Micelles In Aqueous Solution Research Articles

Micelle‐to‐vesicle transition of lipoamino Gemini surfactant induced by metallic salts and its effects on antibacterial activity

Gemini surfactants are amphiphilic molecules formed by two polar heads and two hydrophobic tails joined by a spacer between the polar groups. Their molecular structure gives them particular physico-chemical properties in comparison with their monomeric counterparts. In this work we synthetized a Gemini surfactant (SDDC) derived from the amino acid cystine and decanoic acid. The influence of different metallic salts on the aggregation of the surfactant was studied. SDDC forms core–shell type triaxial ellipsoidal micelles in aqueous solution, but the aggregates suffer a change in morphology, forming vesicles in the presence of copper or silver ions. This behavior was corroborated by TEM and SAXS measurements. With the last technique was possible to estimate that vesicles formed in presence of copper consisted of 7.3 stacked bilayers. It was possible to determine that Cu2+ was reduced to Cu+ in the solution containing SDDC, through EPR and UV–visible spectrophotometry measurements. The reduction of copper was accompanied with the concomitant oxidation of the cystine. The antimicrobial activity of the different aggregates was studied against E. coli and S. aureus and compared with the conventional antibiotic ampicillin. The most efficient system resulted the mixture of SDDC:CuSO4/10:1 against the Gram-negative bacterium, there with the minimum concentration used (0.01 mM) was possible to inhibit 70 % of growth. The new systems characterized in this work have many possibilities for potential applications, mainly in the area of drug delivery systems, templates in the synthesis of nanomaterials or as antibacterial compounds.

Exploration of the Adsorption Kinetics of Surfactants at the Water-Oil Interface via Grand-Canonical Molecular Dynamics Simulations.

It is well-known that surfactants tend to aggregate into clusters or micelles in aqueous solutions due to their special structures, and it is difficult for the surfactant molecules involved in the aggregation to move spontaneously to the oil-water interface. In this article, we developed a new grand-canonical molecular dynamics (GCMD) model to predict the saturated adsorption amount of surfactant with constant concentration of surfactant molecules in the bulk phase, which can prevent surfactants aggregating in the bulk phase and get the atomic details of the interfacial structural change with increase of the adsorption amount through a single GCMD run. The adsorption of anionic surfactant sodium dodecyl sulfate (SDS) at the heptane-water interface was studied to validate the model. The saturated adsorption amount obtained from the GCMD simulation is consistent with the experimental results. The adsorption kinetics of SDS molecules during the simulation can be divided into three stages: linear adsorption stage, transition adsorption stage, and dynamic equilibrium stage. We also carried out equilibrium molecular dynamics (EMD) simulations to compare with GCMD simulation. This GCMD model can effectively reduce the simulation time with correct prediction of the interfacial saturation adsorption. We believe the GCMD method could be especially helpful for the computational study of surfactant adsorption under complex environments or emulsion systems with the adsorption of multiple types of surfactants.

SANS characterization of time dependent, slow molecular exchange in an SDS micellar system.

We have investigated the molecular exchange of sodium dodecyl sulfate (SDS) micelles in aqueous solution by time-resolved small angle neutron scattering (TR-SANS) measurements as a function of the surfactant and salt concentration. Starting with deuterated (d-SDS) and protonated (h-SDS) SDS micelles, surfactant exchange across the micelles leads to a randomized distribution of d-SDS and h-SDS within each micelle. By employing the contrast matching technique, we have studied this randomization process which is a direct measure of the molecular exchange of this system. Our results show that the randomization of the pure h-SDS and d-SDS micelles occurs in two steps: first, an almost instantaneous drop in the scattering intensity is observed where ∼80% of the micelles are randomized (contrast matched). After this, micelle randomization progresses slowly spanning over ∼100 hours. Importantly, we show that the kinetics in the second step are dominated by the formation of domains rich in either h-SDS, d-SDS and randomized (50 : 50 h-SDS : d-SDS). The slow exchange step is modeled via a phenomenological approach by drawing analogy to the Langmuir adsorption theory. Finally, the effects of the surfactant and salt concentrations on the instantaneous, and the time dependent randomization of SDS micelles are discussed.

