The in vivo fate of nanocrystals

Biological Fate Tracking of Nitric Oxide-Propelled Microneedle Delivery System Using an Aggregation-Caused Quenching Probe

Nanoparticle-loaded dissolving microneedles (DMNs) have attracted increasing attention due to their ability to provide high drug loading, adjustable drug release behavior, and enhanced therapeutic efficiency. However, such delivery systems still face unsatisfied drug delivery efficiency due to insufficient driving force to promote nanoparticle penetration and the lack of in vivo fate studies to guide formulation design. Herein, an aggregation-caused quenching (ACQ) probe (P4) was encapsulated in l-arginine (l-Arg)-based nanomicelles, which was further formulated into nitric oxide (NO)-propelled nanomicelle-integrated DMNs (P4/l-Arg NMs@DMNs) to investigate their biological fate. The P4 probe could emit intense fluorescence signals in intact nanomicelles, while quenching with the dissociation of nanomicelles, providing a "distinguishable" method for tracking the fate of nanomicelles at a different status. l-Arg was demonstrated to self-generate NO under the tumor microenvironment with excessive reactive oxygen species (ROS), providing a pneumatic force to promote the penetration of nanomicelles in both three-dimensional (3D)-cultured tumor cells and melanoma-bearing mice. Compared with passive microneedles (P4 NMs@DMNs) without a NO propellant, the P4/l-Arg NMs@DMNs possessed a good NO production performance and higher nanoparticle penetration capacity. In conclusion, this study offered an ACQ probe-based biological fate tracking approach to demonstrate the potential of NO-propelled nanoparticle-loaded DMNs in penetration enhancement for topical tumor therapy.

Recent advances in nanodelivery systems of resveratrol and their biomedical and food applications: a review

Resveratrol is a non-flavonoid polyphenolic compound with numerous functional properties, such as anticancer, anti-inflammation, anti-oxidation, anti-obesity and more. However, resveratrol's poor solubility within aqueous media and low stability usually lead to compromised bioavailability, ultimately limiting its uptake and applications. Nanodelivery technologies have been studied intensively due to their potential in effectively improving resveratrol properties, thereby providing promising solutions for enhancing the bioavailability of resveratrol. Thus, this article aimed to review the recent advances of resveratrol nanodelivery systems, specifically on the types of nanodelivery systems, the corresponding preparation principles, advantages, as well as potential limitations associated. Meanwhile, studies have also found that coupled with nanodelivery systems, the functional properties of resveratrol could trigger apoptosis in cancer cells and inflammatory cells through various signaling pathways. Therefore, this article will also lead into discussions on the application aspects of resveratrol nanodelivery systems, emphasizing toward the fields of biomedical and food sciences. Potential pitfalls of resveratrol nanodelivery systems, such as issues with toxicity and target release, as well as outlooks regarding resveratrol nanodelivery systems are included in the Conclusion section, in the hope to provide insights for relevant future research.

Organic solvent-free benznidazole nanosuspension as an approach to a novel pediatric formulation for Chagas disease

Aim: Benznidazole (BNZ), a class-II drug, is the primary treatment for Chagas disease, but its low aqueous solubility presents challenges in formulation and efficacy. Nanosuspensions (NS) could potentially address these issues.Methods: BNZ-NS were prepared using a simple, organic solvents-free nano-milling approach. Physicochemical characterizations were conducted on both NS and lyophilized solid-state BNZ-nanocrystals (NC).Results: BNZ-NS exhibited particle size <500 nm, an acceptable polydispersity index (0.23), high Z-potential, and physical stability for at least 90 days. BNZ-NC showed tenfold higher solubility than pure BNZ. Dissolution assays revealed rapid BNZ-NS dissolution. BNZ-NC demonstrated biocompatibility on an eukaryotic cell and enhanced BNZ efficacy against trypomastigotes of Trypanosoma cruzi.Conclusion: BNZ-NS offers a promising alternative, overcoming limitations associated with BNZ for optimized pharmacotherapy.

