Studies towards biocompatibility of PAMAM dendrimers--overall hemostasis potential and integrity of the human aortic endothelial barrier

Nanotechnology translation in vascular diseases: From design to the bench

Atherosclerosis is a systemic pathophysiological condition contributing to the development of majority of polyvascular diseases. Nanomedicine is a novel and rapidly developing science. Due to their small size, nanoparticles are freely transported in vasculature, and have been widely employed as tools in analytical imaging techniques. Furthermore, the application of nanoparticles also allows target intervention, such as drug delivery and tissue engineering regenerative methods, in the management of major vascular diseases. Therefore, by summarizing the physical and chemical characteristics of common nanoparticles used in diagnosis and treatment of vascular diseases, we discuss the details of these applications from cellular, molecular, and in vivo perspectives in this review. Furthermore, we also summarize the status and challenges of the application of nanoparticles in clinical translation. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Cardiovascular Disease Implantable Materials and Surgical Technologies > Nanomaterials and Implants Therapeutic Approaches and Drug Discovery > Emerging Technologies.

Proactive Hemocompatibility Platform Initiated by PAMAM Dendrimer Adapting to Key Components in Coagulation System

Surface modification manipulates the application performance of materials, and thrombosis caused by material contact is a key risk factor of biomaterials failure in blood-contacting/implanting devices. Therefore, building a safe and effective hemocompatibility platform is still urgent. Owing to the unique properties of polyamidoamine (PAMAM) dendrimers, in this study, modified surfaces with varying dendrimer densities were interacted with elements maintaining blood homeostasis. These included the plasma proteins bovine serum albumin and fibrinogen, cells in blood (platelets and erythrocyte), as well as endothelial cells (ECs), and the objective was to evaluate the blood compatibility of the chosen materials. Whole blood test and dynamic blood circulation experiment by the arteriovenous shunt mode of rabbit were also conducted, based on the complexity and fluidity of blood. The PAMAM-modified substrates, particularly that with a high density of PAMAM (N1.0), adsorbed proteins with lessened fibrinogen adsorption, reduced platelet activation and aggregation, and suppressed clotting in whole blood and dynamic blood testing. Furthermore, the designed PAMAM dendrimer densities were safe and showed negligible erythrocyte lysis. Concurrently, PAMAM modification could maintain EC growth and did not trigger the release of procoagulant factors. These results suggest that the PAMAM-modified materials are compatible for maintaining blood homeostasis. Thus, PAMAM dendrimers can work as excellent surface modifiers for constructing a hemocompatibility platform and even a primer layer for desired functional design, promoting the service performance of blood-contacting devices.

Immunostimulatory Polymers as Adjuvants, Immunotherapies, and Delivery Systems

Activating innate immunity in a controlled manner is necessary for the development of next-generation therapeutics. Adjuvants, or molecules that modulate the immune response, are critical components of vaccines and immunotherapies. While small molecules and biologics dominate the adjuvant market, emerging evidence supports the use of immunostimulatory polymers in therapeutics. Such polymers can stabilize and deliver cargo while stimulating the immune system by functioning as pattern recognition receptor (PRR) agonists. At the same time, in designing polymers that engage the immune system, it is important to consider any unintended initiation of an immune response that results in adverse immune-related events. Here, we highlight biologically derived and synthetic polymer scaffolds, as well as polymer–adjuvant systems and stimuli-responsive polymers loaded with adjuvants, that can invoke an immune response. We present synthetic considerations for the design of such immunostimulatory polymers, outline methods to target their delivery, and discuss their application in therapeutics. Finally, we conclude with our opinions on the design of next-generation immunostimulatory polymers, new applications of immunostimulatory polymers, and the development of improved preclinical immunocompatibility tests for new polymers.

Folic acid conjugated PAMAM-modified mesoporous silica-coated superparamagnetic iron oxide nanoparticles for potential cancer therapy

In this study, novel folate-receptor-targeted polyamidoamine (PAMAM) dendrimer functional mesoporous silica-coated magnetic nanoparticles were prepared for drug delivery agents for photodynamic therapy applications. The surface of the magnetic nanoparticles was coated with mesoporous silica (M-MSN). The M-MSN nanoparticles were functionalized with siloxane-cored PAMAM dendrons (generation 1 to 3). The surface of the M-MSN-PAMAM nanocarriers was targeted with folic acid. Indocyanine green (ICG) a near-infrared dye was loaded in the M-MSN-PAMAM nanocarriers and the photodynamic therapy efficiency of the drug-loaded nanocarriers was evaluated on MCF-7 cells. MCF-7 cells were subjected to tissue culture E-Plate that was used to generate dynamic real-time data by measuring electrical impedance across interdigitated microelectrodes on the bottom of the plate. Light source (LEDs) was designed as a system that fit 96 well-plate and cells were irradiated at 785 nm for 20 min. Also, these results were confirmed by WST-1 assay in dark and light conditions for MCF-7 cells. The results showed that in vitro application of ICG loaded M-MSN-PAMAM-FA causes apoptosis in the MCF-7 cell line.

