Ostwald ripening of beta-carotene nanoparticles

Nanoparticle-based inhibition of vascular endothelial growth factor receptors alleviates osteoarthritis pain and cartilage damage

Osteoarthritis (OA) is characterized by cartilage damage, inflammation, and pain. Vascular endothelial growth factor receptors (VEGFRs) have been associated with OA severity, suggesting that inhibitors targeting these receptors alleviate pain (via VEGFR1) or cartilage degeneration (via VEGFR2). We have developed a nanoparticle-based formulation of pazopanib (Votrient), an FDA-approved anticancer drug that targets both VEGFR1 and VEGFR2 (Nano-PAZII). We demonstrate that a single intraarticular injection of Nano-PAZII can effectively reduce joint pain for a prolonged time without substantial side effects in two different preclinical OA rodent models involving either surgical (upon partial medial meniscectomy) or nonsurgical induction (with monoiodoacetate). The injection of Nano-PAZII blocks VEGFR1 and relieves OA pain by suppressing sensory neuronal ingrowth into the knee synovium and neuronal plasticity in the dorsal root ganglia and spinal cord. Simultaneously, the inhibition of VEGFR2 reduces cartilage degeneration. These findings provide a mechanism-based disease-modifying drug strategy that addresses both pain symptoms and cartilage loss in OA.

Determination of Reaction Kinetics by Time-Resolved Small-Angle X-ray Scattering during Polymerization-Induced Self-Assembly: Direct Evidence for Monomer-Swollen Nanoparticles

The kinetics of heterogeneous polymerization is determined directly using small-angle X-ray scattering (SAXS). This important advancement is exemplified for the synthesis of sterically-stabilized diblock copolymer nanoparticles by reversible addition-fragmentation chain transfer (RAFT) dispersion polymerization of benzyl methacrylate (BzMA) in mineral oil at 90 °C. The principle of mass balance is invoked to derive a series of equations for the analysis of the resulting time-resolved SAXS patterns. Importantly, there is a continuous change in the X-ray scattering length density for the various components within the reaction mixture. This enables the volume fraction of unreacted BzMA monomer to be calculated at any given time point, which enables the polymerization kinetics to be monitored in situ directly without relying on supplementary characterization techniques. Moreover, SAXS enables the local concentration of both monomer and solvent within the growing swollen nanoparticles to be determined during the polymerization. Data analysis reveals that the instantaneous rate of BzMA polymerization is proportional to the local monomer concentration within the nanoparticles. In principle, this powerful new time-resolved SAXS approach can be applicable to other heterogeneous polymerization formulations.

Design of Redispersible High-Drug-Load Amorphous Formulations: Impact of Ionic vs Nonionic Surfactants on Processing and Performance

Amorphous solid dispersions (ASDs) are an enabling formulation approach used to enhance bioavailability of poorly water-soluble molecules in oral drug products. Drug-rich amorphous nanoparticles generated in situ during ASD dissolution maintain supersaturation that drives enhanced absorption. However, in situ formation of nanoparticles requires large quantities of polymers to release drugs rapidly, resulting in an ASD drug load <25%. Delivering directly engineered drug-rich amorphous nanoparticles can reduce the quantities of polymers significantly without sacrificing bioavailability. Preparation of 90% drug-load amorphous nanoparticles (ANPs) of <300 nm diameter using solvent/antisolvent nanoprecipitation, organic solvent removal, and spray drying was demonstrated previously on model compound ABT-530 with Copovidone and sodium dodecyl sulfate (anionic). In this work, nonionic surfactant d-α-tocopheryl polyethylene glycol succinate (Vitamin E TPGS, or TPGS) was used to prepare ANPs as a comparison. Characterization of ANPs by dynamic light scattering, filtrate potency assay, scanning electron microscopy, and differential scanning calorimetry revealed differences in surface properties of nanoparticles afforded by surfactants. This work demonstrates the importance of understanding the impact of the stabilizing agents on nanoparticle behavior when designing a high-drug-load amorphous formulation for poorly water-soluble compounds as well as the impact on redispersion.

Advances in Designing Essential Oil Nanoformulations: An Integrative Approach to Mathematical Modeling with Potential Application in Food Preservation

Preservation of foods, along with health and safety issues, is a growing concern in the current generation. Essential oils have emerged as a natural means for the long-term protection of foods along with the maintenance of their qualities. Direct applications of essential oils have posed various constraints to the food system and also have limitations in application; hence, encapsulation of essential oils into biopolymers has been recognized as a cutting-edge technology to overcome these challenges. This article presents and evaluates the strategies for the development of encapsulated essential oils on the basis of fascination with the modeling and shuffling of various biopolymers, surfactants, and co-surfactants, along with the utilization of different fabrication processes. Artificial intelligence and machine learning have enabled the preparation of different nanoemulsion formulations, synthesis strategies, stability, and release kinetics of essential oils or their bioactive components from nanoemulsions with improved efficacy in food systems. Different mathematical models for the stability and delivery kinetics of essential oils in food systems have also been discussed. The article also explains the advanced application of modeling-based encapsulation strategies on the preservation of a variety of food commodities with their intended implication in food and agricultural industries.

Osmolality of Excipients for Parenteral Formulation Measured by Freezing Point Depression and Vapor Pressure - A Comparative Analysis

PURPOSE

To investigate the difference in methods to determine the osmolality in solutions of stabilizers used for long-acting injectable suspensions.

