Novel approaches for drug delivery systems in nanomedicine: effects of particle design and shape

Engineered shapes using electrohydrodynamic atomization for an improved drug delivery

The shapes of micro- and nano-products have profound influences on their functional performances, which has not received sufficient attention during the past several decades. Electrohydrodynamic atomization (EHDA) techniques, mainly include electrospinning and electrospraying, are facile in manipulate their products' shapes. In this review, the shapes generated using EHDA for modifying drug release profiles are reviewed. These shapes include linear nanofibers, round micro-/nano-particles, and beads-on-a-string hybrids. They can be further divided into different kinds of sub-shapes, and can be explored for providing the desired pulsatile release, sustained release, biphasic release, delayed release, and pH-sensitive release. Additionally, the shapes resulted from the organizations of electrospun nanofibers are discussed for drug delivery, and the shapes and inner structures can be considered together for developing novel drug delivery systems. In future, the shapes and the related shape-performance relationships at nanoscale, besides the size, inner structure and the related structure-performance relationships, would further play their important roles in promoting the further developments of drug delivery field. This article is categorized under: Therapeutic Approaches and Drug Discovery > Emerging Technologies.

Aspherical, Nano-Structured Drug Delivery System with Tunable Release and Clearance for Pulmonary Applications

Addressing the challenge of efficient drug delivery to the lungs, a nano-structured, microparticulate carrier system with defined and customizable dimensions has been developed. Utilizing a template-assisted approach and capillary forces, particles were rapidly loaded and stabilized. The system employs a biocompatible alginate gel as a stabilizing matrix, facilitating the breakdown of the carrier in body fluids with the subsequent release of its nano-load, while also mitigating long-term accumulation in the lung. Different gel strengths and stabilizing steps were applied, allowing us to tune the release kinetics, as evaluated by a quantitative method based on a flow-imaging system. The micro-cylinders demonstrated superior aerodynamic properties in Next Generation Impactor (NGI) experiments, such as a smaller median aerodynamic diameter (MMAD), while yielding a higher fine particle fraction (FPF) than spherical particles similar in critical dimensions. They exhibited negligible toxicity to a differentiated macrophage cell line (dTHP-1) for up to 24 h of incubation. The kinetics of the cellular uptake by dTHP-1 cells was assessed via fluorescence microscopy, revealing an uptake-rate dependence on the aspect ratio (AR = l/d); cylinders with high AR were phagocytosed more slowly than shorter rods and comparable spherical particles. This indicates that this novel drug delivery system can modulate macrophage uptake and clearance by adjusting its geometric parameters while maintaining optimal aerodynamic properties and featuring a biodegradable stabilizing matrix.

Cyclodextrin-Calcium Carbonate Micro- to Nano-Particles: Targeting Vaterite Form and Hydrophobic Drug Loading/Release

Tailor-made and designed micro- and nanocarriers can bring significant benefits over their traditional macroscopic counterparts in drug delivery applications. For the successful loading and subsequent release of bioactive compounds, carriers should present a high loading capacity, trigger release mechanisms, biodegradability and biocompatibility. Hydrophobic drug molecules can accumulate in fat tissues, resulting in drawbacks for the patient's recovery. To address these issues, we propose to combine the advantageous features of both host molecules (cyclodextrin) and calcium carbonate (CaCO₃) particles in order to load hydrophobic chemicals. Herein, hybrid cyclodextrin-CaCO₃ micro- to nano-particles have been fabricated by combining Na₂CO₃ solution and CaCl₂ solution in the presence of an additive, namely poly (vinylsulfonic acid) (PVSA) or glycerol (gly). By investigating experimental parameters and keeping the Na₂CO₃ and CaCl₂ concentrations constant (0.33 M), we have evidenced that the PVSA or gly concentration and mixing time have a direct impact on the final cyclodextrine-CaCO₃ particle size. Indeed, by increasing the concentration of PVSA (5 mM to 30 mM) or gly (0.7 mM to 4 mM) or the reaction time (from 10 min to 4 h), particles with a size of 200 nm could be reached. Interestingly, the vaterite or calcite form could also be selected, according to the experimental conditions. We hypothesised that the incorporation of PVSA or gly into the precipitation reaction might reduce the nucleation rate by sequestering Ca²⁺. The obtained particles have been found to keep their crystal structure and surface charge after storage in aqueous media for at least 6 months. In the context of improving the therapeutic benefit of hydrophobic drugs, the developed particles were used to load the hydrophobic drug tocopherol acetate. The resulting particles are biocompatible and highly stable in a physiological environment (pH 7.4, 0.15 M NaCl). A selective release of the cargo is observed in acidic media (pH lower than 5).

Active Targeting Significantly Outperforms Nanoparticle Size in Facilitating Tumor-Specific Uptake in Orthotopic Pancreatic Cancer

Nanoparticles are widely studied as theranostic vehicles for cancer; however, clinical translation has been limited due to poor tumor specificity. Features that maximize tumor uptake remain controversial, particularly when using clinically relevant models. We report a systematic study that assesses two major features for the impact on tumor specificity, i.e., active vs passive targeting and nanoparticle size, to evaluate relative influences in vivo. Active targeting via the V7 peptide is superior to passive targeting for uptake by pancreatic tumors, irrespective of nanoparticle size, observed through in vivo imaging. Size has a secondary effect on uptake for actively targeted nanoparticles in which 26 nm nanoparticles outperform larger 45 and 73 nm nanoparticles. Nanoparticle size had no significant effect on uptake for passively targeted nanoparticles. Results highlight the superiority of active targeting over nanoparticle size for tumor uptake. These findings suggest a framework for optimizing similar nonaggregate nanoparticles for theranostic treatment of recalcitrant cancers.

siRNA delivery to macrophages using aspherical, nanostructured microparticles as delivery system for pulmonary administration