Evaluation of the effects of nanoparticles on the therapeutic function of platelet: a review

OBJECTIVES

Nanotechnology and nanoparticles are used in different applications in disease monitoring and therapy in contact with blood. Nanoparticles showed different effects on blood components and reduced or improved the function of therapeutic platelet during the storage time. This review study was performed to evaluate the impacts of various sizes and charges of nanoparticles on platelet function and storage time. The present review contains the literature between 2010 and 2020. The data have been used from different sites such as PubMed, Wiley, ScienceDirect and online electronic journals.

KEY FINDINGS

From the literature survey, it has been demonstrated that among various properties, size and charge of nanoparticles were critical on the function of therapeutic platelet during the storage and inhibition of their aggregation. Overall, this study described that nanoparticles with smaller size and negative charge were more effective in increasing the survival time, inhibition of aggregation and improving the function of therapeutic platelet.

SUMMARY

Based on the current review, it can be confirmed that nanoparticles such as dendrimer, Au, Ag and iron oxide nanoparticles with smaller size and negative charge have significant advantages for improving the efficacy of platelets during the storage chain and inhibition of their aggregation.

Influence cationic and anionic PAMAM dendrimers of low generation on selected hemostatic parameters in vitro

BACKGROUND

Polyamidoamine (PAMAM) dendrimers are a new class of monodisperse polymers that are used for drug delivery in systemic administrations. The influence of PAMAM dendrimers on components of the blood coagulation system has been extensively studied, but their effect on the activity of the fibrinolysis system has not been studied to date.

METHODS

The effect of cationic (G1-G3) and anionic (G1.5-G3.5) PAMAM dendrimers on the conformation and function of the main components of the coagulation and fibrinolysis systems was comparatively studied. Changes in overall plasma hemostatic potential, thrombin generation, prothrombin time, thrombin and tPA activities, the fluorescence of fibrinogen and plasminogen, zeta potential, polymerization of fibrinogen, and activation of plasminogen were analyzed to assess coagulofibrinolytic mechanisms of influence of the charge of the dendrimers.

RESULTS

Cationic dendrimers increased prothrombin time, suppressed thrombin generation in plasma, and changed the conformation and coagulability of fibrinogen, while anionic dendrimers did not have such effects. Anionic dendrimers slightly reduced tPA activity and altered plasminogen conformation much more strongly than the cationic dendrimers. Plasminogen activation by tPA was strongly inhibited by anionic dendrimers and weakly stimulated by cationic dendrimers. All these effects were enhanced with increasing generation and concentration of the dendrimers.

CONCLUSIONS

PAMAM-NH₂ dendrimers inhibit the extrinsic activation pathway of the coagulation system and alter the conformation and function of fibrinogen. PAMAM-COOH dendrimers change the conformation of plasminogen and inhibit its activation by tPA. This study gives new insight into the effect of anionic PAMAM dendrimers on the activity of the fibrinolytic system. For intravenous applications, the antifibrinolytic effect of anionic PAMAM dendrimers of generation ≥G2.5 should be considered.

Biocompatibility Studies of Gadolinium Complexes with Iminodiacetic Acid Derivatives

