Polystyrene microplastics enhance the microcystin-LR-induced gonadal damage and reproductive endocrine disruption in zebrafish.

The coexistence of eutrophication and plastic pollution in the aquatic environment is becoming a realistic water pollution problem worldwide. To investigate the microcystin-LR (MC-LR) bioavailability and the underlying reproductive interferences in the presence of polystyrene microplastic (PSMPs), zebrafish (Danio rerio) were exposed to individual MC-LR (0, 1, 5, and 25 µg/L) and combined MC-LR + PSMPs (100 µg/L) for 60 d. Our results showed that the existence of PSMPs increased the accumulation of MC-LR in zebrafish gonads compared to the MC-LR-only group. In the MC-LR-only exposure group, seminiferous epithelium deterioration and widened intercellular spaces were observed in the testis, and basal membrane disintegration and zona pellucida invagination were noticed in the ovary. Moreover, the existence of PSMPs exacerbated these injuries. The results of sex hormone levels showed that PSMPs enhanced MC-LR-induced reproductive toxicity, which is tightly related to the abnormal increase of 17ß-estradiol (E2) and testosterone (T) levels. The changes of gnrh2, gnrh3, cyp19a1b, cyp11a, and lhr mRNA levels in the HPG axis further proved that MC-LR combined with PSMPs aggravated reproductive dysfunction. Our results revealed that PSMPs could increase the MC-LR bioaccumulation by serving as a carrier and exaggerate the MC-LR-induced gonadal damage and reproductive endocrine disruption in zebrafish.

Antimicrobial peptide-modified liposomes for bacteria targeted delivery of temoporfin in photodynamic antimicrobial chemotherapy.

Photodynamic antimicrobial chemotherapy (PACT) and antimicrobial peptides (AMPs) are two promising strategies to combat the increasing prevalence of antibiotic-resistant bacteria. To take advantage of these two strategies, we integrated a novel antimicrobial peptide (WLBU2) and a potent generation II photosensitizer (temoporfin) into liposomes by preparing WLBU2-modified liposomes, aiming at bacteria targeted delivery of temoporfin for PACT. WLBU2 was successfully coupled to temoporfin-loaded liposomes using a functional phospholipid. The delivery of temoporfin to bacteria was confirmed by fluorescence microscopy and flow cytometry, thus demonstrating that more temoporfin was delivered to bacteria by WLBU2-modified liposomes than by unmodified liposomes. Consequently, the WLBU2-modified liposomes eradicated all methicillin-resistant Staphylococcus aureus (MRSA) and induced a 3.3 log(10) reduction of Pseudomonas aeruginosa in the in vitro photodynamic inactivation test. These findings demonstrate that the use of AMP-modified liposomes is promising for bacteria-targeted delivery of photosensitizers and for improving the PACT efficiency against both gram-positive and gram-negative bacteria in the local infections.

Layer-by-layer pH-sensitive nanoparticles for drug delivery and controlled release with improved therapeutic efficacy in vivo.

In this work, a pH-sensitive liposome-polymer nanoparticle (NP) composed of lipid, hyaluronic acid (HA) and poly(ß-amino ester) (PBAE) was prepared using layer-by-layer (LbL) method for doxorubicin (DOX) targeted delivery and controlled release to enhance the cancer treatment efficacy. The NP with pH-sensitivity and targeting effect was successfully prepared by validation of charge reversal and increase of hydrodynamic diameter after each deposition of functional layer. We further showed the DOX-loaded NP had higher drug loading capacity, suitable particle size, spherical morphology, good uniformity, and high serum stability for drug delivery. We confirmed that the drug release profile was triggered by low pH with sustained release manner in vitro. Confocal microscopy research demonstrated that the NP was able to effectively target and deliver DOX into human non-small cell lung carcinoma (A549) cells in comparison to free DOX. Moreover, the blank NP showed negligible cytotoxicity, and the DOX-loaded NP could efficiently induce the apoptosis of A549 cells as well as free DOX. Notably, in vivo experiment results showed that the DOX-loaded NPs effectively inhibited the growth of tumor, enhanced the survival of tumor-bearing mice and improved the therapeutic efficacy with reduced side-effect comparing with free drug. Therefore, the NP could be a potential intelligent anticancer drug delivery carrier for cancer chemotherapy, and the LbL method might be a useful strategy to prepare multi-functional platform for drug delivery.

