Lipid nanoparticle delivery limits antisense oligonucleotide activity and cellular distribution in the brain after intracerebroventricular injection.

Antisense oligonucleotide (ASO) therapeutics are being investigated for a broad range of neurological diseases. While ASOs have been effective in the clinic, improving productive ASO internalization into target cells remains a key area of focus in the field. Here, we investigated how the delivery of ASO-loaded lipid nanoparticles (LNPs) affects ASO activity, subcellular trafficking, and distribution in the brain. We show that ASO-LNPs increase ASO activity up to 100-fold in cultured primary brain cells as compared to non-encapsulated ASO. However, in contrast to the widespread ASO uptake and activity observed following free ASO delivery in vivo, LNP-delivered ASOs did not downregulate mRNA levels throughout the brain after intracerebroventricular injection. This lack of activity was likely due to ASO accumulation in cells lining the ventricles and blood vessels. Furthermore, we reveal a formulation-dependent activation of the immune system post dosing, suggesting that LNP encapsulation cannot mask cellular ASO backbone-mediated toxicities. Together, these data provide insights into how LNP encapsulation affects ASO distribution as well as activity in the brain, and a foundation that enables future optimization of brain-targeting ASO-LNPs.

The Power of Field-Flow Fractionation in Characterization of Nanoparticles in Drug Delivery.

Asymmetric-flow field-flow fractionation (AF4) is a gentle, flexible, and powerful separation technique that is widely utilized for fractionating nanometer-sized analytes, which extend to many emerging nanocarriers for drug delivery, including lipid-, virus-, and polymer-based nanoparticles. To ascertain quality attributes and suitability of these nanostructures as drug delivery systems, including particle size distributions, shape, morphology, composition, and stability, it is imperative that comprehensive analytical tools be used to characterize the native properties of these nanoparticles. The capacity for AF4 to be readily coupled to multiple online detectors (MD-AF4) or non-destructively fractionated and analyzed offline make this technique broadly compatible with a multitude of characterization strategies, which can provide insight on size, mass, shape, dispersity, and many other critical quality attributes. This review will critically investigate MD-AF4 reports for characterizing nanoparticles in drug delivery, especially those reported in the last 10-15 years that characterize multiple attributes simultaneously downstream from fractionation.

Fast and versatile analysis of liposome encapsulation efficiency by nanoParticle exclusion chromatography.

Liposomes are an attractive drug delivery platform for a wide variety of pharmaceutical molecules. Encapsulation efficiency, which refers to the amount of drug contained inside liposomes compared with the total amount of drug, is a critical quality attribute of liposome products, as the free drug in a liposomal formulation may cause toxicity or undesired biodistribution. The determination of encapsulation efficiency requires the measurement of at least two of the three drug populations: total drug, encapsulated drug and free drug. However, direct measurement of the encapsulated drug and free drug remains a challenging analytical task. Nanoparticle exclusion chromatography (nPEC), an emerging high-performance liquid chromatography (HPLC) technique, has shown great potential in separating and quantifying the free drug in liposomal formulations. In this study, nPEC was systematically evaluated for two representative liposomal formulations containing either hydrophilic or hydrophobic small molecule drugs. It is reported for the first time that the insoluble free drug suspended in the aqueous formulation can be directly measured by nPEC. This free drug in the suspension sample was quantified with excellent accuracy and precision. On the other hand, the total drug measurement from dissociated liposomes was confirmed by the benchmark methodology of reversed phase liquid chromatography (RPLC). The facile quantitation of free and total drug in the liposome formulation enables the fast and accurate determination of the encapsulation efficiency, which can be used to guide the formulation development and characterize the product quality.

Automated high-throughput preparation and characterization of oligonucleotide-loaded lipid nanoparticles.

Lipid nanoparticles (LNPs) are increasingly employed to improve delivery efficiency and therapeutic efficacy of nucleic acids. Various formulation parameters can affect the quality attributes of these nanoparticle formulations, but currently there is a lack of systemic screening approaches to address this challenge. Here, we developed an automated high-throughput screening (HTS) workflow for streamline preparation and analytical characterization of LNPs loaded with antisense oligonucleotides (ASOs) in a full 96-well plate within 3 hrs. ASO-loaded LNPs were formulated by an automated solvent-injection method using a robotic liquid handler, and assessed for particle size distribution, encapsulation efficiency, and stability with different formulation compositions and ASO loadings. Results indicated that the PEGylated lipid content significantly affected the particle size distribution, while the ionizable lipid / ASO charge ratio impacted the encapsulation efficiency of ASOs. Furthermore, results from our HTS approach correlated with those from the state-of-the-art scale-up method using a microfluidic formulator, therefore opening up a new avenue for robust formulation development and design of experiment methods, while reducing material usage by 10 folds, improving analytical outputs and accumulation of information by 100 folds.

