Effects of amphiphilic diblock copolymer on drug nanoparticle formation and stability

Effect of Polymer and Cell Membrane Coatings on Theranostic Applications of Nanoparticles: A Review

The recent decade has witnessed a remarkable surge in the field of nanoparticles, from their synthesis, characterization, and functionalization to diverse applications. At the nanoscale, these particles exhibit distinct physicochemical properties compared to their bulk counterparts, enabling a multitude of applications spanning energy, catalysis, environmental remediation, biomedicine, and beyond. This review focuses on specific nanoparticle categories, including magnetic, gold, silver, and quantum dots (QDs), as well as hybrid variants, specifically tailored for biomedical applications. A comprehensive review and comparison of prevalent chemical, physical, and biological synthesis methods are presented. To enhance biocompatibility and colloidal stability, and facilitate surface modification and cargo/agent loading, nanoparticle surfaces are coated with different synthetic polymers and very recently, cell membrane coatings. The utilization of polymer- or cell membrane-coated nanoparticles opens a wide variety of biomedical applications such as magnetic resonance imaging (MRI), hyperthermia, photothermia, sample enrichment, bioassays, drug delivery, etc. With this review, the goal is to provide a comprehensive toolbox of insights into polymer or cell membrane-coated nanoparticles and their biomedical applications, while also addressing the challenges involved in translating such nanoparticles from laboratory benchtops to in vitro and in vivo applications. Furthermore, perspectives on future trends and developments in this rapidly evolving domain are provided.

Probing non-equilibrium inner structure of polymeric nanoparticle via aggregation-induced emission of luminogen

A molecular segregation inside a nanoparticle was crucial for its properties but usually hard to be determined, especially for organic particles. Herein, non-equilibrium polymeric nanoparticles loading a luminogen via an aggregation-induced emission (AIE) were prepared via an instant formation process, flash nanoprecipitation (FNP). Small organic molecules, polymeric excipients, and oily compounds were used as coprecipitants to reveal effects of conjugate moiety, glass transition temperature (Tg), and a condensed state of a coprecipitant on the fluorescence (FL) intensity of the suspension. The results indicated that the addition of a small molecule in a solid state without any conjugate moiety or a polymeric excipient with high Tg would facilitate enhancing the FL intensity, while a coprecipitant with a conjugate moiety or low Tg or in liquid would decrease the intensity. Moreover, this study revealed that the nanoparticle formed via FNP had a randomly packed inner structure where different compositions tended to evenly distribute inside rather than a micellar structure with a phase-separated core-shell one. These findings provided a guide to selecting a suitable coprecipitant for AIE-luminogen nanoparticles in applications. The developed probing method would also benefit for better understanding the particle formation kinetics in FNP.

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.

Integrated continuous manufacturing of inhalable remdesivir nanoagglomerate dry powders: Design, optimization and therapeutic potential for respiratory viral infections

While inhalable nanoparticle-based dry powders have demonstrated promising potential as next-generation respiratory medicines, erratic particle redispersibility and poor manufacturing reproducibility remain major hurdles hindering their translation from bench to bedside. We developed a one-step continuous process for fabricating inhalable remdesivir (RDV) nanoagglomerate dry powder formulations by integrating flash nanoprecipitation and spray drying. The nanosuspension formulation was optimized using a three-factor Box-Behnken design with a z-average particle size of 233.3 ± 2.3 nm and < 20% size change within six hours. The optimized inhalable nanoagglomerate dry powder formulation produced by spray drying showed adequate aqueous redispersibility (Sf/Si = 1.20 ± 0.01) and in vitro aerosol performance (mass median aerodynamic diameter of 3.80 ± 0.58 µm and fine particle fraction of 39.85 ± 10.16%). In A549 cells, RDV nanoparticles redispersed from the inhalable nanoagglomerate powders displayed enhanced and accelerated RDV cell uptake and negligible cytotoxicity at therapeutic RDV concentrations. No statistically significant differences were observed in the critical quality attributes of the inhalable nanoagglomerate powders produced from the continuous manufacturing and standalone batch modes. This work demonstrates the feasibility of large-scale continuous manufacturing of inhalable nanoagglomerate dry powder formulations, which pave the way for their clinical translation.