METHODS

The osmolality was measured by freezing point depression and vapor pressure for 11 different polymers and surfactants (PEG 3350, 4000, 6000, 8000, 20,000, PVP K12, K17 and K30, poloxamer 188, 388 and 407, HPMC E5, Na-CMC, polysorbate 20 and 80, vitamin E-TPGS, phospholipid, DOSS and SDS) in different concentrations.

RESULTS

Independently of the measuring method, an increase in osmolality with increasing concentration was observed for all polymers and surfactants, as would be expected due to the physicochemical origin of the osmolality. No correlation was found between the molecular weight of the polymers and the measured osmolality. The osmolality values were different for PVPs, PEGs, and Na-CMC using the two different measurement methods. The values obtained by the freezing point depression method tended to be similar or higher than the ones provided by vapor pressure, overall showing a significant difference in the osmolality measured by the two investigated methods.

CONCLUSIONS

For lower osmolality values (e.g. surfactants), the choice of the measuring method was not critical, both the freezing point depression and vapor pressure could be used. However, when the formulations contained higher concentrations of excipients and/or thermosensitive excipients, the data suggests that the vapor pressure method would be more suited.

The mechanism, biopolymers and active compounds for the production of nanoparticles by anti-solvent precipitation: A review

The anti-solvent precipitation method has been investigated to produce biopolymeric nanoparticles in recent years. Biopolymeric nanoparticles have better water solubility and stability when compared with unmodified biopolymers. This review article focuses on the analysis of the state of the art available in the last ten years about the production mechanism and biopolymer type, as well as the used of these nanomaterials to encapsulate biological compounds, and the potential applications of biopolymeric nanoparticles in food sector. The revised literature revealed the importance to understand the anti-solvent precipitation mechanism since biopolymer and solvent types, as well as anti-solvent and surfactants used, can alter the biopolymeric nanoparticles properties. In general, these nanoparticles have been produced using polysaccharides and proteins as biopolymers, especially starch, chitosan and zein. Finally, it was identified that those biopolymers produced by anti-solvent precipitation were used to stabilize essential oils, plant extracts, pigments, and nutraceutical compounds, promoting their application in functional foods.

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

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

Inductive Heating Enhances Ripening in the Aqueous Synthesis of Magnetic Nanoparticles

The search for competitive processes and products using environmentally friendly chemistry is, nowadays, one of the greatest challenges in materials science. In this work, we explore the influence of magnetic inductive heating on the synthesis of magnetic iron oxide nanoparticles in water, either by the coprecipitation of iron(II) and iron(III) salts or by the oxidative precipitation of an iron(II) salt. In the first case, the way the heat is transmitted to the system influences mainly the nanoparticle growth that is thermally activated reaching nanoparticles up to 16 nm. In the second case, it influences magnetic nanoparticle nucleation through the dissolution of the initial iron oxyhydroxide formed (the Green Rust) and the crystallization of magnetic iron oxide leading to nanoparticles up to 55-64 nm. This nonconventional heating method can produce monodisperse populations (size distribution <25%) of bigger magnetic iron oxide nanoparticles if the appropriate magnetic field conditions are used. The results were interpreted as an enhancement of the oriented attachment growth mechanism by the use of inductive heating, and suggest the possibility of increasing the size range of nanomaterials that can be obtained by sustainable aqueous routes using nonconventional heating, while maintaining low size dispersity.

Development and analysis of machine-learning guided flash nanoprecipitation (FNP) for continuous chitosan nanoparticles production

Chitosan-based nanoparticles (CNPs) are widely used in drug delivery, cosmetics formulation and food applications. To accelerate the manufacturing of CNPs, the present study develops a workflow to prepare CNPs in continues model. Based on machine learning, the workflow precisely predicts size and polymer dispersity index (PDI) value of CNPs, which impacts on the colloidal stability and applications. Multi-inlet vortex mixer (MIVM) device was fabricated by 3D printing as the reactor. Peristaltic pump was applied to deliver the reaction streams into the MIVM device and produce CNPs by flash nanoprecipitation (FNP) in continuous way. The developed MIVM device produces CNPs in controlled manner at higher output which is promising for upscale applications. Twelve machine learning algorithms were employed to investigate the potential relationship between the reaction independent variables and hydrodynamic characteristics of CNPs. Random Forest, Decision Tree, Extra Tree and Bagging algorithms performed better than other algorithms with the average prediction accuracy around 90 %. The current study demonstrated that supervised machine learning guided FNP using the developed MIVM device is an effective strategy for accurate and intelligent production of CNPs and other similar nanoparticles.

Mechanisms and Extent of Enhanced Passive Permeation by Colloidal Drug Particles

Formulations containing nanosized drug particles such as nanocrystals and nanosized amorphous drug aggregates recently came into light as promising strategies to improve the bioavailability of poorly soluble drugs. However, the increased solubility due to the reduction in particle size cannot adequately explain the enhanced bioavailability. In this study, the mechanisms and extent of enhanced passive permeation by drug particles were investigated using atazanavir, lopinavir, and clotrimazole as model drugs. Franz diffusion cells with lipid-infused membranes were utilized to evaluate transmembrane flux. The impact of stirring rate, receiver buffer condition, and particle size was investigated, and mass transport analyses were conducted to calculate transmembrane flux. Flux enhancement by particles was found to be dependent on particle size as well as the partitioning behavior of the drug between the receiver solution and the membrane, which is determined by both the drug and buffer used. A flux plateau was observed at high particle concentrations above amorphous solubility, confirming that mass transfer of amorphous drug particles from the aqueous solution to the membrane occurs only through the molecularly dissolved drug. Mass transport models were used to calculate flux enhancement by particles for various drugs at different conditions. Good agreements were obtained between experimental and predicted values. These results should contribute to improved bioavailability prediction of nanosized drug particles and better design of formulations containing colloidal drug particles.

