Cellular Uptake Behavior of Unfunctionalized and Functionalized PBCA Particles Prepared in a Miniemulsion

Continuous Nanoprecipitation of Polycaprolactone in Additively Manufactured Micromixers

The polymeric ouzo effect is an energy-efficient and robust method to create nanoparticles with biologically degradable polymers. Usually, a discontinuous or semi-continuous process is employed due to its low technical effort and the fact that the amount of dispersions needed in a laboratory is relatively small. However, the number of particles produced in this method is not enough to make this process economically feasible. Therefore, it is necessary to improve the productivity of the process and create a controllable and robust continuous process with the potential to control parameters, such as the particle size or surface properties. In this study, nanoparticles were formulated from polycaprolactone (PCL) in a continuous process using additively manufactured micromixers. The main goal was to be able to exert control on the particle parameters in terms of size and zeta potential. The results showed that particle size could be adjusted in the range of 130 to 465 nm by using different flow rates of the organic and aqueous phase and varying concentrations of PCL dissolved in the organic phase. Particle surface charge was successfully shifted from a slightly negative potential of −14.1 mV to a negative, positive, or neutral value applying the appropriate surfactant. In summary, a continuous process of nanoprecipitation not only improves the cost of the method, but furthermore increases the control over the particle’s parameters.

Nano-encapsulated Tinospora cordifolia (Willd.) using poly (D, L-lactide) nanoparticles educe effective control in streptozotocin-induced type 2 diabetic rats

The therapeutics for type 2 diabetes mellitus has emerged in the current century towards nanomedicine incorporated with plant active compounds. In this study, Tinospora cordifolia loaded poly (D, L-lactide) (PLA) nanoparticles (NPs) were evaluated in vivo for their anti-hyperglycemic potency towards streptozotocin-induced type 2 diabetic rats. T. cordifolia loaded PLA NPs were synthesised by the double solvent evaporation method using PLA polymer. The NPs were then characterised and administrated orally for 28 successive days to streptozotocin-induced diabetic rats. The PLA NPs had significant anti-diabetic effects which were equal to the existing anti-diabetic drug glibenclamide. The antidiabetic activity is due to the synergism of compounds present in stem extract of the plant which reduced the side effects and anti-diabetic.

Recent progress and advances in redox-responsive polymers as controlled delivery nanoplatforms

Recent advances and progress in redox-responsive polymeric nanosystems for biomedical applications are discussed in this review article.

Toxicological evaluation of dextran stabilized iron oxide nanoparticles in human peripheral blood lymphocytes

Iron oxide nanoparticles present an attractive choice for carcinogenic cell destruction via hyperthermia treatment due to its small size and magnetic susceptibility. Dextran stabilized iron oxide nanoparticles (DIONPs) synthesized and characterized for this purpose were used to evaluate its effect on cellular uptake, cytotoxicity, and oxidative stress response in human peripheral blood lymphocytes. In the absence of efficient internalization and perceptible apoptosis, DIONPs were still capable of inducing significant levels of reactive oxygen species formation shortly after exposure. Although these particles did not cause any genotoxic effect, they enhanced the expression of a few relevant oxidative stress and antioxidant defense related genes, accompanied by an increase in the glutathione peroxidase activity. These results indicate that under the tested conditions, DIONPs induced only minimal levels of oxidative stress in lymphocytes. Understanding the biological interaction of DIONPs, the consequences as well as the associated mechanisms in vitro, together with information obtained from systemic studies, could be expected to advance the use of these particles for further clinical trials.

Nanoparticles and antigen-specific T-cell therapeutics: a comprehensive study on uptake and release

AIM

T lymphocytes are used as cellular therapeutics in many disease entities including cancer. We investigated the uptake and retention of nanoparticles (NPs) by these nonphagocytic cells.

MATERIALS & METHODS

Uptake, release and toxicity of various polymeric NP preparations were analyzed by flow cytometry, confocal laser scanning microscopy and transmission electron microscopy. T-cell effector functions were measured using IFN-γ-ELISPOT and (51)Chromium-release assays.