Formulation Approaches to Crystalline Status Modification for Carotenoids: Impacts on Dissolution, Stability, Bioavailability, and Bioactivities

Carotenoids, including carotenes and xanthophylls, have been identified as bioactive ingredients in foods and are considered to possess health-promoting effects. From a biopharmaceutical perspective, several physicochemical characteristics, such as scanty water solubility, restricted dissolution, and susceptibility to oxidation may influence their oral bioavailability and eventually, their effectiveness. In this review, we have summarized various formulation approaches that deal with the modification of crystalline status for carotenoids, which may improve their physicochemical properties, oral absorption, and biological effects. The mechanisms involving crystalline alteration and the typical methods for examining crystalline states in the pharmaceutical field have been included, and representative formulation approaches are introduced to unriddle the mechanisms and effects more clearly.

Organosilica-based deformable nanopesticides with enhanced insecticidal activity prepared by flash nanoprecipitation

A flash nanoprecipitation technique was developed for the construction of a novel type of deformable hollow organosilica nanoparticle for pesticide delivery.

Cell-mimetic biosensors to detect avian influenza virus via viral fusion

Avian influenza virus (AIV) causes acute infectious diseases in poultry, critically impacting food supply. Highly pathogenic avian influenza viruses (HPAIVs), in particular, cause morbidity and mortality, resulting in significant economic losses in the poultry industry. To prevent the spread of HPAIVs, detection at early stages is critical to implement effective countermeasures such as quarantine and isolation. Through a viral fusion mechanism, cell-mimetic nanoparticles (CMPs), developed in the current study, can rapidly detect HPAIV and low pathogenic AIV (LPAIV). The CMPs comprise polymeric nanoparticles, which are constructed using sialic acid and fluorescence resonance energy transfer (FRET) dye pairs that expose the FRET off signal in response to LPAIV and HPAIV, after activation by enzymatic cleavage in the endosomal environment. The CMPs detect a wide variety of LPAIVs and HPAIVs in biological environments. Additionally, the cross-reactivity of CMPs is determined by testing their function with different viral species. Therefore, these findings demonstrate the significant potential of the proposed strategy for mimicking viral infection in vitro and using them as a highly effective diagnostic assay to rapidly detect LPAIV and HPAIV, preventing economic losses associated with viral outbreaks.

Rapid Construction of Green Nanopesticide Delivery Systems Using Sophorolipids as Surfactants by Flash Nanoprecipitation

Green delivery carriers of nanopesticides, like sophorolipid biosurfactants, are of great significance to reduce environmental pollution and promote sustainable agricultural development. However, the molecular diversity of an unisolated sophorolipid mixture with almost unpredictable self-assembly properties has limited the in-depth study of its structure-activity relationship and hindered the development of green pesticide delivery systems. In this work, the acidic and lactonic sophorolipids were successfully separated from the sophorolipid mixture through silica gel column chromatography. A series of cost-effective green nanopesticides loaded with lambda-cyhalothrin (LC) were rapidly fabricated based on a combination of the acidic and lactonic sophorolipids as surfactants by flash nanoprecipitation. The effects of the acidic-to-lactonic ratio on particle size, drug loading capacity, and biological activity against Hyphantria cunea of LC-loaded nanoparticles were systematically investigated. The resultant nanopesticides exhibited a better insecticidal efficacy than a commercial emulsifiable concentrate formulation. This work opens up a novel strategy to construct scalable, cost-effective, and environmentally friendly nanopesticide systems.

Single-Step Self-Assembly of Zein–Honey–Chitosan Nanoparticles for Hydrophilic Drug Incorporation by Flash Nanoprecipitation

Zein- and chitosan-based nanoparticles have been described as promising carrier systems for food, biomedical and pharmaceutical applications. However, the manufacture of size-controlled zein and chitosan particles is challenging. In this study, an adapted anti-solvent nanoprecipitation method was developed. The effects of the concentration of zein and chitosan and the pH of the collection solution on the properties of the zein–honey–chitosan nanoparticles were investigated. Flash nanoprecipitation was demonstrated as a rapid, scalable, single-step method to achieve the self-assembly of zein–honey–chitosan nanoparticles. The nanoparticles size was tuned by varying certain formulation parameters, including the total concentration and ratio of the polymers. The zein–honey–chitosan nanoparticles’ hydrodynamic diameter was below 200 nm and the particles were stable for 30 days. Vitamin C was used as a hydrophilic model substance and efficiently encapsulated into these nanoparticles. This study opens a promising pathway for one-step producing zein–honey–chitosan nanoparticles by flash nanoprecipitation for hydrophilic compounds’ encapsulation.