Coordination-driven Metal-polyphenolic Nanoparticles toward Effective Anticancer Therapy

Stabilization of bioactive components, especially for hydrophobic functional factors, is a promising approach for improving their biological activity. Here, a metal-phenolic coordination chemistry that synthesizes biocompatible and biodegradable thin-film based on tannic acid (TA) and trivalent metal ion (Fe³⁺ or Al³⁺ ) is addressed, and the results also demonstrate its use for encapsulating a hydrophobic drug (Nobiletin, NOB) and triggering drug release for cancer treatment both in vitro and in vivo. This assembled system provides drug-loaded nanoparticles (NPs) with small, but uniform, size (∼200 nm). It displays beneficial potential in enhancing colloidal stability and preventing premature drug leakage. Moreover, the metal-phenolic coating is found to possess high cell biocompatibility as a delivery vector for controlled drug delivery, while the final fabricated drug NPs have effective anti-tumor activity by both inducing higher tumor apoptosis and inhibiting tumor metastasis, which is superior to naked drug formulations. Overall, our findings propose an effective and straightforward way for coating hydrophobic drugs employing interfacial adhesion and assembly, which could be a highly promising vehicle for controlled-release biomedical applications for cancer therapy. This article is protected by copyright. All rights reserved.

Control and Preparation of Quaternized Chitosan and Carboxymethyl Chitosan Nanoscale Polyelectrolyte Complexes Based on Reactive Flash Nanoprecipitation

Nanoscale polyelectrolyte complex materials have been extensively investigated for their promising application in protocell, drug carriers, imaging, and catalysis. However, the conventional preparation approach involving positive and negative polyelectrolytes leads to large size, wide size distribution, instability, and aggregation due to the nonhomogeneous mixing process. Herein, we employ reactive flash nanoprecipitation (RFNP) to control the mixing and preparation of the nanoscale polyelectrolyte complex. With RFNP, homogeneous mixing complexation between oppositely charged chitosan derivatives could be achieved, resulting in stable nanoscale complexes (NCs) with controllable size and narrow size distribution. The smallest size of NCs is found at specific pH due to the maximum attraction of positive and negative molecules of chitosan. The size can be modulated by altering the volumetric flow rates of inlet streams, concentration, and charge molar ratio of two oppositely charged chitosan derivatives. The charge molar ratio is also tuned to create NCs with positive and negative shells. There is no significant variation in the size of NCs produced at different intervals of time. This method allows continuous and tunable NC production and could have the potential for fast, practical translation.

Freeze-thaw stability of aluminum oxide nanoparticles

The use of inorganic nanoparticles (NPs) gains interest for pharmaceutical applications, e.g. as adjuvants or drug delivery vehicles. Colloidal stability of NPs in aqueous suspensions is a major development challenge. Both frozen and lyophilized liquids are alternative presentations to liquid dispersion. To improve the basic understanding, we investigated the freeze-thawing stability of model α-Al₂O₃ NPs. Freeze-thawing was conducted in three different buffer types at pH5 and 8 without and with additives to determine fundamental formulation principles. Before freeze-thawing, α-Al₂O₃ NPs could be stabilized in sodium citrate buffer at pH5 and 8, and in sodium or potassium phosphate at pH8. Particles revealed low zeta potential values in phosphate buffers at pH5 indicating insufficient electrostatic stabilization. After freeze-thawing, an increase in NP size was strongly reduced in potassium phosphate and sodium citrate buffers. Subsequent pH measurements upon freezing revealed a drastic acidic pH shift in sodium phosphate which was further demonstrated to destabilize NPs. The ionic stabilizers gelatin A/B, Na-CMC, and SDS, were suitable to improve colloidal stability in phosphate buffers at pH5 highlighting the importance of charge stabilization. Freeze-thawing stability was best in presence of gelatin A/B, followed by PVA, mannitol, or sucrose. Depletion and steric stabilization were insufficient using PEG and surfactants respectively. Thus, we could identify the fundamental formulation principles to preserve inorganic NPs upon freezing: i) sufficient charge stabilization, ii) a maintained pH during freezing, and iii) the addition of a suitable stabilizer, preferably gelatin, not necessarily surfactants. This forms the basis for future studies, e.g. on lyophilization.

A Cost-Effective Nano-Sized Curcumin Delivery System with High Drug Loading Capacity Prepared via Flash Nanoprecipitation

Flash nanoprecipitation (FNP) is an efficient technique for encapsulating drugs in particulate carriers assembled by amphiphilic polymers. In this study, a novel nanoparticular system of a model drug curcumin (CUR) based on FNP technique was developed by using cheap and commercially available amphiphilic poly(vinyl pyrrolidone) (PVP) as stabilizer and natural polymer chitosan (CS) as trapping agent. Using this strategy, high encapsulation efficiency (EE > 95%) and drug loading capacity (DLC > 40%) of CUR were achieved. The resulting CUR-loaded nanoparticles (NPs) showed a long-term stability (at least 2 months) and pH-responsive release behavior. This work offers a new strategy to prepare cost-effective drug-loaded NPs with high drug loading capacity and opens a unique opportunity for industrial scale-up.

