There has been growing interest in designing and development of suitable micro or nano drug delivery system with the ability to target site specifically and release the payload in a predetermined fashion. Recently a new type of system called polyelectrolyte microcapsules and thin films have been proposed and developed for applications such as, biomedical devices to micro sensing and drug delivery. Owing to its advantages of mild preparation conditions, multifunctionality, with programmable characteristics and to encapsulate large amount of materials, it has shown immense potential. In the present research, multilayer polyelectrolyte thin films composed of Poly(methacrylic acid) (PMA) and Poly (vinyl pyrrolidone) (PVP) were deposited on the flat substrates using layer by layer (LBL) technique. The film growth and its deconstruction under physiological conditions were characterized using UV Visible spectrophotometer and Scanning Electron Microscopy (SEM). Hollow microcapsules composed of PMA and PVP were also produced with the help of sacrificial silica template using the same LBL adsorption technique. After coating the desired number of PVP and PMA layers, the colloidal template was removed with a buffer system composed of Hydrofluoric acid (HF) and Ammonium fluoride (NH4F). The obtained capsules were characterized for its surface morphology using SEM and Atomic Force Microscopy (AFM). The hydrogen bonding in capsule formation was confirmed by Fourier Transform Infrared Spectroscopy (FTIR). Encapsulation and release with the microcapsules was carried out using Rifampicin (Antitubercular drug) as a model drug. The interaction of empty and drug loaded capsules with Mycobacterium Smegmatis cell line was investigated. It was found that the empty capsules did not affect the cell growth indicating their biocompatibility. Confocal microscopy studies with Doxorubicin (anticancer drug), which is a naturally fluorescent molecule, showed the drug is indeed encapsulated inside the hollow capsule. From the above studies, it was concluded that polyelectrolyte capsules have the potential to be used for delivering drugs.

Polyelectrolyte capsules fabricated by layer-by-layer (LbL) technique are introduced as a simple and efficient carrier system for spontaneous deposition of proteins and low molecular water soluble drug. The objective of the work was to investigate the applicability of polyelectrolyte capsules as vehicles for sustained or controlled delivery of drugs. Two different polymeric systems composed of weak and strong polyelectrolytes were chosen to study the loading and release behavior in order to meet the requirements of biomedical applications. In the first system, the wall permeability of weak polyelectrolyte (PAH/PMA) capsules could be readily manipulated from open to closed state by simply varying the pH. The open and closed state of the capsules could be attributed to the charge density variation of weak polyelectrolytes, which induces the capsule wall to undergo a transition from continuous to nanoporous morphology due to phase segregation. Bovine Serum Albumin (BSA) was spontaneously deposited in the hollow capsules and deposition was investigated by CLSM, SEM and AFM techniques. The driving force for spontaneous deposition was electrostatic interaction between the preloaded polystyrene sulfonate (PSS) and BSA. The deposition was uniform and concentration of BSA in the capsule interior reached a few hundred times greater than that of bulk. The amount of loading was significantly influenced by the loading pH, loading concentration and charge density of substance to be loaded at the corresponding pH. The deposition was successful up to the isoelectric point of BSA (pH = 4.8) and there was no loading observed above that, since the deposition is based on electrostatic attraction between PSS and BSA. During the release at physiological pH of 7.4, charge reversal of BSA occurred which induced electrostatic repulsion between PSS and BSA thereby triggering the movement of BSA from the interior to the bulk. Release continued up to 5 h in water and a total release of 63 % was observed which increased to 72 % when release was performed in PBS. Spontaneous deposition of low molecular weight, water soluble drug, ciprofloxacin hydrochloride was performed in the same manner and its release profile was studied. Controlling diffusion of smaller drug molecules is extremely difficult in drug delivery applications. Cross linking of capsule wall components could be used to control the release rates of smaller drug molecules. Cross linking density is dependent on the cross linking time and increases the stiffness of the capsule wall. Release of ciprofloxacin hydrochloride was possible even up to 6 h after cross linking. Antibacterial studies showed that the drug released even after 25 h has a significant effect on the bacterial pathogen E.coli. The second system included weak and strong polyelectrolytes (PAH & DS) and a novel route was employed to fabricate optically addressable capsules that could be laser activated for delivery of drugs. This approach involved a combination of LbL assembly and polyol reduction method wherein PEG was used to reduce AgNO3 to Ag nanoparticles (NPs). The capsules were prepared via LbL assembly of PAH and DS on silica template followed by synthesis of silver NPs in the layers and subsequent dissolution of the silica core. The sulfonate groups of DS present in the polyelectrolyte film act as binding sites for the adsorption of silver ions which are then reduced to silver NPs in the presence of PEG. The size of the silver NPs formed was influenced by the AgNO3 concentration used. At lower concentration, smaller particles of uniform distribution were observed which turned into larger particles of random distribution when the concentration of AgNO3 is increased. Silver NPs embedded capsules ruptured when exposed to laser and was significantly influenced by silver NPs size, their distribution, laser intensity and time of exposure. The synthesis of silver NPs increased the permeability of the capsules to higher molecular weight substances like dextran caused by the defects, discontinuities and pores created on the polymeric network due to the newly formed silver NPs. Encapsulation of FITC-dextran was performed using thermal encapsulation method by exploiting temperature induced shrinking of the capsules at elevated temperatures. During heat treatment the porous morphology transformed into smooth pore free structure which prevented the movement of dextran into the bulk and hence enrichment inside the capsules. The loaded dextran was readily released when exposed to laser and the release could be controlled from linear to burst release in order to meet practical requirements in biomedical applications.

