Applications and Limitations of Dendrimers in Biomedicine

Molecules

Dendrimers are drug delivery systems that are characterized by a three-dimensional, star-shaped, branched macromolecular network. They possess ideal properties such as low polydispersity index, biocompatibility and good water solubility. They are made up of the interior and the exterior layers. The exterior layer consists of functional groups that are useful for conjugation of drugs and targeting moieties. The interior layer exhibits improved drug encapsulation efficiency, reduced drug toxicity, and controlled release mechanisms. These unique properties make them useful for drug delivery. Dendrimers have attracted considerable attention as drug delivery system for the treatment of infectious diseases. The treatment of infectious diseases is hampered severely by drug resistance. Several properties of dendrimers such as their ability to overcome drug resistance, toxicity and control the release mechanism of the encapsulated drugs make them ideal systems for the treatment of infectious...

European Journal of Pharmaceutics and Biopharmaceutics, 2009

About forty percent of newly developed drugs are rejected by the pharmaceutical industry and will never benefit a patient because of poor bioavailability due to low water solubility and/or cell membrane permeability. New delivery technologies could help to overcome this challenge. Nanostructures with uniform and well-defined particle size and shape are of eminent interest in biomedical applications because of their ability to cross cell membranes and to reduce the risk of premature clearance from the body. The high level of control over the dendritic architecture (size, branching density, surface functionality) makes dendrimers ideal carriers in these applications. Many commercial small molecule drugs with anticancer, anti-inflammatory, and antimicrobial activity have been successfully associated with dendrimers such as poly(amidoamine) (PAMAM), poly(propylene imine) (PPI or DAB) and poly(etherhydroxylamine) (PEHAM) dendrimers, either via physical interactions or through chemical bonding ('prodrug approach'). Targeted delivery is possible via targeting ligands conjugated to the dendrimer surface or via the enhanced permeability and retention (EPR) effect. The biocompatibility of dendrimers follows patterns known from other small particles. Cationic surfaces show cytotoxicity; however, derivatization with fatty acid or PEG chains, reducing the overall charge density and minimizing contact between cell surfaces and dendrimers, can reduce toxic effects.

Current Topics in Medicinal Chemistry, 2008

Two general aspects which need to be considered for the successful application of dendrimers for biomedical purposes are their availability at an acceptable cost and their suitability as regards their pharmacodynamic and pharmacokinetic properties. These two aspects are covered in this review. In the first part, synthetic strategies for the preparation of dendrimers are outlined and emphasis is given to recent work on methodologies whose aim is the development of more efficient routes to dendrimers in terms of the materials used for their synthesis as well as in terms of the procedures required for their purification. These include procedures involving double-stage and double exponential synthesis, orthogonal coupling strategies, self-assembly and solid-phase approaches, as well as particularly useful synthetic protocols such as those used in "click chemistry". The second part of the review deals with the way in which the size, chemical constitution and physicochemical properties of dendrimers used for drug delivery may affect pharmacodynamic and pharmacokinetic parameters which are important considerations for drug bioavailability. This is illustrated by an overview of examples from recent work involving non-steroidal anti-inflammatory drugs, anticancer drugs and antibacterials.

2007

Nearly 3 decades ago, a dendritic structure was stepwise synthesized for the first time as a new type of molecules with promising applications. During years a huge effort has been devoted to implement the synthetic skills concerning the synthesis of these molecules and especially, new methods for purification and characterization of these compounds that are in the nanoscale range. The chemical manipulation of the surface and inner core of dendrimers were strategically used to allow a tailor-made control of physical-chemical properties and to discover new applications in material science and biomedicine. Although several examples have been reported in the literature describing applications of functionalized dendrimers and acclaiming a key role of these molecules, very scarce examples are actually close to the market. This review summarizes the state of the art of dendrimers and dendritic polymers as anti-infective agents, with a special focus on the strategies to block receptors used by pathogens for attachment, cell entry and dissemination. These nanometre size molecules are very attractive compounds as new drugs easily to be manipulated to improve their activity and scope. This is already a very active area of research, where we are involved, with interesting potential as demonstrated by the Phase I clinical trial of a functionalized dendrimer with real possibilities to reach the market soon. The success of this compound should provoke an enormous stimulus to scientists working in this area as well as in the industrial companies for investment in this topic.