Highly-loaded protein nanocarriers prepared by Flash NanoPrecipitation with hydrophobic ion pairing

The efficient encapsulation of therapeutic proteins into delivery vehicles, particularly without loss of function, remains a significant research hurdle. Typical liposomal formulations achieve drug loadings on the order of 3-5% and encapsulation efficiencies around 50%. We demonstrate the encapsulation of model proteins with isoelectric points above and below pH 7 into nanocarriers (NCs) with protein loadings as high as 46% and encapsulation efficiencies above 95%. This is done by combining the continuous nanofabrication process Flash NanoPrecipitation (FNP) with the technique of hydrophobic ion pairing by forming and encapsulating an ionic complex within a nanocarrier stabilized by a block copolymer surface layer. We complex and encapsulate lysozyme with two anionic hydrophobic counterions, sodium oleate and sodium dodecyl sulfate, using either a pre-formed complex or in situ pairing. The strategy successfully forms NCs ~150 nm in diameter and achieves encapsulation efficiencies over 95%. Protein release rate from the NCs in physiological conditions and the bioactivity of released lysozyme are measured, and both are found to vary with the complexing counterion and the protein/counterion ratio used during formulation. Protein release on the time scale of weeks is observed, and up to 100% bioactivity is measured from released lysozyme. 16 quaternary ammonium cationic counterions are tested to encapsulate ovalbumin in 32 formulations. Of these, 19 successfully form ~150 nm NCs with loadings up to 29% and encapsulation efficiencies up to 88%. We divide the formulations into four regimes and identify chemical factors responsible for the success or failure of a given counterion to formulate NCs with the desirable size, loading, and encapsulation efficiency. A successful ovalbumin NC formulation was then tested in vivo in a mouse nasal vaccine model and found to induce a higher titer of OVA-specific IgG than unencapsulated ovalbumin. Taken together, these findings suggest that Flash NanoPrecipitation with hydrophobic ion pairing is an attractive platform for encapsulating high molecular weight proteins into NCs. In particular, the ability to tune protein release rate by varying the counterion or protein/counterion ratio used during formulation is a useful feature.

Encapsulation and Controlled Release of a Camptothecin Prodrug from Nanocarriers and Microgels: Tuning Release Rate with Nanocarrier Excipient Composition

Nanocarriers (NCs) are an attractive class of vehicles for drug delivery with the potential to improve drug efficacy and safety, particularly for intravenous parenteral delivery. Many therapeutics remain challenging to formulate in NCs due to their intrinsic solubilities that frustrate NC loading or result in too rapid release in vivo. Therapeutic conjugate approaches that alter the solubility of a conjugate "prodrug" have been used to enable NC formation and controlled release from NCs using labile linker chemistry. A limitation of this approach has been that a different linker chemistry must be used to produce an adjustable release rate for a single therapeutic. We report on a new approach where the therapeutic conjugate hydrolysis rates are varied by adjusting the excipient formulation of the NC core, not the conjugate linker chemistry. A hydrophobic therapeutic conjugate of camptothecin (PROCPT) is synthesized by conjugating camptothecin (CPT) with an acid derivative of α-tocopherol (vitamin E). The PROCPT compound can be loaded to 50% wt in poly(lactic acid)-block-poly(ethylene glycol) (PLA-b-PEG)-stabilized NCs produced by Flash NanoPrecipitation with particle diameters between 60 and 80 nm. Co-loading a zwitterionic lipid, 1-palmitoyl-2-oleoyl-glycero-3-phosphocholine, from 0 to 67% core loading tunes the PROCPT hydrolysis from no observable therapeutic release over 200 h to therapeutic conjugate half-life times of 31 h. For a single therapeutic conjugate molecule, the hydrolysis rate can be tuned by modifying the NC formulation with different excipient concentrations. NCs containing a 50% core loading of PROCPT were lyophilized and encapsulated in a PEG hydrogel matrix to make microparticles for depot delivery with an average diameter of 65 ± 10 μm that provide a sustained, first-order release of CPT with a therapeutic conjugate half-life of 240 h. These results demonstrate a new approach to the formulation of therapeutic NCs with variable release profiles using a single molecular entity therapeutic conjugate.

Crystallization of Transition-Metal Oxides in Aqueous Solution beyond Ostwald Ripening

The crystallization mechanism of transition-metal oxides (TMOs) in a solution was examined based on ZnO crystallization using in-situ x-ray absorption fine structure (XAFS) measurements at the Zn K edge and semi-empirical quantum chemistry (SEQC) simulations. The XAFS results quantitatively determine the local structural and chemical properties around a zinc atom at successive stages from Zn(NO₃)₂ to ZnO in an aqueous solution. The results also show that a zinc atom in Zn(NO₃)₂ ions dissolves in a solution and bonds with approximately three oxygen atoms at room temperature (RT). When hexamethylenetetramine (C₆H₁₂N₄) is added to the solution at RT, a stable Zn-O complex consisting of six Zn(OH)₂s is formed, which is a seed of ZnO crystals. The Zn-O complexes partially and fully form into a wurtzite ZnO at 60 and 80 °C, respectively. Based on the structural properties of Zn-O complexes determined by extended-XAFS (EXAFS), SEQC simulations clarify that Zn-O complexes consecutively develop from a linear structure to a polyhedral complex structure under the assistance of hydroxyls (OH^-s) in an aqueous solution. In a solution with a sufficient concentration of OH^-s, ZnO spontaneously grows through the merging of ZnO seeds (6Zn(OH)₂s), reducing the total energy by the reactions of OH^-s. ZnO crystallization suggests that the crystal growth of TMO can only be ascribed to Ostwald ripening when it exactly corresponds to the size growth of TMO particles.

