Simple but Precise Engineering of Functional Nanocapsules through Nanoprecipitation

Poly(vinyl alcohol)s and Their Glycoderivatives as Efficient Shell-Builders of Nanocapsules by Nanoprecipitation

Poly(vinyl alcohol)s (PVAs) are very popular dispersants for the construction of colloids and common shell-constituents of microcapsules but remain mostly unexplored as building blocks for the design of nanocapsules through nanoprecipitation or other processes. Herein, we first show that model commercial PVAs and oils can be concomitantly engaged in solvent-shifting procedures to give rise to oil-filled nanocapsules in one step. Next, we report the synthesis of precisely defined water-soluble glyco-PVAs by reversible addition-fragmentation chain transfer (RAFT) copolymerization of 6-O-vinyladipoyl-d-glucopyranose and vinyl chloroacetate and selective alcoholysis reactions. We finally demonstrate that these glycopolymers are excellent candidates for the straightforward conception of oil- and drug-filled, surface- and/or core-tagged, stealth, and degradable nanocapsules by nanoprecipitation.

Nanoprecipitation through solvent-shifting using rapid mixing: Dispelling the Ouzo boundary to reach large solute concentrations

HYPOTHESIS

The addition of a non-solvent to a solute in good solvent solution leads to nanoprecipitation, which is the spontaneous formation of nanodomains. Yet, increasing solute concentration usually leads to the formation of macrodomains that quickly separate into a bulk phase, which is a severe process limitation. The corresponding concentration threshold, often termed as the Ouzo boundary, remains a mystery that could find its origin in the complex interplay between nanoprecipitation and mixing.

EXPERIMENTS

We performed a systematic investigation of nanoprecipitation thermodynamics and kinetics as well as its interplay with mixing hydrodynamics for the hexadecane-acetone-water system, in the presence of the non-ionic C16EO8 surfactant. The binodal curve and its underlying tie-lines were obtained using Raman spectroscopy, allowing the computation of the spinodal curve. Kinetics were probed using a continuous flow setup that combines two sequential rapid mixers. The impact of mixing efficiency was probed systematically by varying the oil concentration for respectively slow and rapid mixing, while the uncoupling from mixing and nanoprecipitation was quantified by modifying systematically the flow rate in a continuous flow approach.

FINDINGS

We elucidate the nature of the Ouzo boundary that marks the maximal solute concentration leading to nanoobjects. Rather than a thermodynamic boundary, as evidenced by its uncorrelation to the spinodal curve, it results from the coupling of nanoprecipitation and mixing when both processes occur within the same time range, leading to heterogeneous conditions and the escape of some objects to the macroscale. Increasing the solute concentration speeds up nanoprecipitation and thus requires increasingly faster mixing times to uncouple both processes. Accordingly, if the mixing efficiency is large enough, it is possible to dispel the Ouzo boundary and reach very large solute concentrations. Implementing rapid mixing strategies in continuous flow approaches is thus the solution to overcome the most stringent condition of nanoprecipitation and open the way to scale-up, while also providing efficient means to probe its fast mechanism. Overall, the simultaneous control of hydrodynamics and physical chemistry is thus key to boost up the Ouzo effect.

Gout therapeutics and drug delivery

Gout is a common inflammatory arthritis caused by persistently elevated uric acid levels. With the improvement of people's living standards, the consumption of processed food and the widespread use of drugs that induce elevated uric acid, gout rates are increasing, seriously affecting the human quality of life, and becoming a burden to health systems worldwide. Since the pathological mechanism of gout has been elucidated, there are relatively effective drug treatments in clinical practice. However, due to (bio)pharmaceutical shortcomings of these drugs, such as poor chemical stability and limited ability to target the pathophysiological pathways, traditional drug treatment strategies show low efficacy and safety. In this scenario, drug delivery systems (DDS) design that overcome these drawbacks is urgently called for. In this review, we initially describe the pathological features, the therapeutic targets, and the drugs currently in clinical use and under investigation to treat gout. We also comprehensively summarize recent research efforts utilizing lipid, polymeric and inorganic carriers to develop advanced DDS for improved gout management and therapy.