Ion desorption efficiency and internal energy transfer in polymeric electrospun nanofiber-based surface-assisted laser desorption/ionization mass spectrometry.

The understanding of the desorption mechanism in surface-assisted laser desorption/ionization (SALDI) remains incomplete because there are numerous types of SALDI materials with a broad range of physical and chemical properties, many of which impact the ultimate analytical performance in terms of signal generation. In this study, the chemical thermometer molecule, benzylpyridinium chloride, is applied to investigate the desorption process of SALDI using electrospun nanofibrous polymer and polymer composite substrates. The ion desorption efficiency was inversely related to the ion internal energy, which could not be fully explained by a thermal desorption mechanism. A competing non-thermal desorption (i.e., phase transition/explosion) was proposed to be involved in this SALDI process. The influence of the orientation and dimension of the nanofiber structure revealed that a cross-linked nanofiber network with a small diameter favored the nanofiber-assisted LDI to provide efficient ion desorption. Graphical abstract.

Separation and characterization of KRas proteins and tryptic peptides using enhanced-fluidity liquid chromatography tandem mass spectrometry.

Enhanced-fluidity, reversed-phase liquid chromatography was developed using custom instrumentation for separation and characterization of intact KRas proteins and tryptic peptides. The KRas, HRas and NRas function as GDP-GTP regulated binary switches in many signalling pathways, and mutations in Ras proteins are frequently found in human cancers and represent poor prognosis markers for patients. Mutations of the KRas isoform constitute some of the most common aberrations among all human cancers and intensive drug discovery efforts have been directed toward targeting the KRas protein. Separation and characterization of the KRas protein and tryptic peptides are helpful for exploring targeting, which has not been fully investigated using liquid chromatography-tandem mass spectrometry. EFLC-MS provided improved chromatographic performance compared to traditional HPLC-MS in terms of shorter analysis time, increased ion intensity and a shift to higher charge states for intact KRas proteins.

Facile morphology-controlled synthesis of nickel-coated graphite core-shell particles for excellent conducting performance of polymer-matrix composites and enhanced catalytic reduction of 4-nitrophenol.

We have developed a novel seed-mediated growth method to fabricate nickel-coated graphite composite particles (GP@Ni-CPs) with controllable shell morphology by simply adjusting the concentration of sodium hydroxide ([NaOH]). The fabrication of two kinds of typical GP@Ni-CPs includes adsorption of Ni2+ via electrostatic attraction, sufficient heterogeneous nucleation of Ni atoms by an in situ reduction, and shell-controlled growth by regulating the kinetics of electroless Ni plating in turn. High [NaOH] results in fast kinetics of electroless plating, which causes heterogeneous nuclei to grow isotropically. After fast and uniform growth of Ni nuclei, GP@Ni-CPs with dense shells can be achieved. The first typical GP@Ni-CPs exhibit denser shells, smaller diameters and higher conductivities than the available commercial ones, indicating their important applications in the conducting of polymer-matrix composites. On the other hand, low [NaOH] favors slow kinetics. Thus, the reduction rate of Ni2+ slows down to a relatively low level so that electroless plating is dominated thermodynamically instead of kinetically, leading to an anisotropic crystalline growth of nuclei and finally to the formation of GP@Ni-CPs with nanoneedle-like shells. The second typical samples can effectively catalyze the reduction of p-nitrophenol into p-aminophenol with NaBH4 in comparison with commercial GP@Ni-CPs and RANEY® Ni, owing to the strong charge accumulation effect of needle-like Ni shells. This work proposes a model system for fundamental investigations and has important applications in the fields of electronic interconnection and catalysis.

Surface-assisted laser desorption/ionization time-of-flight mass spectrometry of small drug molecules and high molecular weight synthetic/biological polymers using electrospun composite nanofibers.