Modification of the zeta potential of montmorillonite to achieve high active pharmaceutical ingredient nanoparticle loading and stabilization with optimum dissolution properties

Nanoparticles (NPs) of three poorly water-soluble BCS class II active pharmaceutical ingredients (APIs) (clozapine (CLO), curcumin (CUR) and carbamazepine (CBMZ) with zeta potentials -28.5 ± 2.5, -33 ± 1.5 and -13 ± 1.5 mV respectively) were produced, stabilized and isolated into the solid state with the help of Montmorillonite (MMT) clay carrier particles. The nanoparticles of clozapine (27 nm), curcumin (170 nm) and carbamazepine (30 nm) were produced and stabilized in suspension using a reverse antisolvent precipitation technique in the presence of 'as received' MMT carrier particles (∼30 μm) and/or MMT carrier particles whose surface had been slightly modified with a cationic protein, protamine sulphate salt (PA). The resulting nanoparticle carrier composites were isolated directly from suspension into a solid state form by simple filtration followed by air-drying. The API dissolution rates from these dried NP-carrier composites were comparable with those of the respective stabilized API nanoparticles in suspension up to maximum CLO, CUR and CBMZ loadings of 23%, 21.8% and 33.3% (w/w) respectively, although surface modification of the MMT carrier particles with PA was needed for the CLO and CUR NP-carrier composites in order to preserve the fast API nanosuspension-like dissolution rates at higher API loadings. For both of these APIs, the optimal loading of PA on MMT was around 4 mg/g, which likely helped to limit aggregation of the API nanoparticles at the higher API loadings. Interestingly, no MMT surface modification was needed to preserve fast API dissolution rates at higher API loadings in the case of the CBMZ NP-carrier composites. This discrimination among the three APIs for carrier particle surface modification was previously observed in reported studies by our group for three other APIs, namely valsartan, fenofibrate and dalcetrapib. When examined together, the data for all six APIs suggest a general trend whereby API nanoparticles with zeta potentials more positive than around -25 mV do not require carrier particle surface modification with PA in order to preserve their fast dissolution rates from NP-carrier composites at higher API loadings. Thus, this study offers a potentially effective means of transforming poorly water soluble BCS Class II APIs into fast dissolving solid dosage NP-carrier composites, whereby the surface properties of the carrier particle can be tuned with prior knowledge of the zeta potential of the API nanoparticles.

Microfluidics for Production of Particles: Mechanism, Methodology, and Applications

In the past two decades, microfluidics-based particle production is widely applied for multiple biological usages. Compared to conventional bulk methods, microfluidic-assisted particle production shows significant advantages, such as narrower particle size distribution, higher reproducibility, improved encapsulation efficiency, and enhanced scaling-up potency. Herein, an overview of the recent progress of the microfluidics technology for nano-, microparticles or droplet fabrication, and their biological applications is provided. For both nano-, microparticles/droplets, the previously established mechanisms behind particle production via microfluidics and some typical examples during the past five years are discussed. The emerging interdisciplinary technologies based on microfluidics that have produced microparticles or droplets for cellular analysis and artificial cells fabrication are summarized. The potential drawbacks and future perspectives are also briefly discussed.

Difunctional Fluorescence Nanoparticles for Accurate Tracing of Nanopesticide Fate and Crop Protection Prepared by Flash Nanoprecipitation

Facile fabrication of difunctional nanoparticles (NPs) for pesticide delivery and imaging is still a fascinating challenge. Here, water-dispersible difunctional NPs were developed using flash nanoprecipitation (FNP) where self-assembling amphiphilic block copolymers were used to encapsulate a highly hydrophobic model pesticide, Lambda-cyhalothrin, and the fluorescent dye Nile red. The particle size (ranging from 158 to 280 nm) and fluorescence property of NPs could be controlled by varying the flow rate or Nile red feed concentration. The aggregation state and rearrangement of the dye molecules in the NPs were also investigated. IVIS imaging and confocal laser scanning microscopy analysis demonstrated that the resulting difunctional nanopesticide particles could allow accurate in situ tracking of the pesticide on the leaf surface, while effectively avoiding interference from chlorophyll autofluorescence. The difunctional NP suspension maintained high insecticidal activity and stability. This work demonstrates the feasibility and great potential of the FNP method in universal fabrication of multifunctional NPs with in situ pesticide tracing and crop protection capabilities.

