Supported lipid bilayers with encapsulated quantum dots (QDs) via liposome fusion: effect of QD size on bilayer formation and structure

Luminescence of carbon quantum dots and their application in biochemistry

Similar to fullerenes, carbon nanotubes and graphene, carbon dots (CDs) are causing a lot of research work in their own right. CDs are a type of surface-passivated quantum dot that contain carbon atoms. Their distinctive characteristics, such as luminescent emission that varies with size and wavelength, resistance to photobleaching, easy biological binding, lack of toxicity, and economical production without the need for intricate synthetic processes, have led to a noteworthy surge in attention within the research community. Different techniques can be utilized to create these CDs, spanning from basic candle burning to laser ablation. This review article delves into the principles of fluorescence technology, providing insights into how different synthesis methods of quantum dots impact their luminescent properties. Additionally, it highlights the latest applications of quantum dots in catalysis and biomedical fields, with special emphasis on the current status of luminescent properties in biology and chemistry. Towards the end, the article discusses the limitations of quantum dots in current practical applications, pointing out that CDs hold promising potential for future applications.

Ligustrazine as an Extract from Medicinal and Edible Plant Chuanxiong Encapsulated in Liposome–Hydrogel Exerting Antioxidant Effect on Preventing Skin Photoaging

Long-term sunlight exposure will cause the accumulation of free radicals in the skin and lead to oxidative damage and aging, antioxidant drugs have gradually become the focus of research, but there is little research on antioxidant drugs for percutaneous treatment. The purpose of this study was to prepare ligustrazine hydrochloride (TMPZ)-loaded liposome–hydrogel (TMPZ-LG), evaluate its antioxidant properties, and apply it on the skin of mice to observe whether it had preventive and therapeutic effect on the irradiation under the ultraviolet rays, in an attempt to make it into a new kind of delivery through the skin. TMPZ-LG was prepared by the combination of film dispersion and sodium carboxymethylcellulose (2%, CMC-Na) natural swelling method. The release rates in vitro permeation across the dialysis membrane and ex vivo transdermal had both reached 40%; the scavenging effect of TMPZ-LG on 1,1-diphenyl-2-picrylhydrazyl (DPPH) and H₂O₂ were 65.57 ± 4.13% and 73.06 ± 5.65%; the inhibition rate of TMPZ-LG on malondialdehyde (MDA) production in liver homogenate and anti-low density lipoprotein (LDL) oxidation experiments ex vivo were 15.03 ± 0.9% and 21.57 ± 1.2%. Compared with untreated mice, the skin pathological symptoms of mice coated with TMPZ-LG were significantly reduced after ultraviolet irradiation, and there was statistical significance. The results showed TMPZ-LG could exert good antioxidant activity in vitro and ex vivo; therefore, it is feasible to prevent and treat skin oxidation.

Design and Application of Near-Infrared Nanomaterial-Liposome Hybrid Nanocarriers for Cancer Photothermal Therapy

Liposomes are attractive carriers for targeted and controlled drug delivery receiving increasing attention in cancer photothermal therapy. However, the field of creating near-infrared nanomaterial-liposome hybrid nanocarriers (NIRN-Lips) is relatively little understood. The hybrid nanocarriers combine the dual superiority of nanomaterials and liposomes, with more stable particles, enhanced photoluminescence, higher tumor permeability, better tumor-targeted drug delivery, stimulus-responsive drug release, and thus exhibiting better anti-tumor efficacy. Herein, this review covers the liposomes supported various types of near-infrared nanomaterials, including gold-based nanomaterials, carbon-based nanomaterials, and semiconductor quantum dots. Specifically, the NIRN-Lips are described in terms of their feature, synthesis, and drug-release mechanism. The design considerations of NIRN-Lips are highlighted. Further, we briefly introduced the photothermal conversion mechanism of NIRNs and the cell death mechanism induced by photothermal therapy. Subsequently, we provided a brief conclusion of NIRNs-Lips applied in cancer photothermal therapy. Finally, we discussed a synopsis of associated challenges and future perspectives for the applications of NIRN-Lips in cancer photothermal therapy.

Multimodal polymer encapsulated CdSe/Fe3O4 nanoplatform with improved biocompatibility for two-photon and temperature stimulated bioapplications

