Volume 7, Issue 2 - Special issue: Translational Nanomedicine / Guest editor: Frederic Lagarce

This paper summarizes the key points discussed at the international conference held in Angers (France) on translational nanomedicine. During 3 days, more than 150 attendees presented their works and discussed through plenary sessions on how to translate to the clinics the discoveries found at lab scale. The importance of interdisciplinary works has been emphasized. New promising strategies inspired by biology were presented, such as bacteriophage associated silicon particles (BASP) in cancer therapy. Green nanotechnology, which limits the use of potentially toxic excipients to the benefit of natural compounds, is growing. Although there are various financial helps for the research and the training of next generations of researchers, the difficulties to find funding to go to the clinics has been illustrated by the squalene-conjugated nanoparticles that find no industrial support. Large-scale production of nanomedicines is also challenging to implement and pharmaceutical companies are developing new large-scale production tools to reach the patient bedside. Last but not least, regulation requirements and patenting have been forced to evolve and adapt to these particular vectors. As a conclusion, transversal collaborative research and a design of nanomedicine based on simplicity are two important levers to help these promising drugs to reach the patient.

Gene therapy has long been hailed as a revolutionary approach for the treatment of genetic diseases. The enthusiasm that greeted the harnessing of viruses for therapeutic DNA delivery has been tempered by concerns over safety. These concerns led to the development of alternative strategies for nucleic acid delivery to cells. One such strategy is the utilization of cationic peptides for the condensation of therapeutic DNA for delivery to its target. However, success of DNA as a therapy relies on its delivery to the nucleus of target cells, a process that is complicated by the many hurdles encountered following systemic administration. Non-viral peptide gene delivery strategies have sought inspiration from viruses in order to retain DNA delivering potency, but limit virulence. This review summarizes the progression of peptide-based DNA delivery systems, from rudimentary beginnings to the recent development of sophisticated multi-functional vectors that comprise distinct motifs with dedicated barrier evasion functions. The most promising peptides that achieve cell membrane permeabilization, endosomal escape and nuclear delivery are discussed.

For several years, the first line of treatment of glioblastoma (GB) patients is based on surgical resection followed by fractioned radiotherapy with concomitant and adjuvant chemotherapy with temozolomide (TMZ). The effectiveness of this treatment is very limited due to the development by tumor cells of mechanisms of resistance to TMZ such as over-expression of O6-methylguanine DNA methyltransferase (MGMT), epidermal growth factor receptor (EGFR) and galectin-1. In this study, we hypothesized that the targeting of MGMT, EGFR and galectin-1 (alone or in combination) by specifics siRNAs carried by chitosan-lipid nanocapsules (chitosan-LNCs) could enhance the sensitivity of U87MG cells to TMZ. We showed in vitro that (i) anti-MGMT and (ii) anti-EGFR or anti-galectin-1 siRNAs decreased significantly the expression of their corresponding proteins and increased the sensitivity of U87MG cells to TMZ. Additionally, the sensitivity of U87MG/MGMT- cells to TMZ was significantly increased when anti-EGFR and anti-galectin-1 siRNAs were combined with a percentage of living cells of 17.8±1.6% at 0.5 mg/mL concentration of TMZ. The combination of anti-MGMT siRNAs with either anti-EGFR or anti-galectin-1 siRNAs enhanced the sensitivity of U87MG/MGMT+ cells to TMZ in comparison to their separately use. No difference was observed between the association of the three siRNAs and other associations. At 0.5 mg/mL concentration of TMZ, the percentage of living cells decreased from 55.1±1.9% to 36.0±4.1% for anti-MGMT alone and the combination of anti-MGMT/anti-galectin-1/anti-EGFR siRNAs, respectively. These siRNA nanovectors represent a good alternative to enhance the effectiveness of the standard treatment of GB. This method could be implemented in future preclinical models for experimental cancer treatment of GB.

Nanocrystals of ZnO are currently attracting great interest as potential labels for biological applications, such as theranostic devices, due to their luminescent properties and low toxicity in vivo. It has been reported that doping with Mg 2+ ions could enhance the luminescence of ZnO quantum dots (QDs). In the present study Mg-doped ZnO QDs were synthesized by a hydrolysis and condensation reaction. Surface modification of the QDs was performed using oleic acid (OA) to hinder their aggregation and to provide them colloidal stability in non-polar environments. Mg 2+ ions could be incorporated into the ZnO wurtzite lattice owing to the very close values of the Mg 2+ and Zn 2+ ion radii. However, the dopant ions strongly influenced the growth and final size of ZnO nanocrystals, as evidenced by time-resolved synchrotron SAXS measurements. The presence of Mg prevented the aggregation of the primary nanoparticles. Doping with Mg 2+ ions widened the band gap of ZnO QDs and enhanced their visible luminescence. With increasing proportion of Mg 2+ ions, both the absorption and emission spectra experienced a blue shift. The luminescence went through a maximum for a 20 mol% nominal concentration of Mg 2+ ions in the reaction medium. The quantum yield (QY) of 20 mol% Mg-doped ZnO colloidal suspension (64%) was about 6 times higher than that of the ZnO suspension (10%). Mg-doped ZnO QDs capped by OA formed stable colloidal dispersions in chloroforme, with strong visible fluorescence (QY=38%), promising for biological imaging.

Patients diagnosed with an advanced-stage cancer present a dismal prognosis due to the presence of metastases. From the primary tumor, the cancer cells are disseminated via lymphatic circulation; metastases develop initially in lymph nodes. Therefore, the targeting of lymph nodes needs to be improved in the design of future chemotherapy, and one way to ensure this targeting is by using the subcutaneous (SC) route. Using lipid nanocapsules (LNCs) (40 nm and fluorescently-labeled with DiD) as nanocarriers, a correlation between the SC injection site (behind the neck, the right and left flanks, and above the tail) for LNC administration and specific lymph node accumulation (left and right cervical, axillary and inguinal lymph nodes) was achieved for Sprague-Dawley rats. The pharmacokinetic and biodistribution profiles confirmed the absence of LNCs in systemic circulation after SC administration due to the optimal size of the LNCs. With appropriate SC administration, LNCs can accumulate in specific lymph nodes, whereas IV administration led to a weak accumulation of LNCs in all lymph nodes. Specific accumulation followed the lymph flow: bottom-up from the lower to upper limbs and top down from the head, with two lymph circulation partitions: right upper limb and the rest. Administration above the tail presented high inguinal and axillary lymph node accumulation whereas weak accumulation was observed after administration behind the neck. LNCs administered in the left flank only accumulated in the left inguinal and axillary lymph nodes, whereas left and right inguinal and axillary lymph nodes presented accumulation after administration in the right flank. Cervical lymph nodes, in the opposite direction of lymph flow, were never targeted after SC administration, whatever the injection site.

The pathway from discovery of novel candidate drugs, including nanomedicine compounds, to FDA approval is lengthy and may be difficult to navigate. Oftentimes, investigational drugs are appropriately abandoned early in the development pathway due to preclinical failure. Other novel compounds may look quite promising in rodent models and preclinical trials, but prove disappointing when tested in human patients. In fact, only 5% of drugs entering Phase I human cancer clinical trials in the US are ultimately approved. Given the enormous cost, in terms of both financial investment and delay in progress toward improved patient outcome, there is a critical need for a more reliable and efficient process. One solution may be to improve translatability of our preclinical data by including trials in cancer-bearing pet dogs in the drug development pathway.