RESULTS

Amino-functionalized NPs were efficiently ingested by antigen-specific T cells without adversely influencing effector functions. NPs were stored in membrane-surrounded vesicles, with major proportions released extracellularly during 24 h.

CONCLUSION

Amino-functionalized polymeric NPs are efficiently taken up by human T cells and could be used to design nanocarriers for direct access and manipulation of antigen-specific T cells in vivo.

Reversible activation of pH-sensitive cell penetrating peptides attached to gold surfaces

pH-sensitive viral fusion protein mimics are widely touted as a promising route towards site-specific delivery of therapeutic compounds across lipid membranes. Here, we demonstrate that a fusion protein mimic, designed to achieve a reversible, pH-driven helix-coil transition mechanism, retains its functionality when covalently bound to a surface.

Therapeutic efficacy and toxicity of tamoxifen loaded PLA nanoparticles for breast cancer

This study was carried out to assess the therapeutic efficacy and toxicity of tamoxifen (Tmx) loaded poly(d,l-lactic acid) (PLA) nanoparticles (Tmx-NPs) for breast cancer. An in vivo study was conducted to determine the effect of Tmx-NPs on DMBA induced mammary tumor in female Wistar rat. The experimental results showed that the mean diameter of Tmx-NPs was 224 ± 3 nm with 68 ± 2% (w/w) of entrapment efficiency. In in vivo study, the tumor size in rat was significantly reduced (P < 0.001) by treating Tmx-NPs as compared to pure Tmx and untreated group (control DMBA). Tmx-NPs showed the marked reduction in hepatotoxicity and renal toxicity when compared to pure Tmx as evidenced by histopathological examination of liver and kidney tissues as well as estimation of AST, ALT levels, and creatinine, urea, blood urea nitrogen levels. Oxidative stress and lipid peroxidation was estimated in spleen, liver and kidney and was found significantly high in pure Tmx treated group as compared to Tmx-NPs and control group. Immunological parameters like blastogenic response of splenocytes, TLC, DLC were studied and found significantly high in pure Tmx treated group but the variations were nonsignificant in Tmx-NPs group as compared to control. Thus, Tmx-NPs have significant therapeutic efficacy with reduced side effects.

Nanoparticles from renewable polymers

The use of polymers from natural resources can bring many benefits for novel polymeric nanoparticle systems. Such polymers have a variety of beneficial properties such as biodegradability and biocompatibility, they are readily available on large scale and at low cost. As the amount of fossil fuels decrease, their application becomes more interesting even if characterization is in many cases more challenging due to structural complexity, either by broad distribution of their molecular weights (polysaccharides, polyesters, lignin) or by complex structure (proteins, lignin). This review summarizes different sources and methods for the preparation of biopolymer-based nanoparticle systems for various applications.

Direct visualization of the interfacial position of colloidal particles and their assemblies

A method for direct visualization of the position of nanoscale colloidal particles at air-water interfaces is presented. After assembling hard (polystyrene, poly(methyl methacrylate), silica) or soft core-shell gold-hydrogel composite (Au@PNiPAAm) colloids at the air-water interface, butylcyanoacrylate is introduced to the interface via the gas phase. Upon contact with water, an anionic polymerization reaction of the monomer is initiated and a film of poly(butylcyanoacrylate) (PBCA) is generated, entrapping the colloids at their equilibrium position at the interface. We apply this method to investigate the formation of complex, binary assembly structures directly at the interface, to visualize soft, nanoscale hydrogel colloids in the swollen state, and to visualize and quantify the equilibrium position of individual micro- and nanoscale colloids at the air-water interface depending of the amount of charge present on the particle surface. We find that the degree of deprotonation of the carboxyl group shifts the air-water contact angle, which is further confirmed by colloidal probe atomic force microscopy. Remarkably, the contact angles determined for individual colloidal particles feature a significant distribution that greatly exceeds errors attributable to the size distribution of the colloids. This finding underlines the importance of accessing soft matter on an individual particle level.

