Synthesis and Surface Modification of Inorganic Nanoparticles for Application in Physics and Medicine

The core focus of this cumulative thesis is the synthesis, the characterization, and the polymer coating or the surface modification of different types of inorganic nanoparticles (NPs), e.g., semiconductor, magnetic, plasmonic, and titanium oxide NPs. These NPs are used in the field of physics, biotechnology, and in nanomedicine or life sciences for both diagnosis and therapy. The applications of these NPs depend on their unique properties, which are correlated to their size, shape, and the material composition. The colloidal stability of these nanocrystals or NPs in different media (e.g. organic, water, cell culture media) was achieved by means of capping agents or by wrapping suitable ligands or surfactants around the core of the NPs. The colloidal NPs that were synthesised during this research work were capped with hydrophobic ligands (e.g. oleic acid, oleylamine, etc.) to keep them stable in the organic media, e.g., toluene, chloroform, etc. The phase transfer from organic to aqueous is a mandatory step prior to their use in the few desired applications, especially when these NPs are exposed to aqueous medium or cell media. This is carried out by wrapping the NPs with an amphiphilic polymer, i.e., poly(isobutylene-alt-maleic anhydride) (Mw= 6000 Da) that is grafted with hydrophobic side chains of dodecylamine. The mentioned four types of produced NPs were: (i) Semiconductor NPs which include the hydrophobic cadmium sulfide (CdS) quantum dots (QDs) that are used: for organic scintillation neutrino detection experiments; for PPO (2, 5-diphenyloxazole) styrene based plastic scintillator detectors; for time resolved spectral measurement, and for fluorescence studies with different surface coatings; additionally, water soluble CdS, manganese doped CdS, and zinc sulphide (ZnS) with and without manganese doping were synthesized and engineered to run several experiments on nanomaterials’ (NMs) behavior in environmental media, e.g., river and lake water; (ii) magnetic NPs (MNPs) that include core only (iron oxide, e.g. magnetite) and core shell composite iron oxide magnetic NPs combined with cobalt and manganese ferrites; (iii) plasmonic NPs such as gold and silver NPs that were used in combination with iron-oxide NPs (4 nm each) for toxicity screening and dose determination assays, and (vi) titanium dioxide iv (TiO2) NPs with different sizes and shapes (i.e. cube, rods, plates, and bipyramids), which were used for in vivo experiments: To evaluate the bio-distribution, organ accumulation, biological barrier passage, and potential organ toxicity after a single intravenous administration of TiO2 NPs, and to assess the influence of the TiO2 NPs shape and geometry on the mentioned effects. Furthermore TiO2 NPs were also used to perform few more in vivo studies to investigate: (i) The effect of biological environment (e.g. lung lining liquid, saliva, gastric/intestinal fluids) on NPs’ behaviour and toxicity, using complex co-culture systems for the intestine and alveoli, (ii) the effect of NPs on the activation of the inflammasome, and (iii) the influence of NPs on the maturation and activation of dendritic cells. In addition to above mentioned experiments for synthesis and surface modification another study was carried out with the aim to transfer three different types of NPs (i.e. plasmonic, fluorescent and magnetic) in aqueous phase to be employed in hydrogels, aerogels, and heterogels applications. In this study bimetallic (gold-copper) plasmonic nanocubes, fluorescent (cadmium selenide/CdS) core shell nanorods and magnetic iron oxide (Fe3O4) nanospheres were successfully transferred to the aqueous phase irrespective of their different sizes ranging from 5-40 nm in at least one dimension. All water soluble NPs were cleaned by means of gel electrophoresis or by ultracentrifugation to get rid of micelles (empty polymer) followed by sterilization for all in vivo studies. The qualitative and quantitative analyses all of these NPs were performed by means of different characterization techniques, e.g., ultraviolet-visible spectroscopy, fluorescence spectroscopy, dynamic light scattering, zeta potential measurements gel electrophoresis, transmission electron microscopy, inductively coupled plasma mass spectrometry, and the X-ray diffraction analysis

