Gemini-Mediated Self-Disinfecting Surfaces to Address Contact Transmission of Infectious Diseases

According to both the Center for Disease Control (CDC) and the World Health Organization (WHO), contact-transmission (contact between host tissues and a contaminated surface) is the primary transmission route of infectious diseases worldwide. Usually this is mitigated by adherence to a schedule of repeated regular sanitization, yet this approach is inherently limited by sanitization frequency; conventional disinfectants/methods are only germicidal during the period of application, and surfaces are easily re-contaminated in the interim between cleanings. One solution to this problem is to use agents/coatings that impart self-disinfecting properties onto the existing surfaces such that they display sustained virucidal/antimicrobial properties against pathogens that settle upon them. Quaternary-ammonium organosilicon compounds are ideal candidates to achieve this; cationic surfactants are safe and well-established surface disinfectants while organosilanes are used broadly to form durable coatings with altered surface properties on many different materials. Despite their potential to circumvent disadvantages of traditional disinfection methods, extant commercially available quaternary-ammonium silanes do not display comparable efficacy to standard surface disinfectants, nor have their respective coatings been demonstrated to meet the Environmental Protection Agency’s guidelines for residual/extended efficacy. Inspired by powerful surface activity of double-headed “gemini” surfactants, here we present gemini-diquaternary (GQ) silanes with robust residual germicidal efficacy on various surfaces by incorporating a second cationic “head” to the structure of an conventional mono-quaternary-ammonium silane. Aqueous solutions of GQs were tested in suspension- and surface-antimicrobial assays against an array of pathogens, including Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). GQ performance was benchmarked against the common disinfectants, ethanol, hydrogen peroxide and hypochlorite, as well as against a common antimicrobial mono-quaternary (MQ) silane. Solutions of GQ silanes were efficacious when used for immediate disinfection, showing comparable activity to common disinfectants (>106 fold reduction in 15 seconds). Additionally GQ solutions were demonstrated to impart durable self-disinfecting properties to a variety of porous and nonporous surfaces, efficacious after repeated cycles of abrasion and repeated contaminations, and with superior coating ability and activity (>108 higher activity) than that of the popular MQ silane. GQ solutions as surface treatments show great promise to overcome the limitations of traditional disinfectants in preventing the spread of infectious diseases.

Trehalose amide glycolipids as Mincle ligands: Towards new vaccine adjuvants

<p>The development of new vaccines to respond to infectious diseases requires new vaccine adjuvants, which improve vaccine efficacy and shape the immune response. Trehalose glycolipids, consisting of α,α'-trehalose esterified at the 6- and 6'- positions with lipids, exhibit adjuvant activity by binding and activating Macrophage inducible C-type lectin (Mincle). However, the adjuvant activity of trehalose glycolipids could potentially be improved by substituting the ester linkages for more physiologically stable amide bonds. This thesis presents a short protecting group free route to trehalose amide glycolipids, thus allowing for the synthesis of the straight chain glycolipid amides 1a-e in four steps and in excellent (53-61%) overall yields (Figure 1). Amide glycolipids 1a-e were demonstrated to be Mincle agonists with comparable activity to their ester counterparts, as determined using a green fluorescent protein (GFP) reporter cell line assay. A second generation of trehalose amide glycolipids, the lipidated brartemicin amide analogues 2a-c, were subsequently synthesised (Figure 1). This report is the first example of trehalose amide glycolipids acting as Mincle agonists, and further studies into the potential of the amides as vaccine adjuvants will be undertaken in due course.</p>

Trehalose amide glycolipids as Mincle ligands: Towards new vaccine adjuvants

<p>The development of new vaccines to respond to infectious diseases requires new vaccine adjuvants, which improve vaccine efficacy and shape the immune response. Trehalose glycolipids, consisting of α,α'-trehalose esterified at the 6- and 6'- positions with lipids, exhibit adjuvant activity by binding and activating Macrophage inducible C-type lectin (Mincle). However, the adjuvant activity of trehalose glycolipids could potentially be improved by substituting the ester linkages for more physiologically stable amide bonds. This thesis presents a short protecting group free route to trehalose amide glycolipids, thus allowing for the synthesis of the straight chain glycolipid amides 1a-e in four steps and in excellent (53-61%) overall yields (Figure 1). Amide glycolipids 1a-e were demonstrated to be Mincle agonists with comparable activity to their ester counterparts, as determined using a green fluorescent protein (GFP) reporter cell line assay. A second generation of trehalose amide glycolipids, the lipidated brartemicin amide analogues 2a-c, were subsequently synthesised (Figure 1). This report is the first example of trehalose amide glycolipids acting as Mincle agonists, and further studies into the potential of the amides as vaccine adjuvants will be undertaken in due course.</p>

Seriniquinones as Therapeutic Leads for Treatment of BRAF and NRAS Mutant Melanomas