Multimodal polymer encapsulated CdSe/Fe₃O₄ nanoplatforms with dual optical and magnetic properties have been fabricated. We demonstrate that CdSe/Fe₃O₄ nanocapsules (NCs) upon excitation with UV radiation or NIR fs-laser excitation exhibit intense one- or two-photon emission at 535 nm, whereas the combination of an alternating magnetic field and 808 nm IR laser excitation results in heat generation. Since anticancer therapies require relatively high doses of Fe₃O₄ nanoparticles (NPs) to induce biologically relevant temperature jumps, the therapeutic effects of 0.1 and 1 mg/mL Fe₃O₄ NCs and CdSe/Fe₃O₄ NCs were investigated using breast cancer cell lines, ER-positive MCF-7, and triple-negative MDA-MB-231 cells. Improved biocompatibility of CdSe/Fe₃O₄ NCs compared to Fe₃O₄ NCs was revealed at higher NCs concentration suggesting safe potential medical applications of CdSe/Fe₃O₄ NCs. In contrast, 1 mg/mL Fe₃O₄ NCs were found to be more cytotoxic to MDA-MB-231 than MCF-7 cells through iron-induced oxidative stress, lipid peroxidation, and concomitant ferroptotic cell death. We believe that Fe₃O₄ NCs-mediated cellular response may be heterogeneous that reflects, at least in part, cancer cell genotype, molecular phenotype, and pathological classification.

Reviewing nanoplastic toxicology: It's an interface problem

Multiple international agencies have recently raised environmental and health concerns regarding plastics in nanoforms (nanoplastics), but there is insufficient knowledge of their properties to allow for an accurate risk assessment to be conducted and any risks managed. For this reason, research into the toxicity of nanoplastics has focused strongly on documenting their impacts on biological organisms. One scope of this review is to summarise the recent findings on the adverse effects on biological organisms and strategies which can be adopted to advance our understanding of nanoplastic properties and their toxicity. Specifically, a mechanistic approach has already been employed in nanotoxicology, which focuses on the cause-and-effect relationships to establish a tool that predicts the biological impacts based on nanoparticle characteristics. Identifying the chemical and biological bases behind the observed biological effects (such as in vitro cellular response) is a major challenge, due to the intricate nature of nanoparticle-biological molecule complexes and an unawareness of their interaction with other biological targets, particularly at interfacial level. An exemplary case includes protein corona formation and ecological molecule corona (eco-corona) for nanoplastics. Therefore, the second scope of this review is to discuss recent findings and importance of (for both non-plastic and plastic nanoparticles) coronae formation and structure. Finally, we discuss the opportunities provided by model system approaches (model protein corona and lipid bilayer) to deepen the understanding of the above-mentioned perspectives, and corroborate the findings from in vitro experiments.

Controlling the Kinetics of an Enzymatic Reaction through Enzyme or Substrate Confinement into Lipid Mesophases with Tunable Structural Parameters

Lipid liquid crystalline mesophases, resulting from the self-assembly of polymorphic lipids in water, have been widely explored as biocompatible drug delivery systems. In this respect, non-lamellar structures are particularly attractive: they are characterized by complex 3D architectures, with the coexistence of hydrophobic and hydrophilic regions that can conveniently host drugs of different polarities. The fine tunability of the structural parameters is nontrivial, but of paramount relevance, in order to control the diffusive properties of encapsulated active principles and, ultimately, their pharmacokinetics and release. In this work, we investigate the reaction kinetics of p-nitrophenyl phosphate conversion into p-nitrophenol, catalysed by the enzyme Alkaline Phosphatase, upon alternative confinement of the substrate and of the enzyme into liquid crystalline mesophases of phytantriol/H₂O containing variable amounts of an additive, sucrose stearate, able to swell the mesophase. A structural investigation through Small-Angle X-ray Scattering, revealed the possibility to finely control the structure/size of the mesophases with the amount of the included additive. A UV-vis spectroscopy study highlighted that the enzymatic reaction kinetics could be controlled by tuning the structural parameters of the mesophase, opening new perspectives for the exploitation of non-lamellar mesophases for confinement and controlled release of therapeutics.

Structural evolution of supported lipid bilayers intercalated with quantum dots

HYPOTHESIS

Supported lipid bilayers (SLBs) embedded with hydrophobic quantum dots (QDs) undergo temporal structural rearrangement.

EXPERIMENTS

Synchrotron X-ray reflectivity (XRR) was applied to monitor the temporal structural changes over a period of 24 h of mixed SLBs of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) / 1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-ethanolamine (POPE) intercalated with 4.9 nm hydrophobic cadmium sulphide quantum dots (CdS QDs). The QD-embedded SLBs (QD-SLBs) were formed via rupture of the mixed liposomes on a positively charged polyethylene imine (PEI) monolayer. Atomic force microscopy (AFM) imaging provided complementary characterization of the bilayer morphology.

FINDINGS

Our results show time-dependent perturbations in the SLB structure due to the interaction upon QD incorporation. Compared to the SLB without QDs, at 3 h incubation time, there was a measurable decrease in the bilayer thickness and a concurrent increase in the scattering length density (SLD) of the QD-SLB. The QD-SLB then became progressively thicker with increasing incubation time, which - along with the fitted SLD profile - was attributed to the structural rearrangement due to the QDs being expelled from the inner leaflet to the outer leaflet of the bilayer. Our results give unprecedented mechanistic insights into the structural evolution of QD-SLBs on a polymer cushion, important to their potential biomedical and biosensing applications.