Synthesis of advanced inorganic colloidal nanocrystals

Colloidal nanocrystals are crystalline materials of nanometer size which are colloidally suspended in a solution. Typical nanocrystals are made of few tens to some thousands atoms. Because of their small size they exhibit properties different to the conventional bulk materials. In the nanosize regime, in fact, it is not just the composition which determines the properties of a material but also its size and shape. The possibility to control these parameters allows the fabrications of nanocrystals whose properties can be exploited in several fields such as electronics, diagnostics, catalysis and optoelectronics. In this dissertation we will focus on semiconductive nanocrystals with particular attention to a new synthesis process which allows us to have a better control on the size and thus the properties. In particular we show that for small nanocrystals the growth is not continuous. Instead the nanocrystals grow discretely, from one stable configuration to the next bigger stable configuration. The possible stable configurations are termed "magic size clusters". For bigger particles growth is continuous. We report the generalization of the process to grow magic size clusters for several semiconductor materials. Also an application of magic size clusters of CdSe for the fabrication of light emitters is reported. The characterisation and application of particular semiconductive nanomaterials presented in this work will led us to the synthesis of more complex nanostructures such as core@shell nanomaterials and semiconductive-magnetic dimers. We demonstrate in particular the growth of II/VI semiconductor materials on top of FePt nanocrystals. Thus dimeric nanocrystals with a magnetic FePt domain and a II/VI domain are obtained. In these systems it is possible to combine together properties of the different materials in order to fabricate nanoparticles presenting as well a magnetic as a semiconductive domain

Polyelectrolyte Multilayer Capsules for Medical Applications

This thesis deals with the application of polymer capsules for diagnostic and therapeutic purposes in mammalian cells. The capsules comprise a multilayer shell of oppositely charged polyelectrolytes surrounding a cavity and have a size of two to five microns. Concerning diagnostics, capsules were produced to monitor the dynamics of the lysosomal pH in cancer cells. The cavities of the capsules were filled with a fluorescent, pH-sensitive dye for optical readout of the signal. The cells were monitored under physiological conditions upon induced pH imbalances. The results showed that the capsules were appropriate for intracellular long-term measurements and could monitor changes of the pH. For therapy, biodegradable capsules filled with biologically active molecules were synthesized. Two strategies were employed. In one approach, the cavity was filled with polyplexes of DNA or RNA and polyethylenimine, which are used regularly for the delivery of foreign genetic material into host cells. This approach is an example for gene therapy. The results showed that delivery by the capsules was very efficient and the encapsulated polyplexes were less toxic for the cells than their free counterparts. The other strategy was to directly deliver functional enzymes into cells. For this approach, cell models representing lysosomal storage diseases were employed. One of these diseases is Fabry. Patients with Fabry disease are deficient of the enzyme α galactosidase A. The enzyme was encapsulated in biodegradable capsules and given to the cells. This therapy form is called enzyme replacement therapy. The intracellular enzyme activity was determined by quantification of the intracellular level of a fluorescently labeled substrate of α galactosidase A. As the products of the reaction were non-fluorescent, the intracellular fluorescence could be used to quantify the intracellular activity of the encapsulated enzyme. Finally, therapy and diagnostics were combined in a model of Krabbe disease, another lysosomal storage disorder. In Krabbe patients, sphingolipids and cerebrosides accumulate in the oligodendritic glia cells of the patients, as due to a gene defect the enzyme galactocerebrosidase usually converting these agents is not expressed. In the model, the cause of the disease was simulated by incubation of oligodendritic cells with psychosine, which belongs to the group of sphingolipids. Galactocerebrosidase was encapsulated in biodegradable capsules and delivered to the cells. The functionality was tested by a viability assay. Two types of cells were used, wild-type cells expressing galactocerebrosidase and knockout cells, which did not express the enzyme. The viability of the cells in the presence of psychosine was determined with and without addition of galactocerebrosidase-filled capsules. The results showed that the effect of the capsules on the viability of the two different cell types was contrary. Whereas knockout cells gained higher viability when capsules were administered, wild-type cells suffered a loss in viability. The diagnostic part was characterized by monitoring the lysosomal pH upon incubation with psychosine. The dynamics of the lysosomal pH of the two types of cells turned out to be different. Each of the cell types could therefore be identified with a specific pH profile and the decision to treat cells with the enzyme-filled capsules can be based on the measured pH profile. This is considered an in vitro-example of theranostics, the combination of therapy and diagnostics

Polyelectrolyte Microcapsules for controlled cargo-release and sensing applications in living cells