Apart from using as radiopharmaceuticals, iminodiacetic acid derivatives, after complexation with gadolinium, have been also tested as MRI CAs (magnetic resonance imaging contrast agents) since they show high affinity to hepatocytes and therefore provide high-resolution MRI of the liver. The purpose of this study was to evaluate the biocompatibility of four gadolinium complexes with iminodiacetic acid (IDA) derivatives differing in substituent in aromatic ring by estimating their influence on plasma hemostasis, integrity of erythrocyte membrane, and toxicity towards human umbilical vein endothelial cells (HUVECs). The influence of gadolinium-based CAs on plasma hemostasis was evaluated by measuring PT (prothrombin time), APTT (activated partial tromboplastin time), and TT (thrombin time). The effects of tested compounds on RBCs (Red Blood Cells) were assessed using hemolysis assay and microscopy studies. The influence of gadolinium complexes on the barrier properties of HUVECs was assessed by means of real-time method based on the measurements of the impedance changes of the cells. Gadolinium complexes did not affect significantly PT and TT. APTT measurements revealed significant prolongation in the presence of all tested gadolinium complexes at the concentration higher than 0.5 μmol/mL. Hemolysis assay showed that compounds with alkyl substituents in benzene ring without halogen atom (1-3) do not exert unfavorable effect on the integrity of erythrocyte membrane over the entire concentration range. All gadolinium complexes at 1.0 μmol/mL contribute to the decrease in HUVEC viability and integrity. To conclude, the study describes biocompatibility studies of gadolinium-based CAs, provides additional insight into their potential toxicity associated with systemic administration, and underscores the necessity for further research.

Sulfenamide and Sulfonamide Derivatives of Metformin - A New Option to Improve Endothelial Function and Plasma Haemostasis

Type 2 diabetes mellitus (T2DM) is a multi-factorial disease which can cause multiple organ dysfunction, including that of the vascular endothelium. The aim of the present study was to evaluate the effects of metformin, and its sulfenamide and sulfonamide derivatives (compounds 1–8) on the selected markers of endothelial function and blood coagulation. The integrity of endothelial cells(ECs) was examined using the real-time cell electric impedance system. Tissue Factor(TF) production, the release of von Willebrand Factor (vWF) and tissue plasminogen activator(t-PA) from ECs were determined using immunoenzymatic assays, while the process of platelet thrombus formation using the Total Thrombus-Formation Analysis System. Sulfenamide with n-butyl alkyl chain(3) does not interfere with ECs integrity, and viability (nCI_(24h) = 1.03 ± 0.03 vs. 1.06 ± 0.11 for control), but possesses anticoagulation properties manifested by prolonged platelet-dependent thrombus formation (Occlusion Time 370.3 ± 77.0 s vs. 286.7 ± 65.5 s for control) in semi-physiological conditions. Both p- and o-nitro-benzenesulfonamides (compounds7,8) exhibit anti-coagulant properties demonstrated by decreased vWF release and prolonged parameters of platelet thrombus formation and total blood thrombogenicity. In conclusion, chemical modification of metformin scaffold into sulfenamides or sulfonamides might be regarded as a good starting point for the design and synthesis of novel biguanide-based compounds with anticoagulant properties and valuable features regarding endothelial function.

Generation 2 (G2) - Generation 4 (G4) PAMAM dendrimers disrupt key plasma coagulation parameters

The aim of the research was to evaluate the effects of G2 - G4 PAMAM dendrimers on basic plasma haemostasis parameters (Partially Activated Thrombin Time (APTT), Prothrombin Time (PT), Thrombin Time (TT)) as well as the activity of factor X, antithrombin III (AT), protein C and plasmin. Furthermore, tissue factor (TF) synthesis in endothelial cells and viability of smooth muscle cells in the presence of PAMAM dendrimers was investigated. APTT, PT and TT were performed according to the available commercial methods. The activity of factor X was conducted based on deficient plasma factor X. Protein C, AT and plasmin activity were measured spectrophotometrically using chromogenic substrates. Intracellular TF production in human umbilical vein endothelial cells (HUVECs) was measured using immunohistochemical method. Viability of Human Aortal Smooth Muscle cells (hAoSMCs) was established using WST-1 assay. PAMAM dendrimers decreased activity of factor X, and concomitantly prolonged PT and APTT. We also demonstrated shortened TT and increased fibrinogen concentrations in plasma treated with G4 PAMAM dendrimers, suggesting formation of fibrinogen aggregates. G2 - G4 PAMAM dendrimers decreased the activity of both naturally occurring anticoagulants AT and protein C. G2 and G3 PAMAM dendrimers did not affect the proteolytic reaction with plasmin. PAMAM dendrimers were found not to trigger TF production in undisturbed endothelial cells. PAMAM dendrimers, depending on the concentration and generation decreased viability of AoSMCs. The results presented within the current study suggest complex but mostly undesirable effect of G2 - G4 PAMAM dendrimers on plasma haemostasis and underscore the need for further in-depth research.