Fabrication Of Dual pH/redox-Responsive Lipid-Polymer Hybrid Nanoparticles For Anticancer Drug Delivery And Controlled Release.

BACKGROUND: The development of biocompatible nanocarriers that can efficiently encapsulate and deliver anticancer drug to the tumor site and provide controlled release of cargos in response to the specific cues for cancer therapy is of great significance. METHODS: In this work, dual pH/redox-responsive fabrication of hybrid lipid-polymer nanoparticles (LPNPs) self-assembled from amphiphilic polymer poly(ethylene glycol) methyl ether-grafted disulfide-poly(ß-amino esters) (PBAE-ss-mPEG) and PEGylated lipid were prepared and used as drug delivery carriers. The optimization of PEGylated lipid modification was confirmed by analysis of particle size, polydispersity index (PDI), cellular uptake, serum stability, and drug loading capacity. The pK b value of LPNPs was determined as 6.55, indicating the pH-sensitivity. The critical micelle concentration (CMC) values and zeta-potential of LPNPs at different pH values were investigated to confirm its pH-sensitivity. The morphology of LPNPs before and after incubation with reducing agent was imaged to study the redox-responsibility. RESULTS: The in vitro results showed that the drug had controlled release from LPNPs triggered by low pH and high concentration of reducing agent. Furthermore, the cytotoxicity of LPNPs was very low, and the doxorubicin (DOX)-loaded LPNPs could efficiently induce the death of tumor cells in comparison to free DOX. CONCLUSION: All results demonstrated that the fabricated LPNPs could be potential anticancer drug delivery carriers with a pH/redox-triggered drug release profile, and PEGylated lipid modification might be a useful method to fabricate the drug delivery platform.

Linear free energy relationship analysis of permeability across polydimethylsiloxane (PDMS) membranes and comparison with human skin permeation in vitro.

The aim of the present work is to evaluate the similarity between PDMS membranes and human skin in vitro in permeation study by linear free energy relationship (LFER) analyses. The values of the permeability coefficient log Kp (cm/s) under reliable experimental conditions were collected from the literature for a set of 94 compounds including both neutral and ionic species, which cover a broad range of structural diversity. The values of log Kp (cm/s) have been correlated with Abraham descriptors to yield an equation with R2 = 0.952 and SD = 0.38 log units. The established LFER model for log Kp (cm/s) across PDMS membranes showed no close analogy with that through human skin in vitro. A further critical analysis of the coefficients of the LFER models confirmed that the PDMS permeation system is a very poor model for human skin permeation.

Drug delivery strategies for poorly water-soluble drugs.

The drug candidates coming from combinatorial chemistry research and/or the drugs selected from biologically based high-throughput screening are quite often very lipophilic, as these drug candidates exert their pharmacological action at or in biological membranes or membrane-associated proteins. This challenges drug delivery institutions in industry or academia to develop carrier systems for the optimal oral and parenteral administration of these drugs. To mention only a few of the challenges for this class of drugs: their oral bioavailability is poor and highly variable, and carrier development for parenteral administration is faced with problems, including the massive use of surface-active excipients for solubilisation. Formulation specialists are confronted with an even higher level of difficulties when these drugs have to be delivered site specifically. This article addresses the emerging formulation designs for delivering of poorly water-soluble drugs.

Synthesis of chlorambucil-tempol adduct and its delivery using fluoroalkyl double-ended poly (ethylene glycol) micelles.

In our pursuit to find potent anticancer drugs, we have covalently bonded free radical tempol to chlorambucil giving a chlorambucil-tempol (CT) adduct in which both of the anticancer active sites in tempol and chlorambucil were left intact. Analysis using NMR, Maldi-TOF, and EPR verified the designed chemical structure. Because the CT adduct is more hydrophobic than chlorambucil, its delivery also was investigated using fluoroalkyl double-ended poly (ethylene glycol) (Rf-PEG) micelles. Results from EPR spectra and(19) F and(1) H NMR spin lattice relaxation times show that the Rf-PEG micelles are able to encapsulate CT into the Rf cores of the micelles.

Comparison of lipid membrane-water partitioning with various organic solvent-water partitions of neutral species and ionic species: Uniqueness of cerasome as a model for the stratum corneum in partition processes.