Hydrophobic modified poly(l‐glutamic acid) graft copolymer micelles with ultrahigh drug loading capacity for anticancer drug delivery

AbstractSelf‐assembled polymeric nanoparticle (NP) drug carriers are capable of encapsulated and controlled delivery, facilitating improvements in the therapeutic efficiency of drugs. Here we report a series of poly(l‐glutamic acid)‐g‐methoxy poly(ethylene glycol)/4‐phenylbutyl ester (PLG‐g‐mPEG/PB) copolymers, which were synthesized by esterification of 4‐phenylbutanol (PB) and PLG‐g‐mPEG in different feed ratios. The copolymers obtained form into nano‐sized micelles in aqueous solution by a self‐assembly process, with lower critical micelle concentration value for higher PB ratio in the copolymers. Variable temperature infrared spectroscopy and circular dichroism were used to prove the breaking of intermolecular hydrogen bonds after PB modification. Podophyllotoxin (PPT), an effective anticancer agent, was incorporated into the inner core of the micelle system by physical entrapment through hydrophobic interaction between the drug and the PB‐modified copolymers. Both the drug loading content and the loading efficiency increased with PB content in the PLG‐g‐mPEG/PB copolymers and reached an ultrahigh value of 28.2 wt% and 94%, respectively. The PPT‐encapsulated micelles (PPT‐NPs) were stable at pH 7.4 but dissociated and released 80% of loaded PPT in a weak acidic environment (pH 5.0). The in vitro proliferation of non‐small‐cell lung cancer cells (A549) was significantly inhibited by PPT‐NPs in a cytotoxicity assay. These results demonstrate that hydrophobic modification is an efficient route for tuning the self‐assembly behaviour and drug encapsulation of PLG‐g‐mPEG copolymers, and our PLG‐g‐mPEG/PB will serve as a promising carrier for hydrophobic anticancer drug delivery. © 2021 Society of Industrial Chemistry.

Strong Viscosity Increase in Aqueous Solutions of Cationic C22-Tailed Surfactant Wormlike Micelles

The viscoelastic properties and structure parameters have been investigated for aqueous solutions of wormlike micelles of cationic surfactant erucyl bis(hydroxyethyl) methylammonium chloride with long C22 tail in the presence inorganic salt KCl. The salt content has been varied to estimate linear to branched transition conditions due to screening of the electrostatic interaction in the networks. The local cylindrical structure and low electrostatic repulsion was obtained by SANS data. The drastic power law dependencies of rheological properties on surfactant concentrations were obtained at intermediate salt content. Two power law regions of viscosity dependence were detected in semi-dilute solutions related to “unbreakable” and “living” micellar chains. The fast contour length growth with surfactant concentration demonstrated that is in good agreement with theoretical predictions.

Synthesis and micellization of cationic trisiloxane surfactants with poly(ethylene glycol)

PEG based cationic trisiloxane surfactants (Si3min-EO3, Si3min-EO4, and Si3pyr-EO4), containing poly(ethylene glycol) and imidazolium/pyridinium headgroups, were prepared through thiol-ene reaction and confirmed by 1HNMR and FT-IR. Their micellization in aqueous solution were investigated using surface tension measurements, electrical conductivity measurements, dynamic light scattering (DLS), and transmission electron microscope (TEM). Owing to the introduction of ethylene glycol segments onto both end of trisiloxane hydrophobic parts, the PEG based cationic trisiloxane surfactants may adopt the ethylene glycol groups with a suitable conformational structure on the air/water interface resulted in their lower πCMC values, larger γCMC (~33 mN m−1) and Amin values compared with permethyltrisiloxane surfactant, even their corresponding monomeric surfactant (Vi-Si3minCl and Vi-Si3PyrCl). Meanwhile, in aqueous solution, the micellization process of Si3min-EO3, Si3min-EO4, and Si3pyr-EO4 were enthalpy driven and spherical aggregates were observed by TEM.