High throughput onion-like liposome formation with efficient protein encapsulation under flash antisolvent mixing

Achieving a high encapsulation efficiency and loading capacity of proteins in lecithin-based liposomes has always been a challenge. Here, we use Flash Nano-Precipitation (FNP) to produce liposomes and investigated the encapsulation of model protein (Bovine Serum Albumin, BSA). Through rapid turbulent mixing, we obtained liposomes with small size, low polydispersity, and good batch repeatability at a high production rate. We demonstrated that the bilayer of liposomes prepared solely using lecithin was defective, which led to the fusion, and increased size and polydispersity. When cholesterol was added to reach a lecithin-to-cholesterol molar ratio of 5:3, a compact bilayer formed to effectively inhibit liposome fusion. The encapsulation efficiency and loading capacity of BSA was as high as ∼ 68% and ∼ 6% in lecithin-cholesterol liposome, respectively, far exceeding the values reported in the literature. Further study by Quartz Crystal Microbalance with Dissipation (QCM-D) revealed that the highly effective encapsulation was due to the rapid mutual adsorption between BSA and defective/curved lecithin double layers during the liposome formation. Such rapid mutual adsorption leads to the layer-by-layer assembly and formation of onion-like compact liposome structure as revealed by Cryo-TEM. This simple FNP method provides a scalable manufacturing approach for liposomes with efficient protein encapsulation. The revealed adsorption mechanism between protein and lecithin bilayers could also serve as a guide for similar studies.

Near Infrared Fluorescent Nanostructure Design for Organic/Inorganic Hybrid System

Near infrared (NIR) light offers high transparency in biological tissue. Recent advances in NIR fluorophores including organic dyes and lanthanide-doped inorganic nanoparticles have realized the effective use of the NIR optical window for in vivo bioimaging and photodynamic therapy. The narrow energy level intervals used for electronic transition that involves NIR light, however, give rise to a need for guidelines for reducing heat emission in luminescence systems, especially in the development of organic/inorganic hybrid structures. This review presents an approach for employing the polarity and vibrational energy of ions and molecules that surround the luminescence centers for the development of such hybrid nanostructures. Multiphonon relaxation theory, formulated for dealing with heat release in ionic solids, is applied to describe the vibrational energy in organic or molecular systems, referred to as phonon in this review, and we conclude that surrounding the luminescence centers either with ions with low vibrational energy or molecules with small chemical polarity is the key to bright luminescence. NIR photoexcited phosphors and nanostructures in organic/inorganic mixed systems, designed based on the guidelines, for photodynamic therapy are reviewed.

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.

Hydrophilic hindering and hydrophobic growing: a vesicle glycometabolism multi-drug combination therapeutic against Alzheimer's disease

Advanced drug vehicle exploitation and the sophisticated synergy mechanism revelation are two great difficulties in combination therapy. Compared with most readily available polymer micelles, some undiscovered complex chemical design principles limit the expanding research of polymer vesicles. Here, polycaprolactone (PCL)-g-Dextran vesicle that dextran brush steric hindrance guide PCL lamellae-aligned growth was synthesized. The effect of the glycometabolism multi-drug vesicle combination treatment and synergism mechanism were investigated on senescence-accelerated mouse prone 8 (SAMP8) mice. The main insulin sensitizer drug could improve the memory ability of mice to a small extent, and the main insulin secretion promoter drug had little beneficial effect. Moreover, the triple anti-insulin resistant drugs of insulin (INS), repaglinide (REP) and metformin hydrochloride (MET) activated the glycometabolism-related bio-signals, and the energy cycle was normalized successfully. The insulin intracellular uptake and utilization efficiency could be the reason for the gap. The upregulation of the brain-derived neurotrophic factor (BDNF) protein confirmed that the crosstalk between the mitochondria and synapse contributes to the nerve repair. This study provided an excellent drug combination vesicle to treat Alzheimer's disease (AD). The discovery of the combination mechanism leads to an improvement in the AD clinical treatment.