Lipid membrane-water partitions (e.g., immobilized artificial membrane systems where the lipid membrane is a neutral phospholipid monolayer bound to gel beads) were compared to various organic solvent-water partitions using linear free energy relationships. To this end, we also measured the retention factors of 36 compounds (including neutral and ionic species) from water to liposomes made up of 3-sn-phosphatidylcholine and 3-sn-phosphatidyl-l-serine (80:20, mol/mol), employing liposome electrokinetic chromatography in this work. The results show that lipid membranes exhibit a considerably different chemical environment from those of organic solvents. For both neutral species and ionic species, partitions into the more polar hydroxylic solvents are chemically closer to partition into the lipid membrane as compared to partitions into the less polar hydroxylic solvents and into aprotic solvents. This means that solutes partition into the polar parts of lipid membranes, regardless of whether they are charged or not. In addition, cerasome (i.e., liposome composed mainly of stratum corneum lipids) was compared with regular phospholipid liposomes as a possible model for human stratum corneum in partitions. It was found that the cerasome-water partition exhibits a better chemical similarity to skin permeation. This is probably due to the unique structures of ceramides that occur in cerasome and in the stratum corneum lipid domain. We further show that membranes in membrane-water partitions exhibit very different properties.

Analysis of immobilized artificial membrane retention factors for both neutral and ionic species.

Retention data on an immobilised artificial membrane have been taken from the work of Li et al. and from Liu et al., and have been correlated with a set of descriptors that includes descriptors for ionized species, that is anions from deprotonated acids and cations from protonated bases. Log k(IAM) values can be predicted for acids or bases that are partially ionized at the experimental pH and log k(IAM) values for acids and bases can be predicted as a function of the fraction present as the ionized species, equivalent to prediction as a function of pH. It is shown that anions reduce the value of log k(IAM) by about 1.1 log units but that cations have almost no effect by comparison to the neutral species. By comparison to non-polar solvents, carboxylate anions and protonated base cations are considerably stabilized by both water and the IAM phase to about 6-8 log units and so the rather small influence of anions (-1.1 log unit) and cations (-0.1 log unit) on log k(IAM) is due to substantial cancellation of these stabilization effects. Indeed, the effect of change of phase from water to IAM on the neutral species is at least as large as the effect of change of phase on the ionic species.

Skin penetration and deposition of carboxyfluorescein and temoporfin from different lipid vesicular systems: In vitro study with finite and infinite dosage application.

The aim of the present research is to evaluate the influence of different lipid vesicular systems as well as the effect of application mode on skin penetration and deposition behaviors of carboxyfluorescein (hydrophilic model drug) and temoporfin (lipophilic model drug). All of the lipid vesicular systems, including conventional liposomes, invasomes and ethosomes, were prepared by film hydration method and characterized for particle size distribution, ζ-potential, vesicular shape and surface morphology, in vitro human skin penetration and skin deposition. Dynamic light scattering (DLS) and transmission electron microscopy (TEM) defined that all of lipid vesicles had almost spherical structures with low polydispersity (PDI < 0.2) and nanometric size range (z-average no more than 150 nm). In addition, all lipid vesicular systems exhibited a negative zeta potential. In vitro skin penetration and deposition experiments demonstrated that, in the case of CF with finite dose application (10 µl/cm²) and infinite dose application (160 µl/cm²), lipid vesicular systems, especially ethosomes and invasomes, compared with non-vesicular systems, can significantly improve the delivery of hydrophilic drug such as carboxyfluorescein into skin deep layers or across the skin. While in the case of mTHPC with finite and infinite dose application, most of drug accumulation was observed in the skin superficial layer for both lipid vesicular systems and non-vesicular systems. The results also revealed that the factors influencing the drug skin distribution concern the physicochemical characteristics of the drug, the choice of the vehicle formulation and the application mode applied.

Drug delivery strategies for poorly water-soluble drugs: the industrial perspective.