Förster Resonance Energy Transfer-Mediated Globular Protein Sensing Using Polyelectrolyte Complex Nanoparticles

Polyelectrolyte complex nanoparticles (PEC NPs) are synthesized using two oppositely charged polyelectrolytes, i.e., anionic poly(sodium 4-styrene sulfonate) (PSS) and cationic poly(diallyldimethylammoniumchloride), at molar mixing ratios (n ^-/n ⁺) of ≈0.4, 0.67, 0.75, and 1.5 by applying consecutive centrifugation to modify the optical property of PSS. However, for n ^-/n ⁺ ≈ 0.75, PEC NPs exhibit a larger blue shift and a specific emission peak occurs at ≈278 nm for the 225 nm excitation. The mechanism of such modification of PSS emission after complex formation is proposed. This specific emission by PEC NPs nearly matches with the optical absorption wavelength of globular proteins. The emission intensity of PEC NPs is therefore quenched in the presence of globular proteins (bovine serum albumin, human serum albumin, lysozyme, and hemoglobin) through resonance energy transfer between the donor (PEC NPs) and acceptor (globular proteins). The spectral overlap integral and the variation of the separation distance from 1.8 to 2.5 nm between the donor and acceptor confirm the resonance energy transfer. Sensing of proteins by the PEC NPs is possible within the detection limit of 5 nM and therefore such PEC NPs can be used as an efficient and promising protein sensing material.

Spray drying OZ439 nanoparticles to form stable, water-dispersible powders for oral malaria therapy

Background

OZ439 is a new chemical entity which is active against drug-resistant malaria and shows potential as a single-dose cure. However, development of an oral formulation with desired exposure has proved problematic, as OZ439 is poorly soluble (BCS Class II drug). In order to be feasible for low and middle income countries (LMICs), any process to create or formulate such a therapeutic must be inexpensive at scale, and the resulting formulation must survive without refrigeration even in hot, humid climates. We here demonstrate the scalability and stability of a nanoparticle (NP) formulation of OZ439. Previously, we applied a combination of hydrophobic ion pairing and Flash NanoPrecipitation (FNP) to formulate OZ439 NPs 150 nm in diameter using the inexpensive stabilizer hydroxypropyl methylcellulose acetate succinate (HPMCAS). Lyophilization was used to process the NPs into a dry form, and the powder’s in vitro solubilization was over tenfold higher than unprocessed OZ439.

Methods

In this study, we optimize our previous formulation using a large-scale multi-inlet vortex mixer (MIVM). Spray drying is a more scalable and less expensive operation than lyophilization and is, therefore, optimized to produce dry powders. The spray dried powders are then subjected to a series of accelerated aging stability trials at high temperature and humidity conditions.

Results

The spray dried OZ439 powder’s dissolution kinetics are superior to those of lyophilized NPs. The powder’s OZ439 solubilization profile remains constant after 1 month in uncapped vials in an oven at 50 °C and 75% RH, and for 6 months in capped vials at 40 °C and 75% RH. In fasted-state intestinal fluid, spray dried NPs achieved 80–85% OZ439 dissolution, to a concentration of 430 µg/mL, within 3 h. In fed-state intestinal fluid, 95–100% OZ439 dissolution is achieved within 1 h, to a concentration of 535 µg/mL. X-ray powder diffraction and differential scanning calorimetry profiles similarly remain constant over these periods.

Conclusions

The combined nanofabrication and drying process described herein, which utilizes two continuous unit operations that can be operated at scale, is an important step toward an industrially-relevant method of formulating the antimalarial OZ439 into a single-dose oral form with good stability against humidity and temperature.

Electronic supplementary material

The online version of this article (10.1186/s12967-019-1849-8) contains supplementary material, which is available to authorized users.

Rapid Self-Assembly of Metal/Polymer Nanocomposite Particles as Nanoreactors and Their Kinetic Characterization

Self-assembled metal nanoparticle-polymer nanocomposite particles as nanoreactors are a promising approach for performing liquid phase reactions using water as a bulk solvent. In this work, we demonstrate rapid, scalable self-assembly of metal nanoparticle catalyst-polymer nanocomposite particles via Flash NanoPrecipitation. The catalyst loading and size of the nanocomposite particles can be tuned independently. Using nanocomposite particles as nanoreactors and the reduction of 4-nitrophenol as a model reaction, we study the fundamental interplay of reaction and diffusion. The induction time is affected by the sequence of reagent addition, time between additions, and reagent concentration. Combined, our experiments indicate the induction time is most influenced by diffusion of sodium borohydride. Following the induction time, scaling analysis and effective diffusivity measured using NMR indicate that the observed reaction rate are reaction- rather than diffusion-limited. Furthermore, the intrinsic kinetics are comparable to ligand-free gold nanoparticles. This result indicates that the polymer microenvironment does not de-activate or block the catalyst active sites.

On the incorrect use and interpretation of the model for colloidal, spherical crystal growth

HYPOTHESIS

The standard model for diffusion and surface kinetics driven growth of a single spherical particle in solution is applied incorrectly throughout the literature. This leads to inaccurate values for parameter values, such as the diffusion and surface kinetics coefficients. The model cannot even distinguish between diffusion or surface kinetics driven growth.

FINDINGS

It is shown that crystal growth occurs in two distinct stages. The standard model only holds during the late time. Fitting to experimental data, including the early time, leads to incorrect values for the coefficients. It is shown that diffusion and surface kinetics are interchangeable in the model and so indistinguishable. The growth is controlled by a single non-dimensional group. Previous studies, where more independent parameters are calculated have redundancy. The Gibbs-Thomson relation plays an important role but, in the cases studied here, this is only noticeable during the first growth stage where the model does not hold. For the first time an explicit relation for the variation of the radius with time is given. Excellent agreement with experimental data on CdSe growth is shown.