Isolated from the marine bacteria Serinicoccus sp., seriniquinone (SQ1) has been characterized by its selective activity in melanoma cell lines marked by its modulation of human dermcidin and induction of autophagy and apoptosis. While an active lead, the lack of solubility of SQ1 in both organic and aqueous media has complicated its preclinical evaluation. In response, our team turned its effort to explore analogues with the goal of returning synthetically accessible materials with comparable selectivity and activity. The analogue SQ2 showed improved solubility and reached a 30–40-fold greater selectivity for melanoma cells. Here, we report a detailed comparison of the activity of SQ1 and SQ2 in SK-MEL-28 and SK-MEL-147 cell lines, carrying the top melanoma-associated mutations, BRAFV600E and NRASQ61R, respectively. These studies provide a definitive report on the activity, viability, clonogenicity, dermcidin expression, autophagy, and apoptosis induction following exposure to SQ1 or SQ2. Overall, these studies showed that SQ1 and SQ2 demonstrated comparable activity and modulation of dermcidin expression. These studies are further supported through the evaluation of a panel of basal expression of key-genes related to autophagy and apoptosis, providing further insight into the role of these mutations. To explore this rather as a survival or death mechanism, autophagy inhibition sensibilized BRAF mutants to SQ1 and SQ2, whereas the opposite happened to NRAS mutants. These data suggest that the seriniquinones remain active, independently of the melanoma mutation, and suggest the future combination of their application with inhibitors of autophagy to treat BRAF-mutated tumors.

Identification of Novel Type Three Secretion System (T3SS) Inhibitors by Computational Methods and Anti-Salmonella Evaluations

Three type III secretion system (T3SS) inhibitors (compounds 5, 19, and 32) were identified by virtual screening and biological evaluation. These three compounds were evaluated against a panel of Salmonella species strains including S. enteritidis, S. typhi, S. typhimurium, S. paratyphi, and S. abortus equi, and their minimum inhibitory concentrations ranged from 1 to 53 μg/ml. Especially, these compounds showed comparable activity as the of the positive control gatifloxacin towards S. abortus equi. The present results suggest that these new T3SS inhibitors could be used as a potential lead molecule for drug development of anti-Salmonella.

The Synthesis of Carbohydrates for the Treatment of Disease

<p>In this thesis I investigated two aspects of glycobiology. In the first, I investigated the potential of α-GalCer analogues to be used in cancer immunotherapy. Two 4-deoxy α-GalCer analogues, with either a sphinganine or a sphingosine base, were synthesised using a convergent strategy. The α-GalCer sphinganine derivative was synthesised in 14 steps from D-arabinose, and in an overall 13% yield. The α-GalCer sphingosine analogue was synthesised in 13 steps also in 13% yield. Biological analysis revealed that both 4-deoxy analogues possessed comparable activity to α-GalCer in mice, however demonstrated significantly reduced hNKT cell activity. The reduced activity was attributed to species-specific differences in iNKT cell glycolipid recognition rather than reduced CD1d presentation. From these results we suggest that glycolipids developed for potent CD1d-iNKT cell activity in humans should contain a ceramide base with the 4-hydroxyl present. The second part of this thesis focused on protecting group free methodology for the synthesis of sugar mimetics that have proven potential as glycosidase inhibitors. In this work I developed an efficient, high yielding and diastereoselective strategy for the synthesis of a number of five and six membered azasugars. This strategy utilises two novel reaction methodologies. The first enabled the stereoselective formation of cyclic carbamates from olefinic amines, the transition states controlling the stereoselectivity during this reaction are discussed. The second reaction facilitated the synthesis of primary amines without the need for protecting groups, the scope of this reductive amination methodology is also investigated. The five membered azasugars 1,4-dideoxy-1,4-imino-Dxylitol, 1,4-dideoxy-1,4-imino-L-lyxitol, 1,4-dideoxy-1,4-imino-L-xylitol and 1,2,4-trideoxy-1,4-imino-L-xylitol were prepared in 5 steps, in good overall yields (57%, 55%, 54% and 48% respectively), and without the need for protecting groups. The six membered azasugar DGJ was prepared over six steps in 33% yield using similar methodology. The synthesised compounds were also tested for anti-tubercular activity using a BCG alamar blue assay.</p>

