Search

The design and preparation of novel nanocarriers to transport cancer drugs for chemotherapy purposes is an important line of research in the medical field. A new 5-fluorouracil (5-Fu) transporter was designed based on the use of two new biocompatible gold nanosystems: (i) a gold nanoparticle precursor, Au@16-Ph-16, stabilized with the positively charged gemini surfactant 16- Ph-16, and (ii) the compacted nanocomplexes formed by the precursor and DNA/5-Fu complexes, Au@16-Ph-16/DNA-5-Fu. The physicochemical properties of the obtained nanosystems were studied by using UV-visible spectroscopy, TEM, dynamic light scattering, and zeta potential techniques. Method tuning also requires the use of circular dichroism, atomic force microscopy, and fluorescence spectroscopy techniques for the prior selection of the optimal relative Au@16-Ph-16 and DNA concentrations (R = CAu@16-Ph-16/CDNA), biopolymer compaction/decompaction, and 5-Fu release from the DNA/5-Fu complex. TEM experiments revealed the effective internalization of the both precursor and Au@16-Ph-16/DNA-5-Fu-compacted nanosystems into the cells. Moreover, cytotoxicity assays and internalization experiments using TEM and confocal microscopy showed that the new strategy for 5-Fu administration enhanced efficacy, biocompatibility and selectivity against lung cancer cells. The differential uptake among different formulations is discussed in terms of the physicochemical properties of the nanosystems. Universidad de Sevilla 2019/00000570, 2020/00001068, 2010/00000762, PP2016-5937, 2020/00001073 Junta de Andalucía 1804032996/2017, 2018/00000810, 2019/FQM-386

The interaction between calf thymus DNA and the gemini surfactants N,N'-[α,ω-phenylenebis(methylene)bis [N,N'-dimethyl-N-(1-hexadecyl)]-ammonium dibromide], p-16-Ph-16 (α = 1, ω = 3) and m-16-Ph-16 (α = 1, ω = 2), has been investigated via circular dichroism, fluorescence and UV-vis spectroscopy, zeta potential, dynamic light scattering, and AFM microscopy. Measurements were carried out in aqueous media at different molar ratios, R = (C16-Ph-16)/CDNA and C16-Ph-16 always below the critical micellar concentration (CMC) of the surfactant. Under these conditions, DNA undergoes two reversible conformational changes, compaction and decompaction, due to interaction with the surfactant molecules at low and high molar ratios, respectively. The extent of such conformational changes is correlated with both the degree of surfactant partial intercalation, and the size and charge of the surfactant aggregates formed, in each case. Comparison of the results shows that the para-form of the surfactant intercalates into the DNA to a major extent; therefore, the compaction/decompaction processes are more effective. Among these, the structure of the resulting 16-Ph-16/DNA decompacted complex is worthy of note. For the first time it can be demonstrated that the partial intercalation of the 16-Ph-16 gemini surfactants induces the formation of triplex DNA-like structures at a high R ratio.

Diisopropyl allyloxymethylphosphonate prepared by a one-pot procedure was isomerized to give racemic 1-hydroxy-3-butenylphosphonate with LDA by a [2,3]-sigmatropic rearrangement. Chloroacetylation delivered an ester, which was resolved in a two-phase system by using the lipase from Thermomyces lanuginosus. Racemic and (S)-α-hydroxyphosphonate 6 were converted to (±)- and (R)-phosphaaspartic acid by functional-group manipulation. (±)-, (R)- and (S)-6 were first esterified with 4-nitrobenzenesulfonyl chloride before hydroboration to transform the double bond into a hydroxyethyl group. The hydroxyl group was manipulated to give a guanidinyl group and the 4-nitrobenzenesulfonyloxy to give an amino group. Global deprotection of the α-aminophosphonates yielded the desired phosphaamino acids.

We report a practical, economical and sensitive method for DNA and lysozyme biomolecule detection based on previous aggregation of an anionic citrate gold nanoparticle, Au@citrate, induced by N,N’-bis(dimethyldodecyl)-α,ω-alkanediammonium dibromide series (m-s-m, m = 12, s = 3 and 6) gemini surfactants. Starting from Au@citrate/12−s−12 aggregated complexes, disaggregation processes were induced, effectively and immediately, by increasing biopolymer concentrations. This phenomenon that changes the optical properties of the systems was originated by the strong, kinetically rapid interactions of Au@citrate with the biopolymer, favoring the formation of different highly stabilized Au@citrate/biopolymer/12−s−12 complexes, which particular structures were visualized via the AFM technique. In all cases, the order of addition of the reagents was demonstrated to be crucial for the success of the reaction, and therefore effective biomolecule detection. The new approach highlights a way to avoid problems derived from the time lapse observed in previously reported sensors based on gold nanoparticle’ aggregation phenomena, with a limit of detection in the nanomolar range. The results showed a better linear response in sensors prepared from 12−6−12 surfactant, in line with both the greater difference observed between the equilibrium binding constants for 12−6−12/biopolymer and Au@citrate/biopolymer interactions, and the significant interparticle distance among Au@citrate nanoparticles through the aggregates.

