Current Drug Delivery - Volume 8, Issue 3, 2011

Nanomedicine is a new term, used to define the medical applications of nanotechnology. It encompasses the next era in drug delivery and diagnostics and imaging of health and disease conditions. This Special Issue is intended to bring to the forefront some major issues on regulatory challenges, examples for nanopharmaceutical product concepts based on nanoscale materials and evaluation of their safety or potential adverse effects. The urgent need for radical improvement of health and disease management is widely recognized. According to a comprehensive review by PriceWaterhouseCoopers, Pharma 2020: The vision. Which path will you take?, worldwide demand for effective treatments and prophylactics is steadily increasing due to several factors, including 1. global population pressures (projected population of 7.6 billion in 2020, from 6.5 billion in 2005); 2. changing demographics (people 65+ years will comprise about 9.4% of the total population by 2020, compared with 7.3% in 2005); (3) emergence of new pathogens (including bioterrorism) and antibiotic-resistant microorganisms; (4) climate change resulting in an increase in and spread of malaria, respiratory pathogens, common bacteria such as Salmonella and Campylobacter, the main cause of gastroenteritis, and E. coli; and (5) socioeconomic changes in the developing world leading to disease burden patterns resembling those in the developed world. Pharmaceutical companies have begun to struggle with providing innovative drugs for unmet medical needs. This innovation deficit, and the rising interest in personalized medicine, has slowed the pipeline of drug discovery, suggesting that current methods of developing blockbuster drugs may no longer be feasible. In 2007, only 19 new drugs/biologics were approved, the fewest since 1983. Low pharmaceutical R&D productivity, the complexity of applying genomic, proteomic and metabolomic data, the focus on a single molecule per disease, instead of targeting specific diseases with the right combination of treatment, will initiate a shift in global approaches to disease treatment. Additionally, the cost of non-compliance, a staggering $77-300 billion a year in the US alone, and the shift in attitude toward disease prevention necessitate better patient monitoring, personalized therapies, development of more effective vaccines and significant involvement of patients in management of their personal health and treatment regimens. Economic considerations alone would indicate that increased effectiveness is necessary to address the growing needs of patients and society. It is quite certain that the answer to the question of what will take us globally to the next level of effectiveness lies in the application of nanotechnology to health care. Significant initiatives worldwide are indicative of the already happening revolution in nanomedicine research and its translation to the clinic. The highlights of topics in this issue are as follows: Ushering nanomedicines toward clinical applications will require concerted efforts between researchers, pharmaceutical developers and regulatory agencies. The issue's first paper by Bawa emphasizes the need for appropriate regulatory guidance in the area of nanomedicines and enlists the challenges the Food and Drug Administration (FDA) is facing regarding the approval of nanomedicines. He also challenged the validity of evaluating nanoproducts using existing regulations and suggests the need for development of ‘nano’-specific guidelines. Finally, he provided some solutions and suggestions on regulatory requirements for nanomedicines. Applications of nanotechnology are reviewed in several therapeutic areas, such as gene therapy, cancer therapy/immunotherapy and vaccines. Elsabahy and coworkers reviewed the applications of nanoparticles as carriers for nucleic acids. They highlighted the key challenges and future directions of the non-viral vectors for gene therapy. Wong and coworkers reviewed the applications of nanomedicines in cancer therapy. They summarized the recent advances in the design of nanoparticles in cancer therapy. Then, continuing in the same subject, Sengupta and coworkers, reviewed the different cellular signaling pathways implicated in the pathogenesis of cancer and explained how they can be exploited as novel drug targets. They described how these novel drugs can be possibly merged with nanotechnology, to preferentially target the tumor. In a two-part review, Lavasanifar et al. explains the use of targeted nanoparticles in cancer immunotherapy and in imaging the anticancer immune responses. In the first part, a review of the immunotherapeutic strategies that aim to deliver tumor antigens specifically to dendritic cells is presented, including how nano-sized particulate delivery systems can deliver these antigens to dendritic cells in a targeted and specific manner. In the second part, devoted to improvements in imaging of nanomedicine delivery, the potential role of nanoscopic devices in delivering tracking molecules to dendritic cells for molecular imaging is presented. Toth and coworkers showed how nanotechnology could replace the classical vaccines by delivering immunogenic subunits derived from a particular pathogen. They reviewed the use of nanoparticles of different compositions for the delivery of peptide vaccines. As an important component in nanomedicine development, Gu and coworkers reviewed the use of CH50 as a hemolytic complement consumption assay for evaluation of nanoparticles and blood plasma protein interaction. This assay can work as a predictor of in vivo behavior and helps in understanding the mechanisms through which nanoparticles interact with the complement system of innate immunity, which could be very helpful in the nanoparticles design. In addition, they compared this method with alternative complement measurement techniques. Several specific nanomedicine designs are presented in original research papers and intend to highlight advances in noninvasive and targeted applications. Badea et al. introduced an example of a novel non-viral vector, gemini nanoparticles, for the delivery of plasmid DNA. In this study, they investigated the use of novel amino acid-substituted gemini surfactant-based nanoparticles as gene nanocarriers for mucosal applications. Foldvari et al. investigated biphasic vesicles as dermal delivery system for interferon alpha designed for the treatment of human papillomavirus infections. In this study, topical application in human volunteers and patients indicated that these novel delivery systems can deliver clinically significant levels of interferon alpha across intact human skin and wart tissue without the need for needles or other invasive methods. Romero and coworkers reported on the use of archaeosomes for oral drug delivery. They showed that these new delivery systems are superior to conventional liposomes and that they are preferentially taken up by the M cells as compared to liposomes. This Special Issue of Current Drug Delivery is a tiny snapshot of examples of the significant efforts made by the scientific and clinical nanomedicine community that is dynamically shaping the future of medical diagnosis, treatment and prevention of diseases.