Multifunctional biodegradable polymer nanoparticles with uniform sizes: generation and in vitro anti-melanoma activity

We present a simple, yet versatile strategy for the fabrication of uniform biodegradable polymer nanoparticles (NPs) with controllable sizes by a hand-driven membrane-extrusion emulsification approach. The size and size distribution of the NPs can be easily tuned by varying the experimental parameters, including initial polymer concentration, surfactant concentration, number of extrusion passes, membrane pore size, and polymer molecular weight. Moreover, hydrophobic drugs (e.g., paclitaxel (PTX)) and inorganic NPs (e.g., quantum dots (QDs) and magnetic NPs (MNPs)) can be effectively and simultaneously encapsulated into the polymer NPs to form the multifunctional hybrid NPs through this facile route. These PTX-loaded NPs exhibit high encapsulation efficiency and drug loading density as well as excellent drug sustained release performance. As a proof of concept, the A875 cell (melanoma cell line) experiment in vitro, including cellular uptake analysis by fluorescence microscope, cytotoxicity analysis of NPs, and magnetic resonance imaging (MRI) studies, indicates that the PTX-loaded hybrid NPs produced by this technique could be potentially applied as a multifunctional delivery system for drug delivery, bio-imaging, and tumor therapy, including malignant melanoma therapy.

Absolute quantitation of sub-micrometer particles in cells by flow cytometry

Absolute quantitative measurements of nanoparticle (NP) uptake are a prerequisite to determine doses of NPs in pharmacological and toxicological studies. However, absolute quantitation is rarely reported, hindering the comparison between different studies. Here, a new flow cytometric approach is presented to analyze fluorescent NPs with a "standard" non-scanning flow cytometer and to quantify them inside cells. The mean fluorescence intensity of a single particle and the particle concentration (NPs per μL medium) are obtained. A routine for rapid quantitative counting of the endocytosed NPs in HeLa cells by flow cytometry (FC) is developed and validated by confocal laser scanning microscopy. As a proof-of-concept, the quantitative measurements show that the cellular uptake efficiency of negatively charged poly(methyl methacrylate) NPs is very low, that is, in the range of 10(-3) % of the added particle amount.

Complex encounters: nanoparticles in whole blood and their uptake into different types of white blood cells

Aim: A whole blood assay for evaluating the uptake of nanoparticles into white blood cells in order to close the gap between basic studies in cell culture and pharmacokinetic studies in animals was developed. Materials & methods: After drawing peripheral blood into standard blood collection vials with different anticoagulants, amino- and carboxy-functionalized polymeric styrene nanoparticles were added and uptake was evaluated by flow cytometry. Results: By counterstaining surface markers of leukocytes (e.g., monocytes, neutrophil granulocytes, B or T lymphocytes), investigations of different cell types can be conducted in a single run by flow cytometry. The authors demonstrated that anticoagulation should be done with heparin, and not EDTA, in order to prevent hampering of uptake mechanisms. Conclusion: By using heparinized whole blood, the authors demonstrated differences and usefulness of this assay for screening cellular uptake as it should occur in the bloodstream. Nevertheless, animal studies are warranted for final assessment of the nanoparticles.

Original submitted 11 November 2011; Revised submitted 1 July 2012; Published online 31 August 2012

The relative brightness of PEG lipid-conjugated polymer nanoparticles as fluid-phase markers in live cells