Eudragit L100-coated nintedanib nanocrystals improve oral bioavailability by reducing drug particle size and maintaining drug supersaturation

The aim of this study was to prepare nintedanib nanocrystals (BIBF-NCs) to lower the solubility of the drug in the stomach, maintain the supersaturation of the drug in the intestine, and improve the oral absorption of nintedanib (BIBF). In this study, BIBF-NCs were prepared by acid solubilization and alkaline precipitation following nano granding method, with a particle size of 290.80 nm and a zeta potential of -49.13 mV. Subsequently, Nintedanib enteric-coated nanocrystals (BIBF-NCs@L100) were obtained by coating with Eudragit L100. The microscopic morphology, crystalline characteristics, stability, and in vitro dissolution of BIBF-NCs and BIBF-NCs@L100 were also studied. In addition, the in vivo pharmacokinetic behaviors of Samples prepared according to the prescription process of commercially available soft capsules (soft capsules), BIBF-NCs, and BIBF-NCs@L100 were further investigated. The results showed that the oral bioavailability of BIBF-NCs and BIBF-NCs@L100 were increased by 1.43 and 2.58 times, compared with that of the soft capsules. BIBF-NCs@L100 effectively reduced the release of BIBF in the formulation in the stomach, allowing more drug to reach the intestine in the form of nanocrystals, maintaining the supersaturation in the intestine, thereby improving the oral bioavailability of the drug.

Folic Acid-Decorated Nanocrystals as Highly Loaded Trojan Horses to Target Cancer Cells

The nanocrystal (NC) technology has become one of the most commonly used strategies for the formulation of poorly soluble actives. Given their large specific surface, NCs are mainly used to enhance the oral absorption of poorly soluble actives. Differently from conventional nanoparticles, which require the use of carrier materials and have limited drug loadings, NCs' drug loading approaches 100% since they are formed of the pure drug and surrounded by a thin layer of a stabilizer. In this work, we report the covalent decoration of curcumin NCs with folic acid (FA) using EDC/NHS chemistry and explore the novel systems as highly loaded "Trojan horses" to target cancer cells. The decorated NCs demonstrated a remarkable improvement in curcumin uptake, exhibiting enhanced growth inhibition in cancer cells (HeLa and MCF7) while sparing healthy cells (J774A.1). Cellular uptake studies revealed significantly heightened entry of FA-decorated NCs into cancer cells compared to unmodified NCs while also showing reduced uptake by macrophages, indicating a potential for prolonged circulation in vivo. These findings underline the potential of NC highly loaded nanovectors for drug delivery and, in particular, for cancer therapies, effectively targeting folate receptor-overexpressing cells while evading interception by macrophages, thus preserving their viability and offering a promising avenue for precise and effective treatments.

Therapeutic potential of natural flavonoids in pulmonary arterial hypertension: A review

BACKGROUND

Pulmonary arterial hypertension (PAH) is a fatal disease caused by pulmonary vascular remodeling, with a high incidence and mortality. At present, many clinical drugs for treating PAH mainly exert effects by relaxing the pulmonary artery, with limited therapeutic effects, so the search for viable therapeutic agents continues uninterrupted. In recent years, natural flavonoids have shown promising potential in the treatment of cardiovascular diseases. It is necessary to comprehensively elucidate the potential of natural flavonoids to combat PAH.

PURPOSE

To evaluate the potential of natural flavonoids to hinder or slow down the occurrence and development of PAH, and to identify promising drug discovery candidates.

METHODS

Literature was collected from PubMed, Science Direct, Web of science, CNKI databases and Google scholar. The search terms used included "pulmonary arterial hypertension", "pulmonary hypertension", "natural products", "natural flavonoids", "traditional chinese medicine", etc., and several combinations of these keywords.