A series of amidoamine derivatives composed of two amphiphilic units linked with alkyl spacers varying in length was synthesized. The amphiphilic unit consisted of a quaternary ethylammonium headgroup, 14 carbon atoms in the tail and an amide group placed in-between. The aggregation properties of the gemini compounds were examined by tensiometric, conductometric and spectroscopic methods and compared with the properties of their single-tail analogue. In spite of structural relation to gemini surfactants, some significant changes in solution behaviour, in comparison to typical surfactants and previously described gemini surfactants, were found. Most of the compounds within the obtained series aggregated to very small associates rather than to the typical micelles formed by gemini amphiphiles at very low concentrations. The size of aggregates obtained from dynamic light scattering measurements was confirmed by cryo-TEM visualization of the studied assemblies which contained only a few molecules. The size of aggregates and very low aggregation number indicated similarity of the studied compounds to hydrotropes which, despite their amphiphilic structure, do not form micelles. The influence of spacer length on the solution behaviour of geminis was discussed. The solubilization studies of Sudan I showed that the solubility of the hydrophobic dye in water is high at very small concentrations of the studied compounds, significantly smaller than in the case of their single-tail analogue.

MicroRNAs (miRNAs) provide a unique mechanism of gene regulation and play a key role in different pathologies ranging from metabolic diseases to cancer. Thus, they are attractive candidates as therapeutic targets in the clinic. However, delivering miRNAs to specific tissues remains challenging, due to their inherent instability and their low diffusion into tissues, as well as a lack of effective means of delivering them to the cytosols of the specific cells. To overcome these challenges, we constructed a delivery vehicle based on novel gold nanosystems having gemini surfactants which offer a high capacity to induce the miRNAs compression, high stability and cell-entry capability. The synthesis of gold nanoparticles with a positive surface charge, Au@16-Ph-16/miR-21 and Au@16–3-16/miR-21, was carried out in a three-step process. In this method, the hydrogen tetrachloroaurate, sodium tetrahydroborate and 16-Ph-16 or 16–3-16 compounds were used as gold precursor, reducing agent and stabilizers, respectively. The nanoparticles obtained were then covered with miR-21 polymer and were characterized by UV–visible spectroscopy, transmission electron microscopy, atomic force microscopy, dynamic light scattering and zeta potential to measure size and charge distribution. Finally, toxicity was assessed in vivo in mice. Moreover, coherent anti-Stokes Raman spectroscopy and histochemistry analyses showed that Au@16-Ph-16/miR-21 and Au@16–3-16/miR-21 exhibited no toxicity, antimicrobial and biocompatible activities. These nanosystems can be a valuable alternative in therapies associated with diseases where miRNAs play a regulatory role that may be decisive in the improvement or cure of patients. All these characteristics could make of these nanosystems the best potential therapeutic molecules.

A series of anionic sulfonate gemini surfactants with the general structure [(C12H25)(C6H3SO3−)O(CH2)mO(C6H3SO3−)(C12H25)]2Na+, designed as S, where m = 2, 4, 6 and 8 denotes the number of carbon atoms in the oligomethylene spacer, was synthesized, and the surfactants’ physicochemical properties and aggregation behavior were characterized. Compared with their single-tail analog, the gemini surfactants were observed to be more effective in decreasing the surface tension and their critical micelle concentrations (CMC) were at least two orders of magnitude lower. The aggregation process of the gemini surfactants in aqueous solution was investigated by dynamic light scattering (DLS). The formation of multivesicular structures consisting of several small vesicles surrounded by vesicular membrane was observed by cryogenic transmission electron microscopy (cryo-TEM).