Electrophoretic mobility of ester betulin derivatives and their complexation with γ-cyclodextrin studied by capillary electrophoresis in aqueous solutions at different pH values.

In this article, capillary electrophoresis was used to measure the effective electrophoretic mobility of ester betulin derivatives as a pH function and to study their complexation with γ-cyclodextrin (γ-CD). The electrophoretic mobility of betulin 3,28-diphthalate (DPhB) and 3,28-disuccinate (DScB) changed unusually with decreasing pH: instead of decreasing, it first increased and then decreased. This fact as well as the turbidity of sample solutions at pH from 2.5 to 6, broadening of electrophoretic peaks and a decrease in the surface tension of the solutions indicates that these betulin derivatives, being amphiphilic compounds and weak acids, exist as micelles in aqueous solutions at pH 6 and below. The inclusion complexation of betulin derivatives with γ-CD at pH 9.18 and 4.5 was studied by mobility shift affinity capillary electrophoresis. At pH 9.18, the apparent binding (stability) constant logarithms for 1:1 γ-CD complexes of DPhB, betulin 3,28-disulfate (DSB) and DScB with 95% confidence interval limits were equal to 7.44± 0.02, 7.09 (7.01-7.19), and 6.97 (6.87-7.08) at 25°C, respectively. At pH 4.5, the binding constant for the DSB complex was slightly lower, while the micelle formation did not allow determining the exact values of the constants for the DPhB and DScB complexes.

Inducing enantioselective crystallization with and self-assembly of star-shaped hybrid polymers prepared via "grafting to" strategy.

Helical polymers present some interesting and distinctive properties, and one of the most distinguished applications of them is the chiral recognition and resolution of enantiomers. In this work, star-shaped hybrid helical poly (phenyl isocyanide) (PPI) with polyhedral oligomeric silsesquioxanes (POSS) as the core was designed and synthesized by "grafting to" strategy. The homoarm star-shaped hybrid POSS-(PPI)8 was first obtained by the click reaction between azide-modified POSS (POSS-(N3 )8 ) and alkynyl-modified PPI (PPI-Alkynyl). The hybrid POSS-(PPI)8 was with predominated left-handed helical conformation and exhibited excellent ability in the enantioselective crystallization of racemic compounds. In the meantime, heteroarm star-shaped hybrid (PEG)4 -POSS-(PPI)4 was prepared by the click reaction of POSS-(N3 )8 with PPI-Alkynyl and alkynyl-modified poly (ethylene glycol) (PEG-Alkynyl). The hybrid (PEG)4 -POSS-(PPI)4 was amphiphilic, and it could self-assemble to form spherical micelles in aqueous solutions.

Synthesis and properties of stellate lactosamide quaternary ammonium surfactants

A number of stellate lactosamide quaternary ammonium salt surfactants (N-dodecyl-N, N-bis[(3-lactosamide) propyl]-N-alkylamine bromide, C n DBLB, where n represents hydrocarbon chain lengths of 12,14 and 16) was successfully synthesized from lactobionic acid, N-(3-aminopropyl)-N-dodecylpropane-1,3-diamine, and bromoalkane by a two-step method comprising a proamine ester reaction and post-quaternization. The surface activity, adsorption, and aggregation behavior of the surfactants in aqueous solutions were investigated by dynamic/static surface tension, contact angle, dynamic light scattering, proton nuclear magnetic resonance spectroscopy, and transmission electron microscopy measurements. The results demonstrated that the equilibrium surface tension ( γ cmc ) of the C n DBLB surfactant was in the range of 28–35 mN/m; thus, it had a strong ability to reduce the surface tension of water. Furthermore, with increase in the carbon chain length of the surfactant, the saturated adsorption amount (Г max ) increased while A min decreased. However, the adsorption duration of C n DBLB was long, and rapid equilibrium could not be achieved on the surface of the solution, indicating a mixed kinetic adsorption mechanism. All three surfactants formed spherical micelles in aqueous solutions. Because the hydrophobic carbon chain length increased, the molecular structure complexity, steric hindrance, and hydrophobic group–water interaction (repulsion) increased, accounting for the unique aggregation behavior of C n DBLB in aqueous solutions. With increase in the concentration of the C 12 DBLB surfactant, the size of the aggregates formed increased. The sizes of the C 14 DBLB and C 16 DBLB aggregates increased initially, decreased, and subsequently increased again. Moreover, the morphology of molecular self-assembly was discussed. C n DBLB surfactant at low concentration was low toxicity or non-toxic, with the increase of concentration, its toxicity will also increase.