RESULTS

The resources, structural characteristics, mechanisms, potential and prospect strategies of natural flavonoids for treating PAH were summarized. Natural flavonoids offer different solutions as possible treatments for PAH. These mechanisms may involve various pathways and molecular targets related to the pathogenesis of PAH, such as inflammation, oxidative stress, vascular remodeling, genetic, ion channels, cell proliferation and autophagy. In addition, prospect strategies of natural flavonoids for anti-PAH including structural modification and nanomaterial delivery systems have been explored. This review suggests that the potential of natural flavonoids as alternative therapeutic agents in the prevention and treatment of PAH holds promise for future research and clinical applications.

CONCLUSION

Despite displaying the enormous potential of flavonoids in PAH, some limitations need to be further explored. Firstly, using advanced drug discovery tools, including computer-aided design and high-throughput screening, to further investigate the safety, biological activity, and precise mechanism of action of flavonoids. Secondly, exploring the structural modifications of these compounds is expected to optimize their efficacy. Lastly, it is necessary to conduct well controlled clinical trials and a comprehensive evaluation of potential side effects to determine their effectiveness and safety.

Lipid-coated nanocrystals of paclitaxel as dry powder for inhalation: Characterization, in-vitro performance, and pharmacokinetic assessment

BACKGROUND

Nanocrystals can be produced as a dry powder for inhalation (DPIs) to deliver high doses of drug to the lungs, owing to their high payload and stability to the shear stress of aerosolization force. Furthermore, lipid-coated nanocrystals can be formulated to improve the drug accumulation and retention in lung.

OBJECTIVE

The present work involved the fabrication of paclitaxel nanocrystals using hydrophilic marine biopolymer fucoidan as a stabilizer. Thereafter, fabricated nanocrystals (FPNC) were surface-modified with phospholipid to give lipid-coated nanocrystals (Lipo-NCs).

METHODS

The nanocrystals were fabricated by antisolvent crystallization followed by the probe sonication. The lipid coating was achieved by thin film hydration followed ultrasonic dispersion technique. Prepared nanocrystals were lyophilized to obtain a dry powder of FPNC and Lipo-NCs, used later for physicochemical, microscopic, and spectroscopic characterization to confirm the successful formation of desired nanocrystals. In-vitro and in-vivo investigations were also conducted to determine the role of nanocrystal powder in pulmonary drug delivery.

RESULTS

Lipo-NCs exhibited slower drug release, excellent flow properties, good aerosolization performance, higher drug distribution, and prolonged retention in the lungs compared to FPNC and pure PTX.

CONCLUSION

Lipid-coated nanocrystals can be a novel formulation for the maximum localization of drugs in the lungs, thereby enhancing therapeutic effects and avoiding systemic side effects in lung cancer therapy.

Nanomedicines against Chagas disease: a critical review

Chagas disease (CD) is the most important endemic parasitosis in South America and represents a great socioeconomic burden for the chronically ill and their families. The only currently available treatment against CD is based on the oral administration of benznidazole, an agent, developed in 1971, of controversial effectiveness on chronically ill patients and toxic to adults. So far, conventional pharmacological approaches have failed to offer more effective and less toxic alternatives to benznidazole. Nanomedicines reduce toxicity and increase the effectiveness of current oncological therapies. Could nanomedicines improve the treatment of the neglected CD? This question will be addressed in this review, first by critically discussing selected reports on the performance of benznidazole and other molecules formulated as nanomedicines in in vitro and in vivo CD models. Taking into consideration the developmental barriers for nanomedicines and the degree of current technical preclinical efforts, a prospect of developing nanomedicines against CD will be provided. Not surprisingly, we conclude that structurally simpler formulations with minimal production cost, such as oral nanocrystals and/or parenteral nano-immunostimulants, have the highest chances of making it to the market to treat CD. Nonetheless, substantive political and economic decisions, key to facing technological challenges, are still required regarding a realistic use of nanomedicines effective against CD.