Confinement-Dependent Diffusiophoretic Transport of Nanoparticles in Collagen Hydrogels

The transport of nanoparticles in biological hydrogels is often hindered by the strong confinement of the media, thus limiting important applications such as drug delivery and disinfection. Here, we investigate nanoparticle transport in collagen hydrogels driven by diffusiophoresis. Contrary to common expectations for boundary confinement effects where the confinement hinders diffusiophoresis, we observe a nonmonotonic behavior in which maximum diffusiophoretic mobility is observed at intermediate confinement. We find that such behavior is a consequence of the interplay between multiple size-dependent effects. Our results display the utility of diffusiophoresis for enhanced nanoparticle transport in physiologically relevant conditions under tight confinement, suggesting a potential strategy for drug delivery in compressed tissues.

Formulation of tunable size PLGA-PEG nanoparticles for drug delivery using microfluidic technology

Amphiphilic block co-polymer nanoparticles are interesting candidates for drug delivery as a result of their unique properties such as the size, modularity, biocompatibility and drug loading capacity. They can be rapidly formulated in a nanoprecipitation process based on self-assembly, resulting in kinetically locked nanostructures. The control over this step allows us to obtain nanoparticles with tailor-made properties without modification of the co-polymer building blocks. Furthermore, a reproducible and controlled formulation supports better predictability of a batch effectiveness in preclinical tests. Herein, we compared the formulation of PLGA-PEG nanoparticles using the typical manual bulk mixing and a microfluidic chip-assisted nanoprecipitation. The particle size tunability and controllability in a hydrodynamic flow focusing device was demonstrated to be greater than in the manual dropwise addition method. We also analyzed particle size and encapsulation of fluorescent compounds, using the common bulk analysis and advanced microscopy techniques: Transmission Electron Microscopy and Total Internal Reflection Microscopy, to reveal the heterogeneities occurred in the formulated nanoparticles. Finally, we performed in vitro evaluation of obtained NPs using MCF-7 cell line. Our results show how the microfluidic formulation improves the fine control over the resulting nanoparticles, without compromising any appealing property of PLGA nanoparticle. The combination of microfluidic formulation with advanced analysis methods, looking at the single particle level, can improve the understanding of the NP properties, heterogeneities and performance.

Preparation of bioactive glass nanoparticles with highly and evenly doped calcium ions by reactive flash nanoprecipitation

Nanoscale bioactive glass particles have greater bioactivity than microscale bioactive glass particles, due to their high-specific surface area and fast ion release rate in body fluid. However, preparation of bioactive glass nanoparticles (BGNPs) is difficult since calcium is not easy to be highly doped into the forming silica atom network, leading to an uneven distribution and a low content of calcium. In addition, BGNPs are usually prepared in a dilute solution to avoid agglomeration of the nanoparticles, which decreases the production efficiency and increases the cost. In this work, BGNPs are prepared by a method of the reactive flash nanoprecipitation (RFNP) as well as a traditional sol-gel method. The results indicate that the BGNPs by the RFNP present a smaller size, narrower size distribution, more uniform composition, and better bioactivity than those by the traditional sol-gel method. The obtained BGNPs have uniform compositions close to the feed values. The high and even doping of calcium in the BGNPs is achieved. This successful doping of calcium into nanoparticles by the RFNP demonstrates a promising way to effectively generate high-quality BGNPs for bone repairs.

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.