Topic of the presented work is the preparation of multifunctional polymer microcapsules for biological and biomedical applications. The fabrication of such capsules is based on the layered adsorption of oppositely charged polymers, the so-called polyelectrolytes, onto charged templates (layer-by-layer assembly). As spherical base for the capsules porous calcium carbonate particles have been used. In addition to molecules that were encapsulated into the final polymer capsules further properties such as fluorescence, paramagnetic behavior or the ability to convert light energy into heat were embedded into the polymer shell by implementing nanoparticles. These functional groups were crucial for the realization of the experimental demands on the microsystems. In addition to the functionalization of the shell an efficient filling of the capsules with a multitude of different molecules was one of the major developments. Besides a coprecipitation method (pre-filling of the templates), a post-loading technique as well as the enrichment of the capsules with amphiphilic polymer micelles were used for loading the capsules. This last approach even allowed for filling both, hydrophilic and hydrophobic molecules into the the polymer microcapsules. The prepared materials were observed via absorbance or fluorescence spectroscopy or electron- and optical microscopy, the capsules were tested specifically for their intended applications. Here, special emphasis was placed on the intracellular release of the encaged cargo materials. Numerous experiments were performed to test the release of the cargo molecules within living cells. The efficient release via external laser-triggered heating was proven and improved by variation of gold-nanoparticle concentration attached to the polymer shells. In addition, the released content distributed into the cells, was observed to react after its liberation. Reactive substances, which have been separately encapsulated could successfully be released intracellularly and the occurring reactions were detected. Furthermore, nucleic acid chains (mRNA) could be encapsulated and successfully be released within cells. The cellular production of the RNA-encoded proteins was demonstrated. Another aim of the study was the targeted delivery of capsules to a desired place. In a flow chaannel, the flow of blood in living organisms was simulated. Capsules modified with ironoxide nanoparticles could be deposited selectively on a cell layer with the help of magnetic field gradients. This enabled for deposition of capsules on a large scale area as well as on on small, sub-millimeter patterns. Additionally to the release of materials and controlled deposition of capsules, the presented work is also studying the possible use of microcapsules as sensors for the composition of the environmental solution. These sensor properties were tested on the basis of ion-selective fluorescent dyes in the extracellular as well as in the intracellular space. In summary, the presented polymer microcapsules were proven as an advanced and versatile approach towards bio-medical requirements for drug delivery and sensing applications

Surface Modification and Functionalization of Colloidal Nanoparticles

Den Schwerpunkt dieser Dissertation stellt die Synthese multifunktionaler Nanopartikel, sowie deren Oberflächen-Modifikation und –Funktionalisierung für biologische Anwendungen dar. Kolloidale Nanopartikel haben gemeinsame, größenabhängige physikalische und chemische Eigenschaften inne, die in einer Weise kontrollierbar sind, wie es für makroskopische Festkörper nicht möglich ist. Multimodale, molekulare Bildgebung ist die synergetische Kombination aus zwei oder mehr Detektionstechniken, ermöglicht durch multimodale Objekte und Bildgebungsverfahren und gewährleistet eine verbesserte Visualisierung biologischer Materialien. Einige Prototypen, die auf multimodalen Nanopartikeln basieren, sind entwickelt worden. Kolloidale Nanopartikel,aufgebaut aus einem anorganischen Kern und einer Polymerhülle wurden synthetisiert. Sowohl der Kern als auch die Polymerhülle können je nach Zweckmäßigkeit für die Bildgebung/Detektion fluoreszent, magnetisch oder radioaktiv sein. Das Polymer enthält Carboxygruppen, die die Partikel durch elektrostatische Repulsion stabilisieren und darüber hinaus als Bindungsstellen für weitere chemische Funktionalisierungen zur Verfügung stehen. Hydrophobe Nanopartikel (CdSe/ZnS, Fe2O3 oder Gold-198) wurden anhand unterschiedlich modifizierter Polymere (mit Gadolinium, organischen Fluorophoren oder Indium-111) in eine wässrige Phase überführt. Zur Untersuchung nanopartikel-basierter Sensoren wurde eine FRET-Struktur eingeführt, in der ein organischer Farbstoff (ATTO-590) als Akzeptor direkt in die Polymerhülle eingebettet wurde, die die kolloidale Stabilität der als Donor fungierenden CdSe/ZnS Quantenpunkte generierte. Zur Detektion von Protonen wurden sowohl negativ als auch positiv geladene Goldnanopartikel mit einem ionensensitiven Farbstoff (SNARF) modifiziert. Es wurde außerdem demonstriert, dass das Sensor-Signal nicht durch die reale Konzentration, sondern die lokale Konzentration, in der „nano“-Umgebung der Partikeloberfläche generiert wird. Darüber hinaus wurde in einer kollaborativen Arbeit demonstriert, dass Nanopartikel-Kerne kombiniert mit Polymerhüllen für die Induktion von Zellschädigungen verantwortlich sind, nicht jedoch die Hüllen allein. Es wurde festgestellt, dass das Aufnahmeverhalten und die zellulär unfreundlichen Effekte von der Dauer der Aussetzung, vom Zelltyp und der Zellkultur abhängen. Außerdem wurden Goldnanopartikel mit und ohne PEG-Modifizierung in der „rainbow trout gill“ Zelllinie RTGill-W untersucht, wobei Goldnanopartikel mit PEG-Modifizierung eine geringere Toxizität auf die Alge als nicht PEG-modifizierte Partikel zeigten