Nanocrystal technologies in biomedical science: From the bench to the clinic

The pharmaceutical industry is grappling with a pressing crisis in drug development characterized by soaring R&D costs, setbacks in blockbuster drug development due to poor aqueous solubility, and patent-related limitations on newly approved molecules. To combat these challenges, diverse strategies have emerged to enhance the solubility and dissolution rates of Biopharmaceutics Classification System (BCS) II and IV drug molecules. Enter drug nanocrystals, a revolutionary nanotechnology-driven, carrier-free colloidal drug delivery system. This review provides a comprehensive insight into nanocrystal strategies, stabilizer selection criteria, preparation methods, advanced characterization techniques, the evolving nanocrystal technological landscape, current market options, and exciting clinical prospects for reshaping the future of pharmaceuticals.

Progress of Drug Nanocrystal Self-Stabilized Pickering Emulsions: Construction, Characteristics In Vitro, and Fate In Vivo

A drug nanocrystal self-stabilized Pickering emulsion (DNSPE) is a novel Pickering emulsion with drug nanocrystals as the stabilizer. As a promising drug delivery system, DNSPEs have attracted increasing attention in recent years due to their high drug loading capacity and ability to reduce potential safety hazards posed by surfactants or specific solid particles. This paper comprehensively reviews the progress of research on DNSPEs, with an emphasis on the main factors influencing their construction, characteristics and measurement methods in vitro, and fate in vivo, and puts forward issues that need to be studied further. The review contributes to the advancement of DNSPE research and the promotion of their application in the field of drug delivery.

Drug Nanocrystals: A Delivery Channel for Antiviral Therapies

Viral infections represent a significant threat to global health due to their highly communicable and potentially lethal nature. Conventional antiviral interventions encounter challenges such as drug resistance, tolerability issues, specificity concerns, high costs, side effects, and the constant mutation of viral proteins. Consequently, the exploration of alternative approaches is imperative. Therefore, nanotechnology-embedded drugs excelled as a novel approach purporting severe life-threatening viral disease. Integrating nanomaterials and nanoparticles enables ensuring precise drug targeting, improved drug delivery, and fostered pharmacokinetic properties. Notably, nanocrystals (NCs) stand out as one of the most promising nanoformulations, offering remarkable characteristics in terms of physicochemical properties (higher drug loading, improved solubility, and drug retention), pharmacokinetics (enhanced bioavailability, dose reduction), and optical properties (light absorptivity, photoluminescence). These attributes make NCs effective in diagnosing and ameliorating viral infections. This review comprises the prevalence, pathophysiology, and resistance of viral infections along with emphasizing on failure of current antivirals in the management of the diseases. Moreover, the review also highlights the role of NCs in various viral infections in mitigating, diagnosing, and other NC-based strategies combating viral infections. In vitro, in vivo, and clinical studies evident for the effectiveness of NCs against viral pathogens are also discussed.

New Insights into Pharmaceutical Nanocrystals for the Improved Topical Delivery of Therapeutics in Various Skin Disorders

Nanotechnology has provided nanostructure-based delivery of drugs, among which nanocrystals have been investigated and explored for feasible topical drug delivery. Nanocrystals are nano-sized colloidal carriers, considered pure solid particles with a maximum drug load and a very small amount of stabilizer. The size or mean diameter of the nanocrystals is less than 1 μm and has a crystalline character. Prominent synthesis methods include the utilization of microfluidic- driven platforms as well as the milling approach, which is both adaptable and adjustable. Nanocrystals have shown a high capacity for loading drugs, utilization of negligible amounts of excipients, greater chemical stability, lower toxic effects, and ease of scale-up, as well as manufacturing. They have gained interest as drug delivery platforms, and the significantly large surface area of the skin makes it a potential approach for topical therapeutic formulations for different skin disorders including fungal and bacterial infections, psoriasis, wound healing, and skin cancers, etc. This article explores the preparation techniques, applications, and recent patents of nanocrystals for treating various skin conditions.