Polyacrylonitrile/Nafion®/carbon nanotube (PAN/Nafion®/CNT) composite nanofibers were prepared using electrospinning. These electrospun nanofibers were studied as possible substrates for surface-assisted laser desorption/ionization (SALDI) and matrix-enhanced surface-assisted laser desorption/ionization time-of-flight mass spectrometry (ME-SALDI/TOF-MS) for the first time in this paper. Electrospinning provides this novel substrate with a uniform morphology and a narrow size distribution, where CNTs were evenly and firmly immobilized on polymeric nanofibers. The results show that PAN/Nafion®/CNT nanofibrous mats are good substrates for the analysis of both small drug molecules and high molecular weight polymers with high sensitivity. Markedly improved reproducibility was observed relative to MALDI. Due to the composite formation between the polymers and the CNTs, no contamination of the carbon nanotubes to the mass spectrometer was observed. Furthermore, electrospun nanofibers used as SALDI substrates greatly extended the duration of ion signals of target analytes compared to the MALDI matrix. The proposed SALDI approach was successfully used to quantify small drug molecules with no interference in the low mass range. The results show that verapamil could be detected with a surface concentration of 220 femtomoles, indicating the high detection sensitivity of this method. Analysis of peptides and proteins with the electrospun composite substrate using matrix assisted-SALDI was improved and a low limit of detection of approximately 6 femtomoles was obtained for IgG. Both SALDI and ME-SALDI analyses displayed high reproducibility with %RSD ≤ 9% for small drug molecules and %RSD ≤ 14% for synthetic polymers and proteins.

Solid-phase extraction approach for phospholipids profiling by titania-coated silica microspheres prior to reversed-phase liquid chromatography-evaporative light scattering detection and tandem mass spectrometry analysis.

A novel strategy for selectively adsorbing phospholipids (PLs) on titania-coated silica core-shell microspheres (TiO2/SiO2) was developed. The TiO2/SiO2 microspheres were prepared through water-vapor-induced internal hydrolysis and then characterized by SEM, UV-vis spectroscopy, X-ray diffraction, and measurements of Brunauer-Emmett-Teller surface area. Analyses showed that the titania layer was uniformly distributed onto the surface of silica particles. The TiO2/SiO2 microspheres were employed as sorbent in solid-phase extraction (SPE), and their absorptive ability was investigated by reversed-phase liquid chromatography-evaporative light scattering detection (RPLC-ELSD). Important factors that affect the extraction, such as loading buffer, eluting buffer, and elution volume, were investigated in detail and optimized by using standard samples. Results reveal that the developed SPE approach had higher recoveries for PLs than that based on pure TiO2 particles. The proposed SPE method was used for extraction of PLs from serum and showed great potential for identifying more kinds of endogenous PL metabolites by ultra performance liquid chromatography with quadrupole time-of-flight mass spectrometry (UPLC-QTOF MS). The proposed SPE method with the composite sorbent was used to screen PLs from a biological matrix with high selectivity and efficiency. This approach is a promising method for selective extraction of PLs in lipidomics or phospholipidomics.

Rapid determination of protein binding constant by a pressure-mediated affinity capillary electrophoresis method.

A new pressure-mediated affinity capillary electrophoresis method for the rapid and accurate determination of drug-protein binding constants is described. A special combination of pressure and electrophoresis is used to shorten the electrophoresis and the overall analysis time to only a few minutes. At the same time, the suitability of this method is checked against a traditional fluorescence spectroscopy method. The binding constants of bovine serum albumin and a total of eight drugs with different pK(a) have been evaluated and compared with those determined by the fluorescence spectroscopy method and other methods in literature. The results indicate that the P-ACE method is well suited for the determination of binding constants with weak interaction (K(b) <10(5) M(-1)).

14-3-3 proteins interact with the beta-thymosin repeat protein Csp24.

Conditioned stimulus pathway protein 24 (Csp24) is a beta-thymosin-like protein that is homologous to other members of the family of beta-thymosin repeat proteins that contain multiple actin binding domains. Actin co-precipitates with Csp24 and co-localizes with it in the cytosol of type-B photoreceptor cell bodies. Several signal transduction pathways have been shown to regulate the phosphorylation of Csp24 and contribute to cellular plasticity. Here, we report the identification of the adapter protein 14-3-3 in lysates of the Hermissenda circumesophageal nervous system and its interaction with Csp24. Immunoprecipitation experiments using an antibody that is broadly reactive with several isoforms of the 14-3-3 family of proteins showed that Csp24 co-precipitates with 14-3-3 protein, and nervous systems stimulated with 5-HT exhibited a significant increase in co-precipitated Csp24 probed with a phosphospecific antibody as compared with controls. These results indicate that post-translational modifications of Csp24 regulate its interaction with 14-3-3 protein, and suggest that this mechanism may contribute to the control of intrinsic enhanced excitability.