Various arylamines were converted in two steps to N-Boc-N-arylphosphoramidates. LiTMP and LDA induced directed ortho-metalation at temperatures from −78 to 0 °C. The ensuing [1,3]-migration of the phosphorus atom with its substituents from the nitrogen to the ortho-carbanionic carbon atom gave N-Boc-protected o-aminoarylphosphonates. The nature of the substituent of 3-substituted phenylphosphoramidates strongly influenced the regioselectivity of phosphonate formation. A crossover experiment with a deuterated phosphoramidate proved the intramolecular course of the rearrangement. Three representative N-Boc-o-aminoarylphosphonates were deprotected to access the corresponding o-aminoarylphosphonic acids. Graphical Abstract

Various arylamines were converted in two steps to N-Boc-N-arylphosphoramidates. LiTMP and LDA induced directed ortho-metalation at temperatures from −78 to 0 °C. The ensuing [1,3]-migration of the phosphorus atom with its substituents from the nitrogen to the ortho-carbanionic carbon atom gave N-Boc-protected o-aminoarylphosphonates. The nature of the substituent of 3-substituted phenylphosphoramidates strongly influenced the regioselectivity of phosphonate formation. A crossover experiment with a deuterated phosphoramidate proved the intramolecular course of the rearrangement. Three representative N-Boc-o-aminoarylphosphonates were deprotected to access the corresponding o-aminoarylphosphonic acids.

A series of cationic gemini surfactants containing different spacer length were synthesized and analyzed structurally. It was shown that the surface tension (σ) and critical micelle concentration (CMC), which had a maximum for the n-C4H8 spacer depended on the spacer length. The foaming ability and foam stability are high for the gemini surfactants with short spacers (C2H4 to n-C4H8), while longer spacers lead to a distinct decrease of these foam parameters. Foaming properties are discussed in terms of configuration and conformation of a surfactant molecule and in relation to micellization state kinetic.

Three series of the gemini surfactants (diquaternary amines) anionic clusters with formate or bromide anions were studied in the gas phase by ER-MS on triple quadrupole mass spectrometer. The gemini series were: alkanediyl-α,ω-bis-(N,N-dimethyl-N-dodecyl ammonium), alkanediyl-α,ω-bis-(N-hydroxyethyl-N-methyl-N-dodecyl ammonium) and oligo(oxa)ethyl-α,ω-bis-(N,N-dimethyl-N-dodecyl ammonium), where the alkyl spacer size was from 2 to 12 methyl groups, and the oxaethyl range was from 2 to 8 units. The clusters were formed by one dication and three anions with formulas: [MBr3]−, [MBr2HCOO]−, [MBr(HCOO)2]− and [M(HCOO)3]−. Collisions induced internal reactions: nucleophilic substitutions SN2 at nitrogen α-carbons, eliminations E2, and hydrogen transfer from hydroxy group to the anion. By quantitative determination of the amounts of fragments in each dissociation channel and by plotting the ratios in function of the spacer lengths it was found that the clusters with short and long spacers formed two distinct reaction patterns. By comparisons to the cationic cluster reactions it was found that crowding inside the anionic cluster caused by the extra anions makes them to reacts through pathways they avoided in cationic clusters. Mixed anion clusters were determined to produce the same sets of fragments as homogeneous clusters in the amount which roughly corresponds to the increment of a given anion; on these bases, it was decided that anions are mobile in the cluster prior to dissociation reaction. When ethyloxy group in the mixed cluster was one of the nitrogen substituents a slight preference was toward formate anion products was observed, which was explained by formation of hydrogen bonding.

Fragmentation by collisionally induced dissociation in triple quadrupole mass spectrometer of pairs of six series of quaternary diamines (gemini surfactants) with two anions: formate and bromide has been studied. Amines included alkanediyl-α,ω-bis-(N,N-dimethyl-N-dodecyl ammonium bromide), alkanediyl-α,ω-bis-(N-hydroxyethyl-N-methyl-N-dodecyl ammonium bromide), oligo(oxa)ethyl-α,ω-bis-(N,N-dimethyl-N-dodecyl ammonium bromide) and three series of hexadecyl homologues. Range of atoms forming spacer varied from 2 to 23. It was confirmed that fragmentation occurs via either nucleophilic substitution or elimination reactions. All possible α-carbon atoms can be attacked in the substitution reaction, so can be all possible hydrogens of β-carbon in the elimination reaction. Additionally transferred to anion can be hydroxy group hydrogen. It leads together to eight different reaction paths. Depending on the spacer size and the kind of anion the ratio of fragmentation channels varies dramatically. For short spacers length ion pairs with formic anion dissociate through elimination, while bromide through substitution at spacer carbon. When spacer length is long enough to accommodate central anion between two quaternary nitrogens the substitution channel becomes the dominating one for both anions with exception when one of the substituents is hydroxyethyl. Then elimination is the only channel for ion pairs with formate anions, but for bromide anion division between substitution and elimination channels is not much affected. From the trends in channel ration and additional experiment with asymmetric geminis reveal it was concluded that the transition state is probably substantially different for long and short spacer geminis.