An Intelligent Nanoscale Insulin Delivery System

Insulin injection relies on strict blood glucose monitoring. However, existing techniques and algorithms for blood glucose monitoring cannot be completed in a timely way. In this study, we have developed a new intelligent glucose-sensitive insulin delivery system to stabilize blood glucose levels in the body. This system does not require real-time detection of blood glucose. First, we successfully synthesized a nanoscale material called PAM-PAspPBA-b-PEG by using chemical methods. We then conducted TEM, DLS, and ¹H-NMR analyses to characterize the physicochemical properties, such as size, molecular composition, and configuration of the nanomaterial. We verified the glucose responsibility of the insulin loading nanoscale material in vitro and evaluated its safety and effect on mice in vivo. Results showed that insulin-loaded PAM-PAspPBA-b-PEG is glucose-sensitive, safer and more effective than regular insulin injection. This study provides a basis for future development of smart insulin delivery systems.

Construction of Hyaluronic Tetrasaccharide Clusters Modified Polyamidoamine siRNA Delivery System

The CD44 protein, as a predominant receptor for hyaluronan (HA), is highly expressed on the surface of multiple tumor cells. HA, as a targeting molecule for a CD44-contained delivery system, increases intracellular drug concentration in tumor tissue. However, due to the weak binding ability of hyaluronan oligosaccharide to CD44, targeting for tumor drug delivery has been restricted. In this study, we first use a HA tetrasaccharide cluster as the target ligand to enhance the binding ability to CD44. A polyamidoamine (PAMAM) dendrimer was modified by a HA tetrasaccharide cluster as a nonviral vector for small interfering RNA (siRNA) delivery. The dendrimer/siRNA nanocomplexes increased the cellular uptake capacity of siRNA through the CD44 receptor-mediated endocytosis pathway, allowing the siRNA to successfully escape the endosome/lysosome. Compared with the control group, nanocomplexes effectively reduced the expression of GFP protein and mRNA in MDA-MB-231-GFP cells. This delivery system provides a foundation to increase the clinical applications of PAMAM nanomaterials.

Poly (amidoamine) (PAMAM) dendrimer mediated delivery of drug and pDNA/siRNA for cancer therapy

Poly (amidoamine) (PAMAM) dendrimers are well-defined, highly branched macromolecules with numerous active amine groups on the surface. Because of their unique properties, PAMAM dendrimers have steadily grown in popularity in drug delivery, gene therapy, medical imaging and diagnostic application. This review focuses on the recent developments on the application in PAMAM dendrimers as effective carriers for drug and gene (pDNA, siRNA) delivery in cancer therapy, including: a) PAMAM for anticancer drug delivery; b) PAMAM and gene therapy; c) PAMAM used in overcoming tumor multidrug resistance; d) PAMAM used for hybrid nanoparticles; and e) PAMAM linked or loaded in other nanoparticles.

Synthesis and Biocompatibility Studies of New Iminodiacetic Acid Derivatives

BACKGROUND

Iminodiacetic acid (IDA) derivatives can be used as ligands to form complexes with technetium, with potential application as hepatobiliary diagnostic agents. The aim of this study was to synthesize five novel IDA derivatives and to compare their effects on plasma haemostasis with clinically approved ligands for technetium complexation.

METHODS

The influence of synthesized IDA derivatives on plasma haemostasis was evaluated spectrophotometrically by clot formation and lysis test (CL-test), coagulation assay, Prothrombin Time and Activated Partial Tromboplastin Time. The effects of the tested compounds on erythrocytes were assessed using haemolysis assays, microscopy and flow cytometry studies.

RESULTS

Despite their significant influence on the kinetic parameters of the process of clot formation and fibrinolysis, the tested ligands, at potential diagnostic concentrations, did not alter the overall potential of clot formation and lysis (CLAUC). At potential diagnostic concentrations (0.4 μmol/mL) all the tested compounds showed no adverse effects on the membranes of RBCs (Red Blood Cells).

CONCLUSION

IDA derivatives with methoxy substituents in aromatic ring, exert multidirectional effects on plasma haemostasis and should be considered safe as their significant impacts were mostly observed at 4 μmol/mL, which is about 10-fold higher than the theoretical plasma concentrations of these compounds.