Light addressable gold electrodes

The main objective carried out in this dissertation was to fabricate Light Amplified Potentiometric sensors (LAPS) based upon the semiconductor nanoparticles (quantum dots) instead of its bulk form. Quantum dots (QDs) were opted for this device fabrication because of their superior fluorescent, electric and catalytic properties. Also in comparison to their bulk counterparts they will make device small, light weighted and power consumption is much lower. QDs were immobilized on a Au substrate via 1,4 benzene dithiol (BDT) molecule. Initially a self-assembled monolayer (SAM) of BDT was established on Au substrate. Because of SAM, the conductivity of Au substrate decreased dramatically. Furthermore QDs were anchored with the help of BDT molecule on Au substrate. When QDs immobilized on Au substrate (QD/Au) via BDT molecule were irradiated with UV-visible light, electron-hole pairs were generated in QDs. The surface defect states in QDs trapped the excited electrons and long lived electron-hole pairs were formed. By the application of an appropriate bias potential on Au substrate the electrons could be supplied or extracted from the QDs via tunneling through BDT. Thus a cathodic or anodic current could be observed depending upon bias potential under illumination. However without light illumination the QD/Au electrode remained an insulator. To improve the device different modifications were made, including different substrates (Au evaporated on glass, Au evaporated on mica sheets and Au sputtered on SiO2/Si) and different dithiol molecules (capped and uncapped biphenyl 4,4 dithiol and capped and uncapped 4,4 dimercaptostilbenes) were tried. Also different QD immobilization techniques (normal incubation, spin coating, layer by layer assembly (LbL) of polyelectrolytes and heat immobilization) were employed. This device was able to detect electrochemically different analytes depending upon the QDs incorporated. For example CdS QDs were able to detect 4-Aminophenol, a product of an enzymatic reaction of Alkaline Phosphatase with p-Aminophenyl Phosphate. Subsequently this reaction was observed at CdS/Au electrode, by enzyme-substrate reaction within the electrolyte solution, and also by immobilizing the enzyme on top of QDs via LbL assembly of polyelectrolytes. With another kind of CdS-FePt dimer QDs, detection of hydrogen peroxide (H2O2) was demonstrated. Only at CdS/Au electrode there was no impact made by H2O2 but with the presence of Pt within QDs H2O2 was detected via reduction even at a bias potential of -100mV

Synthesis and characterization of particles fabricated by layer-by-layer assembly