Modulation of Oil/Polymer Nanocapsule Size via Phase Diagram-Guided Microfluidic Coprecipitation

Flow-based nanoprecipitation of different solutes via rapid mixing of two miscible liquids is a scalable strategy for manufacturing nanoparticles with various shapes and morphologies. Controlling the size of nanoparticles in flow-based nanoprecipitation, however, is often left to empirical variations in the flow rate ratios or the total flow rate of the two streams. In this work, we investigate the coprecipitations of oil and polymer to form nanocapsules via the Ouzo effect using glass capillary microfluidics across a range of mixing conditions. In the range of flow rates studied, the two streams mix convectively in micro-vortices formed at the junction of the two stream inlets. Using computational fluid dynamics simulations and glass capillary microfluidic nanoprecipitation, we establish a relationship between the precipitation conditions occurring experimentally in situ and the location on the ternary Ouzo phase diagram where precipitation is taking place. We find that a key variable in the resulting average diameter of the fabricated capsules is the degree of supersaturation experienced by both the oil and the polymer in the vortex zone of the device, showing a strong correlation between the two values. The control over the nanocapsule size by varying the extent of supersaturation of both precipitants is demonstrated by using two oils having distinct phase diagrams. This work provides a systematic approach to controlling the size of nanoparticles fabricated via continuous nanoprecipitation by linking the in situ flow conditions to ternary phase diagram behavior, enabling accurate control over nanocapsule size.

Encapsulated Peptides and Proteins with an Effect on Satiety

The world scenario has undergone a nutritional transition in which some countries have left the reality of malnutrition and now face an epidemic of excess body weight. Researchers have been looking for strategies to reverse this situation. Peptides and proteins stand out as promising molecules with anti-obesity action. However, oral administration and passage through the gastrointestinal tract face numerous physiological barriers that impair their bioactive function. Encapsulation aims to protect the active substance and modify the action, one possibility of potentiating anti-obesity activity. Research with encapsulated peptides and proteins has demonstrated improved stability, delivery, controlled release, and increased bioactivity. However, it is necessary to explore how proteins and peptides affect weight loss and satiety, can impact the nutritional status of obesity, and how encapsulation can enhance the bioactive effects of these molecules. This integrative review aimed to discuss how the encapsulation of protein molecules impacts the nutritional status of obesity. From the studies selected following pre-established criteria, it was possible to infer that the encapsulation of proteins and peptides can contribute to greater efficiency in reducing weight gain, changes in adipose tissue function, and lower hormone levels that modulate appetite and body weight in animals with obesity.

Recent advances in mixing-induced nanoprecipitation: from creating complex nanostructures to emerging applications beyond biomedicine

Mixing-induced nanoprecipitation (MINP) is an efficient, controllable, scalable, versatile, and cost-effective technique for the preparation of nanoparticles. In addition to the formulation of drugs, MINP has attracted tremendous interest in other fields. In this review, we highlight recent advances in the preparation of nanoparticles with complex nanostructures via MINP and their emerging applications beyond biomedicine. First, the mechanisms of nanoprecipitation and four mixing approaches for MINP are briefly discussed. Next, three strategies for the preparation of nanoparticles with complex nanostructures including sequential nanoprecipitation, controlling phase separation, and incorporating inorganic nanoparticles, are summarized. Then, emerging applications including the engineering of catalytic nanomaterials, environmentally friendly photovoltaic inks, colloidal surfactants for the preparation of Pickering emulsions, and green templates for the synthesis of nanomaterials, are reviewed. Furthermore, we discuss the structure-function relationships to gain more insight into design principles for the development of functional nanoparticles via MINP. Finally, the remaining issues and future applications are discussed. This review will stimulate the development of nanoparticles with complex nanostructures and their broader applications beyond biomedicine.

Continuous Nanoprecipitation of Polycaprolactone in Additively Manufactured Micromixers

The polymeric ouzo effect is an energy-efficient and robust method to create nanoparticles with biologically degradable polymers. Usually, a discontinuous or semi-continuous process is employed due to its low technical effort and the fact that the amount of dispersions needed in a laboratory is relatively small. However, the number of particles produced in this method is not enough to make this process economically feasible. Therefore, it is necessary to improve the productivity of the process and create a controllable and robust continuous process with the potential to control parameters, such as the particle size or surface properties. In this study, nanoparticles were formulated from polycaprolactone (PCL) in a continuous process using additively manufactured micromixers. The main goal was to be able to exert control on the particle parameters in terms of size and zeta potential. The results showed that particle size could be adjusted in the range of 130 to 465 nm by using different flow rates of the organic and aqueous phase and varying concentrations of PCL dissolved in the organic phase. Particle surface charge was successfully shifted from a slightly negative potential of −14.1 mV to a negative, positive, or neutral value applying the appropriate surfactant. In summary, a continuous process of nanoprecipitation not only improves the cost of the method, but furthermore increases the control over the particle’s parameters.