On the Stability of Nano-formulations Prepared by Direct Synthesis: Simulated Ostwald Ripening of a Typical Nanocrystal Distribution Post-nucleation

Compared to more traditional top-down processing, the less common route to preparing drug nanocrystals through direct synthesis, e.g., starting with the nucleation of dissolved drug molecules (bottom-up processing), can offer both speed and cost advantages that makes it worthy of investigation. The current, theoretical work puts forth a technical basis and simulated results that could provide additional impetus for conducting further experimental work in this area. Specifically, an asymmetrical particle size distribution generated through the nucleation of a typical small-molecule drug, mirrored after carbamazepine hydrate based on a recent work [Skrdla PJ. J Phys Chem C 116:214-25, 2012], is subject to growth over time by a particle-coarsening mechanism using simulations of Ostwald ripening. Compared to a symmetrical, Gaussian distribution under the same conditions (fixed, relatively low concentration of free drug molecules in solution), it is found that, at longer times, the asymmetrical distribution formed through nucleation broadens more slowly. This finding could represent an additional benefit of synthetic strategies for the preparation of nano-formulations, previously unreported.

Application of flash nanoprecipitation to fabricate poorly water-soluble drug nanoparticles

Nanoparticles are considered to be a powerful approach for the delivery of poorly water-soluble drugs. One of the main challenges is developing an appropriate method for preparation of drug nanoparticles. As a simple, rapid and scalable method, the flash nanoprecipitation (FNP) has been widely used to fabricate these drug nanoparticles, including pure drug nanocrystals, polymeric micelles, polymeric nanoparticles, solid lipid nanoparticles, and polyelectrolyte complexes. This review introduces the application of FNP to produce poorly water-soluble drug nanoparticles by controllable mixing devices, such as confined impinging jets mixer (CIJM), multi-inlet vortex mixer (MIVM) and many other microfluidic mixer systems. The formation mechanisms and processes of drug nanoparticles by FNP are described in detail. Then, the controlling of supersaturation level and mixing rate during the FNP process to tailor the ultrafine drug nanoparticles as well as the influence of drugs, solvent, anti-solvent, stabilizers and temperature on the fabrication are discussed. The ultrafine and uniform nanoparticles of poorly water-soluble drug nanoparticles prepared by CIJM, MIVM and microfluidic mixer systems are reviewed briefly. We believe that the application of microfluidic mixing devices in laboratory with continuous process control and good reproducibility will be benefit for industrial formulation scale-up.

Homogenization and Growth Behavior of Second-Phase Particles in a Deformed Zr–Sn–Nb–Fe–Cu–Si–O Alloy

Homogeneous distribution of fine second-phase particles (SPPs) fabricated by cycles of deformation and annealing in zirconium alloys is a critical consideration for the corrosion resistance of fuel claddings. Different deformation degrees of zirconium alloys would result in distinctive microstructures, leading to a distinct growth of SPPs during subsequent annealing. Unfortunately, the homogenization and growth behavior of SPPs in deformed zirconium alloys have not been well studied. In this work, a β-quenched Zr–Sn–Nb–Fe–Cu–Si–O alloy was rolled and annealed at 580 °C or 680 °C. The morphologies, distributions, and sizes of SPPs resulting from the different processing procedures were investigated. A linear distribution of SPPs is found in the β-quenched sample. Afterward, SPPs grow and are randomly distributed during heat treatment as the deformation degree or annealing time (or temperature) increases. The homogenization and growth of SPPs are attributed to the Ostwald ripening mechanism that is governed by lattice diffusion and short-circuit diffusion. The sample with a higher deformation degree is speculated to have a larger number of defects that provide more shortcuts for the mass transfer of SPPs, thereby facilitating a homogeneous distribution of fine SPPs during annealing.

Morphology Tuning of Aggregation-Induced Emission Probes by Flash Nanoprecipitation: Shape and Size Effects on in Vivo Imaging

Aggregation-induced emission (AIE) imaging probes have recently received considerable attention because of their unique property of high performance in the aggregated state and their imaging capability. However, the tendency of AIE molecules to aggregate into micron long irregular shapes, which significantly limits their application in vivo, is becoming a serious issue that needs to be addressed. Here, we introduce a novel engineering strategy to tune the morphology and size of AIE nanoaggregates, based on flash nanoprecipitation (FNP). Quinolinemalononitrile (ED) is encapsulated inside properly selected amphiphilic block copolymers of varying concentration. This leads to a variety of ED particle morphologies with different sizes. The shape and size are found to have strong influences on tumor targeting both in vitro and in vivo. The current results therefore indicate that the FNP method together with optimal choice of an amphiphilic copolymer is a universal method to systematically control the aggregation state of AIE materials and hence tune the morphology and size of AIE nanoaggregates, which is potentially useful for precise imaging at specific tumor sites.