The delivery of oligonucleotides such as siRNA to the lung is a major challenge, as this group of drugs has difficulties to overcome biological barriers due to its polyanionic character and the associated hydrophilic properties, resulting in inefficient delivery. Especially in diseases such as asthma, chronic obstructive pulmonary disease and cystic fibrosis, where increased proinflammation is present, a targeted RNA therapy is desirable due to the high potency of these oligonucleotides. To address these problems and to ensure efficient uptake of siRNA in macrophages, a microparticulate, cylindrical delivery system was developed. In the first step, this particle system was tested for its aerodynamic characteristics to evaluate the aerodynamic properties to optimize lung deposition. The mass median aerodynamic diameter of 2.52 ± 0.23 µm, indicates that the desired target should be reached. The inhibition of TNF-α release, as one of the main mediators of proinflammatory reactions, was investigated. We could show that our carrier system can be loaded with siRNA against TNF-α. Gel electrophoreses allowed to demonstrate that the load can be incorporated and released without being degraded. The delivery system was found to transport a mass fraction of 0.371% [%w/w] as determined by inductively coupled plasma mass spectroscopy. When investigating the release kinetics, the results showed that several days are necessary to release a major amount of the siRNA indicating a sustained release. The cylindrical microparticles with an aspect ratio of 3.3 (ratio of length divided by width) were then tested in vitro successfully reducing TNF-α release from human macrophages significantly by more than 30%. The developed formulation presents a possible oligonucleotide delivery system allowing due to its internal structure to load and protect siRNA.

Nanotechnology for the Treatment of Spinal Cord Injury

Spinal cord injury (SCI) affects the central nervous system (CNS) and there is currently no treatment with the potential for rehabilitation. Although several clinical treatments have been developed, they are still at an early stage and have not shown success in repairing the broken fiber, which prevents cellular regeneration and integral restoration of motor and sensory functions. Considering the importance of nanotechnology and tissue engineering for neural tissue injuries, this review focuses on the latest advances in nanotechnology for SCI treatment and tissue repair. The PubMed database was used for the bibliographic survey. Initial research using the following keywords "tissue engineering and spinal cord injury" revealed 970 articles published in the last 10 years. The articles were further analyzed, excluding those not related to SCI or with results that did not pertain to the field of interest, including the reviews. It was observed that a total of 811 original articles used the quoted keywords. When the word "treatment" was added, 662 articles were found and among them, 529 were original ones. Finally, when the keywords "Nanotechnology and spinal cord injury" were used, 102 articles were found, 65 being original articles. A search concerning the biomaterials used for SCI found 700 articles with 589 original articles. A total of 107 articles were included in the discussion of this review and some are used for the theoretical framework. Recent progress in nanotechnology and tissue engineering has shown promise for repairing CNS damage. A variety of in vivo animal testing for SCI has been used with or without cells and some of these in vivo studies have shown successful results. However, there is no translation to humans using nanotechnology for SCI treatment, although there is one ongoing trial that employs a tissue engineering approach, among other technologies. The first human surgical scaffold implantation will elucidate the possibility of this use for further clinical trials. This review concludes that even though tissue engineering and nanotechnology are being investigated as a possibility for SCI treatment, tests with humans are still in the theoretical stage. Impact statement Thousands of people are affected by spinal cord injury (SCI) per year in the world. This type of lesion is one of the most severe conditions that can affect humans and usually causes permanent loss of strength, sensitivity, and motor function below the injury site. This article reviews studies on the PubMed database, assessing the publications on SCI in the study field of tissue engineering, focusing on the use of nanotechnology for the treatment of SCI. The review makes an evaluation of the biomaterials used for the treatment of this condition and the techniques applied for the production of nanostructured biomaterials.

Cellular fate of deformable needle-shaped PLGA-PEG fibers

Deformability of micro/nanometer sized particles plays an important role in particle-cell interactions and thus becomes a key parameter in carrier design in biomedicine application such as drug delivery and vaccinology. Yet the influence of material's deformability on the cellular fate of the particles as well as physiology response of live cells are to be understood. Here we show the cellular fate of needle shaped (high aspect ratio ~25) PLGA-PEG copolymer fibers depending on their deformability. We found that all the fibers entered murine macrophage cells (RAW 264.7) via phagocytosis. While the fibers of high apparent Young's modulus (average value = 872 kPa) maintained their original shape upon phagocytosis, their counterparts of low apparent Young's modulus (average value = 56 kPa) curled in cells. The observed deformation of fibers of low apparent Young's modulus in cells coincided with abnormal intracellular actin translocation and absence of lysosome/phagosome fusion in macrophages, suggesting the important role of material mechanical properties and mechano-related cellular pathway in affecting cell physiology. STATEMENT OF SIGNIFICANCE: Particles are increasingly important in the field of biomedicine, especially when they are serving as drug carriers. Physical cues, such as mechanical properties, were shown to provide insight into their stability and influence on physiology inside the cell. In the current study, we managed to fabricate 5 types of needle shaped PLGA-PEG fibers with controlled Young's modulus. We found that hard fibers maintained their original shape upon phagocytosis, while soft fibers were curled by actin compressive force inside the cell, causing abnormal actin translocation and impediment of lysosome/phagosome fusion, suggesting the important role of material mechanical properties and mechano-related cellular pathway in affecting cell physiology.

Influence of N-acylhomoserine lactonase silver nanoparticles on the quorum sensing system of Helicobacter pylori: A potential strategy to combat biofilm formation

The treatment of Helicobacter pylori usually fails due to their ability to form biofilms and resistance to antibiotics. This might potentially lead to gastric carcinoma and mucosa-associated lymphoid tissue lymphoma. In the present study, we elucidate the potential role of N-acylhomoserine lactonase stabilized silver nanoparticles (AiiA-AgNPs) in treating biofilms produced by H. pylori. AiiA-AgNPs inhibited quorum sensing (QS) by degradation of QS molecules, thereby reducing biofilm formation, urease production, and altering cell surface hydrophobicity of H. pylori. AiiA-AgNPs showed no cytotoxic effects on RAW 264.7 macrophages at the effective concentration (1-5 µM) of antibiofilm activity. In addition, AiiA-AgNP in high concentration (80-100 µM) exhibited cytotoxicity against HCT-15 carcinoma cells, depicting its therapeutic role in treating cancer.