Exploring Various Techniques for the Chemical and Biological Synthesis of Polymeric Nanoparticles

Nanoparticles (NPs) have remarkable properties for delivering therapeutic drugs to the body’s targeted cells. NPs have shown to be significantly more efficient as drug delivery carriers than micron-sized particles, which are quickly eliminated by the immune system. Biopolymer-based polymeric nanoparticles (PNPs) are colloidal systems composed of either natural or synthetic polymers and can be synthesized by the direct polymerization of monomers (e.g., emulsion polymerization, surfactant-free emulsion polymerization, mini-emulsion polymerization, micro-emulsion polymerization, and microbial polymerization) or by the dispersion of preformed polymers (e.g., nanoprecipitation, emulsification solvent evaporation, emulsification solvent diffusion, and salting-out). The desired characteristics of NPs and their target applications are determining factors in the choice of method used for their production. This review article aims to shed light on the different methods employed for the production of PNPs and to discuss the effect of experimental parameters on the physicochemical properties of PNPs. Thus, this review highlights specific properties of PNPs that can be tailored to be employed as drug carriers, especially in hospitals for point-of-care diagnostics for targeted therapies.

Versatile Polymer Nanocapsules via Redox Competition

Polymer nanocapsules have demonstrated significant value in materials science and biomedical technology, but require complicated and time-consuming synthetic steps. We report here the facile synthesis of monodisperse polymer nanocapsules via a redox-mediated kinetic strategy from two simple molecules: dopamine and benzene-1,4-dithiol (BDT). Specifically, BDT forms core templates and modulates the oxidation kinetics of dopamine into polydopamine (PDA) shells. These uniform nanoparticles can be tuned between ≈70 and 200 nm because the core diameter directly depends on BDT while the shell thickness depends on dopamine. The supramolecular core can then rapidly disassemble in organic solvents to produce PDA nanocapsules. Such nanocapsules exhibit enhanced physicochemical performance (e.g., loading capacity, photothermal transduction, and anti-oxidation) versus their solid counterparts. Particularly, this method enables a straightforward encapsulation of functional nanoparticles providing opportunities for designing complex nanostructures such as yolk-shell nanoparticles.

Nanoprecipitation as a simple and straightforward process to create complex polymeric colloidal morphologies

Polymeric nanoparticles are highly important functional nanomaterials for a large range of applications from therapeutics to energy. Advances in nanotechnology have enabled the engineering of multifunctional polymeric nanoparticles with a variety of shapes and inner morphologies. Thanks to its inherent simplicity, the nanoprecipitation technique has progressively become a popular approach to construct polymeric nanoparticles with precise control of nanostructure. The present review highlights the great capability of this technique in controlling the fabrication of various polymeric nanostructures of interest. In particular, we show here how the nanoprecipitation of either block copolymers or mixtures of homopolymers can afford a myriad of colloids displaying equilibrium (typically onion-like) or out-of-equilibrium (stacked lamellae, porous cores) morphologies, depending whether the system "freezes" while passing the glass transition or crystallization point of starting materials. We also show that core-shell morphologies, either from polymeric or oil/polymer mixtures, are attainable by this one-pot process. A final discussion proposes new directions to enlarge the scope and possible achievements of the process.

Nanocapsules Produced by Nanoprecipitation of Designed Suckerin-Silk Fusion Proteins

Herein, we report on the precise design of a modular fusion protein amenable to the construction of nanocapsules by nanoprecipitation. The central squid suckerin-derived peptide block provides structural stability, whereas both termini from spider silk fibroins make the protein highly soluble at physiological pH, a critical requirement for the nanoprecipitation process. With this design, nanocapsules consisting of fusion protein shells and oily cores with sizes in the range of 190-250 nm are built in a straightforward manner.

Oleic Acid Copolymer as A Novel Upconversion Nanomaterial to Make Doxorubicin-Loaded Nanomicelles with Dual Responsiveness to pH and NIR

Oleic acid (OA) as main component of plant oil is an important solvent but seldom used in the nanocarrier of anticancer drugs because of strong hydrophobicity and little drug release. In order to develop a new type of OA nanomaterial with dual responses to pH and near infrared light (NIR) to achieve the intelligent delivery of anticancer drugs. The novel OA copolymer (mPEG-PEI-(NBS, OA)) was synthesized by grafting OA and o-nitrobenzyl succinate (NBS) onto mPEGylated polyethyleneimine (mPEG-PEI) by amidation reaction. It was further conjugated with NaYF₄:Yb³⁺/Er³⁺ nanoparticles, and encapsulated doxorubicin (DOX) through self-assembly to make upconversion nanomicelles with dual response to pH and NIR. Drug release behavior of DOX, physicochemical characteristics of the nanomicelles were evaluated, along with its cytotoxic profile, as well as the degree of cellular uptake in A549 cells. The encapsulation efficiency and drug loading capacity of DOX in the nanomicelles were 73.84% ± 0.58% and 4.62% ± 0.28%, respectively, and the encapsulated DOX was quickly released in an acidic environment exposed to irradiation at 980 nm. The blank nanomicelles exhibited low cytotoxicity and excellent biocompatibility by MTT assay against A549 cells. The DOX-loaded nanomicelles showed remarkable cytotoxicity to A549 cells under NIR, and promoted the cellular uptake of DOX into the cytoplasm and nucleus of cancer cells. OA copolymer can effectively deliver DOX to cancer cells and achieve tumor targeting through a dual response to pH and NIR.