While conjugated polymer nanoparticles (CPNs) have been widely touted as ultra-bright labels for biological imaging, no direct comparative measurements of their intracellular brightness have been reported. Simple in vitro comparisons are not definitive since fluorophore brightness in vitro may not correspond with intracellular brightness. We have compared the fluorescence brightness of J774A.1 cells loaded with 24 nm methoxy-capped 2,000 M(r) polyethylene glycol lipid PFBT nanoparticles (PEG lipid-PFBT CPNs) to cells loaded with carboxy-functionalized quantum dots (Qdots) or a dextran-linked small molecule organic dye, Alexa Fluor 488 dextran (AF488-dex). Under conditions likely to be used for biological imaging or flow cytometry, these CPNs are 175× brighter than Qdots and 1,400× brighter than AF488-dex in cells. Evaluation of the minimum incubation concentration required for detection of nanoparticle fluorescence with a commercial flow cytometer indicated that the limit of detection for PEG lipid-PFBT CPNs was 19 pM (86 ppb), substantially lower than values obtained for Qdots (980 pM) or AF488-dex (11.2 nM). Investigation of the mechanism of cellular uptake of the three fluid-phase labels indicates that these particles are passively taken into macrophage cells via macropinocytosis without interaction with cell surface receptors, and ultimately localize in lysosomes. In addition, no cytotoxicity could be observed at any of the CPN concentrations tested. Together, these data suggest that these CPNs are appropriate and attractive candidates as fluid-phase markers with significantly greater fluorescence brightness than existing dyes or nanoparticles. We expect that these CPNs will find application in both imaging and flow cytometry.

Suppressing unspecific cell uptake for targeted delivery using hydroxyethyl starch nanocapsules

Synthesizing nanocarriers with stealth properties and delivering a "payload" to the particular organ remains a big challenge but is the prime prerequisite for any in vivo application. As a nontoxic alternative to the modification by poly(ethylene glycol) PEG, we describe the synthesis of cross-linked hydroxyethyl starch (HES, M(w) 200,000 g/mol) nanocapsules with a size range of 170-300 nm, which do not show nonspecific uptake into cells. The specific uptake was shown by coupling a folic acid conjugate as a model targeting agent onto the surface of the nanocapsules, because folic acid has a high affinity to a variety of human carcinoma cell lines which overexpress the folate receptor on the cell surface. The covalent binding of the folic acid conjugate onto HES capsules was confirmed by FTIR and NMR spectroscopy. The coupling efficiency was determined using fluorescence spectroscopy. The specific cellular uptake of the HES nanocapsules after folic acid coupling into the folate-receptor presenting cells was studied by confocal laser scanning microscopy (CLSM) and flow cytometry.

DNA amplification via polymerase chain reaction inside miniemulsion droplets with subsequent poly(n-butylcyanoacrylate) shell formation and delivery of polymeric capsules into mammalian cells

There is a growing interest in the development of stable nanocapsules that could deliver the bioactive compounds within the living organism, and to release them without causing any toxic effects. Here the miniemulsion droplets were first used as "nanoreactors" for the amplification of single-molecule dsDNA template (476 and 790 base pairs) through PCR. Afterwards, each droplet was surrounded with a biodegradable PBCA shell by interfacial anionic polymerization, enabling therefore to deliver the PCR products into the cells. The size of the initial miniemulsion droplets and the final polymeric capsules was in the range of 250 and 320 nm, mainly depending on the type of the continuous phase and presence of dsDNA template molecules. The formation of PCR products was resolved with gel electrophoresis and detected with fluorescence spectroscopy in the presence of DNA specific dye (SYBRGreen). TEM studies were performed to prove the formation of the polymeric shell. The shell thickness was measured to be within 5-15 nm and the average molecular weight of the formed PBCA polymer was around 75000 g · mol(-1) . For the cell uptake experiments, the obtained nanocapsules were transferred from the organic phase into aqueous medium containing a water-soluble surfactant. The effect of the surfactant type (anionic, cationic or non-ionic) on the HeLa cell viability and nanocapsule uptake behavior was studied by CLSM and FACS. Confocal analysis demonstrated that nanocapsules stabilized with cationic (CTMA-Cl) and non-ionic (Lutensol AT50) surfactants show almost the same uptake, whereas capsules redispersed in anionic (SDS) surfactant possess a 30% higher uptake. The release of the encapsulated material within the cell was studied on the example of Cy5-labeled oligonucleotides showing the colocalization with mitochondria of MSCs cells.