Biocompatible sulfenamide and sulfonamide derivatives of metformin can exert beneficial effects on plasma haemostasis

As the pharmacokinetic properties of metformin are unfavourable, several analogues and prodrugs have been synthesised to improve its bioavailability. The aim of this study was to assess the plasma stability of sulfenamide and sulfonamide derivatives of metformin and establish their effects on plasma haemostasis and integrity of red blood cells (RBCs). The overall haemostasis potential was evaluated spectrophotometrically by clot formation and lysis test (CL-test). PT (Prothrombin Time) and APTT (Activated Partial Tromboplastin Time) were used to evaluate the effects if the compounds on the extrinsic and intrinsic coagulation pathway. Haemolysis assay, microscopy and flow cytometry studies were conducted to determine the effect of the compounds on RBCs. Two sulfonamide and one sulfenamide derivatives of metformin were associated with a statistically significant decrease in the overall potential of clot formation and fibrinolysis (↓ CL_AUC), suggesting that these compounds may exert beneficial effects regarding plasma haemostasis, which is frequently impaired in diabetic patients. p- and o-Nitrobenzene sulfonamides contributed to the beneficial change in kinetic parameters of clot formation and fibrinolysis. o-Nitrobenzene sulfonamide significantly increased thrombin generation time (↑ TGt) and was also found to prolong both APTT and PT. All compounds did not exert any effects on the integrity of RBCs over the concentration range 0.006-0.6 μmol/mL which constitutes the expected therapeutic concentration. In conclusion, sulfonamide derivatives of metformin present potentially beneficial properties in terms of plasma haemostasis which is frequently impaired in T2DM patients. Therefore, metformin sulfonamides may become a prototype for further design and synthesis of novel metformin analogues and prodrugs with improved pharmacokinetic properties.

New prodrugs of metformin do not influence the overall haemostasis potential and integrity of the erythrocyte membrane

Although metformin, an oral anti-diabetic drug, has been found to have multidirectional effects over the past decade, it is characterised by unfavourable pharmacokinetic properties. This study discusses the effects of metformin, phenformin and three prodrugs of metformin on the haemostasis and integrity of Red Blood Cells (RBCs). The influence of examined biguanide derivatives on haemostasis was evaluated spectrophotometrically by clot formation and lysis test (CL-test) at 405nm. The extrinsic and intrinsic coagulation pathway were examined by measuring the PT (Prothrombin Time) and aPTT (Activated Partial Tromboplastin Time). Haemolysis assay, microscopy and flow cytometry studies were used to assess the effect of the tested compounds on RBCs. Although none of the tested biguanide derivatives significantly influenced the overall potential of clot formation and fibrinolysis (CL_AUC constants), statistically significant changes were seen in the values of the kinetic parameters of fibrinolysis. Furthermore, only prodrug 2, with an 8-carbon alkyl chain, unfavourably affected RBCs by interaction with the erythrocyte membrane leading to significant haemolysis. Our results provide a further insight into the effects of metformin and its prodrugs on haemostasis and RBCs and underscore the necessity for further research.

Production of Hollow Bacterial Cellulose Microspheres Using Microfluidics to Form an Injectable Porous Scaffold for Wound Healing

Bacterial cellulose (BC) is a biocompatible material with high purity and robust mechanical strength used to fabricate desirable scaffolds for 3D cell culture and wound healing. However, the chemical resistance of BC and its insolubility in the majority of solutions make it difficult to manipulate using standard chemical methods. In this study, a microfluidic process is developed to produce hollow BC microspheres with desirable internal structures and morphology. Microfluidics is used to generate a core-shell structured microparticle with an alginate core and agarose shell as a template to encapsulate Gluconacetobacter xylinus for long-term static culture. G. xylinus then secretes BC, which becomes entangled within the shell of the structured hydrogel microparticles and forms BC microspheres. The removal of the hydrogel template via thermal-chemical treatments yields robust BC microspheres exhibiting a hollow morphology. These hollow microspheres spontaneously assemble as functional units to form a novel injectable scaffold. In vitro, a highly porous scaffold is created to enable effective 3D cell culture with a high cell proliferation rate and better depth distribution. In vivo, this injectable scaffold facilitates tissue regeneration, resulting in rapid wound-healing in a Sprague Dawley rat skin model.