Pyramid-Shaped PEG-PCL-PEG Polymeric-Based Model Systems for Site-Specific Drug Delivery of Vancomycin with Enhance Antibacterial Efficacy

Antibacterial resistance remains a major global problem due to frequent prescriptions, leading to significant toxicities. To overcome the limitations of antibiotic therapy, it is highly desirable to provide site-specific delivery of drugs with controlled release. Inspired by the biocompatible, biodegradable, and site-specific mimicking behavior of poly(ethylene glycol) (PEG) and poly(caprolactone) (PCL), we developed vancomycin-PEG-PCL-PEG conjugates to maximize the pharmacological effects and minimize the side effects. Drug-loaded vancomycin-PEG-PCL-PEG conjugates are influenced by size, shape, surface area, encapsulation efficiency, in vitro drug release, hemolysis assay, cytotoxicity, and antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA) and bacterial kill kinetics. The results demonstrated that vancomycin (VCM) release from PEG-PCL-PEG triblock revealed a biphasic manner. Hemolysis assay showed the nonprescription nature of VCM-PEG-PCL-PEG. Cytotoxicity studies confirmed the biocompatibility of VCM-PEG-PCL-PEG. The in vitro antibacterial results showed enhance activity with minimum inhibitory concentration compared to bare VCM. Molecular dynamics simulation study revealed that binding between VCM and PEG-PCL-PEG by hydrophobic interactions offers molecular encapsulation and steric barrier to drug degradation. This newly developed therapeutic delivery system can offer to enhance activity and delivery VCM against MRSA.

Simple Method to Supply Organic Nanoparticles with Excitation-Wavelength-Dependent Photoluminescence

Organic fluorescent nanoparticles (FNPs) have become increasingly prevalent in a variety of applications but the creation of organic FNPs using a simple procedure and that possess diverse morphology, multicolor luminescence, and high brightness has been challenging. Herein, a facile strategy to prepare this class of organic FNPs is established by way of preformed organic nanoparticles themselves. It was found that as long as the nanoparticles contained aromatic/heterocyclic rings in their base unit and regardless of morphologies (e.g., small-molecule micelles, polymeric micelles, reverse micelles, solid microspheres, and vesicles), simple UV irradiation can result in the particles exhibiting excitation-wavelength-dependent photoluminescence with considerable quantum yields (∼8.3-16.7% for tested particles). Upon initial investigation of the mechanism, the photoluminescence behavior was attributed to a polycyclic aromatic hydrocarbon (PAH) process. Furthermore, the application of the synthesized organic FNPs in cancer cell imaging is demonstrated as just one of the many potential applications. The straightforward method to supply preformed organic nanoparticles with photoluminescence would be attractive for scientists in both academia and industry.

Anti-tumor effect of PEG-coated PLGA nanoparticles of febuxostat on A549 non-small cell lung cancer cells

In the present study, febuxostat (FBX)-loaded PEG-coated PLGA nanoparticles (FBX-PLGA-PEG) were developed and its anticancer activity on lung cancer cells was evaluated. FBX-PLGA-PEG were prepared by nanoprecipitation technique and characterized for particle size, size distribution, entrapment efficiency, and in vitro drug release study. The optimized formulations were used to evaluate cell viability, apoptosis, cell cycle, and caspase activity in A549 lung cancer cells. The optimized formulation showed spherical particle with average particle size of 180 ± 4.72 nm, particle-size distribution 0.223 ± 0.003, entrapment efficiency (70 ± 2.56%), and drug release (99.1 ± 2.33%) at 12 h. MTT cytotoxicity assay showed better cytotoxic potential of FBX-NPs than FBX solution against NSCLC A549 cells. The lower IC50 of FBX-NP (52.62 ± 2.52 µg/mL) compared to FBX (68.0 ± 4.12 µg/mL) are suggestive of a potential cytotoxic effect of nano-formulation compared to the drug itself. Furthermore, flow cytometry analysis showed significantly higher percentage of total apoptotic cells in FBX-NPs (10.38 ± 1.57%) as compared to FBX solution (2.76 ± 0.17%) showed strong proapoptotic potential of FBX nano-formulation. The increased caspase activity and percent of cells at G2/M phase of cell cycle increased for FBX nanoparticles were more effective than FBX solution in increasing caspase activity and percent of cells at G2/M phase of cell cycle. Our studies with FBX nanoparticles exhibited promising outcome which could be used as a strategies to combat lung cancer.