Prophylactic Antiviral Activity of Sulfated Glycomimetic Oligomers and Polymers

In this work, we investigate the potential of highly sulfated synthetic glycomimetics to act as inhibitors of viral binding/infection. Our results indicate that both long-chain glycopolymers and short-chain glycooligomers are capable of preventing viral infection. Notably, glycopolymers efficiently inhibit Human Papillomavirus (HPV16) infection in vitro and maintain their antiviral activity in vivo, while the glycooligomers exert their inhibitory function post attachment of viruses to cells. Moreover, when we tested the potential for broader activity against several other human pathogenic viruses, we observed broad-spectrum antiviral activity of these compounds beyond our initial assumptions. While the compounds tested displayed a range of antiviral efficacies, viruses with rather diverse glycan specificities such as Herpes Simplex Virus (HSV), Influenza A Virus (IAV), and Merkel Cell Polyomavirus (MCPyV) could be targeted. This opens new opportunities to develop broadly active glycomimetic inhibitors of viral entry and infection.

Highly Photostable and Two-Photon Active Quantum Dot-Polymer Multicolor Hybrid Coacervate Droplets

Fabrication and precise control of the physicochemical properties of multifunctional organic-inorganic hybrid nanocomposites find great importance in various research fields. Herein, we report the fabrication of a new class of luminescent hybrid coacervate droplets from CdTe quantum dots (QDs) and a poly(diallyldimethylammonium chloride) (PDADMAC) aqueous mixture. The colloidal stability of these droplets has been explored over wide ranges of composition, pH, and ionic strength. Although these hybrid droplets are quite stable in a low-ionic-strength medium (<100 mM NaCl) and neutral/basic pH (pH >6.5), they are unstable in a higher-ionic-strength medium (>100 mM NaCl) and acidic pH (pH <5.5). Our findings indicate specific electrostatic interactions between negatively charged QDs and positively charged PDADMAC behind the observed coacervation. They exhibit the preferential sequestration of organic dyes and serum albumins. The intrinsic luminescent properties of these hybrid droplets have been explored using confocal laser scanning microscopy (CLSM) and epifluorescence microscopy. CLSM reveals the formation of intrinsically luminescent hybrid droplets. In addition, mixed two-color luminescent droplets have been fabricated by simultaneously mixing green- and red-emitting QDs with PDADMAC aqueous solution. Epifluorescence imaging reveals highly photostable and nonbleaching photoluminescence (PL) from individual droplets as a consequence of efficient surface passivation by polymeric chains of PDADMAC. Moreover, using two-photon (2P) confocal imaging we have shown that these hybrid droplets are ideal candidates for 2P confocal imaging applications. The present study can be easily extended to fabricate a wide range of hybrid droplets with various inorganic counterparts having unique optoelectronic properties, which will further expand their applicability in nanocatalysis, bioimaging, and biosensing.

Redox Responsive Polymersomes for Enhanced Doxorubicin Delivery

In the present investigation, the potential of a novel, self-assembled, biocompatible, and redox-sensitive copolymer system with disulfide bond was explored for doxorubicin (DOX) delivery through polymersome nanostructures of ∼120 nm. The polymer system was synthesized with less steps, providing a high yield of 86%. The developed polymersomes showed admirable biocompatibility with high dose tolerability in vitro and in vivo. The colloidal stability of DOX-loaded polymersomes depicted a stable and uniform particle size over a period of 72 h. The cellular internalization of polymersomes was assessed in HeLa and MDA-MB-231 cell lines, where enhanced cellular internalization was observed. The dose-dependent cytotoxicity was observed for DOX-loaded polymersomes by MTT cytotoxicity assay in the above cell lines. The tumor suppression studies were assessed in Ehrlich ascites tumor (EAT) carrying Swiss albino mice, where polymersomes exhibited a 7.16-fold reduction in tumor volume correlated with control and 5.39-fold higher tumor inhibition capacity compared to conventional chemotherapy (free DOX treatment). The developed polymersomes gave safer insights concerning DOX associated toxicities by histopathology and serum biochemistry analysis. Thus, results focus on the potential of redox responsive polymersomes for efficacious and improved DOX therapy with enhanced antitumor activity and insignificant cardiotoxicity which can be translated to clinical settings.