Doxorubicin-loaded natural daptomycin micelles with enhanced targeting and anti-tumor effect invivo.

Development of a simple method to enhance targeting and anti-tumor effect of the chemotherapeutic agents invivo is a major problem. Amphipathic and natural daptomycin is biocompatible antibacterial polypeptide used in clinical practice. Herein, doxorubicin (DOX) was stabilized by zwitterionic daptomycin (Dap) micelles in aqueous solution to form a zwitterionic nanodrug (Dap-DOX micelles). The hydrodynamic size and zeta potential of Dap-DOX micelles were 85nm and-10 mV, respectively. The study on the controlled release showed that more DOX molecules were released from Dap-DOX micelles at acidic condition of tumor tissue than that at neutral condition of normal tissue which was due to pH responsiveness of Dap-DOX micelles. Dap-DOX micelles exhibited good stability in fibrinogen solution. Moreover, MTT studies showed that Dap-DOX micelles had higher cytotoxicity than free DOX. Notably, the results of flow cytometry indicated that the average fluorescence intensity of Dap-DOX micelle-treated cells was higher than that of free DOX-treated cells, and acidic conditions were more favorable for Dap-DOX micelles than normal pH in cell uptake assay. More importantly, Dap-DOX micelles were biocompatible invivo based on the changes of weight and blood indexes of mice. Dap-DOX micelles were selectively accumulated at tumor sites invivo through EPR effect, which reduced the toxicity of free DOX and achieved excellent tumor inhibition effect. The tumor inhibition rate of Dap-DOX micelles reached 96%. Dap-DOX micelles also effectively inhibited the growth of bacterial. Taken together, Dap-based drug delivery systems are promising and effective in cancer therapy.

Hybridization of Poly(oxazoline) and Poly(ethylene oxide)-Based Amphiphilic Copolymers into Thermosensitive Mixed Micelles of Tunable Cloud Point.

This paper reports the development in aqueous solution of mixed micelles of tunable cloud point temperature through blending in various proportions of two copolymers of different chemical natures. For that purpose, a lipid-b-poly(2-isopropyl-2-oxazoline) (lipid-b-P(iPrOx)) copolymer, self-assembling into thermosensitive micelles that phase-separate above a cloud point temperature of 38 °C, was blended in various proportions with commercial C18-b-PEOx. The latter was constituted of a hydrophobic saturated C18 chain and a hydrophilic poly(ethylene oxide) (PEO) block with varying polymerization degrees (x) and does not have any thermosensitive properties on the studied temperature range for any value of x. The different blends were thoroughly characterized by light scattering and UV-visible spectroscopy, revealing that hybridization between both copolymers always occurred, independent of the PEO block length. The resulting mixed micelles present TCP values progressively increasing with the C18-b-PEOx proportion, from 38 to 61 °C. This study demonstrates the relevance of the blending approach to tune the phase separation of micellar systems by formulation rather than by more tedious synthetic efforts. Shifting TCP through this approach extends the range of temperature where lipid-b-P(iPrOx) can find an application.