Nanoparticle-based Gene Therapy for Neurodegenerative Disorders

Neurological disorders present a formidable challenge in modern medicine due to the intricate obstacles set for the brain and the multipart nature of genetic interventions. This review article delves into the promising realm of nanoparticle-based gene therapy as an innovative approach to addressing the intricacies of neurological disorders. Nanoparticles (NPs) provide a multipurpose podium for the conveyance of therapeutic genes, offering unique properties such as precise targeting, enhanced stability, and the potential to bypass blood-brain barrier (BBB) restrictions. This comprehensive exploration reviews the current state of nanoparticle-mediated gene therapy in neurological disorders, highlighting recent advancements and breakthroughs. The discussion encompasses the synthesis of nanoparticles from various materials and their conjugation to therapeutic genes, emphasizing the flexibility in design that contributes to specific tissue targeting. The abstract also addresses the low immunogenicity of these nanoparticles and their stability in circulation, critical factors for successful gene delivery. While the potential of NP-based gene therapy for neurological disorders is vast, challenges and gaps in knowledge persist. The lack of extensive clinical trials leaves questions about safety and potential side effects unanswered. Therefore, this abstract emphasizes the need for further research to validate the therapeutic applications of NP-mediated gene therapy and to address nanosafety concerns. In conclusion, nanoparticle-based gene therapy emerges as a promising avenue in the pursuit of effective treatments for neurological disorders. This abstract advocates for continued research efforts to bridge existing knowledge gaps, unlocking the full potential of this innovative approach and paving the way for transformative solutions in the realm of neurological health.

Intravenous nanocrystals: fabrication, solidification, in vivo fate, and applications for cancer therapy

INTRODUCTION

Intravenous nanocrystals (INCs) have shown intrinsic advantages in antitumor applications, particularly their properties of high drug loading, low toxicity, and controllable size. Therefore, it has a very bright application prospect as a drug delivery system.

AREAS COVERED

The ideal formulation design principles, fabrication, solidification, in vivo fate of INCs, the applications in drug delivery system (DDS) and the novel applications are covered in this review.

EXPERT OPINION

It is vital to select a suitable formulation and fabrication method to produce a stable and sterile INCs. Besides, the type of stabilizers and physical characteristics can also influence the in vivo fate of INCs, which is worthy of further studying. Based on wide researches about applications of INCs in cancer, biomimetic INCs are concerned increasingly for its favorable compatibility. The output of these studies suggested that INCs-based drug delivery could be a novel strategy for addressing the delivery of the drug that faces solubility, bioavailability, and toxicity problems.

Research progress on the preparation and application of flavonoid nanocrystals

Flavonoids have been reported to possess significant pharmacological activities,such as antioxidant, anti-inflammatory and anticancer effects. However, the low solubility and low bioavailability limits their clinical application. Nanocrystal technology can solve the delivery problems of flavonoids by reducing particle size, increasing the solubility of insoluble drugs and improving their bioavailability. This article summaries nanosuspension preparation methods and the stabilizers for flavonoid nanocrystals, and reviews the drug delivery routes including oral, Injection and transdermal of flavonoid nanocrystals, to provide information for further research on nanocrystal delivery system of flavonoids.

Nanocrystals in cosmetics and cosmeceuticals by topical delivery

The main issues with local delivery of cosmetics are their high sensitivity and limited drug loading of active pharmaceutical ingredient. Nanocrystal technology offers consumers cutting-edge and effective products and exhibits enormous development potential in the beauty business as a new delivery method to address the issue of low solubility and low permeability of sensitive chemicals. In this review, we described the processes for making NCs, along with the impacts of loading and the uses of different carriers. Among them, nanocrystalline loaded gel and emulsion are widely used and may further improve the stability of the system. Then, we introduced the beauty efficacy of drug NCs from five aspects: anti-inflammation and acne, anti-bacterial, lightening and freckle removal, anti-aging as well as UV protection. Following that, we presented the current scenario about stability and safety. Finally, the challenges and vacancy were discussed along with the potential uses of NCs in the cosmetics industry. This review serves as a resource for the advancement of nanocrystal technology in the cosmetics sector.