General and Scalable Approach to Bright, Stable, and Functional AIE Fluorogen Colloidal Nanocrystals for in Vivo Imaging

Fluorescent nanoparticles built from aggregation-induced emission-active organic molecules (AIE-FONs) have emerged as powerful tools in life science research for in vivo bioimaging of organs, biosensing, and therapy. However, the practical use of such biotracers has been hindered owing to the difficulty of designing bright nanoparticles with controlled dimensions (typically below 200 nm), narrow size dispersity and long shelf stability. In this article, we present a very simple yet effective approach to produce monodisperse sub-200 nm AIE fluorescent organic solid dispersions with excellent redispersibility and colloidal stability in aqueous medium by combination of nanoprecipitation and freeze-drying procedures. By selecting polymer additives that simultaneously act as stabilizers, promoters of amorphous-crystalline transition, and functionalization/cross-linking platforms, we demonstrate a straightforward access to stable nanocrystalline FONs that exhibit significantly higher brightness than their amorphous precursors and constitute efficient probes for in vivo imaging of the normal and tumor vasculature. FONs design principles reported here are universal, applicable to a range of fluorophores with different chemical structures and crystallization abilities, and are suitable for high-throughput production and manufacturing of functional imaging probes.

Transparent Silk Fibroin Microspheres from Controlled Droplet Dissolution in a Binary Solution

Silk is a natural polymer with a broad range of potential applications in textiles, advanced materials, biomedical devices, and drug delivery. The ability to control the morphology and assembly of silk fibroin is essential for the fabrication of silk-based structured materials. Here, we report an effective and simple approach based on droplet dissolution for weaving silk fibroin into spheres of several hundred micrometers in diameter. The spheres possess regular wrinkled microstructures on the surface and switchable transparency for visible light. To produce these silk spheres, we immersed a sessile microdrop of the silk fibroin aqueous solution in a surrounding phase of ethanol in toluene at low concentration (<10%). The droplet experienced a two-phase process: the first phase of volume expansion due to the intake of organic solvents from the surrounding phase and the second phase of droplet dissolution. The dissolution rate is closely related to the dynamics of the droplet, while the resulting microstructure of the silk microsphere is simply adjusted by the composition of the surrounding solution. At high concentrations of ethanol, silk fibroin formed a thin shell around the droplet during the initial expansion of the droplet in volume. As the droplet shrank at a later stage, the shell around the droplet wrinkled and crumpled, leading to regular ridges and crevices on the microsphere surface. This work demonstrates that controlled droplet dissolution may be explored as a novel and effective way to tailor microstructures of silk assemblies. The as-prepared silk microspheres may be potentially used as optical units or microcarriers.

Nanoprecipitation of PHPMA (Co)Polymers into Nanocapsules Displaying Tunable Compositions, Dimensions, and Surface Properties

A series of PHPMA homopolymers and of mannose- and dimethylamino-functionalized copolymers, were prepared by RAFT polymerization and engaged in the preparation of oil-loaded nanocapsules using the "Shift'N'Go" process. Playing with the phase diagrams of both oil and homo- or copolymers afforded the preparation of functional camptothecin-loaded nanocapsules displaying tunable dimensions (90-350 nm), compositions and surface properties.

Shear-Assisted Fabrication of Block Copolymer Agglomerates with Various Morphologies in Viscous Medium

In this work, we have investigated the effect of laminar flow shearing on the formation of block copolymer agglomerates in viscous medium. Under a laminar flow shearing, the block copolymer solution droplets were spontaneously emulsified and were then elongated into protofibers, which in turn transformed into particles with various morphologies. Besides micro-/nanorods, which were previously reported for homopolymers, sphere and sheetlike structures were unexpectedly fabricated from block copolymers depending on the solvent quality, solvent exchange rates, and the entanglement of the polymer chains. In particular, the sheet structure, fabricated from poly(ethylene glycol)-b-polystyrene (PEG-b-PS), can be fixed by UV irradiation when photo-crosslinkable azide groups were introduced onto the polystyrene block. Surprisingly, we found that the fixed sheetlike structures show demulsification capability in tens of seconds, which may have great potential application in the separation of oil from emulsions.

Modular construction of single-component polymer nanocapsules through a one-step surfactant-free microemulsion templated synthesis

Formation of O/W surfactant-free microemulsions from water/oil/acetone ternary systems is exploited to construct precisely-defined shell-functionalized core-loaded nanocapsules with tunable diameters (ranging from 50 to 190 nm) in one step.