Hypoxia-responsive block copolymer polyprodrugs for complementary photodynamic-chemotherapy

The inherent hypoxic microenvironment of solid tumors has an important influence on tumor growth, distant metastasis, and invasiveness. The heterogeneous distribution of hypoxic regions inside tumors limits the therapeutic efficacy of O2-assisted therapeutic strategy (e.g. photodynamic therapy (PDT)). On the other hand, the hypoxia-activable prodrugs cannot work effectively in the regions with enough O2 concentration. To address the issues, we prepare a block copolymer polyprodrug consisting of polyethylene glycol (PEG) and copolymerized segments of nitroimidazole-linked camptothecin (CPT) methacrylate and 5,10,15,20-tetraphenylporphyrin (TPP)-containing methacrylate monomers for complementary photodynamic-chemotherapy. The polyprodrug can self-assemble into polymeric micelles in aqueous solution with suitable size and high stability. After intravenous injection, the polyprodrug micelles show tumor accumulation. Followed by light irradiation (650 nm) at tumor sites, TPP moieties induce singlet oxygen (1O2) production in the oxygen-rich area to exert PDT and cause transformation of the oxygen-rich areas into hypoxia. Simultaneously, in the hypoxic areas, the hypoxia-responsive polyprodrugs can be activated to release free CPT due to the cleavage of nitroimidazole linkages. The polyprodrug micelles with the segments for PDT and hypoxia-activable CPT efficiently suppress the growth of HeLa tumors. The well-defined polyprodrug amphiphiles offer an effective strategy to overcome the disadvantages of single treatment of PDT or hypoxia-responsive prodrugs for complementary photodynamic-chemotherapy of cancers.

Polyether-Based Diblock Terpolymer Micelles with Pendant Anthracene Units-Light-Induced Crosslinking and Limitations Regarding Reversibility.

The synthesis of 9-methylanthracenyl glycidyl ether (AnthGE) as a crosslinkable monomer that can be applied in anionic ring opening polymerization is reported. Diblock terpolymers of the composition methoxy-poly(ethylene oxide)-block-poly(2-ethylhexyl glycidyl ether-co-9-methylanthracenyl glycidyl ether) (mPEO-b-P(EHGE-co-AnthGE) with 10 to 24 wt% of AnthGE are synthesized and characterized. Their micellization behavior, as well as their light-induced core-crosslinking via irradiation with UV light (λ = 365nm) is studied. The results are compared with studies on the dimerization, and the dimer cleavage via irradiation with UV-C light (λ = 254nm), of the same diblock terpolymer in organic solution, and the small-molecule model compound 9-methoxymethylanthracene. Differences in 1 H NMR spectra of the crosslinked or dimerized compounds and reaction kinetics of the dimerization reactions under different conditions suggest possible side reactions for the case of the core-crosslinking of micelles in aqueous solution. These side reactions limit the reversibility of the anthracene dimerization reaction in aqueous solutions, even if the anthracene molecule is encapsulated within the hydrophobic core of a polymeric micelle.

Self-aggregation of synthetic zinc 3-hydroxymethyl-chlorophyll-a derivatives possessing electron-withdrawing groups at the 20-position in aqueous micelle solution

Zinc methyl 3-hydroxymethyl-pyropheophorbides-[Formula: see text] bearing an acetyl or nitro group at the 20-position were prepared by chemically modifying natural chlorophyll-[Formula: see text]. The synthetic zinc 20-substituted bacteriochlorophyll-[Formula: see text] analogs self-aggregated in an aqueous Triton X-100 micelle solution to give red-shifted and broadened electronic absorption bands, similarly as in one of the photosynthetic light-harvesting antennas, chlorosomes. Although the sterically bulky 20-substituents of the semisynthetic zinc 31-hydroxy-131-oxo-chlorins partially disturbed the chlorosomal self-aggregates which would be produced by the [Formula: see text]–[Formula: see text] stacking of the chlorin chromophores, their electron-withdrawing abilities should enhance the specific, intermolecular interaction of Zn[Formula: see text]O32–H[Formula: see text]O=C-13 which was essential for the chlorosomal self-aggregation. Such self-assemblies using these model pigments would provide a new clue for constructing of artificial photosynthetic systems.