Biomaterials, 2008

We have developed poly(amidoamine) (PAMAM) dendrimers that have poly(ethylene glycol) (PEG) grafts at all dendrimer chain ends. To obtain PEG-modified dendrimers with sites for conjugation of anticancer drugs for this study, we prepared PAMAM G4 dendrimers that have a glutamic acid (Glu) residue at every chain end of dendrimer; PEG chains were attached to amino groups of Glu residues. We then combined the anticancer drug adriamycin to side chains of the Glu residues using an amide bond, [PEGeGlu(ADR)-G4], or hydrazone bond, [PEGe Glu(NHNeADR)-G4]. For the dendrimers bearing adriamycin through amide linkage, adriamycin was released only slightly at pH 7.4 and 5.5. Although a negligible level of release occurred at pH 7.4 for dendrimers with adriamycin via hydrazone linkage, a remarkable extent of adriamycin release was induced at pH 5.5, which corresponds to the pH of late endosome. These adriamycin-bearing dendrimers showed much lower toxicity to HeLa cells than did free adriamycin. However, compared to PEGeGlu(ADR)-G4, PEGeGlu(NHNeADR)-G4 exhibited 7 times higher cytotoxicity, suggesting the importance of pH-sensitive hydrazone linkage for high cytotoxicity. Furthermore, the PEG-modified dendrimers exhibited an equivalent level of toxicity to that of adriamycin-resistant SBC-3/ADR100 cells and their parent adriamycin-sensitive SBC-3 cells.

Aristotle University Medical Journal, 2009

Dendrimers, like all nanosystems, appear to be very interesting in modern therapeutics. Their multi-branched polymer structure as well as their physicochemical properties attribute a promising role in drug administration. Dendrimers can be used for chemotherapy, antibiotics administration etc. Their main advance is the target release of the drug in particular cell types and even in intracellular compartments. Moreover they may cross anatomical barriers while protecting the attached agent from early procession. Although the application of dendrimers in theurapeutics is significant, further evaluation of their safety as drug carriers is required.

Journal of Drug Delivery and Therapeutics, 2016

This review gives concise information about the dendrimers, properties, synthesis and application in drug delivery, diagnosis and therapy. Due to their unique architecture these have improved physical and chemical properties. They show high solubility, miscibility and reactivity due to their terminal groups. Dendrimers have well defined size, shape, molecular weight and monodispersity. These properties make the dendrimers a suitable carrier in drug delivery application. Dendrimers are unimolecular miceller in nature and due to this enhances the solubility of poorly soluble drugs. Their compatibility with DNA, heparin and polyanions make them more versatile. Dendrimers, also referred as modern day polymers, they offer much more good properties than the conventional polymers. Due to their multivalent and mono disperse character dendrimers have stimulated wide interest in the field of chemistry biology, especially in applications like drug delivery, gene therapy and chemotherapy. Self assembly produces a faster means of generating nanoscopic functional and structural systems. But their actual utility in drug delivery can be assessed only after deep understanding of factors affecting their properties and their behavior in vivo.

Journal of Pharmacy and Bioallied Sciences, 2014

Molecules, 2021

Dendrimers comprise a specific group of macromolecules, which combine structural properties of both single molecules and long expanded polymers. The three-dimensional form of dendrimers and the extensive possibilities for use of additional substrates for their construction creates a multivalent potential and a wide possibility for medical, diagnostic and environmental purposes. Depending on their composition and structure, dendrimers have been of interest in many fields of science, ranging from chemistry, biotechnology to biochemical applications. These compounds have found wide application from the production of catalysts for their use as antibacterial, antifungal and antiviral agents. Of particular interest are peptide dendrimers as a medium for transport of therapeutic substances: synthetic vaccines against parasites, bacteria and viruses, contrast agents used in MRI, antibodies and genetic material. This review focuses on the description of the current classes of dendrimers, the...

Journal of Controlled Release, 2014

This paper reviews the biodistribution, toxicity and pharmacokinetics of pure dendrimers and their complexes with nucleic acids (dendriplexes) in animals, including mice, rats, rabbits, and guinea pigs. Methods and results will both be discussed. The paradigm about dendrimers' toxicity based on in vitro studies should be revised; almost all dendrimers of low and middle generations are non-toxic in vivo, despite showing some cytotoxic effects in vitro. Only the high generations of unmodified cationic dendrimers in high doses have some toxicity in vivo.