The Antiadhesive Strategy in Crohn's Disease: Orally Active Mannosides to Decolonize Pathogenic Escherichia coli from the Gut

Blocking the adherence of bacteria to cells is an attractive complementary approach to current antibiotic treatments, which are faced with increasing resistance. This strategy has been particularly studied in the context of urinary tract infections (UTIs), in which the adhesion of pathogenic Escherichia coli strains to uroepithelial cells is prevented by blocking the FimH adhesin expressed at the tips of bacteria organelles called fimbriae. Recently, we extended the antiadhesive concept, showing that potent FimH antagonists can block the attachment of adherent-invasive E. coli (AIEC) colonizing the intestinal mucosa of patients with Crohn's disease (CD). In this work, we designed a small library of analogues of heptyl mannoside (HM), a previously identified nanomolar FimH inhibitor, but one that displays poor antiadhesive effects in vivo. The anomeric oxygen atom was replaced by a sulfur or a methylene group to prevent hydrolysis by intestinal glycosidases, and chemical groups were attached at the end of the alkyl tail. Importantly, a lead compound was shown to reduce AIEC levels in the feces and in the colonic and ileal mucosa after oral administration (10 mg kg(-1) ) in a transgenic mouse model of CD. The compound showed a low bioavailability, preferable in this instance, thus suggesting the possibility of setting up an innovative antiadhesive therapy, based on the water-soluble and non-cytotoxic FimH antagonists developed here, for the CD subpopulation in which AIEC plays a key role.

Silica Ouzo Effect: Amphiphilic Drugs Facilitate Nanoprecipitation of Polycondensed Mercaptosilanes

Amphiphilic drugs are therapeutic agents whose molecular structures contain both hydrophobic and hydrophilic portions. Here we report a systematic study on how amphiphilic drugs can assist in silica nanoprecipitation. 3-Mercaptopropyltrimethoxysilane (MPTMS) was used as the sole silica material and 12 amphiphilic drugs spanning a wide spectrum of therapeutic categories were included. MPTMS polycondensation was conducted in a DMSO-based organic phase. After a sufficient time, particle formation was induced by injecting a small amount of the organic phase into a water solution containing various amphiphiles. The results show that all amphiphilic drugs studied exerted concentration-dependent facilitating effect on nanoparticle formation. Under certain preparation conditions, the particle solution showed physical stability over a long period and the formed particles could be as small as 100 nm. By systematically varying drug concentrations and injection volumes, the ability of each amphiphile to promote nanoprecipitation can be quantified and compared, based on two novel indices: the area under the critical volume-concentration curve (AUC) and the critical stabilization concentration (CSC). We demonstrate that both ability indices significantly correlated with the drug's log P and critical micelle concentrations (CMC). Furthermore, we have optimized the aging and particle purification condition and extensively characterized our system through comprehensive TEM and zeta-potential measurements, as well as determinations for drug entrapment and release. In conclusion, we have established a quantitative structure-activity relationship for amphiphilic small-molecular drugs in their ability to interact with poly(mercaptopropyl)silsesquioxane species and form nanoparticles via solvent shifting. We speculate that both hydrophobic and electrostatic interactions play important roles in the formation and stabilization of nanoparticles.

A library of heptyl mannose-functionalized copolymers with distinct compositions, microstructures and neighboring non-sugar motifs as potent antiadhesives of type 1 piliated E. coli

Heptyl Mannose-functionalized copolymers are efficient anti-adhesives of type 1 Piliated E. coli.

Development of Heptylmannoside-Based Glycoconjugate Antiadhesive Compounds against Adherent-Invasive Escherichia coli Bacteria Associated with Crohn's Disease

The ileal lesions of Crohn’s disease (CD) patients are colonized by adherent-invasive Escherichia coli (AIEC) bacteria. These bacteria adhere to mannose residues expressed by CEACAM6 on host cells in a type 1 pilus-dependent manner. In this study, we investigated different antagonists of FimH, the adhesin of type 1 pili, for their ability to block AIEC adhesion to intestinal epithelial cells (IEC). Monovalent and multivalent derivatives of n-heptyl α-d-mannoside (HM), a nanomolar antagonist of FimH, were tested in vitro in IEC infected with the AIEC LF82 strain and in vivo by oral administration to CEACAM6-expressing mice infected with LF82 bacteria. In vitro, multivalent derivatives were more potent than the monovalent derivatives, with a gain of efficacy superior to their valencies, probably owing to their ability to form bacterial aggregates. Of note, HM and the multi-HM glycoconjugates exhibited lower efficacy in vivo in decreasing LF82 gut colonization. Interestingly, HM analogues functionalized with an isopropylamide (1A-HM) or β-cyclodextrin pharmacophore at the end of the heptyl tail (1CD-HM) exerted beneficial effects in vivo. These two compounds strongly decreased the amount of LF82 bacteria in the feces of mice and that of bacteria associated with the gut mucosa when administered orally at a dose of 10 mg/kg of body weight after infection. Importantly, signs of colitis and intestinal inflammation induced by LF82 infection were also prevented. These results highlight the potential of the antiadhesive compounds to treat CD patients abnormally colonized by AIEC bacteria and point to an alternative to the current approach focusing on blocking proinflammatory mediators.