Flash nanoprecipitation of ultra-small semiconducting polymer dots with size tunability

Small-sized semiconducting polymer dots (Pdots) provide better tissue and subcellular penetration while minimizing unspecific interactions, and make the fast clearance of Pdots from human bodies possible by urinary excretion. We employ a powerful and scalable technology, flash nanoprecipitation, to prepare Pdots with small sizes (hydrodynamic diameters ∼10 nm).

Nanoformulation-by-design: an experimental and molecular dynamics study for polymer coated drug nanoparticles

Experimental studies of drug–polymer nanoparticle formation combined with molecular dynamics simulations provide atomistic explanations for the high drug loadings obtained.

Rapid, Single-Step Protein Encapsulation via Flash NanoPrecipitation

Flash NanoPrecipitation (FNP) is a rapid method for encapsulating hydrophobic materials in polymer nanoparticles with high loading capacity. Encapsulating biologics such as proteins remains a challenge due to their low hydrophobicity (logP < 6) and current methods require multiple processing steps. In this work, we report rapid, single-step protein encapsulation via FNP using bovine serum albumin (BSA) as a model protein. Nanoparticle formation involves complexation and precipitation of protein with tannic acid and stabilization with a cationic polyelectrolyte. Nanoparticle self-assembly is driven by hydrogen bonding and electrostatic interactions. Using this approach, high encapsulation efficiency (up to ~80%) of protein can be achieved. The resulting nanoparticles are stable at physiological pH and ionic strength. Overall, FNP is a rapid, efficient platform for encapsulating proteins for various applications.

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.

Phthalocyanine photosensitizer in polyethylene glycol-block-poly(lactide-co-benzyl glycidyl ether) nanocarriers: Probing the contribution of aromatic donor-acceptor interactions in polymeric nanospheres

For best photosensitizer activity phthalocyanine dyes used in photodynamic therapy should be molecularly dispersed. Polyethylene glycol-block-polylactide derivatives presenting benzyl side-groups were synthesized to encapsulate a highly lipophilic phthalocyanine dye (AlClPc) and evaluate the effect of π-π interactions on the nanocarrier colloidal stability and dye dispersion. Copolymers with 0, 1, 2 and 6 mol% of benzyl glycidyl ether (BGE) were obtained via polyethylene glycol initiated ring-opening copolymerization of D,l-lactide with BGE. The block copolymers formed stable, monodisperse nanospheres with low in vitro cytotoxicity. AlClPc loading increased the nanosphere size and affected their colloidal stability. The photo-physical properties of the encapsulated dye, studied in batch and after separation by field flow fractionation, demonstrated the superiority of plain PEG-PLA over BGE-containing copolymers in maintaining the dye in its monomeric (non-aggregated) form in aqueous suspension. High dye encapsulation and sustained dye release suggest that these nanocarriers are good candidates for photodynamic therapy.

Application of an assay Cascade methodology for a deep preclinical characterization of polymeric nanoparticles as a treatment for gliomas

Glioblastoma multiforme (GBM) is the most devastating primary brain tumor due to its infiltrating and diffuse growth characteristics, a situation compounded by the lack of effective treatments. Currently, many efforts are being devoted to find novel formulations to treat this disease, specifically in the nanomedicine field. However, due to the lack of comprehensive characterization that leads to insufficient data on reproducibility, only a reduced number of nanomedicines have reached clinical phases. In this context, the aim of the present study was to use a cascade of assays that evaluate from physical-chemical and structural properties to biological characteristics, both in vitro and in vivo, and also to check the performance of nanoparticles for glioma therapy. An amphiphilic block copolymer, composed of polyester and poly(ethylene glycol; PEG) blocks, has been synthesized. Using a mixture of this copolymer and a polymer containing an active targeting moiety to the Blood Brain Barrier (BBB; Seq12 peptide), biocompatible and biodegradable polymeric nanoparticles have been prepared and extensively characterized. In vitro studies demonstrated that nanoparticles are safe for normal cells but cytotoxic for cancer cells. In vivo studies in mice demonstrated the ability of the Seq12 peptide to cross the BBB. Finally, in vivo efficacy studies using a human tumor model in SCID mice resulted in a significant 50% life-span increase, as compared with non-treated animals. Altogether, this assay cascade provided extensive pre-clinical characterization of our polymeric nanoparticles, now ready for clinical evaluation.