Effect of physical stimuli on hair follicle deposition of clobetasol-loaded Lipid Nanocarriers

Clobetasol propionate (CLO) is a potent glucocorticoid used to treat inflammation-based skin, scalp, and hair disorders. In such conditions, hair follicles (HF) are not only the target site but can also act as drug reservoirs when certain formulations are topically applied. Recently, we have demonstrated nanostructured lipid carriers (NLC) containing CLO presenting epidermal-targeting potential. Here, the focus was evaluating the HF uptake provided by such nanoparticles in comparison to a commercial cream and investigating the influence of different physical stimuli [i.e., infrared (IR) irradiation (with and without metallic nanoparticles-MNP), ultrasound (US) (with and without vibration) and mechanical massage] on their follicular targeting potential. Nanosystems presented sizes around 180 nm (PdI < 0.2) and negative zeta potential. The formulation did not alter skin water loss measurements and was stable for at least 30 days at 5 °C. Nanoparticles released the drug in a sustained fashion for more than 3 days and increased passively about 40 times CLO follicular uptake compared to the commercial cream. Confocal images confirmed the enhanced follicular delivery. On the one hand, NLC application followed by IR for heat generation showed no benefit in terms of HF targeting even at higher temperatures generated by metallic nanoparticle heating. On the other hand, upon US treatment, CLO retention was significantly increased in deeper skin layers. The addition of mechanical vibration to the US treatment led to higher follicular accumulation compared to passive exposure to NLC without stimuli. However, from all evaluated stimuli, manual massage presented the highest follicular targeting potential, driving more than double the amount of CLO into the HF than NLC passive application. In conclusion, NLC showed great potential for delivering CLO to HF, and a simple massage was capable of doubling follicular retention.

PEGylated mucus-penetrating nanocrystals for lung delivery of a new FtsZ inhibitor against Burkholderia cenocepacia infection

C109 is a potent but poorly soluble FtsZ inhibitor displaying promising activity against Burkholderia cenocepacia, a high-risk pathogen for cystic fibrosis (CF) sufferers. To harness C109 for inhalation, we developed nanocrystal-embedded dry powders for inhalation suspension consisting in C109 nanocrystals stabilized with D-α-tocopheryl polyethylene glycol 1000 succinate (TPGS) embedded in hydroxypropyl-β-cyclodextrin (CD). The powders could be safely re-dispersed in water for in vitro aerosolization. Owing to the presence of a PEG shell, the rod shape and the peculiar aspect ratio, C109 nanocrystals were able to diffuse through artificial CF mucus. The promising technological features were completed by encouraging in vitro/in vivo effects. The formulations displayed no toxicity towards human bronchial epithelial cells and were active against planktonic and sessile B. cenocepacia strains. The efficacy of C109 nanosuspensions in combination with piperacillin was confirmed in a Galleria mellonella infection model, strengthening their potential for combined therapy of B. cenocepacia lung infections.

From stars to stripes: RNA-directed shaping of plant viral protein templates-structural synthetic virology for smart biohybrid nanostructures

The self-assembly of viral building blocks bears exciting prospects for fabricating new types of bionanoparticles with multivalent protein shells. These enable a spatially controlled immobilization of functionalities at highest surface densities-an increasing demand worldwide for applications from vaccination to tissue engineering, biocatalysis, and sensing. Certain plant viruses hold particular promise because they are sustainably available, biodegradable, nonpathogenic for mammals, and amenable to in vitro self-organization of virus-like particles. This offers great opportunities for their redesign into novel "green" carrier systems by spatial and structural synthetic biology approaches, as worked out here for the robust nanotubular tobacco mosaic virus (TMV) as prime example. Natural TMV of 300 x 18 nm is built from more than 2,100 identical coat proteins (CPs) helically arranged around a 6,395 nucleotides ssRNA. In vitro, TMV-like particles (TLPs) may self-assemble also from modified CPs and RNAs if the latter contain an Origin of Assembly structure, which initiates a bidirectional encapsidation. By way of tailored RNA, the process can be reprogrammed to yield uncommon shapes such as branched nanoobjects. The nonsymmetric mechanism also proceeds on 3'-terminally immobilized RNA and can integrate distinct CP types in blends or serially. Other emerging plant virus-deduced systems include the usually isometric cowpea chlorotic mottle virus (CCMV) with further strikingly altered structures up to "cherrybombs" with protruding nucleic acids. Cartoon strips and pictorial descriptions of major RNA-based strategies induct the reader into a rare field of nanoconstruction that can give rise to utile soft-matter architectures for complex tasks. This article is categorized under: Biology-Inspired Nanomaterials > Protein and Virus-Based Structures Nanotechnology Approaches to Biology > Nanoscale Systems in Biology Biology-Inspired Nanomaterials > Nucleic Acid-Based Structures.

Preparation and characterization of nano amitriptyline hydrochloride particles by spray freeze drying

Aim: To investigate the enhancement of bioavailability by the usage of drug nanoparticles for increasing the efficacy of antidepressant therapeutic value. Materials & methods: Nano-amitriptyline HCI (AMT·HCl) particles were successfully prepared via a simple spray freeze drying (SFD) method. Results: The as-prepared nanoparticles are amorphous instead of crystalline. The mean size of AMT·HCl nanoparticles is 90 nm. In in vitro evaluation, AMT·HCl nanoparticles have greatly improved the dissolution compared with pure bulk materials, which have potential for enhancing human bioavailability and diminishing toxic effect. A nanoparticle formation mechanism was also proposed. Conclusion: These findings promote the development of antidepressant therapeutic evaluation based on the usage of AMT·HCl nanoparticles by SFD method and indicate that SFD is an alternative for a range of nanoparticle preparation in industrial pharmacy.

Absorption, distribution, metabolism and excretion of the biomaterials used in Nanocarrier drug delivery systems

Nanocarriers (NCs) are a type of drug delivery system commonly used to regulate the pharmacokinetic and pharmacodynamic properties of drugs. Although a wide variety of NCs has been developed, relatively few have been registered for clinical trials and even fewer are clinically approved. Overt or potential toxicity, indistinct mechanisms of drug release and unsatisfactory pharmacokinetic behavior all contribute to their high failure rate during preclinical and clinical testing. These negative characteristics are not only due to the NCs themselves but also to the materials of the drug nanocarrier system (MDNS) that are released in vivo. In this article, we review the main analytical techniques used for bioassay of NCs and MDNS and their pharmacokinetics after administration by various routes. We anticipate our review will serve to improve the understanding of MDNS pharmacokinetics and facilitate the development of NC drug delivery systems.