The Synthesis of Carbohydrates for the Treatment of Disease

<p>In this thesis I investigated two aspects of glycobiology. In the first, I investigated the potential of α-GalCer analogues to be used in cancer immunotherapy. Two 4-deoxy α-GalCer analogues, with either a sphinganine or a sphingosine base, were synthesised using a convergent strategy. The α-GalCer sphinganine derivative was synthesised in 14 steps from D-arabinose, and in an overall 13% yield. The α-GalCer sphingosine analogue was synthesised in 13 steps also in 13% yield. Biological analysis revealed that both 4-deoxy analogues possessed comparable activity to α-GalCer in mice, however demonstrated significantly reduced hNKT cell activity. The reduced activity was attributed to species-specific differences in iNKT cell glycolipid recognition rather than reduced CD1d presentation. From these results we suggest that glycolipids developed for potent CD1d-iNKT cell activity in humans should contain a ceramide base with the 4-hydroxyl present. The second part of this thesis focused on protecting group free methodology for the synthesis of sugar mimetics that have proven potential as glycosidase inhibitors. In this work I developed an efficient, high yielding and diastereoselective strategy for the synthesis of a number of five and six membered azasugars. This strategy utilises two novel reaction methodologies. The first enabled the stereoselective formation of cyclic carbamates from olefinic amines, the transition states controlling the stereoselectivity during this reaction are discussed. The second reaction facilitated the synthesis of primary amines without the need for protecting groups, the scope of this reductive amination methodology is also investigated. The five membered azasugars 1,4-dideoxy-1,4-imino-Dxylitol, 1,4-dideoxy-1,4-imino-L-lyxitol, 1,4-dideoxy-1,4-imino-L-xylitol and 1,2,4-trideoxy-1,4-imino-L-xylitol were prepared in 5 steps, in good overall yields (57%, 55%, 54% and 48% respectively), and without the need for protecting groups. The six membered azasugar DGJ was prepared over six steps in 33% yield using similar methodology. The synthesised compounds were also tested for anti-tubercular activity using a BCG alamar blue assay.</p>

Modular synthesis of carbazole substituted phthalimides as potential photocatalysts

Herein, we report the modular synthesis of carbazole functionalized phthalimides (PI), and demonstrated their applicability as catalyst in selected photocatalytic transformations. The developed synthetic approach provides high variability of phthalimide considering that the synthesis of the phthalimide core can be easily performed. Starting from fluorophthalic acid anhydrides, the corresponding fluorophthalimides were prepared with various amines, and the fluoro function ensured the introduction of carbazoles into the phthalimide framework through aromatic nucleophilic substitution. Besides the synthetic developments, we tested some of the carbazolyl phthalimides in four different photocatalytic transformations, and found attractive and comparable activity to the known 4-CzIPN and noble metal complexes.

DYRK1A Kinase Inhibitors Promote β-Cell Survival and Insulin Homeostasis

The rising prevalence of diabetes is threatening global health. It is known not only for the occurrence of severe complications but also for the SARS-Cov-2 pandemic, which shows that it exacerbates susceptibility to infections. Current therapies focus on artificially maintaining insulin homeostasis, and a durable cure has not yet been achieved. We demonstrate that our set of small molecule inhibitors of DYRK1A kinase potently promotes β-cell proliferation, enhances long-term insulin secretion, and balances glucagon level in the organoid model of the human islets. Comparable activity is seen in INS-1E and MIN6 cells, in isolated mice islets, and human iPSC-derived β-cells. Our compounds exert a significantly more pronounced effect compared to harmine, the best-documented molecule enhancing β-cell proliferation. Using a body-like environment of the organoid, we provide a proof-of-concept that small–molecule–induced human β-cell proliferation via DYRK1A inhibition is achievable, which lends a considerable promise for regenerative medicine in T1DM and T2DM treatment.

Robust SARS-CoV-2-specific and heterologous immune responses after natural infection in elderly residents of Long-Term Care Facilities

Long term care facilities (LTCF) provide residential and/or nursing care support for frail and elderly people and many have suffered from a high prevalence of SARS-CoV-2 infection. Although mortality rates have been high in LTCF residents there is little information regarding the features of SARS-CoV-2-specific immunity after infection in this setting or how this may influence immunity to other infections. We studied humoral and cellular immunity against SARS-CoV-2 in 152 LTCF staff and 124 residents over a prospective 4-month period shortly after the first wave of infection and related viral serostatus to heterologous immunity to other respiratory viruses and systemic inflammatory markers. LTCF residents developed high levels of antibodies against spike protein and RBD domain which were stable over 4 months of follow up. Nucleocapsid-specific responses were also elevated in elderly donors but showed waning across all populations. Antibodies showed stable and equivalent levels of functional inhibition against spike-ACE2 binding in all age groups with comparable activity against viral variants of concern. SARS-CoV-2 seropositive donors showed high levels of antibodies to other beta-coronaviruses but serostatus did not impact humoral immunity to influenza or RSV. SARS-CoV-2-specific cellular responses were equivalent across the life course but virus-specific populations showed elevated levels of activation in older donors. LTCF residents who are survivors of SARS-CoV-2 infection thus show robust and stable immunity which does not impact responses to other seasonal viruses. These findings augur well for relative protection of LTCF residents to re-infection. Furthermore, they underlie the potent influence of previous infection on the immune response to Covid-19 vaccine which may prove to be an important determinant of future vaccine strategy.