Current treatments for Crohn’s disease (CD), including immunosuppressive agents, anti-tumor necrosis factor alpha (anti-TNF-α) and anti-integrin antibodies, focus on the symptoms but not on the cause of the disease. Adherent-invasive Escherichia coli (AIEC) bacteria abnormally colonize the ileal mucosa of CD patients via the interaction of the mannose-specific adhesin FimH of type 1 pili with CEACAM6 mannosylated proteins expressed on the epithelial cell surface. Thus, we decided to develop an antiadhesive strategy based on synthetic FimH antagonists specifically targeting AIEC bacteria that would decrease intestinal inflammation. Heptylmannoside (HM)-based glycocompounds strongly inhibit AIEC adhesion to intestinal epithelial cells in vitro. The antiadhesive effect of two of these compounds of relatively simple chemical structure was also observed in vivo in AIEC-infected CEACAM6-expressing mice and was associated with a reduction in the signs of colitis. These results suggest a new therapeutic approach for CD patients colonized by AIEC bacteria, based on the development of synthetic FimH antagonists.

Solvent Effects on the Formation of Surface Nanodroplets by Solvent Exchange

Solvent exchange is a simple process to form oil nanodroplets at solid-liquid interfaces with well-defined location and morphology. In this process, a good solvent of the oil is displaced by a poor solvent, leading to the nucleation and growth of oil droplets from a transient oversaturation at the mixing front. Our recent work has shown that the final volume of the droplets is related to the flow conditions. In this work, we investigate the effects of the type and the composition of solvents on the droplet formation under the same flow conditions. Water nanodroplets were produced by ethanol/cyclohexane (solution A) and cyclohexane (solution B) on a hydrophilic substrate. We found that the droplet size increases first and then decreases with an increase of the initial ethanol concentration in solution A. This is attributed to the phase separation of ethanol-cyclohexane-water; in particular, the composition of solution A on the phase boundary above the Ouzo region. The same reason also contributes to the lower efficiency in droplet formation for a longer alkane. The important implication from this work is that the maximal droplet volume is limited by the phase separation of the solvents used in the solvent exchange.

Formation of surface nanodroplets under controlled flow conditions

Nanodroplets on a solid surface (i.e., surface nanodroplets) have practical implications for high-throughput chemical and biological analysis, lubrications, laboratory-on-chip devices, and near-field imaging techniques. Oil nanodroplets can be produced on a solid-liquid interface in a simple step of solvent exchange in which a good solvent of oil is displaced by a poor solvent. In this work, we experimentally and theoretically investigate the formation of nanodroplets by the solvent exchange process under well-controlled flow conditions. We find significant effects from the flow rate and the flow geometry on the droplet size. We develop a theoretical framework to account for these effects. The main idea is that the droplet nuclei are exposed to an oil oversaturation pulse during the exchange process. The analysis shows that the volume of the nanodroplets increases with the Peclet number Pe of the flow as ∝ Pe(3/4), which is in good agreement with our experimental results. In addition, at fixed flow rate and thus fixed Peclet number, larger and less homogeneously distributed droplets formed at less-narrow channels, due to convection effects originating from the density difference between the two solutions of the solvent exchange. The understanding from this work provides valuable guidelines for producing surface nanodroplets with desired sizes by controlling the flow conditions.

Biocompatible Glycopolymer Nanocapsules via Inverse Miniemulsion Periphery RAFT Polymerization for the Delivery of Gemcitabine

Encapsulation of hydrophilic cancer drugs in polymeric nanocapsules was achieved in a one-pot process via the inverse miniemulsion periphery RAFT polymerization (IMEPP) approach. The chosen guest molecule was gemcitabine hydrochloride, which is used as the first-line treatment of pancreatic cancer. The resulting nanocapsules were confirmed to be ∼200 nm, with excellent encapsulation (∼96%) and loading (∼12%) efficiency. Postpolymerization reaction was successfully conducted to create glyocopolymer nanocapsules without any impact on the loads as well as the nanocapsules size or morphology. The loaded nanocapsules were specifically designed to be responsive in a reductive environment. This was confirmed by the successful disintegration of the nanocapsules in the presence of glutathione. The gemcitabine-loaded nanocapsules were tested in vitro against pancreatic cancer cells (AsPC-1), with the results showing an enhancement in the cytotoxicity by two fold due to selective accumulation and release of the nanocapsules within the cells. The results demonstrated the versatility of IMEPP as a tool to synthesize functionalized, loaded-polymeric nanocapsules suitable for drug-delivery application.