There is enormous excitement and expectation surrounding the multidisciplinary field of nanomedicine - the application of nanotechnology to healthcare - which is already influencing the pharmaceutical industry. This is especially true in the design, formulation and delivery of therapeutics. Currently, nanomedicine is poised at a critical stage. However, regulatory guidance in this area is generally lacking and critically needed to provide clarity and legal certainty to manufacturers, policymakers, healthcare providers as well as the public. There are hundreds, if not thousands, of nanoproducts on the market for human use but little is known of their health risks, safety data and toxicity profiles. Less is known of nanoproducts that are released into the environment and that come in contact with humans. These nanoproducts, whether they are a drug, device, biologic or combination of any of these, are creating challenges for the Food and Drug Administration (FDA), as regulators struggle to accumulate data and formulate testing criteria to ensure development of safe and efficacious nanoproducts (products incorporating nanoscale technologies). Evidence continues to mount that many nanoproducts inherently possess novel size-based properties and toxicity profiles. Yet, this scientific fact has been generally ignored by the FDA and the agency continues to adopt a precautionary approach to the issue in hopes of countering future potential negative public opinion. As a result, the FDA has simply maintained the status quo with regard to its regulatory policies pertaining to nanomedicine. Therefore, there are no specific laws or mechanisms in place for oversight of nanomedicine and the FDA continues to treat nanoproducts as substantially equivalent (“bioequivalent”) to their bulk counterparts. So, for now, nanoproducts submitted for FDA review will continue to be subjected to an uncertain regulatory pathway. Such regulatory uncertainty could negatively impact venture funding, stifle nanomedicine research and development (R&D) and erode public acceptance of nanoproducts. The end-result of this could be a delay or loss of commercialized nanoproducts. Whether the FDA eventually creates new regulations, tweaks existing ones or establishes a new regulatory center to handle nanoproducts, for the time being it should at least look at nanoproducts on a case-by-case basis. The FDA should not attempt regulation of nanomedicine by applying existing statutes alone, especially where scientific evidence suggests otherwise. Incorporating nanomedicine regulation into the current regulatory scheme is a poor idea. Regulation of nanomedicine must balance innovation and R&D with the principle of ensuring maximum public health protection and safety.

Gene therapy holds the promise of correcting a genetic defect. It can be achieved with the introduction of a normal wild-type transgene into specific cells of the patient where the endogenous gene is underexpressing or by the introduction of a therapeutic agent, such as, antisense oligonucleotides (AON) or small interfering RNA (siRNA) to inhibit transcription and/or translation of an overexpressing endogenous gene or a cancer causing oncogene. Gene therapy has been utilized for vaccination and for the treatment of several diseases, such as, cancer, viral infections and dermatological diseases. However, there are many hurdles to overcome in developing effective gene-based therapeutics, including cellular barriers, enzymatic degradation and rapid clearance after administration. Successful transfer of nucleic acids (e.g. plasmid DNA, AON, siRNA, small hairpin RNA and micro RNA) into cells usually relies on the use of efficient carriers, commonly viral or non-viral vectors. Presently, viral vectors are more efficient than non-viral systems. However, immunogenicity, inflammatory reactions and problems associated with scale-up limit their clinical use. The ideal carriers for gene delivery should be safe and yet ensure that the DNA/RNA survives the extra- and intracellular environment and efficiently transfer to the appropriate cellular compartments. This review discusses some of the strategies that have been employed to overcome the barriers towards successful gene delivery.