Action of Nanoparticles on Platelet Activation and Plasmatic Coagulation

Nanomaterials can get into the blood circulation after injection or by release from implants but also by permeation of the epithelium after oral, respiratory or dermal exposure. Once in the blood, they can affect hemostasis, which is usually not intended. This review addresses effects of biological particles and engineered nanomaterials on hemostasis. The role of platelets and coagulation in normal clotting and the interaction with the immune system are described. Methods to identify effects of nanomaterials on clotting and results from in vitro and in vivo studies are summarized and the role of particle size and surface properties discussed. The literature overview showed that mainly pro-coagulative effects of nanomaterials have been described. In vitro studies suggested stronger effects of smaller than of larger NPs on coagulation and a greater importance of material than of surface charge. For instance, carbon nanotubes, polystyrene particles, and dendrimers inferred with clotting independent from their surface charge. Coating of particles with polyethylene glycol was able to prevent interaction with clotting by some particles, while it had no effect on others and the more recently developed bio-inspired surfaces might help to design coatings for more biocompatible particles. The mainly pro-coagulative action of nanoparticles could present a particular risk for individuals affected by common diseases such as diabetes, cancer, and cardiovascular diseases. Under standardized conditions, in vitro assays using human blood appear to be a suitable tool to study mechanisms of interference with hemostasis and to optimize hemocompatibility of nanomaterials.

How do the full-generation poly(amido)amine (PAMAM) dendrimers activate blood platelets? Activation of circulating platelets and formation of "fibrinogen aggregates" in the presence of polycations

Direct use of poly(amido)amine (PAMAM) dendrimers as drugs may be limited, due to uncertain (cyto)toxicity. Peripheral blood components, which constitute the first line of a contact with administered pharmaceuticals, may become vastly affected by PAMAM dendrimers. The aim of this study was to explore how PAMAMs' polycationicity might affect blood platelet activation and reactivity, and thus trigger various haemostatic events. We monitored blood platelet reactivity in rats with experimental diabetes upon a long-term administration of the unmodified PAMAM dendrimers. In parallel, the effects on blood flow in a systemic circulation was recorded intravitally in mice administered with PAMAM G2, G3 or G4. Compounding was the in vitro approach to monitor the impact of PAMAM dendrimers on blood platelet activation and reactivity and on selected haemostatic and protein conformation parameters. We demonstrated the activating effects of polycations on blood platelets. Some diversity of the revealed outcomes considerably depended on the used approach and the particular technique employed to monitor blood platelet function. We discovered undesirable impact of plain PAMAM dendrimers on primary haemostasis and their prothrombotic influence. We emphasize the need of a more profound verifying of all the promising findings collected for PAMAMs with the use of well-designed in vivo preclinical studies.

Stability of erythrocyte membrane and overall hemostasis potential - A biocompatibility study of mebrofenin and other iminodiacetic acid derivatives

BACKGROUND

Intravenous injection seems to be the most convenient way of administering drugs and contrast agents, which makes components of the blood the first and usually unwanted target of their action. Binding of intravenously administered compounds to erythrocytes, blood platelets and vascular wall may have serious clinical implications. The aim of this study was to examine the influence of four iminodiacetic acid derivatives, potential ligands for gadolinium complexation, on the process of coagulation and fibrinolysis, activity of thrombin and hemolysis.

METHODS

Kinetic parameters of coagulation and fibrinolysis process were determined during an optical CL-test based on measurement of transmittance alterations. Thrombin (0.5 IU/mL) and t-PA (240 ng/mL) were used to obtain a clotting and lysis curve. The activity of thrombin was determined with a chromogenic substrate S-2238. Hemolysis was examined spectrophotometrically and expressed as a percentage of released hemoglobin.

RESULTS

Exposure to iminodiacetic acid derivatives resulted in a significant increase in the overall potential of clotting and lysis (CLAUC), as well as with the significant changes in the key parameters of these processes (thrombin time, initial plasma clotting velocity, clot stabilization time). Furthermore, iminodiacetic acid derivatives caused a significant decrease in the amidolytic activity of thrombin and enhanced hemolysis in a concentration-dependent manner.

CONCLUSION

Despite their influence on the process of coagulation and fibrinolysis, amidolytic activity of thrombin and hemolysis, iminodiacetic acid derivatives should be generally considered safe as the significant effects were observed mostly at 4 μmol/mL, which is about 10-fold higher than the theoretical plasma concentration of these compounds.