Determination of the size distribution of non-spherical nanoparticles by electric birefringence-based methods

The in situ determination of the size distribution of dispersed non-spherical nanoparticles is an essential characterization tool for the investigation and use of colloidal suspensions. In this work, we test a size characterization method based on the measurement of the transient behaviour of the birefringence induced in the dispersions by pulsed electric fields. The specific shape of such relaxations depends on the distribution of the rotational diffusion coefficient of the suspended particles. We analyse the measured transient birefringence with three approaches: the stretched-exponential, Watson-Jennings, and multi-exponential methods. These are applied to six different types of rod-like and planar particles: PTFE rods, goethite needles, single- and double-walled carbon nanotubes, sodium montmorillonite particles and gibbsite platelets. The results are compared to electron microscopy and dynamic light scattering measurements. The methods here considered provide good or excellent results in all cases, proving that the analysis of the transient birefringence is a powerful tool to obtain complete size distributions of non-spherical particles in suspension.

Factors relating to the biodistribution & clearance of nanoparticles & their effects on in vivo application

Nanoparticles have promising biomedical applications for drug delivery, tumor imaging and tumor treatment. Pharmacokinetics are important for the in vivo application of nanoparticles. Biodistribution and clearance are largely defined as the key points of pharmacokinetics to maximize therapeutic efficacy and to minimize side effects. Different engineered nanoparticles have different biodistribution and clearance processes. The interactions of organs with nanoparticles, which are determined by the characteristics of the organs and the biochemical/physical properties of the nanoparticles, are a major factor influencing biodistribution and clearance. In this review, the clearance functions of organs and the properties related to pharmacokinetics, including nanoparticle size, shape, biodegradation and surface modifications are discussed.

Self-assembled filomicelles prepared from polylactide-poly(ethylene glycol) diblock copolymers for sustained delivery of cycloprotoberberine derivatives

Polylactide-poly(ethylene glycol) (PLA-PEG) block copolymers were synthesized by ring opening polymerization of l-lactide using a monomethoxy PEG (mPEG) as macroinitiator and zinc lactate as catalyst. The resulting diblock copolymers were characterized by ¹H NMR and GPC. Polymeric micelles were prepared by self-assembly of copolymers in distilled water using co-solvent evaporation or membrane hydration methods. The resulting micelles are worm-like in shape as shown by TEM measurements. A hydrophobic anticancer drug, cycloprotoberberine derivative A35, was successfully loaded in PLA-PEG filomicelles with high encapsulation efficiency (above 88%). Berberine (BBR) was studied for comparison. In both methods, PLA-PEG filomicelles were prepared with a theoretical loading of 5%, 10% and 20%. Physical stability studies indicated that BBR/A35-loaded filomicelles were more stable when stored at 4 °C than at 25 °C. Compared with BBR-loaded filomicelles, A35-loaded filomicelles exhibited higher antitumor activity. Importantly, the in vitro cytotoxicity and stability of A35-loaded filomicelles evidenced the potential of drug-loaded filomicelles in the development of drug delivery systems.

Red blood cell-like particles with the ability to avoid lung and spleen accumulation for the treatment of liver fibrosis

Micro-sized drug-carrier particles accumulate mainly in the lungs and nano-sized particles tend to accumulate in the liver and spleen. Here, we show that micro-particles designed to mimic red blood cells (RBCs) can overcome these limitations. The RBC-MPs created in this study have a unique intra-particle elasticity distribution (IED), enabling them to bend around the central axis of the RBC-like dent, enabling them to pass through pores smaller than their diameter, mechanically behaving as authentic RBCs. In contrast, spherical MPs (SPH-MPs) and RBC-MPs hardened by incorporating a siloxane network (SiO₂-RBC-MPs), could not. In addition to the IED, we discovered that the deformability also depends on the shape and average particle elasticity. RBC-MPs did not accumulate in the lungs and the spleen, but were targeted specifically to the liver instead. In contrast, non-RBC-MPs such as SPH-MPs and SiO₂-RBC-MPs showed heavy accumulation in the lungs and/or spleen, and were dispersed non-specifically in various organs. Thus, controlling the shape and mechanical properties of RBC-MPs is important for achieving the desired biodistribution. When RBC-MPs were loaded with a (TGF)-β receptor inhibitor, RBC-MPs could treat liver fibrosis without pneumotoxicity.

Precision Epitaxy for Aqueous 1D and 2D Poly(ε-caprolactone) Assemblies

The fabrication of monodisperse nanostructures of highly controlled size and morphology with spatially distinct functional regions is a current area of high interest in materials science. Achieving this control directly in a biologically relevant solvent, without affecting cell viability, opens the door to a wide range of biomedical applications, yet this remains a significant challenge. Herein, we report the preparation of biocompatible and biodegradable poly(ε-caprolactone) 1D (cylindrical) and 2D (platelet) micelles in water and alcoholic solvents via crystallization-driven self-assembly. Using epitaxial growth in an alcoholic solvent, we show exquisite control over the dimensions and dispersity of these nanostructures, allowing access to uniform morphologies and predictable dimensions based on the unimer-to-seed ratio. Furthermore, for the first time, we report epitaxial growth in aqueous solvent, achieving precise control over 1D nanostructures in water, an essential feature for any relevant biological application. Exploiting this further, a strong, biocompatible and fluorescent hydrogel was obtained as a result of living epitaxial growth in aqueous solvent and cell culture medium. MC3T3 and A549 cells were successfully encapsulated, demonstrating high viability (>95% after 4 days) in these novel hydrogel materials.

Dynamic electrophoretic mobility and electric permittivity of concentrated suspensions of plate-like gibbsite particles

In this paper we present experimental results on the electrokinetic behavior of planar gibbsite particles in concentrated suspensions. The dc electrophoretic mobility measurements are in this case of little significance, as they are scarcely informative. In the present investigation, we show that the dielectric dispersion and dynamic electrophoresis can in contrast provide such information. The complicating factors are of course the non-spherical shape and the finite particle concentration, as no complete theory of these phenomena exists for such systems. We propose to use first of all a model of dynamic electrophoresis of spheroids in which the effect of volume fraction is considered by means of an approximate theory previously obtained for spheres, based on the evaluation of electrical and hydrodynamic interactions between particles. In addition, the role of volume fraction on the high frequency inertial relaxation is also ascertained and used to obtain a volume fraction-independent radius of the gibbsite spheroids. A similar approach is used for the evaluation of dielectric dispersion data. Both the dynamic mobility and dielectric constant dependencies on frequency were obtained for gibbsite suspensions of different volume fractions in 0.5mMKCl. The theoretical treatments elaborated were applied to these data, and a coherent picture of the geometrical and electrical characteristics of the particles was obtained.