INTRODUCTION: For poorly soluble compounds, a good bioavailability is typically needed to assess the therapeutic index and the suitability of the compound for technical development. In industry, the selection of the delivery technology is not only driven by technical targets, but also by constraints, such as production costs, time required for development and the intellectual property situation. AREAS COVERED: This review covers current developments in parenteral and oral delivery technologies and products for poorly water-soluble compounds, such as nano-suspensions, solid dispersions and liposomes. In addition, the use of biorelevant dissolution media to assess dissolution and solubility properties is described. Suggestions are also included to systematically address development hurdles typical of poorly water-soluble compounds intended for parenteral or oral administration. EXPERT OPINION: A holistic assessment is recommended to select the appropriate delivery technology by taking into account technical as well as intellectual property considerations. Therefore, first and foremost, a comprehensive physico-chemical characterization of poorly water-soluble compounds can provide the key for a successful selection and development outcome. In this context, the identified physical form of the compound in the formulation is used as a guide for a risk-benefit assessment of the selected oral delivery technology. The potential of nano-suspensions for intravenous administration is unclear. In the case of oral administration, nano-suspensions are mainly used to improve the oral absorption characteristics of micronized formulations. The development of an in situ instantaneous solubilization method, based on stable, standardized liposomes with low toxicity, opens new avenues to solubilize poorly water-soluble compounds.

Transfer mechanism of temoporfin between liposomal membranes.

The transfer kinetics of temoporfin, a classic photosensitizer, was analyzed by investigating the influence of total lipid content, temperature, as well as charge, acyl chain length, and saturation of the lipids in donor vesicles using a mini ion exchange column technique. The obtained results are consistent with an apparent first order kinetics in which the transfer proceeds through both liposome collisions and through the aqueous phase. We present a corresponding theoretical model that accounts for the detailed distribution of drug molecules in donor and acceptor liposomes and predicts the transfer rates as a function of drug concentration and number of donor and acceptor liposomes. The experimentally observed transfer rates depended strongly on the temperature and comply with the Arrhenius equation. Thermodynamic calculations indicate the transfer process to be entropically controlled. In terms of the charge of donor liposomes, positively charged liposomes showed transfer rates faster than negatively charged liposomes whereas the maximum amount transferred was almost the same. A more rigid structure of the donor liposomes increases the transfer rate of temoporfin, which is caused by expelling the drug from the membrane interior, as proposed in former work. In summary, our combined theoretical/experimental approach offers a systematic way to study the mechanism of drug release from liposome-based delivery systems.

Linear free energy relationship analysis of retention factors in cerasome electrokinetic chromatography intended for predicting drug skin permeation.

The retention factors of neutral, positively charged, and negatively charged solutes were determined in a liposome electrokinetic chromatography (EKC) system, where cerasome was used as the investigated liposome. The Abraham linear free energy relationship (LFER) for neutral and ionized solutes gave a good account of the retention factors (N = 71, R(2) = 0.814, and SD = 0.29 log units). It was shown that the calculated retention factors for 16 neutral acids were about four times higher than those of the corresponding anions, whereas the calculated retention factors for neutral bases were less than those for the corresponding cations by a factor of 0.36. The LFER equation for neutral species, anions, and cations was compared with those for partition from water into a number of solvents and for n-octanol-water distribution coefficients. It was shown that the cerasome EKC system is substantially different to the other systems and consequently it could be a very useful additional model system, possibly for predicting skin permeation. It was further shown that there are considerable advantages in the use of Abraham LFERs that can encompass not only neutral molecules but also ionic species.

Utilization of liposomes for studying drug transfer and uptake.

On entry into the body of the patient, drugs have to overcome many barriers in order to reach the target. The knowledge of the ability of drugs to cross these barriers, which mostly consist of lipid membranes, is of utmost interest in pharmacy.High values of lipophilicity of a drug might be a good pre-requisite for crossing these barriers. It also led liposomologists to think that highly lipophilic drugs may "stick" in the lipophilic interior of liposomal phospholipid membranes and therefore these liposomes may act as a retard formulation of the lipophilic drug.The presented method here estimates the transfer time of lipophilic drugs between liposomal lipid bilayers. This may help to judge the presumed retardation function of a specific liposomal delivery system for a chosen lipophilic drug.

Skin delivery of ferulic acid from different vesicular systems.