Selective aggregation of PAMAM dendrimer nanocarriers and PAMAM/ZnPc nanodrugs on human atheromatous carotid tissues: a photodynamic therapy for atherosclerosis

Photodynamic therapy (PDT) involves the action of photons on photosensitive molecules, where atomic oxygen or OH(-) molecular species are locally released on pathogenic human cells, which are mainly carcinogenic, thus causing cell necrosis. The efficacy of PDT depends on the local nanothermodynamic conditions near the cell/nanodrug system that control both the level of intracellular translocation of nanoparticles in the pathogenic cell and their agglomeration on the cell membrane. Dendrimers are considered one of the most effective and promising drug carriers because of their relatively low toxicity and negligible activation of complementary reactions. Polyamidoamine (PAMAM) dendrite delivery of PDT agents has been investigated in the last few years for tumour selectivity, retention, pharmacokinetics and water solubility. Nevertheless, their use as drug carriers of photosensitizing molecules in PDT for cardiovascular disease, targeting the selective necrosis of macrophage cells responsible for atheromatous plaque growth, has never been investigated. Furthermore, the level of aggregation, translocation and nanodrug delivery efficacy of PAMAM dendrimers or PAMAM/zinc phthalocyanine (ZnPc) conjugates on human atheromatous tissue and endothelial cells is still unknown. In this work, the aggregation of PAMAM zero generation dendrimers (G0) acting as drug delivery carriers, as well as conjugated G0 PAMAM dendrimers with a ZnPc photosensitizer, to symptomatic and asymptomatic human carotid tissues was investigated by using atomic force microscopy (AFM). For the evaluation of the texture characteristics of the AFM images, statistical surface morphological and fractal analytical methodologies and Minkowski functionals were used. All statistical quantities showed that the deposition of nanodrug carriers on healthy tissue has an inverse impact when comparing to the deposition on atheromatous tissue with different aggregation features between G0 and G0/ZnPc nanoparticles and with considerably larger G0/ZnPc aggregations on the atheromatous plaque. The results highlight the importance of using PAMAM dendrimer carriers as a novel and promising PDT platform for atherosclerosis therapies.

Anticancer siRNA cocktails as a novel tool to treat cancer cells. Part (B). Efficiency of pharmacological action

This paper examines a perspective to use newly engineered nanomaterials as effective and safe carriers for gene therapy of cancer. Three different groups of cationic dendrimers (PAMAM, phosphorus, and carbosilane) were complexed with anticancer siRNA and the biophysical properties of the dendriplexes created were analyzed. The potential of the dendrimers as nanocarriers for anticancer Bcl-xl, Bcl-2, Mcl-1 siRNAs and additionally a scrambled sequence siRNA has been explored. Dendrimer/siRNA complexes were characterised by various methods including fluorescence, zeta potential, dynamic light scattering, circular dichroism, gel electrophoresis and transmission electron microscopy. In this part of study, the transfection of complexes in HeLa and HL-60 cells was analyzed using both single apoptotic siRNAs and a mixture (cocktail) of them. Cocktails were more effective than single siRNAs, allowing one to decrease siRNAs concentration in treating cells. The dendrimers were compared as siRNA carriers, the most effective being the phosphorus-based ones. However, they were also the most cytotoxic on their own, so that in this regard the application of all dendrimers in anticancer therapy will be discussed.

Study on the prostate cancer-targeting mechanism of aptamer-modified nanoparticles and their potential anticancer effect in vivo

Ligand-mediated prostate cancer (PCa)-targeting gene delivery is one of the focuses of research in recent years. Our previous study reported the successful preparation of aptamer-modified nanoparticles (APT-NPs) in our laboratory and demonstrated their PCa-targeting ability in vitro. However, the mechanism underlying this PCa-targeting effect and their anticancer ability in vivo have not yet been elucidated. The objective of this study was to assess the feasibility of using APT-NPs to deliver micro RNA (miRNA) systemically to PCa cells, to testify their tumor-targeting efficiency, and to observe their biodistribution after systemic administration to a xenograft mouse model of PCa. In addition, the effect of APT depletion and endocytosis inhibitors on cellular uptake was also evaluated quantitatively in LNCaP cells to explore the internalization mechanism of APT-NPs. Finally, blood chemistry, and renal and liver function parameters were measured in the xenograft mouse model of PCa to see whether APT-NPs had any demonstrable toxicity in mice in vivo. The results showed that APT-NPs prolonged the survival duration of the PCa tumor-bearing mice as compared with the unmodified NPs. In addition, they had a potential PCa-targeting effect in vivo. In conclusion, this research provides a prototype for the safe and efficient delivery of miRNA expression vectors to PCa cells, which may prove useful for preclinical and clinical studies on the treatment of PCa.