Preparation and Characterization of Size-Controlled Nanoparticles for High-Loading λ-Cyhalothrin Delivery through Flash Nanoprecipitation

Environmental concerns and low efficacy pose a challenge for the application of traditional insecticide formulations. In this study, a series of λ-cyhalothrin (LC)-loaded nanoparticles (NPs) were produced by flash nanoprecipitation (FNP), and the parameters that influence nanoparticle size were systematically studied. The narrowly distributed and size-controllable NPs formed stable suspensions in aqueous solution without organic solvents. The amphiphilic block polymer PEG-PDLLA played an important role as a drug carrier, and the encapsulation content was as high as 99%. The obtained NPs with high loading of LC exhibited toxicity comparable to those of two commercial formulations at low doses. This confirms that FNP technology is a promising and scalable method for agrochemical delivery.

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.

Spherical and Spindle-Like Abamectin-Loaded Nanoparticles by Flash Nanoprecipitation for Southern Root-Knot Nematode Control: Preparation and Characterization

Southern root-knot nematode (Meloidogyne incognita) is a biotrophic parasite, causing enormous loss in global crop production annually. Abamectin (Abm) is a biological and high-efficiency pesticide against Meloidogyne incognita. In this study, a powerful method, flash nanoprecipitation (FNP), was adopted to successfully produce Abm-loaded nanoparticle suspensions with high drug loading capacity (>40%) and encapsulation efficiency (>95%), where amphiphilic block copolymers (BCPs) poly(lactic-co-glycolic acid)-b-poly(ethylene glycol) (PLGA-b-PEG), poly(d,l-lactide)-b-poly(ethylene glycol) (PLA-b-PEG), or poly(caprolactone)-b-poly(ethylene glycol) (PCL-b-PEG) were used as the stabilizer to prevent the nanoparticles from aggregation. The effect of the drug-to-stabilizer feed ratio on the particle stability were investigated. Moreover, the effect of the BCP composition on the morphology of Abm-loaded nanoparticles for controlling Meloidogyne incognita were discussed. Notably, spindle-like nanoparticles were obtained with PCL-b-PEG as the stabilizer and found significantly more efficient (98.4% mortality at 1 ppm particle concentration) than spherical nanoparticles using PLGA-b-PEG or PLA-b-PEG as the stabilizer. This work provides a more rapid and powerful method to prepare stable Abm-loaded nanoparticles with tunable morphologies and improved effectiveness for controlling Meloidogyne incognita.

Photosensitizer-loaded nanoparticles: characterization and encapsulation efficiency

Amphiphilic diblock copolymers, methoxy poly(ethylene glycol)/poly(ε-caprolactone) (PECL), were synthesized by ring-opening polymerization of ε-caprolactone initiated by the hydroxyl groups of methoxy poly(ethylene glycol). The prepared PECL diblock copolymers were characterized using Fourier transform infrared spectroscopy, proton (1H) nuclear magnetic resonance spectroscopy, gel permeation chromatography, differential scanning calorimetry and wide-angle X-ray diffraction. Nanoparticles of these copolymers were prepared by the double-emulsification solvent evaporation method and were used to load methylene blue (MB) as a model drug photosensitizer. Scanning electron microscopy micrographs revealed that the unloaded nanoparticles were nearly spherical and had particle sizes ranging from 263 to 346 nm with relatively uniform size distribution. It was found that the hydrophobic block length of PECL nanoparticles was a crucial factor in controlling the size of MB-loaded nanoparticles and the encapsulation efficiency. The MB-loaded nanoparticles were irregular and not uniform and had a larger size that ranged from 304 to 367 nm. Moreover, MB encapsulation efficiency increased by about 30% with reducing content of the hydrophobic poly(ε-caprolactone) in PECL copolymer nanoparticles. The amphiphilic PECL nanoparticles in this study offer potential as alternative nanomaterial vehicles for MB aimed at photodynamic therapy applications.