The subject of this doctoral dissertation is the synthesis and characterization of microcapsules and nanoparticles fabricated by Layer-by-Layer (LbL) assembly. The technique is based on the electrostatically-driven alternated adsorption of cationic and anionic charged polymers in a layer-by-layer fashion, similar to the layer structure of an onion. During these syntheses polyelectrolyte multilayer shells were formed via electrostatic interactions on calcium carbonate (CaCO3) microparticles and gold (Au) nanoparticles (NPs). Due to differences in the size range between microcapsules and nanoparticles, two different strategies were used for the self-assembly of polyelectrolytes. This work first aimed to investigate the LbL assembly of polyelectrolytes oppositely charged on calcium carbonate spherical particles, which size diameter ranges from 1 to 6 μm. Polyelectrolytes with different nature property have been employed to produce polyelectrolyte multilayer (PEM) capsules: i) sulfate/polyarginine (DEXS/PARG) for biodegradable shell formation and ii) poly(sodium- 4-styrenesulfonate)/poly(allylamine hydrochloride) (PSS/PAH) for non-biodegradable shell formation. In addition, one kind of silica (SiO2) capsules have been fabricated and their properties such as degradability and release of molecules have been compared with polyelectrolyte capsules. In order to encapsulate different molecular cargo inside the capsules (with silica or polyelectrolyte shells), two main procedures have been employed: i) co-precipitation (or pre-loading) and ii) post-loading. The encapsulation efficiency of both procedures has been investigated. Moreover, multifunctional capsules have been produced by embedding magnetic NPs or plasmonic NPs into the hull of the capsule. The functionalization was performed using again electrostatic interactions as the major driving force in the assembly between nanoparticles and polyelectrolytes. Thus, some applications of these carrier systems for delivery and sensing were investigated. Firstly, polyelectrolyte capsules post-loaded with the pH indicator seminaphtharhodafluor (SNARF) in their cavity with and without polymer coated iron oxide NPs in their hull were synthesized. The composition of the walls of these magnetic PEM capsules was (PSS/PAH)2 magnetic NPs (PSS/PAH)2. The results indicated that encapsulated ion-sensitive fluorophores can be used to detect fast changes of pH and the capsules can be manipulated (i.e., change the location) in microfluidic devices using magnetic fields. Finally, non-biodegradable capsules loaded with cubic magnetic NPs were produced to study their opening upon the application of an alternating magnetic field. The polymer poly(acrylamide-co-diallyldimethyl- ammonium chloride) (P(Am-DDA)) which is strongly positively charged was added within the polyelectrolyte shell to enhance the attachment and increase VI the concentration of magnetic NPs. The final architecture of the LbL shell was (PSS/PAH)(PSS/P(Am-DDA) magnetic NPs (PAH)(PSS/PAH)2. Magnetic NPs can be heated by the application of an alternating magnetic field. This fact was used to disrupt and open PEM capsules containing magnetic nanoparticles in the shell. The capsules released then their molecular cargo loaded in their interior

Examining Uptake of Nanomaterials by Eukaryotic Cells with Digital Image Cytometry

Due to their small size and related interesting properties, artificial nanoma-terials are utilized for a great number of biological and medical applications. Cell entry routes, intracellular trafficking and processing of nanoparticles, which determine their fate, efficiency, and toxicity, are depending on various parameters of the specific nanomaterial, such as size, surface charge, surface chemistry and elasticity. Nanoparticle-cell interactions are typically elucidated by means of fluorescence microscopy. Cell functions can be observed by a multiplicity of commercially available probes. For the quantification of cell features from images (image cytometry), computer-based algorithms are favoured to avoid bias introduced by the subjective perception of the observer. By applying high throughput microscopy in combination with digital image cytometry the screening of high numbers of cells is made possible. With the large quantity of obtained data, cell populations can be identified and, in general, results that are statistically meaningful are obtained. In the first part of this work this method is applied in order to examine the cellular responses upon exposure to plasmonic poly(methacrylic acid)-coated gold nanoparticles (Au NPs) with respect to morphology and viability of human endothelial and epithelial cells (HUVECs and HeLa cells). Au NPs of 4-5 nm size were chosen which had been thoroughly characterized in terms of their physico-chemical parameters. These particles bear interesting properties for biomedical applications and, for several years, have been in the focus of research. In this work significant impacts on mitochondrial and lysosomal morphology upon exposure to the Au NPs are reported. The alteration of the structure of the cytoskeleton and a dramatically reduced proliferation are described. Interestingly, the smallest dose inducing the described cellular responses was of one or two magnitudes lower than those, where acute cytotoxicity and an increase in the production of reactive oxygen species (ROS) were observed. In the second part the process of endocytosis of polymer capsules is examined. These systems are seen as a promising tool for intracellular cargo delivery and release. After lipid raft-mediated phagocytosis, the capsules are transferred from the neutral extracellular medium to increasingly acidic intracellular vesicles. By embedding a pH-sensitive fluorescent dye into the cavity of the capsule the uptake process and the associated acidification can be monitored time-dependently. It is demonstrated that the kinetic of the acidification process strongly depends on the stiffness of the capsules. Soft particles with minor stiffness are transported faster into lysosomal structures than stiffer ones. Additionally, these sensor particles are used to confirm the importance of the V1G1-subunit of the vacuolar ATPase being responsible for vesicle acidification

Novel Hybrid Polymeric and Inorganic Structures for Applications in Nanobiotechnology