Die Elektrorotation von fixierten Erythrozyten wurde im Frequenzbereich von 16 Hz bis 33 MHz untersucht. Zwischen 16 Hz und 1 kHz zeigen die fixierten Erythrozyten eine Rotation parallel zur Feldrichtung mit einer maximalen Rotationsgeschwindigkeit zwischen 30 Hz und 70 Hz. Es wurde sowohl die Abhängigkeit von der äußeren Leitfähigkeit untersucht als auch von der Oberflächenladung. Die experimentellen Resultate erwiesen sich als konsistent mit einer erst kürzlich entwickelten Theorie zur Elektrorotation im niederfrequenten Bereich (LFER). Sie zeigen, daß die Elektrorotation im niederfrequenten Bereich von der Oberflächenladung und -leitfähigkeit entscheidend mitbestimmt werden kann. Fixierte Thrombozyten wurden mittels Elektrorotation im Frequenzbereich von 16 Hz bis 33 MHz untersucht. Zur Interpretation der Daten wurde ein theoretisches Modell weiterentwickelt, welches die innere vesikuläre Struktur der Thrombozyten berücksichtigt, und mit dem niederfrequenten Modell zur Elektrorotation superponiert. In Lösungen mit Dextran unterschiedlicher Molekulargewichte und Konzentrationen wurde sowohl die elektrophoretische Mobilität als auch Elektrorotation von fixierten Erythrozyten untersucht. Es konnte gezeigt werden, daß sich im niederfrequenten Bereich Depletionschichten an Hand von Elektrorotationsspektren erfassen lassen. Diese Daten bestätigen auch die Theorie zur LFER. Messungen der elektrophoretischen Mobilität von nativen Erythrozyten wurden in Lösungen mit dem Polyelektrolyten Polystyrensulfonat in Anhängigkeit vom Molekulargewicht und der Salzkonzentration durchgeführt. Es zeigte sich, daß das Polymer zum einen reversibel adsorbiert und zum anderen einen deutlichen Depletioneffekt herbeiführt. Im letzten Teil der Arbeit wurde ein Verfahren entwickelt, welches die Herstellung von Polyelektrolyt-Kapseln auf der Grundlage von biologischen Zellen ermöglicht, welche in Form und Größe identisch mit den verwendeten biologischen Templaten sind. / Electrorotation of fixed red blood cells (RBC) has been investigated in a frequency range between 16 Hz and 33 Mhz. Between 16 Hz and 1 kHz fixed red blood cells undergo co-field rotation with a maximum of rotation betwen 30 and 70 Hz. The rotation was studied as a function of electrolyte conductivity and surface charge density. These observations are consistent with a recently developed theory of the low frequency electrorotation (LFER) and demonstrate that the surface charge and the surface conductivity can play a significant role in this frequency range. Fixed platalets were investigated by means of electrorotation in the frequency range from 16 Hz to 33 Mhz. For the interpretation of the data a model which takes into account the inner structure of the platalets was developed and added to the theory which describes the rotation in the low frequency range. In solutions with Dextran and fixed platalets the electrophoretic mobility as well as the electrorotation was measured. It was shown that in the low frequency range depletion layers are detectable. Furthermore this results verify the LFER theory. Measurements of the electrophoretic mobility of native RBC were carried out in solutions of the polyelectrolyte Polystyrenesulfonate in dependence on the molecular weight and the ionic strength. It was shown that the polymer adsorbs reversible and forms a significant depletion effect. In the last part of this work a method was developed, which allows the construction of polyelectrolyte caspules with biological cells as template, which are identical in size and shape with the templates used.

