the protein adsorption patterns were analyzed by two-dimensional electrophoresis. Considerable differences in the protein adsorption with regard to preferential adsorbed proteins were detectable for the different functional groups. Possible correlations between the surface characteristics and the protein adsorption are shown and discussed. The knowledge concerning the interactions of proteins and nanoparticles can be used for a rational development of particulate drug carriers and can also be useful for an optimized design of medical devices, e.g., hemodialysis membranes or implants.

Flow cytometry based detection of HLA alloantibody mediated classical complement activation

Complement-dependent cytotoxicity (CDC) panel reactive antibody (PRA) testing is used to assess recipient presensitization and post-transplant alloantibody formation in transplant recipients. However, CDC test results can be affected by false-positive reactions brought about by autoantibodies or antilymphocyte reagents. As an alternative to the CDC-PRA assay, detection of HLA alloantibodies using HLA antigen-coated microbeads (FlowPRA test) was recently established. FlowPRA testing, however, does not distinguish between (presumably more harmful) complement-fixing and noncomplement-fixing alloantibodies. In this study, we established a novel assay allowing flow cytometric detection of HLA alloantibody dependent classical complement activation using the FlowPRA test. For the detection of complement activation, FlowPRA beads were incubated with sera from highly sensitized dialysis patients (CDC-PRA reactivity >60%) and then stained for C4 (C4d, C4c) and C3 (C3d, C3c) fragments, as well as C1q deposition using indirect immunofluorescence. We demonstrate alloantibody induced induction of C4 fragment, and in parallel C1q deposition to HLA class I or class II beads. As shown by immunoblotting, C4 staining was not due to the presence of preformed C4 fragment-IgG/M complexes. Indeed, C4 fragment deposition in our in vitro system was demonstrated to result from de novo complement activation. First, inactivation of C4 by treatment of sera with methylamine, which inhibits cleavage of the internal thioester, completely abolished C4 fragment deposition. Second, C4 fragment deposition was not observed in the evaluation of C4-free immunoadsorption eluates obtained from highly sensitized dialysis patients. After supplementation with complement, however, eluates induced C4 deposition. Deposition of C4 split products and C1q was temperature-dependent with maximum binding after incubation at 4 degrees C for 60 min. In contrast, maximum C3 fragment deposition was found at 37 degrees C. At this temperature, C3 deposition occurred in an alloantibody and C4-independent fashion, presumably as a result of alternative complement activation. In summary, we describe a novel cell-independent and easy-to-perform PRA test that permits flow cytometry based detection of alloantibody induced classical complement activation. Future studies will have to evaluate its possible relevance as an alternative to CDC-PRA testing in clinical transplantation.

Interaction of bronchoalveolar lavage fluid with polyplexes and lipoplexes: analysing the role of proteins and glycoproteins

BACKGROUND

Plasmid DNA complexed with cationic lipids (lipoplexes) or cationic polymers (polyplexes) has been used for gene transfer into the lung. Topical gene administration of lipoplexes or polyplexes into the lung after intratracheal instillation or aerosolisation could cause interaction of the complexes with extracellular substances of the airway surface liquid (ASL). These extracellular interactions might be causal for the observed inefficient transfection rate in vivo after topical administration. Therefore, we studied the impact of bronchoalveolar lavage fluid (BALF) on reporter gene expression mediated by non-viral gene vectors. BALF was considered as a model system to mimic possible interactions of the gene vectors with the ASL.

METHODS

BALF was taken from 15 patients who underwent diagnostic bronchoscopy. Lipoplexes and polyplexes were incubated with increasing concentrations of BALF and major components of the BALF such as albumin, mucin and alpha(1)-glycoprotein, as a representative of glycosylated proteins. As cationic polymers, we tested dendrimers (fractured PAMAM) and polyethylenimine 25 kDa (PEI) and, as cationic liposomes, we used Lipofect-AMINE. The effect of BALF on polyplexes and lipoplexes was analysed by transfection experiments, fluorescence-quenching assay, 2-D-gel electrophoresis, SDS-PAGE, DNAse protection assay, size and zeta-potential measurements.

RESULTS

BALF inhibited polyplex- and lipoplex-mediated gene transfer. Analysing components of BALF, we found that dendrimer-mediated gene transfer was not inhibited by any specific component. PEI-mediated gene transfer was dose-dependently inhibited by alpha(1)-glycoprotein, slightly inhibited by mucin, but not inhibited in the presence of albumin. Lipoplex-mediated gene transfer was inhibited by mucin at higher concentrations and by albumin, but not by alpha(1)-glycoprotein. 2-D-gel electrophoresis revealed that proteins of the BALF were adsorbed more intensively to lipoplexes than to polyplexes. In addition, mucin and alpha(1)-glycoprotein also adsorbed more intensively to lipoplexes than to polyplexes. Adsorption of BALF components led to a decrease in the positive zeta-potential of lipoplexes and led to a negative zeta-potential of polyplexes. Complement cleavage fragment C3 beta, and in the case of lipoplexes also the C3 alpha fragment, were found among the proteins opsonised on gene vectors.