Nanomaterial applications for neurological diseases and central nervous system injury

The effectiveness of noninvasive treatment for neurological disease is generally limited by the poor entry of therapeutic agents into the central nervous system (CNS). Most CNS drugs cannot permeate into the brain parenchyma because of the blood-brain barrier thus, overcoming this problem has become one of the most significant challenges in the development of neurological therapeutics. Nanotechnology has emerged as an innovative alternative for treating neurological diseases. In fact, rapid advances in nanotechnology have provided promising solutions to this challenge. This review highlights the applications of nanomaterials in the developing neurological field and discusses the evidence for their efficacies.

1D vs. 2D shape selectivity in the crystallization-driven self-assembly of polylactide block copolymers

2D materials such as graphene, LAPONITE® clays or molybdenum disulfide nanosheets are of extremely high interest to the materials community as a result of their high surface area and controllable surface properties. While several methods to access 2D inorganic materials are known, the investigation of 2D organic nanomaterials is less well developed on account of the lack of ready synthetic accessibility. Crystallization-driven self-assembly (CDSA) has become a powerful method to access a wide range of complex but precisely-defined nanostructures. The preparation of 2D structures, however, particularly those aimed towards biomedical applications, is limited, with few offering biocompatible and biodegradable characteristics as well as control over self-assembly in two dimensions. Herein, in contrast to conventional self-assembly rules, we show that the solubility of polylactide (PLLA)-based amphiphiles in alcohols results in unprecedented shape selectivity based on unimer solubility. We use log Poct analysis to drive solvent selection for the formation of large uniform 2D diamond-shaped platelets, up to several microns in size, using long, soluble coronal blocks. By contrast, less soluble PLLA-containing block copolymers yield cylindrical micelles and mixed morphologies. The methods developed in this work provide a simple and consistently reproducible protocol for the preparation of well-defined 2D organic nanomaterials, whose size and morphology are expected to facilitate potential applications in drug delivery, tissue engineering and in nanocomposites.

Design and Characterization of Metformin-Loaded Solid Lipid Nanoparticles for Colon Cancer

Colorectal cancer is a global concern, and its treatment is fraught with non-selective effects including adverse side effects requiring hospital visits and palliative care. A relatively safe drug formulated in a bioavailability enhancing and targeting delivery platform will be of significance. Metformin-loaded solid lipid nanoparticles (SLN) were designed, optimized, and characterized for particle size, zeta potential, drug entrapment, structure, crystallinity, thermal behavior, morphology, and drug release. Optimized SLN were 195.01 ± 6.03 nm in size, -17.08 ± 0.95 mV with regard to surface charge, fibrous in shape, largely amorphous, and release of metformin was controlled. The optimized size, charge, and shape suggest the solid lipid nanoparticles will migrate and accumulate in the colon tumor preventing its proliferation and subsequently leading to tumor shrinkage and cell death.

Influence of different stabilizers on the encapsulation of desmopressin acetate into PLGA nanoparticles

To address targeting and bioavailability issues of peptidic drugs like desmopressin, the encapsulation into nanoparticles (NP) has become standard in pharmaceutics. This study investigated the encapsulation of desmopressin into PLGA NP by the use of pharmaceutically common stabilizers as a precursor to future, optional targeting and bioavailability experiments. Polymer dry weights were measured by freeze drying and thermo gravimetric analysis (TGA). Particle sizes (ranging between 105 and 130nm, PDI<0.1) and zeta potentials (-35 to -45mV) were analyzed with Dynamic Light Scattering (DLS) and Laser-Doppler-Anemometry (LDA) respectively. Highest loading efficiencies, quantified by RP-HPLC, were achieved with Pluronic F-68 as stabilizer of the inner aqueous phase (1.16±0.07μg desmopressin/mg PLGA) and were significantly higher than coating approaches and approaches without stabilizer (0.74±0.01μg/mg). Optimized nanoformulations are thus in competition with the concentration of commercial non-nanoparticulate desmopressin products. Stability of desmopressin after the process was evaluated by HPLC peak purity analysis (diode array detector) and by mass spectrometry. Desmopressin was shown to remain intact during the whole process; however, despite these very good results the encapsulation efficiency turned out to be a bottle neck and makes the system a challenge for potential applications.

Design Advances in Particulate Systems for Biomedical Applications

The search for more efficient therapeutic strategies and diagnosis tools is a continuous challenge. Advances in understanding the biological mechanisms behind diseases and tissues regeneration have widened the field of applications of particulate systems. Particles are no more just protective systems for the encapsulated drugs, but they play an active role in the success of the therapy. Moreover, particles have been explored for innovative purposes as templates for cells growth and as diagnostic tools. Until few years ago the most relevant parameters in particles formulation were the chemistry and the size. Currently, it is known that other physical characteristics can remarkably affect the performance of particulate systems. Particles with non-conventional shapes exhibit advantages due to the increasing circulation time in blood stream, less clearance by the immune system and more efficient cell internalization and trafficking. Creation of compartments has been found useful to control drug release, to tune the transport of substances across biological barriers, to supply the target with more than one bioactive agent or even to act as theranostic systems. It is expected that such complex shaped and compartmentalized systems improve the therapeutic outcomes and also the patient's compliance, acting as advanced devices that serve for simultaneous diagnosis and treatment of the disease, combining agents of very different features, at the same time. In this review, we overview and analyse the most recent advances in particle shape and compartmentalization and applications of newly designed particulate systems in the biomedical field.