We proposed a new electrochemical strategy to characterize the hydrophobic microenvironment of micellar-hybridized supramolecular gels. The micellar-hybridized systems consist of micelles formed from gemini surfactants and supramolecular gels formed by self-assembly of the gelator N,N-dibenzoyl-l-cystine (DBC). SEM images indicated that the microscopic morphology of micellar-hybridized DBC gels possessed a denser three-dimensional network structure. An important feature of micellar-hybridized supramolecular gels is the presence of hydrophobic microdomains within the systems. The interaction of Methylene Blue (MB) and the hydrophobic microdomains can be quantitatively characterized by the net positive shifts of the redox formal potential (E0′) and the change of peak currents (ip) obtained from the cyclic voltammograms of MB. ΔE0′ between the micellar-hybridized DBC gel and non-hybridized gel was much larger than that between the micellar solution and aqueous solution, implying that the alteration of hydrophobicity of microdomains in hybrid system. By comparing the apparent diffusion coefficients of MB in the varied systems, it is indicative that the apparent diffusion coefficients of MB can be also employed to characterize the hydrophobicity change of hybrid systems. The fluorescent spectra of 1,8-anilinonaphthalenesulfonic acid within the hybrid gels further verified the results of the cyclic voltammograms. It is suggested that the cyclic voltammograms are a facile and sensitive method to monitor the hydrophobic microenvironment of the micellar-hybridized supramolecular gels.

The enantiomers of 1-phenylethylamine were phosphorylated with diethyl chlorophosphate/Et(3)N and then Boc-protected (Boc=tert-butoxycarbonyl) at the nitrogen atom. These phosphoramidates were metalated by using sBuLi/N,N,N',N'-tetramethylethylenediamine (TMEDA) to give alpha-aminobenzyllithiums that isomerised to alpha-aminophosphonates in yields of up to 80 % with retention of the configuration at the carbon atom. The intermediate tertiary organolithiums were found to be microscopically configurationally stable from -78 to 0 degrees C in Et(2)O. The protected alpha-aminophosphonates were deblocked by using boiling 6 M HCl or preferably Me(3)SiBr/(allyl)SiMe(3). When the Boc group was replaced by the diethoxyphosphinyl group, the alpha-aminobenzyllithium intermediate partially enantiomerised even at -78 degrees C and rearranged to yield an alpha-aminophosphonate with 50 % ee (ee=enantiomeric excess). Similarly, N-Boc-protected phosphoramidates derived from racemates and/or enantiomers of 1-(1-naphthyl)ethyl-, 1-indanyl- and 1,2,3,4-tetrahydro-1-naphthylamine or 1-azidoindan- and 1-azido-1,2,3,4-tetrahydronaphthalene were converted to aminophosphonates in good yields. Deblocking gave alpha-aminophosphonic acids of excellent enantiomeric excess (97-99 %), as determined by means of HPLC on a chiral ion-exchange stationary phase based on quinine carbamate. When racemic Boc-protected diethyl phosphoramidate derived from 1,2,3,4-tetrahydro-1-naphthylamine was metalated with LiTMP/TMEDA (TMP=2,2,6,6-tetramethylpiperidine), 1-hydroxyethylphosphonamidates resulted. The configuration of the main isomer was determined by means of a single-crystal X-ray structure analysis.

The DNA conformational changes induced by different members of the N,N0-bis(dimethyldodecyl)-a-ualkanediammonium dibromide series (m-s-m, m ¼ 12, s ¼ 3 and 6) and the analogous series of hexadecyl gemini surfactants (m ¼ 16, s ¼ 3 and 6) were investigated in aqueous media by means of circular dichroism (CD), zeta potential, dynamic light scattering (DLS), viscometry, and atomic force microscopy (AFM) methods. The measurements were carried out by varying the gemini surfactant–DNA molar ratio, R ¼ Cm-s-m/CDNA. For the conditions investigated two significantly different conformational changes were observed, the second of them being worth noting. At low molar ratios, all methods concurred by showing that gemini surfactants were able to form ordered aggregates which precedes DNA compaction. The second effect observed, at high molar ratios, corresponds to the transition from the compact state to a new more extended conformation. The degree of decompaction and the morphologies of the visualized structures are different not only depending on the surfactant tail's length, but also on the spacer's length. The results obtained for the 16-3-16/DNA and 16-6-16/DNA systems point out that the compaction/decompaction processes are somewhat different to those previously visualized for the analogous monoquaternary chain surfactant CTAB. Consejería de Educación y Ciencia of the Junta de Andalucía FQM-03623