Interactions between PAMAM dendrimers and DOPC lipid multilayers: Membrane thinning and structural disorder

BACKGROUND

Understanding the structure of hybrid nanoparticle-lipid multilayers is of fundamental importance to their bioanalytical applications and nanotoxicity, where nanoparticle-membrane interactions play an important role. Poly(amidoamine) (PAMAM) dendrimers are branched polymeric nanoparticles with potential biomedical applications due to precise tunability of their physicochemical properties. Here, the effect of PAMAM dendrimers (2.9-4.5 nm) with either a hydrophilic amine (NH₂) or a hydrophobic C₁₂ chain surface termination on the 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) multilayers has been studied for the first time.

METHODS

DOPC multilayers were created by the liposome-rupture method via drop-casting dendrimer-liposome dispersions with the dendrimers added at different concentrations and at three different stages. The multilayer structure was evaluated via the analysis of the synchrotron X-ray reflectivity (XRR) curves, obtaining the bilayer d-spacing, the coherence length from the Scherrer (L_s) analysis of the Bragg peaks, and the paracrystalline disorder parameter (g).

RESULTS

Dendrimer addition led to lipid bilayer thinning and more disordered multilayer structures. Larger hydrophobic dendrimers caused greater structural disruption to the multilayers compared to the smaller dendrimers. The smallest, positively charged dendrimers at their highest concentration caused the most pronounced bilayer thinning. The dendrimer-liposome mixing method also affected the multilayer structure due to different dendrimer aggregation involved.

CONCLUSIONS

These results show the complexity of the effect of dendrimer physicochemical properties and the addition method of dendrimers on the structure of mixed dendrimer-DOPC multilayers.

GENERAL SIGNIFICANCE

These insights are useful for fundamental understanding of nanotoxicity and future biomedical application of nanocomposite multilayer materials in which nanoparticles are added for enhanced properties and functionality.

Translocation of a hydroxyl functionalized carbon dot across a lipid bilayer: an all-atom molecular dynamics simulation study

Passive permeation of CD across lipid bilayer is almost impossible. Forced permeation results membrane rupture.

Interactions between Mutant Bacterial Lipopolysaccharide (LPS-Ra) Surface Layers: Surface Vesicles, Membrane Fusion, and Effect of Ca2+and Temperature

Lipopolysaccharides (LPS) are a major component of the protective outer membrane of Gram-negative bacteria. Understanding how the solution conditions may affect LPS-containing membranes is important to optimizing the design of antibacterial agents (ABAs) which exploit electrostatic and hydrophobic interactions to disrupt the bacteria membrane. Here, interactions between surface layers of LPS (Ra mutants) in aqueous media have been studied using a surface force apparatus (SFA), exploring the effects of temperature and divalent Ca²⁺ cations. Complementary dynamic light scattering (DLS) characterization suggests that vesicle-like aggregates of diameter ∼28-80 nm are formed by LPS-Ra in aqueous media. SFA results show that LPS-Ra vesicles adsorb weakly onto mica in pure water at room temperature (RT) and the surface layers are readily squeezed out as the two surfaces approach each other. However, upon addition of calcium (Ca²⁺) cations at near physiological concentration (2.5 mM) at RT, LPS multilayers or deformed LPS liposomes on mica are observed, presumably due to bridging between LPS phosphate groups and between LPS phosphates and negatively charged mica mediated by Ca²⁺, with a hard wall repulsion at surface separation D₀ ∼ 30-40 nm. At 40 °C, which is above the LPS-Ra β-α acyl chain melting temperature (T_m = 36 °C), fusion events between the surface layers under compression could be observed, evident from δD ∼ 8-10 nm steps in the force-distance profiles attributed to LPS-bilayers being squeezed out due to enhanced fluidity of the LPS acyl-chain, with a final hard wall surface separation D₀ ∼ 8-10 nm corresponding to the thickness of a single bilayer confined between the surfaces. These unprecedented SFA results reveal intricate structural responses of LPS surface layers to temperature and Ca²⁺, with implications to our fundamental understanding of the structures and interactions of bacterial membranes.

Nanoparticles and organized lipid assemblies: from interaction to design of hybrid soft devices

This contribution reviews the state of art on hybrid soft matter assemblies composed of inorganic nanoparticles (NP) and lamellar or non-lamellar lipid bilayers. After a short outline of the relevant energetic contributions, we address the interaction of NPs with synthetic lamellar bilayers, meant as cell membrane mimics. We then review the design of hybrid nanostructured materials composed of lipid bilayers and some classes of inorganic NPs, with particular emphasis on the effects on the amphiphilic phase diagram and on the additional properties contributed by the NPs. Then, we present the latest developments on the use of lipid bilayers as coating agents for inorganic NPs. Finally, we remark on the main achievements of the last years and our vision for the development of the field.