Nanotechnology is a cutting edge and rapidly evolving technology in medicine. The potential of nanomedicine in cancer therapy is infinitely promising due to the fact that novel developments are constantly being explored. This is particularly the case in the use of nanoparticles in both tumor diagnosis, as well as treatment. This article will attempt to describe some recent advances using nanoparticle drug delivery system in cancer therapy. The evolution history, the challenges and the role of nanoparticles in cancer drug delivery will briefly be discussed together with additional opportunities in cancer therapy. An overall understanding of these issues will help with further advancement of designing better drug delivery system that can be applied clinically.

Understanding the mechanisms underlying different cellular signaling pathways implicated in the pathogenesis of cancer are leading to the identification of novel drug targets as well as novel drug candidates. Multiple targeted therapeutics that modulate aberrant molecular pathways have already reached the clinic. However, targeted therapeutics can exert mechanism-driven side effects as a result of the implication of the molecular target in normal physiological functions besides tumorigenesis. We hypothesize that targeted therapeutics can be optimized by merging them with nanotechnology, which offers the potential for preferential targeting to the tumor, resulting in increased intratumoral concentrations of the active agent with reduced distribution to other parts of the body. This review will address some of the emerging concepts that integrate these two disciplines to engineer novel nanovectors that target different signaling pathways.

Dendritic cells (DCs) are the key antigen presenting cells that link innate and adaptive immunity. In the periphery, DCs capture antigens, process them and migrate into the regional lymph nodes where they could initiate antigen specific T cell immune responses. Immunotherapeutic strategies that aim to deliver tumor antigens specifically to DCs could not only boost anti-tumor immune responses but also could alleviate non-specific immune activation and/or unwanted side effects. Nano-sized particulate delivery systems are efficient modalities that can deliver tumor antigens to DCs in a targeted and specific manner. This review will provide general information on the rationale behind targeting antigens to DCs and the crucial role of DCs in initiating antigen specific T cell responses. Different strategies that have been employed in delivering antigens to DCs will be also discussed. A special emphasis will be put on specific targeting of cancer vaccine formulations to DC-specific receptors (e.g. CD11c, CD40, Fcγ, CCR6, pathogenic recognition receptors such as Toll-like receptors (TLRs) and C-type lectin receptors (CLRs)).

The interaction of dendritic cells (DCs) and T cells has been the cornerstone of approaches to cancer immunotherapy. Antitumoral immune responses can be elicited by delivering cancer antigens to DCs. As antigen presenting cells, these DCs activate cancer antigen specific T cells. Whereas the first part of the review discusses methods for delivery of cancer vaccines to DCs, in this part the focus is on the potential role of nanoscopic devices for molecular imaging of these immune responses. Nanoscopic devices could potentially deliver tracking molecules to DCs, enabling monitoring of DCs and/or T cell activation and tumoricidal activity during immunotherapy, using non-invasive imaging modalities such as nuclear imaging (single photon emission computed tomography (SPECT), positron emission tomography (PET)), magnetic resonance imaging (MRI) and optical imaging.

Classical vaccines incorporating live or attenuated microorganisms possess several disadvantages and cannot be applied against cancer and some pathogens. Modern vaccines utilizing immunogenic subunits derived from a particular pathogen are able to overcome these obstacles but need a specific delivery system for their efficacy. Nanotechnology has opened a new window into these delivery methodologies. A nano-sized formulation of subunit vaccines has been proven to be very effective in inducing cellular and humoral immune responses. Here, we review a number of peptide vaccine delivery strategies based on nanoparticles composed of polymers, peptides, lipids, and inorganic materials.

The use of nanoparticles as platforms or vehicles for applications in nanomedicine, such as drug delivery and medical imaging, has been widely reported in the literature. A key area of potential improvement in the development and implementation of nanoparticles is the design of surface treatments to maximize residence time in the bloodstream. Major obstacles to the prolonged circulation of nanoparticles include complement activation and opsonization, both of which contribute to the removal of foreign matter from the vasculature. A greater understanding of the mechanisms through which nanoparticles interact with the complement system of innate immunity may be necessary in future endeavours to optimize nanoparticle design. The range of experimental techniques available for measuring complement interaction is presented. In particular, an in vitro hemolytic complement consumption assay called the CH50 method is compared with alternative complement measurement techniques and cellular uptake studies in order to demonstrate its effectiveness as a quantitative evaluation of overall complement interaction. Moreover, establishing the usefulness of CH50 results as predictors of in vivo behaviour is identified as a critical area for future research.

