Click And Bioorthogonal Chemistry For The Chemical Modification Of Nanomaterials

The goal of this Ph.D. thesis work is the development of novel reactive nanomaterial templates that can be chemically modified in a facile and robust (i.e., formation of covalent bonds) way for the further modification of the nanomaterial’s physical-chemical properties by the reaction partner molecular system. This type of technology was employed to further expand the application of nanomaterials in nanomedicine, chemical biology and materials science. In order to reach this goal, as a proof of concept, small (d = 3nm) gold nanoparticles (AuNPs) and carbon nanotubes (CNT) were used as the nanomaterial substrates. Innovative synthetic strategies for the introduction of click and bioorthogonal functional groups onto the surface of these nanomaterials were developed. These functional groups include a maleimide that can undergo three click reactions with different functional groups (i.e., Michael addition with nucleophiles, Diels-Alder cycloaddition with dienes, dipolar cycloadditions with dipolar molecules), strained alkynes for bioorthogonal strain-promoted cycloaddition reactions with azides and nitrones, and methyl-2-(diphenylphosphino)benzoate moieties for the bioorthogonal Staudinger-Bertozzi ligation with azides. In order to study and characterize these clickable and bioorthogonal nanomaterial templates, methodologies for the determination of the amount of reactive functionalities introduced onto the nanomaterial’s surface and the evaluation of their proper reactivity were also developed. 1H NMR spectroscopy, transmission electron microscopy, and thermogravimetric analysis, were methodically used for the quantification of the interfacial reactive functionalities. 1H NMR spectroscopy was also employed to follow the correct interfacial reactivity of the nanomaterial template. Finally, in collaboration with Surface Science Western, the use of X-ray photoelectron spectroscopy (XPS) was developed as a method to independently confirm all the previously obtained results and, more specifically, quantitate the amount of interfacial reactive molecules that were introduced, track the interfacial organic chemistry of the nanomaterial template, and determine interfacial reaction yields. In all cases the clickable and bioorthogonal nanomaterial templates were found to react quickly, efficiently and chemoselectively with their chemical reporter through a simple pour-and-mix type of chemistry. The utility of these clickable and bioorthogonal nanomaterial templates was finally showcased in bioconjugation, for the synthesis of fluorogenic biosensors, nanomaterial hybrids and nanomaterial-based MRI contrast agents

Dipole Moment Effect on the Electrochemical Desorption of Self-Assembled Monolayers of 310-Helicogenic Peptides on Gold

AbstractThe front cover artwork is provided by Pierangelo Gobbo and Flavio Maran, University of Padova (Italy). The image highlights how the orientation of the dipole moment associated with helical peptides affects the electrodesorption potential of the corresponding self‐assembled monolayers. Read the full text of the Article at 10.1002/celc.201600573

Spontaneous membrane-less multi-compartmentalisation via aqueous two-phase separation in complex coacervate microdroplets

Polyelectrolyte/nucleotide multiphase complex coacervate droplets are produced by internalized aqueous two-phase separation and used for the spatially dependent chemical transfer of sugar molecules, providing a step towards the development of membrane-free "organelles" within coacervate-based protocells

Colloidosomes as a Protocell Model: Engineering Life-Like Behaviour through Organic Chemistry

The bottom-up synthesis of self-assembled micro-compartmentalised systems that mimic basic characteristics of living cells is rapidly evolving. These types of systems are termed “protocells” and can be chemically programmed to grow and divide, to send and receive chemical signals, to transcript and translate chemical information, to adhere to surfaces or to other protocells, and to perform rudimental enzyme-mediated metabolic processes. An emerging protocell model that is attracting great attention is the colloidosome. Colloidosomes are microcapsules with a chemically crosslinked, semipermeable membrane composed of amphiphilic nanoparticles. Colloidosomes display important advantages over other protocell models (e. g., vesicles and coacervate micro-droplets) due to their physical-chemical properties that can be easily tuned through the careful engineering of their synthetic building blocks. In this review, we deliver an overview of the different types of colloidosomes that have been developed thus far and discuss how organic chemistry contributes to the design and bottom-up synthesis of novel types of colloidosomes endowed with advanced chemically programmed bio-inspired functions

An Azide-Functionalized Nitronyl Nitroxide Radical: Synthesis, Characterization and Staudinger-Bertozzi Ligation Reactivity

An azide-functionalized nitronyl nitroxide was successfully synthesized and its reactivity towards the Staudinger-Bertozzi ligation was explored. While a model reaction in solution showed the conversion of the nitronyl nitroxide to an imino nitroxide radical, the same reaction at the interface of gold nanoparticles allowed for successful covalent incorporation of the nitronyl nitroxide radical onto the nanoparticles

Orthogonal Light-Dependent Membrane Adhesion Induces Social Self-Sorting and Member-Specific DNA Communication in Synthetic Cell Communities