Pickering Emulsions Enhance Oral Bioavailability of Curcumin Nanocrystals: The Effect of Oil Types

Nanocrystals (NCs) have the potential to enhance the oral bioavailability of Class IV drugs in the Biopharmaceutical Classification System (BCS) due to the absorption of the intact crystals. The performance is compromised by the dissolution of NCs. Drug NCs have recently been adopted as solid emulsifiers to prepare nanocrystal self-stabilized Pickering emulsions (NCSSPEs). They are advantageous in high drug loading and low side effects due to the specific drug loading mode and the absence of chemical surfactants. More importantly, NCSSPEs may further enhance the oral bioavailability of drug NCs by impeding their dissolution. This is especially true for BCS IV drugs. In this study, curcumin (CUR), a typical BCS IV drug, was adopted to prepare CUR-NCs stabilized Pickering emulsions using either indigestible (isopropyl palmitate, IPP) or digestible (soybean oil, SO) oils, i.e., IPP-PEs and SO-PEs. The optimized formulations were spheric with CUR-NCs adsorbed on the water/oil interface. The CUR concentration in the formulation reached 20 mg/mL, which was far beyond the solubility of CUR in IPP (158.06 ± 3.44 μg/g) or SO (124.19 ± 2.40 μg/g). Moreover, the Pickering emulsions enhanced the oral bioavailability of CUR-NCs, being 172.85% for IPP-PEs and 152.07% for SO-PEs. The digestibility of the oil phase affected the amounts of CUR-NCs that remained intact in lipolysis and, thus, the oral bioavailability. In conclusion, converting NCs into Pickering emulsions provides a novel strategy to enhance the oral bioavailability of CUR and BCS IV drugs.

Recent advances in bioactive nanocrystal-stabilized Pickering emulsions: Fabrication, characterization, and biological assessment

Numerous literatures have shown the advantages of Pickering emulsion (PE) for the delivery of bioactive ingredients in the fields of food, medicine, and cosmetics, among others. On this basis, the multi-loading mode of bioactives (internal phase encapsulation and/or loading at the interface) in small molecular bioactives nanocrystal-stabilized PE (BNC-PE) enables them higher loading efficiencies, controlled release, and synergistic or superimposed effects. Therefore, BNC-PE offers an efficacious delivery system. In this review, we briefly summarize BNC-PE fabrication and characterization, with a focus on the processes of possible evolution and absorption of differentially applied BNC-PE when interacting with the body. In addition, methods of monitoring changes and absorption of BNC-PE in vivo, from the nanomaterial perspective, are also introduced. The purpose of this review is to provide an accessible and comprehensive methodology for the characterization and evaluation of BNC-PE after formulation and preparation, especially in relation to biological assessment and detailed mechanisms throughout the absorption process of BNC-PE in vivo.

Exploring the translocation behaviours in vivo of herpetrione amorphous nanoparticles via oral delivery

Nanotechnology has been a primary strategy to enhance oral bioavailability of poorly water soluble drugs. However, the limited information in vivo fate of impedes the development of nanoparticles via the oral delivery, especially the amorphous nanoparticles with high energy states are rarely reported. This study is to track the translocation of oral herpetrione amorphous nanoparticles (HPE-ANPs). We prepare amorphous particles (ANPs) of various sizes (200 nm and 450 nm), which are embedded with an aggregation-caused quenching (ACQ) dyes for tracking the intact nanoparticles. Nanoparticles remain in the gastrointestinal tract (GIT) for 8 h following oral administration, suggesting that most ANPs was mainly degraded or absorbed in the small intestine. Ex vivo imaging shows that the fluorescent signals are observed in the GIT and liver but not in other organs, which attributed to low absorption of integral nanoparticles. Besides, HPE-ANPs may be directly interact with GIT epithelia, and ileum provides better absorption than the jejunum. Cellular studies prove that integral HPE-ANPs can be taken up by enterocyte, while it penetrates cell monolayers only small amounts. In conclusion, we speculate that the drug in the form of integral nanoparticles and small molecules may be co-absorbed to improve bioavailability in vivo.