CONCLUSIONS

Our study shows that BALF contains inhibitory components for non-viral gene transfer. We could not detect a specific inhibitory component, but inhibition was most likely due to the change in the surface charge of the gene vectors. Interestingly, there is evidence for complement activation when the route of pulmonary gene vector administration is chosen. Consequently, shielding of gene vectors to circumvent interaction with the ASL environment should be a focus for pulmonary administration in the future.

In vitro phagocytosis and monocyte-macrophage activation with poly(lactide) and poly(lactide-co-glycolide) microspheres

Treatment of many intracellular infections in the mononuclear phagocytic system (MPS), requires targeting of antibiotics by a drug delivery system. The objective of this study was to examine whether the particular nature of microspheres, made of end-group capped and uncapped poly(lactide) [PLA] and poly(lactide-co-glycolide) [PLGA 50:50 and PLGA 75:25], affect the uptake into and also the activation of monocyte-macrophages. Placebo and gentamicin sulfate containing microspheres were incubated with J774 murine monocyte-macrophages and fresh human blood monocytes. Phagocytosis became more efficient with increasing polymer hydrophobicity, whereas opsonization of the particles in serum exerted inconsistent effects. Monocyte activation was determined by flow cytometry and measured as oxidative burst. The cellular oxidative burst induced by the particles was higher for end-group uncapped polymers. Opsonization increased significantly the oxidative activity of J774 monocytes, but affected inconsistently that of human blood monocytes. The results demonstrate that PLA and PLGA microspheres loaded with gentamicin sulfate were efficiently phagocytosed in vitro. The end-group uncapped polymer-type microspheres promoted significantly cell activation, which may be of importance for drug delivery and targeting to intracellular infections.

Comparison of protein adsorption patterns onto differently charged hydrophilic superparamagnetic iron oxide particles obtained in vitro and ex vivo

Protein adsorption patterns of superparamagnetic iron oxides (SPIO) were evaluated by two-dimensional electrophoresis (2-DE) after in vitro incubation of the particles in plasma or serum. SPIO particles having positive (MKK 1211), negative (MKA 1211), or neutral (MKG 1411) charge were used. Protein adsorption patterns of different charged SPIO particles acquired in vitro and recollected 5 min after intravenous injection into rats (ex vivo) were compared. For the uncharged MKG 1411 particles, the differences of protein adsorption patterns were negligible and only minor differences were found for the negatively charged MKA 1211 and positively charged MKK 1211 particles. A good correlation between in vitro and ex vivo data could be shown. For the evaluation of protein adsorption patterns of SPIO particles determining organ distribution and allowing estimation of site-specific delivery (drug targeting), the currently used protocol for 2-DE analysis could be confirmed.

Endogenous carriers and ligands in non-immunogenic site-specific drug delivery

Targeted drug delivery has gained recognition in modern therapeutics and attempts are being made to explore the potentials and possibilities of cell biology related bioevents in the development of specific, programmed and target oriented systems. The components which have been recognized to be tools include receptors and ligands, where the receptors act as molecular targets or portals, and ligands, with receptor specificity and selectivity, are trafficked en route to the target site. Although ligands of exogenous or synthetic origin contribute to the selectivity component of carrier constructs, they may impose immunological manifestations of different magnitudes. The latter may entail a continual quest for bio-compatible, non-immunogenic and target orientated delivery. Endogenous serum, cellular and extracellular bio-ligands interact with the colloidal carrier constructs and influence their bio-fate. However, these endogenous bio-ligands can themselves serve as targeting modules either in their native form or engineered as carrier cargo. Bio-regulatory, nutrient and immune ligands are sensitive, specific and effective site directing handles which add to targeted drug delivery. The present review provides an exhaustive account of the identified bio-ligands, which are not only non-immunogenic in nature but also site-specific. The cell-related bioevents which are instrumental in negotiating the uptake of bio-ligands are discussed. Further, a brief account of ligand-receptor interactions and the set of biological events which ensures ligand-driven trafficking of the ligand-receptor complex to the cellular interior is also presented. Since ligand-receptor interaction is a critical pre-requisite for negotiating cellular uptake of endogenous ligands and anchored carrier cargo, an attempt has been made to identify differential expression of receptors and bio-ligands under normal and etiological conditions. Studies which judiciously utilized bio-ligands or their analogs in negotiating site-specific drug delivery have been reviewed and presented. Targeted delivery of bioactives using endogenous bio-ligands offers enormous options and opportunities through carrier construct engineering and could become a future reality in clinical practice.

Proteomics: applications and opportunities in preclinical drug development

Advances in DNA sequencing and the near-term availability of whole genome sequences for several pharmaceutically relevant organisms promise to dramatically alter the breadth and scale of high-throughput proteomic studies. The substantial amount of literature is available in the public domain, demonstrate the potential of proteomics in the preclinical phases of pharmaceutical development. Over the next few years, it is anticipated that functional genomics and proteomics will have major impacts on the clinical phases of drug development. Expected benefits are earlier proof-of-concept studies in man and increased efficiency of clinical trials through the availability of biologically relevant markers for drug efficacy and safety.