This cumulative doctoral dissertation deals with the use of diverse polymers in different applications within nanoscience. The synthesis and characterization of several nano and microstructures is also explained, focusing on the later surface modification via the use of different polymers. Polymers are chemical compounds formed by the combination of several repeating structural units (monomers) in a process called polymerization. These structures are assembled following a specific pattern and their subsequent properties are given by the monomers added in the polymerization process. Several uses of polymers have been reported, being their use in the process of engineering novel composite materials for applications within fields like aerospace industry, biotechnology or medicine. The work shown in this thesis aimed to implement novel applications for some of the general polymer uses found in literature and the employment of amphiphilic zwitterionic polymers to test their stability for different biological applications. The dissertation is first focused on the study of three different applications of polymers inside nanotechnology. One of the most common applications of the use of amphiphilic polymers is the coating of inorganic NPs initially synthesized in organic solutions, transferring them into aqueous solutions. The resulting polymer coated NPs count on functional groups on their surface allowing further modifications for new functionalities. This procedure is applied to NPs with different size (ranging from 4 to 29 nm core size) and material (gold and iron oxide). A second application of the polymers is the protection of highly unstable, water and oxygen-sensitive clusters from degradation in aqueous environments. For that purpose gold NPs (Au NPs) of 4 nm were used as template and the clusters were collected between the surface of the NP and the amphiphilic polymer shell. The kinetic activity of the clusters was studied in aqueous environment, obtaining signal in at least the first 24 hours after the coating. As a complementary study inside this dissertation, different amphiphilic zwitterionic polymers were synthesized and optimized for a correct stabilization of NPs in water. The influence of parameters like pH, protein concentration and ionic strength was studied to obtain a complete description of the stability of the different zwitterionic polymer-coated NPs, comparing them to the single charge polymer coated NPs (e.g. fully positive or fully negative). A third application involves the self-assembly of alternating-charge polyelectrolyte layers deposited via adsorption on sacrificial calcium carbonate cores, yielding polymeric hollow microstructures able to be provided with physical and biological properties. Both properties are obtained via the accumulation of iron oxide nanoparticles between the polymer layers and the attachment of specific antibodies vion the outermost polymer layer, giving physical (magnetic) and biological (specific recognition) properties to the whole structure. These microcapsules were utilized to obtain a magnetic immunosensor able to specifically recognize and extract horseradish peroxidase (used as protein model) from a solution

Nanoparticles: Synthesis, Surface Modification and Functionalization for Biological and Environmental Applications

In addition to the type or nature of the nanoparticles (NPs) core, the surface of the obtained nanoparticles plays a crucial role and has great impact on the physicochemical properties of the nanoparticles which reflect in turn on the nanomaterials interactions (with the surrounding medium, biological systems and environment), functionalities and their possible applications. The general focus of this doctoral dissertation has been paid to the synthesis, controlled surface modification, functionalization, purification and characterization of different types of (plasmonic, semiconductor and magnetic) nanoparticles providing water soluble and highly colloidally stable nanoparticles proper for environmental and biological applications. Most of the as synthesized nanoparticles are inorganic particles (e.g. 5 nm Au NPs, 12 nm magnetic iron oxide NPs, 3 nm iron platinum NPs, 8 nm cobalt platinum NPs, CdSe/ZnS core/shell QDs of different sizes from 3-5 nm to 7 nm ZnO QDs) stabilized by hydrophobic organic molecules known as the surfactant or ligand which play an important role to control the shape and growth of the during the nanoparticles synthesis in addition to its role as stabilizing agents preventing the nanoparticles to be agglomerated. In case of water insoluble (hydrophobically capped) nanoparticles (not suitable for the biological applications), they were transformed from organic phase to aqueous environment using a very general protocol known as amphiphilic polymer coating which is based on the hydrophobic interaction between the hydrophobic ligands on the surface of the nanoparticles and the hydrophobic side chains of the used polymer. The polymer coating of originally organic-solvent soluble nanoparticles converts them to water soluble ones (thanks to the free carboxylate groups on surface) which have the ability to be further functionalized with extra functional and/or biologically active molecules of interest. The obtained polymer coated nanoparticles were purified and characterized using different techniques, such as agarose gel electrophoresis, size exclusion chromatography, UV-Vis spectroscopy, fluorescence spectroscopy (in case of fluorescent materials), transmission electron microscopy (TEM) and dynamic light scattering (DLS). Monodisperse different types of polymer coated nanoparticles were obtained with a high quality and colloidal stability as inferred from their physicochemical properties such as narrow hydrodynamic diameter distribution and the negative surface charges expressed as zeta potential. Furthermore, the surface of some water soluble polymer coated nanoparticles was modified with different functionalities such as some fluorophores (e.g. Dy-495, DY-647 and rhodamine), polyethylene glycol, folic acid and methotrexate to obtain multifunctional nanoparticles that could be useful for a wide range of biological applications such as tracking, labeling and multimodal imaging and targeting drug delivery