Disulfiram-loaded mixed nanoparticles with high drug-loading and plasma stability by reducing the core crystallinity for intravenous delivery

To develop an injectable formulation and improve the stability of disulfiram (DSF), DSF was encapsulated into mixed nanoparticles (DSF-NPs) through a high-pressure homogenization method. The Flory-Huggins interaction parameters (χ_FH) were calculated to predict the miscibility between DSF and the hydrophobic core, resulting in PCL₅₀₀₀ selected as the hydrophobic block to encapsulate the DSF, as PCL₅₀₀₀ had a lower χ_FH 3.39 and the drug loading of the nanoparticles prepared by mPEG₅₀₀₀-PCL₅₀₀₀ was relatively higher. mPEG₅₀₀₀-PCL₅₀₀₀ and PCL₅₀₀₀ were blended to reduce the leakage of DSF during preparation, as well as increase the stability of the nanoparticles. The cargo-loading capacity of the nanoparticles was improved from 3.35% to 5.50% by reducing the crystallinity of the PCL nanoparticle core, and the crystallinity decreased from 51.13% to 25.15% after adding medium chain triglyceride (MCT). The DSF-NPs prepared by the above method had a small particle size of 98.1 ± 10.54 nm, with a polydispersity index (PDI) of 0.036, as well as drug loading of 5.50%. Furthermore, DSF-NPs containing MCT showed higher stability than DSF-NPs without MCT and DSF-sol (DSF dissolved in Cremophor EL and ethanol) in water and 90% plasma-containing PBS. The pharmacokinetics proved that DSF-NPs containing MCT enhanced the DSF concentration in the blood. Finally, DSF-NPs effectively inhibited H22 xenograft tumor growth in vivo.

Fabrication of Charge-Conversion Nanoparticles for Cancer Imaging by Flash Nanoprecipitation

Traditional charge-conversion nanoparticles (NPs) need the breakage of acid-labile groups on the surface, which impedes the rapid response to the acidic microenvironment. Here, we developed novel rodlike charge-conversion NPs with amphiphilic dextran- b-poly(lactic- co-glycolic acid), poly(2-(dimethylamino) ethylmethylacrylate)- b-poly(ε-caprolactone), and an aggregation-induced emission-active probe through flash nanoprecipitation (FNP). These NPs exhibit reversible negative-to-positive charge transition at a slightly acidic pH relying on the rapid protonation/deprotonation of polymers. The size and the critical charge-conversion pH can be further tuned by varying the flow rate and polymer ratio. Consequently, the charge conversion endows NPs with resistance to protein adsorption at physiological pH and enhanced internalization to cancer cells under acidic conditions. Ex vivo imaging on harvest organs shows that charge-conversion NPs were predominantly distributed in tumors after intravenous administration to mice due to the robust response of NPs to the acidic microenvironment in tumor tissue, whereas control NPs or free probes were broadly accumulated in tumor, liver, kidney, and lung. These results suggest the great potential of the current FNP strategy in the facile and generic fabrication of charge-conversion NPs for tumor-targeting delivery of drugs or fluorescent probes.

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.

Synthesis of Poly(lactic acid)-block-poly(N,N-dimethylaminoethyl methacrylate) Copolymers with Controllable Block Structures via Reversible Addition Fragmentation Polymerization from Aminolyzed Poly(lactic acid)

Poly(lactic acid)-block-poly(N,N-dimethylaminoethyl methacrylate) (PLA-PDMAEMA) copolymers were synthesized from aminolyzed PLA via reversible addition fragmentation (RAFT) polymerization. PLA undergoes aminolytic degradation with ethylenediamine (EDA). The kinetics of the aminolysis reaction of PLA at different temperatures and EDA concentrations was investigated in detail. The molar masses of products rapidly decreased in the initial stage at low aminolytic degree. Meanwhile, reactive –NH2 and –OH groups were introduced to the end of shorter PLA chains and used as sites to further immobilize the RAFT agent. PLA-PDMAEMA block copolymers were synthesized. A pseudo-first-order reaction kinetics was observed for the RAFT polymerization of PDMAEMA at a low conversion. By controlling the aminolysis reaction of PLA and RAFT polymerization degree of DMAEMA, the length distributions of the PLA and PDMAEMA blocks can be controlled. This method can be extended to more systems to obtain block copolymers with controllable block structure.