Labeling of mesenchymal stromal cells with iron oxide-poly(L-lactide) nanoparticles for magnetic resonance imaging: uptake, persistence, effects on cellular function and magnetic resonance imaging properties

Background aims. Mesenchymal stromal cells (MSC) are the focus of research in regenerative medicine aiming at the regulatory approval of these cells for specific indications. To cope with the regulatory requirements for somatic cell therapy, novel approaches that do not interfere with the natural behavior of the cells are necessary. In this context in vivo magnetic resonance imaging (MRI) of labeled MSC could be an appropriate tool. Cell labeling for MRI with a variety of different iron oxide preparations is frequently published. However, most publications lack a comprehensive assessment of the noninterference of the contrast agent with the functionality of the labeled MSC, which is a prerequisite for the validity of cell-tracking via MRI. Methods.We studied the effects of iron oxide-poly(L-lactide) nanoparticles in MSC with flow cytom-etry, transmission electron microscopy (TEM), confocal laser scanning microscopy (CLSM), Prussian blue staining, CyQuant® proliferation testing, colony-forming unit-fibroblast (CFU-F) assays, flow chamber adhesion testing, immuno-logic tests and differentiation tests. Furthermore iron-labeled MSC were studied by MRI in agarose phantoms and Wistar rats. Results. It could be demonstrated that MSC show rapid uptake of nanoparticles and long-lasting intracellular persistence in the endosomal compartment. Labeling of the MSC with these particles has no influence on viability, differentiation, clonogenicity, proliferation, adhesion, phenotype and immunosuppressive properties. They show excellent MRI properties in agarose phantoms and after subcutaneous implantation in rats over several weeks. Conclusions. These particles qualify for studying MSC homing and trafficking via MRI.

Surfactant concentration regime in miniemulsion polymerization for the formation of MMA nanodroplets by high-pressure homogenization

This article focuses on the adequate surfactant concentration regime in which MMA droplets are stabilized sufficiently against coalescence during high-pressure homogenization but still no diffusion processes from droplets to micelles take place in the polymerization. Monomer miniemulsions with different surfactant concentrations were prepared with different energy inputs. Emulsions result that depend either on the surfactant concentration or on the energy input of the homogenization process. For both cases, the occupancy of the interface is compared as a function of the droplet size. It is shown that the surfactant concentration needed for the stabilization of a specified interface area decreases with increasing droplet size. For the dependence of droplet size on the energy input, it is shown that more surfactant can be applied before emulsion polymerization starts, but the applicable surfactant concentration is lower than the cmc and also depends on droplet size.

Miniemulsion polymerization and the structure of polymer and hybrid nanoparticles

The miniemulsion process allows the formation of complex structured polymeric nanoparticles and the encapsulation of a solid or liquid, an inorganic or organic, or a hydrophobic or hydrophilic material into a polymer shell. Many different materials, ranging from organic and inorganic pigments, magnetite, or other solid nanoparticles, to hydrophobic and hydrophilic liquids, such as fragrances, drugs, or photoinitators, can be encapsulated. Functionalization of the nanoparticles can also be easily obtained. Compared to polymerization processes in organic solvents, polymerization to obtain polymeric nanoparticles can be performed in environmentally friendly solvents, usually water.

Synthesis of fluorescent polyisoprene nanoparticles and their uptake into various cells

Fluorescent polyisoprene nanoparticles were synthesized by the miniemulsion technique as marker particles for cells. The uptake of the non-functionalized polyisoprene nanoparticles, without any transfection agents, into different adherent (HeLa) and also suspension (Jurkat) cell lines is strikingly efficient and fast compared to other polymeric particles, and leads to high loading of the cells. The intracellular polyisoprene particles are localized as single particles in endosomes distributed throughout the entire cytoplasm. The uptake kinetics shows that particle internalization starts during the first minutes of incubation and is finished after 48 h of incubation. Since (unfunctionalized) polystyrene particles show a comparable, low uptake behavior in cells, the uptake rates can be tuned by the amount of polystyrene in polyisoprene/polystyrene copolymer particles. As polyisoprene nanoparticles are internalized by different cell lines that are relevant for biomedical applications, they can be used to label these cells efficiently if a marker is incorporated in the particles. As polyisoprene is not or is hardly biodegradable the particles should be suited for long-term applications.