Click preparation and mechanism on amphiphilic oleophobic/hydrophilic behavior of fluorinated diblock copolymers

AbstractIn this article, amphiphilic fluorinated diblock copolymers of poly(perfluorohexylethyl acrylate)‐block‐allylpolyethyleneglycol (PF6A‐b‐APEG1200) are synthesized by reversible addition‐fragmentation transfer (RAFT) polymerization and sequential thiol‐ene click reaction. The molecular structure is characterized by 1H nuclear magnetic resonance (1H NMR) spectra and Fourier transform infrared (FTIR) spectra. Morphology and particle size of resultant copolymer micelles in aqueous solution are analyzed by transmission electron microscope (TEM) and dynamic light scattering (DLS). The wettability and relative element contents of PF6A‐b‐APEG1200 coatings are investigated with contact angle (CA) and X‐ray photoelectron spectroscopy (XPS). When PF6A‐b‐APEG1200 coating is stimulated by water, the fluorine content at the top fluoropolymer‐air interface decreases and the water contact angle of the surface decreases over time, showing the hydrophilicity. While stimulated by n‐hexadecane, the fluorine content of the film surface increases, showing the oleophobicity with a stable apparent oil contact angle of 72 ± 1°. According to the detailed analysis of XPS results, the stimuli‐responsive behavior of the amphiphilic polymers can be ascribed to the migration and rearrangement of the two blocks in PF6A‐b‐APEG1200, which might probably be one of the universally accepted oleophobic/hydrophilic mechanisms.

Nanoengineered polypeptides from tetraphenylethylene-functionalized N-carboxyanhydride: Synthesis, self-assembly and intrinsic aggregation-induced emission

Ring-opening polymerization of N-carboxyanhydrides (NCAs) bearing pendant groups creates functional polypeptides. In this paper, we report the design, synthesis and polymerization of tetraphenylethylene (TPE)-modified NCA, which is used to incorporate aggregation-induced emission (AIE)-active segments into polypeptides. Specifically, we attempted the synthesis of amphiphilic methoxy poly(ethyleneglycol)-block-poly(γ-benzyl-l-glutamate)-block-poly(γ-4-(1,2,2-triphenylvinyl)benzyl-l-glutamate) (PEG-PBLG-PTPELG), which had well-controlled molecular weight and narrow polydispersity. The hydrophilic PEG and hydrophobic PBLG-PTPELG assembled into micelles in aqueous solution with diameter around 70 ​nm, displaying AIE at 480 ​nm. Our work demonstrates that the TPE-modified NCA is applicable for the preparation of the AIE-active polypeptides, integrating the AIE luminogens into the polypeptides which may offer unique opportunities for tuning AIE properties by adjusting the composition and conformation of polypeptides. We preliminarily explored the use of the amphiphilic polypeptides for the formulation of doxorubicin-containing micelles that can potentially be used for real-time monitoring of the nanomedicine distribution.

Preparation of astaxanthin micelles self-assembled by a mechanochemical method from hydroxypropyl β-cyclodextrin and glyceryl monostearate with enhanced antioxidant activity

This research aimed to overcome the current challenges in the application of natural carotenoid antioxidants, such as their complex preparation processes, low bioavailability and poor drug stability. Herein, a mechanochemical method was used to prepare an inclusion complex (IC) that self-assembles into micelles in aqueous solution and achieves solid-phase loading of astaxanthin (AST). The NMR analysis, thermodynamics study, particle size analysis and electron microscopy image results showed that AST, hydroxypropyl β-cyclodextrin (HPβ-CD) and glyceryl monostearate (GMS) formed self-assembled micelles and maintained good stability in aqueous solution. The antioxidant performance experiments showed that the formation of IC increases free radical scavenging activity. The pharmacokinetic studies showed that the bioavailability of the astaxanthin inclusion complex increased 4-fold. The tissue distribution experiments showed that the astaxanthin inclusion complex targets the liver to exert its antioxidant effects. The proposed method uses an innovative preparation technology to produce an efficient drug delivery system without solvents, and it exerts powerful antioxidant activity against astaxanthin.