Size Dependent Cellular Uptake of Rod-like Bionanoparticles with Different Aspect Ratios

Understanding the cellular internalization mechanism of nanoparticles is essential to study their biological fate. Especially, due to the anisotropic properties, rod-like nanoparticles have attracted growing interest for the enhanced internalization efficiency with respect to spherical nanoparticles. Here, to elucidate the effect of aspect ratio of rod-like nanoparticles on cellular uptake, tobacco mosaic virus (TMV), a typical rod-like bionanoparticle, is developed as a model. Nanorods with different aspect ratios can be obtained by ultrasound treatment and sucrose density gradient centrifugation. By incubating with epithelial and endothelial cells, we found that the rod-like bionanoparticles with various aspect ratios had different internalization pathways in different cell lines: microtubules transport in HeLa and clathrin-mediated uptake in HUVEC for TMV₄ and TMV₈; caveolae-mediated pathway and microtubules transport in HeLa and HUVEC for TMV₁₇. Differently from most nanoparticles, for all the three TMV nano-rods with different aspect ratios, macropinocytosis takes no effect on the internalization in both cell types. This work provides a fundamental understanding of the influence of aspect ratio on cellular uptake decoupled from charge and material composition.

Non-affinity factors modulating vascular targeting of nano- and microcarriers

Particles capable of homing and adhering to specific vascular biomarkers have potential as fundamental tools in drug delivery for mediation of a wide variety of pathologies, including inflammation, thrombosis, and pulmonary disorders. The presentation of affinity ligands on the surface of a particle provides a means of targeting the particle to sites of therapeutic interest, but a host of other factors come into play in determining the targeting capacity of the particle. This review presents a summary of several key considerations in nano- and microparticle design that modulate targeted delivery without directly altering epitope-specific affinity. Namely, we describe the effect of factors in definition of the base carrier (including shape, size, and flexibility) on the capacity of carriers to access, adhere to, and integrate in target biological milieus. Furthermore, we present a summary of fundamental dynamics of carrier behavior in circulation, taking into account interactions with cells in circulation and the role of hemodynamics in mediating the direction of carriers to target sites. Finally, we note non-affinity aspects to uptake and intracellular trafficking of carriers in target cells. In total, recent findings presented here may offer an opportunity to capitalize on mitigating factors in the behavior of ligand-targeted carriers in order to optimize targeting.

pH-Responsive Wormlike Micelles with Sequential Metastasis Targeting Inhibit Lung Metastasis of Breast Cancer

Cancer metastasis is the main cause for the high mortality in breast cancer patients. Herein, we first report succinobucol-loaded pH-responsive wormlike micelles (PWMs) with sequential targeting capability to inhibit lung metastasis of breast cancer. PWMs can in a first step be delivered specifically to the sites of metastases in the lungs and then enable the intracellular pH-stimulus responsive drug release in cancer cells to improve the anti-metastatic effect. PWMs are identified as nanofibrillar assemblies with a diameter of 19.9 ± 1.9 nm and a length within the 50-200 nm range, and exhibited pH-sensitive drug release behavior in response to acidic intracellular environments. Moreover, PWMs can obviously inhibit the migration and invasion abilities of metastatic 4T1 breast cancer cells, and reduce the expression of the metastasis-associated vascular cell adhesion molecule-1 (VCAM-1) at 400 ng mL(-1) of succinobucol. In particular, PWMs can induce a higher specific accumulation in lung and be specifically delivered to the sites of metastases in lung, thereby leading to an 86.6% inhibition on lung metastasis of breast cancer. Therefore, the use of sequentially targeting PWMs can become an encouraging strategy for specific targeting and effective treatment of cancer metastasis.

Meeting report VLPNPV: Session 5: Plant based technology

The VLPNPV 2014 Conference that was convened at the Salk institute was the second conference of its kind to focus on advances in production, purification, and delivery of virus-like particles (VLPs) and nanoparticles. Many exciting developments were reported and discussed in this interdisciplinary arena, but here we report specifically on the contributions of plant-based platforms to VLP vaccine technology as reported in the section of the conference devoted to the topic as well in additional presentations throughout the meeting. The increasing popularity of plant production platforms is due to their lower cost, scalability, and lack of contaminating animal pathogens seen with other systems. Reports include production of complex VLPs consisting of 4 proteins expressed at finely-tuned expression levels, a prime-boost strategy for HIV vaccination using plant-made VLPs and a live viral vector, and the characterization and development of plant viral nanoparticles for use in cancer vaccines, drug delivery, and bioimaging.

The influence of the size and aspect ratio of anisotropic, porous CaCO3 particles on their uptake by cells

BACKGROUND

Recent reports highlighting the role of particle geometry have suggested that anisotropy can affect the rate and the pathway of particle uptake by cells. Therefore, we investigate the internalization by cells of porous calcium carbonate particles with different shapes and anisotropies.

RESULTS

We report here on a new method of the synthesis of polyelectrolyte coated calcium carbonate particles whose geometry was controlled by varying the mixing speed and time, pH value of the reaction solution, and ratio of the interacting salts used for particle formation. Uptake of spherical, cuboidal, ellipsoidal (with two different sizes) polyelectrolyte coated calcium carbonate particles was studied in cervical carcinoma cells. Quantitative data were obtained from the analysis of confocal laser scanning microscopy images.

CONCLUSIONS

Our results indicate that the number of internalized calcium carbonate particles depends on the aspect ratio of the particle, whereby elongated particles (higher aspect ratio) are internalized with a higher frequency than more spherical particles (lower aspect ratio). The total volume of internalized particles scales with the volume of the individual particles, in case equal amount of particles were added per cell.

5-Fluorouracil intercalated iron oxide@layered double hydroxide core-shell nano-composites with isotropic and anisotropic architectures for shape-selective drug delivery applications

We report the synthesis, characterization and in vitro release behavior of anti-cancer drug carrying iron oxide@layered double hydroxide core-shell nanocomposites with sizes ranging from 40 to 300 nm, good drug loading capacities and soft ferromagnetic properties. HRTEM analyses verified that nearly spherical isotropic carriers were obtained by coating spherical magnetite particles while anisotropic carriers were obtained by coating spindle-shaped hematite particles. They both displayed a fluctuating in vitro release profile with a higher release percentage for the anisotropic carrier.