Targeted delivery aids in minimizing most of the drug-originated systemic toxic effects as well as improving the pharmacokinetic properties of anticancer therapeutics. Tumor targeting using hyaluronic acid (HA) as the targeting ligand has attracted a great deal of interest among a host of strategies developed to target the overexpressed tumor specific receptors. HA is an endogenous molecule that possesses a lot of biological functions in the human body. The role of HA synthases, HA degrading enzymes and the interaction of HA with its primary receptor CD44 in tumor metastasis and angiogenesis is really complex and controversial to date. However, overexpression of CD44receptors on tumor surface has been well studied, which have been utilized to direct tumor targeted drugs. Most of the HA based targeting systems were HA drug conjugates and surface modified colloidal carriers which required covalent modification. The lack of accurate structural characterization of these systems resulted in modification of HA binding sites that could affect the efficient cellular uptake. LbL technique is a simple and facile method to incorporate several materials into polyelectrolyte assemblies for drug delivery applications. HA being a negatively charged polysaccharide can be easily incorporated into such systems without any covalent modification. Although HA based polyelectrolyte multilayer films and microcapsules have been reported in combination with polycations like PAH, PLL and chitosan, their application as targeted drug delivery systems have not yet been explored. Herein, two LbL architectures with HA as the terminal layer have been investigated as targeted drug carriers, which can recognize overexpressed CD44 receptors in metastatic breast cancer cells. In the first part of the thesis, a novel polyelectrolyte nanocapsule system composed of biopolymers HA and protamine sulphate (PR) as the wall components was prepared and characterized. These pH and enzyme responsive nanocapsules were then utilized for efficient loading and release of anticancer drug doxorubicin (dox). Higher drug release was observed in simulated intracellular conditions like acidic pH and presence of hyaluronidase enzyme as compared to physiological pH. In the second part of the thesis, dox incorporated bovine serum albumin (BSA) nanoparticles modified with HA-Poly(l-Lysine) multilayers were developed and characterized. The drug release pattern of the dox loaded BSA nanoparticles was found to depend on the presence of a protease enzyme trypsin than pH variations. Both of these drug delivery systems were then evaluated for their cell targeting efficiency and cytotoxicity in CD44+ positive metastatic breast cancer cell line MDA MB 231. The final layer HA facilitated targeted delivery of these drug carriers via CD44 receptor mediated endocytosis. The enhanced cellular uptake followed by sustained delivery of dox by virtue of slow intracellular enzymatic degradation of the drug carriers resulted in their improved cytotoxicity as compared to free dox. Further in vitro biodistribution and tumor suppression efficiency of both the systems were studied in breast cancer xenograft models using BALB/c nude mice. Enhance accumulation of dox in the tumor tissue and significant tumor reduction were observed when treated with encapsulated dox using the HA based nanocarriers as opposed to free dox.

The past few years have witnessed significant work being directed towards drug delivery systems with layer-by layer (LbL) technique prominently featured as one of the most sought after approach. However, majority of the studies were focused on the fabrication of microcapsules which produced numerous drawbacks resulting in reduced applicability. This has spurred research into nanocapsules which has proved to overcome most of the drawbacks that plagued microcapsules by being able to evade the reticulo-endothelial system, exhibit enhanced permeability and retention in tumours etc. The capsules fabricated by the LbL technique requires a suitable combination of cationic and anionic polyelectrolytes which ensures that it is able to effectively protect the cargo it encapsulates as well as enhance its bio-applications. With numerous advantages such as biocompatibility and biodegradability to name a few, chitosan has proved to be an ideal cationic polyelectrolyte. Thus, this thesis focuses on the various therapeutic applications of LbL fabricated chitosan based nanocapsules. The first work focuses on the targeted delivery of the somatostatin analogue, Octreotide conjugated nanocapsules to over expressed somatostatin receptors. These LbL fabricated nanocapsules composed of chitosan and dextran sulfate (CD) encapsulate the anti cancer drug, doxorubicin and are found to attain site specificity as well as enhanced anti-proliferative activity. The results indicated that the nanocapsules were biocompatible and when conjugated with octreotide was found to have an enhanced internalization into SSTR expressing cells, thereby making it a viable strategy for the treatment of tumors that has an over expression of somatostatin receptors such as pancreatic carcinoma, breast carcinoma etc. The objective of the second work was to develop an efficient drug delivery system such as CD nanocapsules for encapsulation of Ciprofloxacin in order to combat infection by Salmonella, an intracellular and intra-phagosomal pathogen. In vitro and in vivo experiments showed that this delivery system can be used effectively to clear Salmonella infection. The increased retention of ciprofloxacin in tissues delivered by CD nanocapsules as compared to the conventional delivery proved that the same therapeutic effect was obtained with reduced dosage and frequency of Ciprofloxacin administration. The third work deals with the probiotic, Saccharomyces boulardii which is found to be effective against several gastrointestinal diseases but had limited clinical application due to its sensitivity to acidic environment. However, encapsulation of S. boulardii with chitosan and dextran sulfate ensured enhanced viability and selective permeability on exposure to acidic and alkaline conditions experienced during gastro intestinal transit. The final work involves the fabrication of novel pH responsive nanocapsules composed of chitosan-heparin which facilitate the intracellular delivery of a model anti-cancer drug, doxorubicin.