Developing orthogonal chemical communication pathways in diverse synthetic cell communities is a considerable challenge due to the increased crosstalk and interference associated with large numbers of different types of sender-receiver pairs. Herein, the authors control which sender-receiver pairs communicate in a three-membered community of synthetic cells through red and blue light illumination. Semipermeable protein-polymer-based synthetic cells (proteinosomes) with complementary membrane-attached protein adhesion communicate through single-stranded DNA oligomers and synergistically process biochemical information within a community consisting of one sender and two different receiver populations. Different pairs of red and blue light-responsive protein-protein interactions act as membrane adhesion mediators between the sender and receivers such that they self-assemble and socially self-sort into different multicellular structures under red and blue light. Consequently, distinct sender-receiver pairs come into the signaling range depending on the light illumination and are able to communicate specifically without activation of the other receiver population. Overall, this work shows how photoswitchable membrane adhesion gives rise to different self-sorting protocell patterns that mediate member-specific DNA-based communication in ternary populations of synthetic cells and provides a step towards the design of orthogonal chemical communication networks in diverse communities of synthetic cells

Reemergence of Strongyloidiasis, Northern Italy

Strongyloidiasis is a helminth infection caused by Strongyloides stercoralis, a nematode ubiquitous in tropical and subtropical countries and occasionally reported in temperate countries, including Italy (1). Sources of infection are filariform strongyloid larvae present in soil contaminated by infected feces; the larvae penetrate through the skin of a human host. After the first life cycle, a process of autoinfection begins, which persists indefinitely in the host if the infection is not effectively treated. The infection can remain totally asymptomatic for many years or forever or cause cutaneous (itching and rash), abdominal (epigastric pain, pseudoappendicitis, diarrhea), respiratory (cough, recurrent asthma), and systemic (weight loss, cachexia) symptoms that can be enervating. More importantly, when host immunity is impaired because of a concurrent disease or immunosuppressive therapy (including corticosteroids, sometimes used to treat symptoms of the unrecognized infection or the concurrent eosinophilia), disseminated strongyloidiasis may occur (2\u20134), causing a massive and almost invariably fatal invasion of virtually all organs and tissues by filariform larvae and even adult worms (Figure), often combined with bacterial superinfection. This complication is believed to be rare but is probably underestimated because of the extreme variability of the clinical presentation. Although strongyloidiasis can be suspected in the presence of symptoms or eosinophilia (which is frequent but not mandatory), the low sensitivity of direct diagnostic methods often lets the disease go unrecognized (5\u20137). By far the most sensitive diagnostic tools are serologic tests: sensitivity and specificity of indirect fluorescent antibody test (IFAT) (in-house produced IFAT) are 97.4% and 97.9%, respectively, at a dilution >1/20, and 70.5% and 99.8% at a dilution >1/80 (6). A suspected case is defined by a positive antibody titer >20 (IFAT); a case is confirmed by a positive direct test result (culture in agar being the most sensitive direct technique) or by a positive antibody titer >80 (6). Despite some anecdotal reports on the presence of strongyloidiasis in Italy (1,6), reliable information about the real prevalence of the infection is lacking. After seeing several patients affected by the disease, 1 of whom died because of dissemination (Z. Bisoffi, unpub. data), we decided to carry out a preliminary rapid assessment of the extent of the problem in elderly patients with eosinophilia. During a 4-month period, from February through May 2008, every patient born in 1940 or earlier who came to the clinical laboratories of 2 contiguous health districts in northern Italy (Mantova, Lombardy Region, and Legnago, Veneto Region) for a diagnostic blood test (hematocrit and leukocyte count/formula) for whatever reason and having a eosinophil count >500 cells/\u3bcL was asked to join the study. This study was the pilot phase of a larger, multicentered study, which obtained formal approval from the Ethical Committee of Sacro Cuore Hospital of Negrar, Verona. Informed consent was required of each patient. Of the 132 patients eligible for inclusion (mean age 76.4 years, range 68\u201390 years, male:female ratio 1.6), none refused to give informed consent. Serum specimens were subjected to the IFAT for S. stercoralis at the Sacro Cuore Hospital Centre for Tropical Diseases. Unexpectedly, we found that 37 (28%) of 132 patients were positive, with titers ranging between 20 and >320 (and >80 in most cases). However, caution should be exercised in interpreting the results because the patients may not be representative of the general population. Moreover, our results are based on an indirect (although highly sensitive and specific) test. Because the reported cases involve only a few patients every year (of whom some are anecdotally reported as dying from the infection, usually unpublished), we suspect that most strongyloidiasis cases remain undetected. If relevant transmission still exists in the area, it is unknown but is unlikely because of the improvement of hygienic conditions in the past 5 decades. Reports of the infection in children or young adults with no travel history outside Italy are lacking. Strongyloidiasis in the elderly is therefore most likely to result from an infection that occurred much earlier in life, either in infancy or at a young age, while walking or working barefoot in agricultural fields. The long persistence is the consequence of the autoinfection cycle typical of this parasite as described above. The result is an important and unrecognized public health problem affecting the geriatric population of northern Italy. These preliminary results confirm the need for the already planned, multicentered study involving a larger sample and a wider geographic area