One-trial in vitro conditioning of hermissenda regulates phosphorylation of ser-122 of csp24.

The regulation of the intrinsic excitability of a neuron is an important aspect of cellular and synaptic plasticity underlying learning and memory. Various voltage-dependent K(+) channels have been shown to be critical for the modification of membrane excitability. Components of the cytoskeleton have been proposed to contribute to the location, distribution, and function of diverse K(+) channels. However, the mechanisms underlying the regulation of the cytoskeleton by signaling pathways and the role of the cytoskeleton in the induction of intrinsic excitability is not understood. Hermissenda Csp24 is a beta-thymosin-like protein containing multiple actin-binding domains that contributes to intrinsic enhanced excitability produced by Pavlovian conditioning. One-trial in vitro conditioning produces a significant reduction in the A-type transient K(+) current (I(A)) and a depolarized shift in the steady-state activation curve of I(A). Intermediate and long-term enhanced excitability produced by one-trial conditioning is also dependent on the expression and phosphorylation of Csp24. Blocking the expression of Csp24 with an antisense oligonucleotide inhibits the development of intermediate-term enhanced excitability and the concomitant reduction in I(A) normally produced by one-trial in vitro conditioning. In this report using two-dimensional gel PAGE and electrospray mass spectrometry, we have identified two phosphorylation sites on Csp24. Using phospho-specific antibodies with Western blot analysis and immunoprecipitation procedures we show that one-trial in vitro conditioning results in an increase in the phosphorylation of Ser-122, but not Ser-49 of Csp24.

Rho/ROCK and Cdk5 effects on phosphorylation of a beta-thymosin repeat protein in Hermissenda.

Rho GTPases acting through effector proteins regulate actin dynamics and cytoskeletal structure. In Hermissenda Csp24 is a cytoskeletal-related protein that contributes to the development of intermediate-term memory, and is homologous to other beta-thymosin-like repeat proteins containing multiple actin-binding domains. We have examined the role of Rho GTPase activity and its downstream target ROCK, and cyclin-dependent kinase 5 (Cdk5) on the phosphorylation of Csp24 using 32PO4 labeling of proteins separated with 2-D PAGE. The ROCK inhibitor Y-27632 significantly increased Csp24 phosphorylation, and the Rho activator lysophosphatidic acid (LPA) or the Cdk5 inhibitor butyrolactone significantly decreased Csp24 phosphorylation. Pretreatment with Y-27632 before LPA application significantly reduced the decreased phosphorylation of Csp24 normally detected in nervous systems exposed to LPA. Using a pull-down assay we found that LPA treatments activated Rho and exposure to 5-HT decreased Rho activity. Our results indicate that the Rho/ROCK and Cdk5 signaling pathways contribute to the regulation of Csp24 phosphorylation.

Inhibition of conditioned stimulus pathway phosphoprotein 24 expression blocks the development of intermediate-term memory in Hermissenda.

Studies of memory consolidation have identified multiple phases or stages in the formation of memories. The multiple components of memory can be broadly divided into the three phases; short-term, intermediate-term, and long-term. Although molecular changes underlying short- and long-term memory have been examined extensively, the molecular mechanisms supporting the formation of intermediate-term memory are poorly understood. In several examples of cellular and synaptic plasticity, intermediate memory depends on translation but not transcription. One-trial conditioning in Hermissenda results in the development of intermediate memory that is associated with enhanced cellular excitability and the phosphorylation of a 24 kDa protein referred to as conditioned stimulus pathway phosphoprotein (Csp24). Using amino acid sequences derived from Csp24 peptide fragments, a full-length cDNA was cloned and shown to contain multiple beta-thymosin-like domains. The expression of Csp24 and the development of enhanced excitability, a characteristic of intermediate memory, were blocked by antisense oligonucleotide-mediated downregulation of Csp24 without affecting the induction of immediate enhanced excitability, a characteristic of short-term memory. These results demonstrate that the synthesis of Csp24 is required for the development and maintenance of intermediate memory.