Impact of molecular rearrangement of amphiphilic stabilizers on physical stability of itraconazole nanoparticles prepared by flash nanoprecipitation

Flash nanoprecipitation (FNP) is a controlled antisolvent precipitation process that has proven effective for consistent production of drug nanoparticles with a defined mean particle size and narrow particle size distribution. However, physical instability of the generated nanoparticles remains a major challenge in the application of this technology in pharmaceutical formulation. Aimed at resolving this problem, the present study has investigated the FNP process and associated stabilization mechanism of itraconazole (ITZ) nanoparticles through in-depth nanoparticle characterization. Results showed that ITZ nanoparticles could be reproducibly produced with a mean particle size <100 nm and a polydispersity index <0.2 in the presence of amphiphilic stabilizers (ASs). Surface analysis of freshly formed nanoparticles by X-ray photoelectron spectroscopy (XPS) revealed initially a disordered packing structure and subsequently a time-dependent molecular rearrangement of incorporated AS towards a micelle-like structure. The faster the molecular rearrangement of AS, the more stable the nanoparticles, as monitored by the change in particle size with time. These findings may have important implications for the selection of effective ASs for formulating stable drug nanoparticles. The present study is the first of its kind to demonstrate the utility of XPS to track the molecular transport of stabilizers in rapidly generated nanoparticles.

The influence of natural deep eutectic solvents on bioactive natural products: studying interactions between a hydrogel model and Schisandra chinensis metabolites

Natural Deep Eutectic Solvent (NADES) species can exhibit unexpected solubilizing power for lipophilic molecules despite their simple composition: hydrophilic organic molecules and water. In the present study, the unique properties of NADES species were applied in combination with a model polymer system: a hydrophilic chitosan/alginate hydrogel. Briefly, NADES species (e.g., mannose-dimethylurea-water, 2:5:5, mole/mole) formed matrices to 1) dissolve lipophilic molecules (e.g., curcumin), 2) load lipophilic molecule(s) into the hydrogel, and 3) spontaneously vacate from the system. NADES species ubiquitously occur in natural sources, and a crude extract is a mixture of the NADES species and bioactive metabolites. Based on these ideas, we hypothesized that the crude extract may also allow the loading of natural bioactive molecules from a natural NADES species into (bio)hydrogel systems. To evaluate this hypothesis in vitro, Schisandra chinensis fruit extract was chosen as a representative mixture of lipophilic botanical molecules and hydrophilic NADES species. The results showed that the NADES matrix of S. chinensis was capable of loading at least three bioactive lignans (i.e., gomisin A, gomisin J, and angeloylgomisin H) into the polymer system. The lipophilic metabolites can subsequently be released from the hydrogel. The outcomes suggest that a unique drug delivery mechanism may exist in nature, thereby potentially improving the bioavailability of lipophilic metabolites through physicochemical interactions with the NADES.

Physicochemical Properties of Whey-Protein-Stabilized Astaxanthin Nanodispersion and Its Transport via a Caco-2 Monolayer

Astaxanthin nanodispersion was prepared using whey protein isolate (WPI) and polymerized whey protein (PWP) through an emulsification-evaporation technique. The physicochemical properties of the astaxanthin nanodispersion were evaluated, and the transport of astaxanthin was assessed using a Caco-2 cell monolayer model. The astaxanthin nanodispersions stabilized by WPI and PWP (2.5%, w/w) had a small particle size (121 ± 4.9 and 80.4 ± 5.9 nm, respectively), negative ζ potential (-19.3 ± 1.5 and -35.0 ± 2.2 mV, respectively), and high encapsulation efficiency (92.1 ± 2.9 and 93.5 ± 2.4%, respectively). Differential scanning calorimetry curves indicated that amorphous astaxanthin existed in both astaxanthin nanodispersions. Whey-protein-stabilized astaxanthin nanodispersion showed resistance to pepsin digestion but readily released astaxanthin after trypsin digestion. The nanodispersions showed no cytotoxicity to Caco-2 cells at a protein concentration below 10 mg/mL. WPI- and PWP-stabilized nanodispersions improved the apparent permeability coefficient (P_app) of Caco-2 cells to astaxanthin by 10.3- and 16.1-fold, respectively. The results indicated that whey-protein-stabilized nanodispersion is a good vehicle to deliver lipophilic bioactive compounds, such as astaxanthin, and to improve their bioavailability.

Millisecond Self-Assembly of Stable Nanodispersed Drug Formulations

We report the development of a new spray-drying and nanoparticle assembly process (SNAP) that enables the formation of stable, yet rapidly dissolving, sub-200 nm nanocrystalline particles within a high T_g glassy matrix. SNAP expands the class of drugs that spray-dried dispersion (SDD) processing can address to encompass highly crystalline, but modestly hydrophobic, drugs that are difficult to process by conventional SDD. The process integrates rapid precipitation and spray-drying within a custom designed nozzle to produce high supersaturations and precipitation of the drug and high T_g glassy polymer. Keeping the time between precipitation and drying to tens of milliseconds allows for kinetic trapping of drug nanocrystals in the polymer matrix. Powder X-ray diffraction, solid state 2D NMR, and SEM imaging shows that adding an amphiphilic block copolymer (BCP) to the solvent gives essentially complete crystallization of the active pharmaceutical ingredient (API) with sub-200 nm domains. In contrast, the absence of the block copolymer results in the API being partially dispersed in the matrix as an amorphous phase, which can be sensitive to changes in bioavailability over time. Quantification of the API-excipient interactions by 2D ¹³C-¹H NMR correlation spectroscopy shows that the mechanism of enhanced nanocrystal formation is not due to interactions between the drug and the BCP, but rather the BCP masks interactions between the drug and hydrophobic regions of the matrix polymers. BCP-facilitated SNAP samples show improved stability during aging studies and rapid dissolution and release of API in vitro.