The Impact of Aspect Ratio on the Biodistribution and Tumor Homing of Rigid Soft-Matter Nanorods

The size and shape of nanocarriers can affect their fate in vivo, but little is known about the effect of nanocarrier aspect ratio on biodistribution in the setting of cancer imaging and drug delivery. The production of nanoscale anisotropic materials is a technical challenge. A unique biotemplating approach based on of rod-shaped nucleoprotein nanoparticles with predetermined aspect ratios (AR 3.5, 7, and 16.5) is used. These rigid, soft-matter nanoassemblies are derived from tobacco mosaic virus (TMV) components. The role of nanoparticle aspect ratio is investigated, while keeping the surface chemistries constant, using either PEGylated stealth nanoparticles or receptor-targeted RGD-displaying formulations. Aspect ratio has a profound impact on the behavior of the nanoparticles in vivo and in vitro. PEGylated nanorods with the lowest aspect ratio (AR 3.5) achieve the most efficient passive tumor-homing behavior because they can diffuse most easily, whereas RGD-labeled particles with a medium aspect ratio (AR 7) are more efficient at tumor targeting because this requires a balance between infusibility and ligand-receptor interactions. The in vivo behavior of nanoparticles can therefore be tailored to control biodistribution, longevity, and tumor penetration by modulating a single parameter: the aspect ratio of the nanocarrier.

Reproducible Access to Tunable Morphologies via the Self-Assembly of an Amphiphilic Diblock Copolymer in Water

We report on the preparation of positively charged crew-cut nanoaggregates in water with various nonspherical (i.e., worm, flower, and large compound) and spherical (i.e., vesicle and sphere) morphologies by the self-assembly of a single diblock copolymer in water. Our facile procedure for preparing positively charged nanoparticles, when combined with the techniques for obtaining negatively charged and neutral nanoaggregates already established by Eisenberg et al., provides a versatile toolbox for the reproducible production of uniformly nanostructured particles with control over both morphology and surface chemistry. Such nanoparticles offer opportunities for the fundamental study of nanobio interactions and may open the door to novel drug and gene delivery applications.

Macrophage uptake of cylindrical microparticles investigated with correlative microscopy

Cylindrical particles offer the opportunity to develop controlled and sustained release systems for the respiratory tract. One reason is that macrophages can phagocyte such particles only from either of the two ends. We investigated the uptake behaviour of murine alveolar macrophages incubated with elongated submicron-structured particles. For that purpose, fluorescent model silica nanoparticles were interconnected with the biocompatible polysaccharide agarose, building up cylindrical particles within the pores of track-etched membranes. In contrast to common approaches we determined the uptake at different time points with scanning electron microscopy, fluorescence microscopy, and the combination of both techniques - correlative microscopy (CLEM). As a consequence, we could securely identify uptake events and observe in detail the engulfment of particles and confirm, that phagocytosis could only be observed from the tips of the cylinders. CLEM allowed a comparison of the uptake measured with different techniques at identical macrophages. Qualitative and quantitative evaluation of this cylindrical particle uptake showed substantial differences between fluorescence microscopy, electron microscopy and the combination of both (CLEM) within 24h.

Synergistic role of self-emulsifying lipids and nanostructured porous silica particles in optimizing the oral delivery of lovastatin

Aim: To investigate the role of self-emulsifying lipids and porous silica particles in enhancing supersaturated drug loading and biopharmaceutical performance of nanostructured silica–lipid hybrid (SLH) systems. Materials & methods: Two lovastatin (LOV)-SLHs were engineered from self-emulsifying lipid (Gelucire® 44/14; Gattefossé, Lyon, France) and Aerosil® 380 (SLH-A; Evonik Industries, Essen, Germany) or Syloid® 244FP silica (SLH-S; Grace Davison Discovery Sciences, Rowville, Australia). Results & discussion: The LOV-SLHs encapsulated LOV at 10% w/w, which is ≥3-fold higher than typical lipid formulations in the absence of porous silica. The LOV-SLHs retained self-emulsifying lipid-associated solubilization benefits and improved drug solubilization by twofold in simulated intestinal condition. SLH-S, with larger surface area (299 m2/g), was superior to SLH-A (184 m2/g) in optimizing oral bioavailability, suggesting a critical role of the silica geometry. Bioavailability of SLH-S was 2.8- and 1.3-fold higher than pure drug and drug suspension in Gelucire 44/14, respectively. Conclusion: In conclusion, SLHs profit from advantages associated with both self-emulsifying lipids and porous silica, and provide potentially improved therapy against coronary artery disease.

Non-spherical micro- and nanoparticles: fabrication, characterization and drug delivery applications

INTRODUCTION

Micro- and nanoparticles in drug and vaccine delivery have opened up new possibilities in pharmaceutics. In the past, researchers focused mainly on particle size, surface chemistry and the use of various materials to control particle characteristics and functions. Lately, shape has been acknowledged as an important design parameter having an impact on the interaction with biological systems.

AREAS COVERED

In this review, we report on the latest developments in fabrication methods to tailor particle geometry, summarize analytical techniques for non-spherical particles and highlight the most important findings regarding their interaction with biological systems and their potential applications in drug delivery.

EXPERT OPINION

The impact of shape on particle internalization into different cell types and particle biodistribution has been extensively studied in the past. Current research focuses on shape-dependent uptake mechanisms and applications for tumour therapy and vaccination. Different fabrication methods can be used to produce a variety of different particle types and shapes. Key challenges will be the transfer of new non-spherical particle fabrication methods from lab-scale to industrial large-scale production. Not all techniques may be scalable for the production of high quantities of particles. It will also be challenging to transfer the promising in vitro findings to suitable in vivo models.

Antibiotic-free nanotherapeutics: ultra-small, mucus-penetrating solid lipid nanoparticles enhance the pulmonary delivery and anti-virulence efficacy of novel quorum sensing inhibitors