Gene based therapy represents an important advance in the treatment of diseases that heretofore have had either no treatment or cure. To capitalize on the true potential of gene therapy, there is a need to develop better delivery systems that can protect these therapeutic biomolecules and deliver them safely to the target sites. Recently, we have designed and developed a series of novel amino acid-substituted gemini surfactants with the general chemical formula C12H25(CH3)2N+- (CH2)3-N(AA)-(CH2)3-N+(CH3)2-C12H25 (AA= glycine, lysine, glycyl-lysine and, lysyl-lysine). These compounds were synthesized and tested in rabbit epithelial cells using a model plasmid and a helper lipid. Plasmid/gemini/lipid (P/G/L) nanoparticles formulated using these novel compounds achieved higher gene expression than the nanoparticles containing the parent unsubstituted compound. In this study, we evaluated the cytotoxicity of P/G/L nanoparticles and explored the relationship between transfection efficiency/toxicity and their physicochemical characteristics (such as size, binding properties, etc.). An overall low toxicity is observed for all complexes with no significant difference among substituted and unsubstituted compounds. An interesting result revealed by the dye exclusion assay suggests a more balanced protection of the DNA by the glycine and glycyl-lysine substituted compounds. Thus, the higher transfection efficiency is attributed to the greater biocompatibility and flexibility of the amino acid/peptide-substituted gemini surfactants and demonstrates the feasibility of using amino acid-substituted gemini surfactants as gene carriers for the treatment of diseases affecting epithelial tissue.

Purpose: Topical biphasic vesicle delivery system encapsulating interferon alpha (IFN α) was developed as an alternative to injections used to treat human papillomavirus (HPV) infections. Methods: Biphasic lipid vesicles encapsulating increasing doses of IFN α (biphasic IFN α) were characterized for encapsulation efficiency, size, zeta potential and vesicle structure by centrifugation, dynamic light scattering, confocal microscopy and small-angle x-ray scattering. Biphasic IFNα delivery into human skin in vivo and topical efficacy in patients with genital warts were evaluated. Results: Average encapsulation efficiency of IFN α was 81-91%. The average particle size was 1000-1100 nm and zeta potential +70 to +78 mV. After application of 5, 15 and 40MU/g biphasic IFN α formulation in a topical patch on the upper inner arm in healthy volunteers, skin IFN α levels increased to 120±30, 380±60 and 400±80 IU/mg protein in skin homogenates (n=5, 5, and 7), respectively. Topical application of biphasic IFN α (1 MU/dose) twice daily for two weeks in a pilot study with 12 patients with external condylomata acuminata resulted in a decrease in lesion size, in 2',5'-oligoadenylate synthetase activity and in tissue viral load. Conclusions: Biphasic vesicles delivered clinically significant levels of IFN α across intact human skin and elicited marked therapeutic effect in patients.

The archaeolipids (lipids extracted from archaebacterias) are non saponificable molecules that form self sealed mono or bilayers (archaeosomes-ARC). Different to liposomes with bilayers made of conventional glycerophospholipids, the bilayer of ARC posses a higher structural resistance to physico chemical and enzymatic degradation and surface hydrophobicity. In this work we have compared the binding capacity of ARC exclusively made of archaeols containing a minor fraction of sulphoglycophospholipids, with that of liposomes in gel phase on M-like cells in vitro. The biodistribution of the radiopharmaceutical 99mTc-DTPA loaded in ARC vs that of liposomes upon oral administration to Wistar rats was also determined. The fluorescence of M-like cells upon 1 and 2h incubation with ARC loaded with the hydrophobic dye Rhodamine-PE (Rh-PE) and the hydrophilic dye pyranine (HPTS) dissolved in the aqueous space, was 4 folds higher than upon incubation with equally labeled liposomes. Besides, 15% of Rh-PE and 13 % of HPTS from ARC and not from liposomes, were found in the bottom wells, a place that is equivalent to the basolateral pocket from M cells. This fact suggested the occurrence of transcytosis of ARC. Finally, 4 h upon oral administration, ARC were responsible for the 22.3 % (3.5 folds higher than liposomes) shuttling of 99mTc-DTPA to the blood circulation. This important amount of radioactive marker in blood could be a consequence of an extensive uptake of ARC by M cells in vivo, probably favored by their surface hydrophobicity. Taken together, these results suggested that ARC, proven their adjuvant capacity when administered by parenteral route and high biocompatibility, could be a suitable new type of nanoparticulate material that could be used as adjuvants by the oral route.