Surface Plasmon Resonance (SPR) for the Evaluation of Shear-Force-Dependent Bacterial Adhesion

The colonization of Escherichia coli (E. coli) to host cell surfaces is known to be a glycan-specific process that can be modulated by shear stress. In this work we investigate whether flow rate changes in microchannels integrated on surface plasmon resonance (SPR) surfaces would allow for investigating such processes in an easy and high-throughput manner. We demonstrate that adhesion of uropathogenic E. coli UTI89 on heptyl α-d-mannopyranoside-modified gold SPR substrates is minimal under almost static conditions (flow rates of 10 µL·min⁻¹), and reaches a maximum at flow rates of 30 µL·min⁻¹ (≈30 mPa). This concept is applicable to the investigation of any ligand-pathogen interactions, offering a robust, easy, and fast method for screening adhesion characteristics of pathogens to ligand-modified interfaces.

Glycopolymers as Antiadhesives of E. coli Strains Inducing Inflammatory Bowel Diseases

n-Heptyl α-d-mannose (HM) is a nanomolar antagonist of FimH, a virulence factor of E. coli. Herein we report on the construction of multivalent HM-based glycopolymers as potent antiadhesives of type 1 piliated E. coli. We investigate glycopolymer/FimH and glycopolymer/bacteria interactions and show that HM-based glycopolymers efficiently inhibit bacterial adhesion and disrupt established cell-bacteria interactions in vitro at very low concentration (0.1 μM on a mannose unit basis). On a valency-corrected basis, HM-based glycopolymers are, respectively, 10(2) and 10(6) times more potent than HM and d-mannose for their capacity to disrupt the binding of adherent-invasive E. coli to T84 intestinal epithelial cells. Finally, we demonstrate that the antiadhesive capacities of HM-based glycopolymers are preserved ex vivo in the colonic loop of a transgenic mouse model of Crohn's disease. All together, these results underline the promising scope of HM-based macromolecular ligands for the antiadhesive treatment of E. coli induced inflammatory bowel diseases.

Solvent selection causes remarkable shifts of the "Ouzo region" for poly(lactide-co-glycolide) nanoparticles prepared by nanoprecipitation

Polymer nanoparticles (NPs) offer versatile novel biological features of interest for drug delivery applications. "Ouzo diagrams" allowed for a systematic manufacture of specified colloidal formulations by the widely used nanoprecipitation process. Surprisingly, despite the well-documented relevance of the applied organic solvent for nanoprecipitation, its effect on the actual status of the "Ouzo region" was so far not studied. Herein, investigations were undertaken to account for the potential impact of the solvent type on the "Ouzo diagrams" for poly(lactide-co-glycolide) (PLGA) and tetrahydrofuran (THF), 1,4-dioxane, acetone and dimethyl sulfoxide (DMSO). The "Ouzo region" shifted considerably to higher polymer fractions upon solvent change (rank order: THF < 1,4-dioxane < acetone < DMSO). Assuming a one-to-one transformation of detached PLGA-bearing solvent droplets (droplet diameter for THF: ∼800 nm, 1,4-dioxane: ∼700 nm, acetone: ∼500 nm and DMSO: ∼300 nm) into non-divisible polymer aggregates upon solvent displacement, facilitated to predict the size of NPs found within the "Ouzo region" (size range: 40-200 nm). In conclusion, application of "Ouzo diagrams" is a valuable tool for drug delivery research and will most-likely replace the "trial-and-error"-approach to identify the operating window for the production of stable colloidal formulations by the nanoprecipitation technique.

Influence of additives on the structure of surfactant-free microemulsions

In surfactant-free microemulsions, the combination ethanol/antagonistic salt behaves like a surfactant.

Brilliant glyconanocapsules for trapping of bacteria

n-Heptyl α-d-mannose-functionalized nanocapsules are prepared by the Shift'N'Go process and post-modified to ensure aggregation and efficient removal of bacteria.

From nanodroplets by the ouzo effect to interfacial nanolenses

Polymerizing nanodroplets at solid-liquid interfaces is a facile solution-based approach to the functionalization of large surface areas with polymeric lens-shaped nanostructures. In this work, we have applied a one-pot approach to obtain polymeric nanolenses with controlled sizes and densities. We take advantage of the formation mechanism by the direct adsorption of nanodroplets from a surfactant-free microemulsion onto an immersed hydrophobic substrate. The interfacial nanodroplets were photopolymerized to produce polymeric nanolenses on the substrate surface. The surfactant-free microemulsion of the monomer nanodroplets was obtained through the spontaneous emulsification (i.e., ouzo effect) in the tertiary system of ethanol, water, and precusor monomer. The size of nanolenses on the surface was adjusted by the nanodroplet size, following a linear relationship with the ratio of the components in the microemulsion. This simple approach is applicable to produce nanolenses over the entire surface area or on any specific area at will by depositing a drop of the microemulsion. Possessing high optical transparency, the resulting substrates may have potential application as functional biomedical supporting materials or effective light-harvesting coatings.