Cystic fibrosis (CF) is a genetic disease mainly manifested in the respiratory tract. Pseudomonas aeruginosa (P. aeruginosa) is the most common pathogen identified in cultures of the CF airways, however, its eradication with antibiotics remains challenging as it grows in biofilms that counterwork human immune response and dramatically decrease susceptibility to antibiotics. P. aeruginosa regulates pathogenicity via a cell-to-cell communication system known as quorum sensing (QS) involving the virulence factor (pyocyanin), thus representing an attractive target for coping with bacterial pathogenicity. The first in vivo potent QS inhibitor (QSI) was recently developed. Nevertheless, its lipophilic nature might hamper its penetration of non-cellular barriers such as mucus and bacterial biofilms, which limits its biomedical application. Successful anti-infective inhalation therapy necessitates proper design of a biodegradable nanocarrier allowing: 1) high loading and prolonged release, 2) mucus penetration, 3) effective pulmonary delivery, and 4) maintenance of the anti-virulence activity of the QSI. In this context, various pharmaceutical lipids were used to prepare ultra-small solid lipid nanoparticles (us-SLNs) by hot melt homogenization. Plain and QSI-loaded SLNs were characterized in terms of colloidal properties, drug loading, in vitro release and acute toxicity on Calu-3 cells. Mucus penetration was studied using a newly-developed confocal microscopy technique based on 3D-time-lapse imaging. For pulmonary application, nebulization efficiency of SLNs and lung deposition using next generation impactor (NGI) were performed. The anti-virulence efficacy was investigated by pyocyanin formation in P. aeruginosa cultures. Ultra-small SLNs (<100nm diameter) provided high encapsulation efficiency (68-95%) according to SLN composition, high burst in phosphate buffer saline compared to prolonged release of the payload over >8h in simulated lung fluid with minor burst. All types and concentrations of plain and QSI-loaded SLNs maintained the viability of Calu-3 cells. 3D time-lapse confocal imaging proved the ability of SLNs to penetrate into artificial sputum model. SLNs were efficiently nebulized; NGI experiments revealed their deposition in the bronchial region. Overall, nanoencapsulated QSI showed up to sevenfold superior anti-virulence activity to the free compound. Most interestingly, the plain SLNs exhibited anti-virulence properties themselves, which was shown to be related to anti-virulence effects of the emulsifiers used. These startling findings represent a new perspective of ultimate significance in the area of nano-based delivery of novel anti-infectives.

Inhibition of the multidrug resistance P-glycoprotein: time for a change of strategy?

P-glycoprotein (P-gp) is a key player in the multidrug-resistant phenotype in cancer. The protein confers resistance by mediating the ATP-dependent efflux of an astonishing array of anticancer drugs. Its broad specificity has been the subject of numerous attempts to inhibit the protein and restore the efficacy of anticancer drugs. The general strategy has been to develop compounds that either compete with anticancer drugs for transport or act as direct inhibitors of P-gp. Despite considerable in vitro success, there are no compounds currently available to "block" P-gp-mediated resistance in the clinic. The failure may be attributed to toxicity, adverse drug interaction, and numerous pharmacokinetic issues. This review provides a description of several alternative approaches to overcome the activity of P-gp in drug-resistant cells. These include 1) drugs that specifically target resistant cells, 2) novel nanotechnologies to provide high-dose, targeted delivery of anticancer drugs, 3) compounds that interfere with nongenomic transfer of resistance, and 4) approaches to reduce the expression of P-gp within tumors. Such approaches have been developed through the pursuit of greater understanding of resistance mediators such as P-gp, and they show considerable potential for further application.

Fluorescent nanodiamonds embedded in biocompatible translucent shells

High pressure high temperature (HPHT) nanodiamonds (NDs) represent extremely promising materials for construction of fluorescent nanoprobes and nanosensors. However, some properties of bare NDs limit their direct use in these applications: they precipitate in biological solutions, only a limited set of bio-orthogonal conjugation techniques is available and the accessible material is greatly polydisperse in shape. In this work, we encapsulate bright 30-nm fluorescent nanodiamonds (FNDs) in 10-20-nm thick translucent (i.e., not altering FND fluorescence) silica shells, yielding monodisperse near-spherical particles of mean diameter 66 nm. High yield modification of the shells with PEG chains stabilizes the particles in ionic solutions, making them applicable in biological environments. We further modify the opposite ends of PEG chains with fluorescent dyes or vectoring peptide using click chemistry. High conversion of this bio-orthogonal coupling yielded circa 2000 dye or peptide molecules on a single FND. We demonstrate the superior properties of these particles by in vitro interaction with human prostate cancer cells: while bare nanodiamonds strongly aggregate in the buffer and adsorb onto the cell membrane, the shell encapsulated NDs do not adsorb nonspecifically and they penetrate inside the cells.

Carbon nanotubes hybrid hydrogels in drug delivery: a perspective review

The use of biologics, polymers, silicon materials, carbon materials, and metals has been proposed for the preparation of innovative drug delivery devices. One of the most promising materials in this field are the carbon-nanotubes composites and hybrid materials coupling the advantages of polymers (biocompatibility and biodegradability) with those of carbon nanotubes (cellular uptake, stability, electromagnatic, and magnetic behavior). The applicability of polymer-carbon nanotubes composites in drug delivery, with particular attention to the controlled release by composites hydrogel, is being extensively investigated in the present review.

Applications of inorganic nanoparticles as therapeutic agents

During the last decade, various functional nanostructured materials with interesting optical, magnetic, mechanical and chemical properties have been extensively applied to biomedical areas including imaging, diagnosis and therapy. In therapeutics, most research has focused on the application of nanoparticles as potential delivery vehicles for drugs and genes, because nanoparticles in the size range of 2-100 nm can interact with biological systems at the molecular level, and allow targeted delivery and passage through biological barriers. Recent investigations have even revealed that several kinds of nanomaterials are intrinsically therapeutic. Not only can they passively interact with cells, but they can also actively mediate molecular processes to regulate cell functions. This can be seen in the treatment of cancer via anti-angiogenic mechanisms as well as the treatment of neurodegenerative diseases by effectively controlling oxidative stress. This review will present recent applications of inorganic nanoparticles as therapeutic agents in the treatment of disease.

Heteromultivalent ligand-decoration for actively targeted nanomedicine

Active targeting has become an important component of nanomedicine design where nanovehicles are surface-decorated with cell receptor-specific or disease matrix-specific ligands to enable site-selective binding, retention and delivery of theranostic cargo. In this context, there have been numerous reports regarding surface-modification of nanovehicles with antibodies, antibody fragments, carbohydrates, aptamers and peptides as targeting ligands. However, majority of these reports have focused on using a single type of targeting moiety on the vehicle surface. In any disease development and progression, multiple receptors and proteins are often spatio-temporally upregulated simultaneously and heterogeneously. Rationalizing from this, a significant advantage can be envisioned in targeting multiple entities simultaneously using vehicle co-decoration with multiple types of ligands, to enhance binding activity and targeting specificity. To this end, we present a comprehensive up-to-date review on research endeavors in heteromultivalent ligand-modification of nanovehicles and provide a mechanistic rationale as well as an insightful discussion of this promising area, including findings from our own research.