The aim of the present research is to evaluate the skin delivery capabilities of different vesicular systems, including conventional liposomes (CL), Tween 80-based deformable liposomes (DL), invasomes (INS) and ethosomes bearing ferulic acid (FA) being an antioxidant exhibiting a wide range of therapeutic effects against various diseases. All of the test formulations were characterized for particle size distribution, zeta-potential, vesicular shape and surface morphology, in vitro human skin permeation and skin deposition. Dynamic Light Scattering (DLS) and Transmission Electron Microscopy (TEM) defined that all of liposomal vesicles were almost spherical, displaying unilamellar structures with low polydispersity (PDI < 0.2) and nanometric size range (z-average no more than 150 nm). In addition, all the vesicular systems except conventional liposomes were negatively charged to a certain extent. In vitro skin permeation and skin deposition experiments demonstrated that the permeation profile of ferulic acid through human stratum corneum epidermis membrane (SCE) and the drug deposition in skin were both improved significantly using these vesicular liposomal systems. Permeation and skin deposition enhancing effect was highlighted by the ethosomal system containing 18.0 mg/ml of ferulic acid with an significantly (P < 0.01) enhanced skin flux (267.8 +/- 16.77 microg/cm2/h) and skin drug deposition (51.67 +/- 1.94 microg/cm2), which was 75 times and 7.3 times higher than those of ferulic acid from saturated PBS (pH 7.4) solution, respectively. This study demonstrated that ethosomes are promising vesicular carriers for delivering ferulic acid into or across the skin.

Micro-structured smart hydrogels with enhanced protein loading and release efficiency.

A series of temperature-responsive poly(N-isopropylacrylamide) (PNIPAAm) hydrogels with highly porous microstructures were successfully prepared by using hydrophobic polydimethylsiloxane (PDMS) and sodium dodecyl sulfate as liquid template and stabilizer, respectively. These newly prepared hydrogels possess highly porous structures. In contrast to the conventional PNIPAAm hydrogel, the swelling ratios of the porous gels at room temperature were higher, and their response rates were significantly faster as the temperature was raised above the lower critical solution temperature. For example, the novel hydrogel prepared with 40% PDMS template lost over 95% water within 5 min, while the conventional PNIPAAm gel only lost approximately 14% water in the same time. The improved properties are achieved due to the presence of liquid PDMS templates in the reaction solutions, which lead to the formation of porous structures during the polymerization/crosslinking. Lysozyme and bovine serum albumin (BSA) as protein models were for the first time loaded into these micro-structured smart hydrogels through a physical absorption method. The experimental results show that the loading efficiency of BSA with a higher molecular weight is lower than that of lysozyme due to the size exclusion effect, and the loading efficiencies of both proteins in the porous hydrogel are much higher than those in the conventional PNIPAAm hydrogel. For example, the loading efficiency of BSA in porous hydrogel is 0.114, approximately 200% higher than that in conventional hydrogel (0.035). Both lysozyme and BSA were completely released from the porous hydrogel at 22 degrees C. Furthermore, the release kinetics of the proteins from the porous hydrogel could be modulated by tuning the environmental temperature. These newly prepared porous materials provide an avenue to increase the loading efficiency and to control the release patterns of macromolecular drugs from hydrogels, and show great promise for application in protein or gene delivery.

Model of drug-loaded fluorocarbon-based micelles studied by electron-spin induced (19)f relaxation NMR and molecular dynamics simulation.

Rf-IPDU-PEGs belong to a class of fluoroalkyl-ended poly(ethylene glycol) polymers (Rf-PEGs), where the IPDU (isophorone diurethane) functions as a linker to connect each end of the PEG chain to a fluoroalkyl group. The Rf-IPDU-PEGs form hydrogels in water with favorable sol-gel coexistence properties. Thus, they are promising for use as drug delivery agents. In this study, we introduce an electron-spin induced 19F relaxation NMR technique to probe the location and drug-loading capacity for an electron-spin labeled hydrophobic drug, CT (chlorambucil-tempol adduct), enclosed in the Rf-IPDU-PEG micelle. With the assistance of molecular dynamics simulations, a clear idea regarding the structures of the Rf-IPDU-PEG micelle and its CT-loaded micelle was revealed. The significance of this research lies in the finding that the hydrophobic drug molecules were loaded within the intermediate IPDU shells of the Rf-IPDU-PEG micelles. The molecular structures of IPDU and that of CT are favorably comparable. Consequently, it appears that this study opens a window to modify the linker between the Rf group and the PEG chain for achieving customized structure-based drug-loading capabilities for these hydrogels, while the advantage of the strong affinity among the Rf groups to hold individual micelles together and to interconnect the micellar network is still retained in hopes of maintaining the sol-gel coexistence of the Rf-PEGs.