Mercury-containing supramolecular micelles with highly sensitive pH-responsiveness for selective cancer therapy

Construction and manipulation of metal-based supramolecular polymers—which are based on a combination of nucleobase hydrogen bonding interactions and functional metal ions—to obtain the desired physicochemical properties and achieve the efficacy and safety required for biomedical applications remain extremely challenging. We successfully designed and synthesized a new mercury-based supramolecular polymer, Hg-BU-PPG, containing an oligomeric polypropylene glycol backbone and pH-sensitive uracil-mercury-uracil (U-Hg-U) linkages. This multifunctional metallo-supramolecular material spontaneously self-organizes into nanosized spherical micelles in aqueous solution. The micelles possess several attractive properties, including desired long-term structural stability in serum-rich conditions, unique fluorescence behavior and highly sensitive, well-controlled pH-responsiveness. Interestingly, Hg-BU-PPG micelles exhibited strong, selective cytotoxic effects towards cancer cells in vitro, without harming normal cells. The highly selective cytotoxicity can be attributed to rapid dissociation of the U-Hg-U complexes within the micelles in the mildly acidic intracellular pH of cancer cells, followed by release of inherently toxic mercury ions. Importantly, fluorescence microscopy and flow cytometry clearly demonstrated that Hg-BU-PPG selectively entered the cancer cells via endocytosis and rapidly promoted massive apoptotic cell death. In contrast, internalization of Hg-BU-PPG by normal cells was limited, resulting in high biocompatibility and no cytotoxic effects. Thus, this newly discovered ‘cytotoxicity-concealing’ supramolecular system could represent a viable route to enhance the safety and efficacy of cancer therapy and bioimaging via a strategy that does not require incorporation of anticancer drugs and fluorescent probes. Statement of significanceWe report a significant breakthrough in the construction of mercury-containing supramolecular polymers, namely the creation of multifunctional micelles with unique chemical and physical properties conferred by pH-sensitive uracil-mercury-uracil (U-Hg-U) linkages and tunable structural and dynamical features due to the presence of hydrogen-bonded uracil moieties. Importantly, in vitro experiments clearly demonstrated that introduction of the U-Hg-U complexes into the micelles not only improved the efficiency of selective uptake via endocytosis into cancer cells, but also accelerated the induction of massive apoptotic cell death. Thus, this work provides crucial new insight for the development of metallo-supramolecular polymeric micelles that may substantially enhance the safety and efficacy of cancer therapy and bioimaging without requiring incorporation of anticancer drugs or fluorescent probes.

31-Substituent-dependent Self-aggregation of Bacteriochlorophyll-d Analogs in Aqueous Micelles

Zinc bacteriochlorophyll-d analogs possessing 31-ethyl, vinyl, and ethynyl groups instead of the original 31-methyl group were prepared by chemically modifying chlorophyll-a. The 31-substituents affected their 31-diastereomerically controlled self-aggregation in an aqueous Triton X-100 micelle solution, where the (31R)-epimers of the ethylated and vinylated derivatives readily formed chlorosomal self-aggregates with red-shifted absorption bands due to exciton coupling in the supramolecule, but the corresponding ethynylated epimer was monomeric.

Self-aggregation of Synthetic 20-O-Substituted Bacteriochlorophyll-d Analogs

Zinc 20-acyloxy-bacteriochlorophyll-d analogs were prepared from naturally occurring chlorophyll(Chl)-a. The semi-synthetic Chl-a derivatives self-aggregated in an aqueous Triton X-100 micelle solution to give red-shifted and broadened visible absorption bands, similarly to native chlorosome, one of the photosynthetic light-harvesting antenna systems. The present compounds are the first examples of a 20-O-substituted chlorosomal pigment model.