Tacrolimus nanocrystals microneedle patch for plaque psoriasis

Plaque psoriasis is characterized by an abnormal thickening of the epidermis, which causes great difficulties for traditional topical drug delivery. Microneedles can pierce the thickened epidermis and deliver drugs to the skin for psoriasis treatment. Tacrolimus is a poorly water-soluble immunosuppressant used for the treatment of psoriasis. In this study, tacrolimus (TAC) nanocrystals (NCs) were produced using a bottom-up technique that dispersed TAC into a sodium hyaluronate-based microneedle patch (MNP), and its therapeutic efficacy was evaluated. The average particle size of the TAC NCs was 259.6 ± 2.3 nm. The mechanical strength of the microneedles was 0.41 ± 0.06 N/needle, which was sufficient to penetrate psoriatic skin. Microneedles were detached from the substrate 10 min after insertion into the psoriasis skin with an insertion depth of 258.8 ± 14.4 μm. The intradermal retention of the MNP (8.40 ± 0.33 μg/cm²) was six times that of the commercial ointment (1.40 ± 0.12 μg/cm²). In pharmacodynamic experiments, results indicated improvement in the phenotypic and histopathological features and reduction in the level of TNF-α, IL-17A, and IL-23 of psoriatic skin treated with TAC NCs MNP. Therefore, MNP loaded with TAC NCs may be a promising approach for psoriasis treatment.

Biological and Intracellular Fates of Drug Nanocrystals through Different Delivery Routes: Recent Development Enabled by Bioimaging and PK Modeling

Nanocrystals have contributed to exciting improvements in the delivery of poorly water-soluble drugs. The biological and intracellular fates of nanocrystals are currently under debate. Due to the remarkable commercial success in enhancing oral bioavailability, nanocrystals have originally been regarded as a simple formulation approach to enhance dissolution. However, the latest findings from novel bioimaging tools lead to an expanded view. Intact nanocrystals may offer long-term durability in the body and offer drug delivery capabilities like those of other nano-carriers. This review renews the understanding of the biological fates of nanocrystals administered via oral, intravenous, and parenteral (e.g., dermal, ocular, and pulmonary) routes. The intracellular pathways and dissolution kinetics of nanocrystals are explored. Additionally, the future trends for in vitro and in vivo quantification of nanocrystals, as well as factors impacting the biological and intracellular fates of nanocrystals are discussed. In conclusion, nanocrystals present a promising and underexplored therapeutic opportunity with immense potential.

Benefits and limitations of nanomedicine treatment of brain cancers and age-dependent neurodegenerative disorders

The treatment of central nervous system (CNS) malignancies, including brain cancers, is limited by a number of obstructions, including the blood-brain barrier (BBB), the heterogeneity and high invasiveness of tumors, the inaccessibility of tissues for early diagnosis and effective surgery, and anti-cancer drug resistance. Therapies employing nanomedicine have been shown to facilitate drug penetration across the BBB and maintain biodistribution and accumulation of therapeutic agents at the desired target site. The application of lipid-, polymer-, or metal-based nanocarriers represents an advanced drug delivery system for a growing group of anti-cancer chemicals. The nanocarrier surface is designed to contain an active ligand (cancer cell marker or antibody)-binding structure which can be modified to target specific cancer cells. Glioblastoma, ependymoma, neuroblastoma, medulloblastoma, and primary CNS lymphomas were recently targeted by easily absorbed nanocarriers. The metal- (such as transferrin drug-loaded systems), polymer- (nanocapsules and nanospheres), or lipid- (such as sulfatide-containing nanoliposomes)-based nano-vehicles were loaded with apoptosis- and/or ferroptosis-stimulating agents and demonstrated promising anti-cancer effects. This review aims to discuss effective nanomedicine approaches designed to overcome the current limitations in the therapy of brain cancers and age-dependent neurodegenerative disorders. To accent current obstacles for successful CNS-based cancer therapy, we discuss nanomedicine perspectives and limitations of nanodrug use associated with the specificity of nervous tissue characteristics and the effects nanocarriers have on cognition.

The Effect of Particle Size on the Absorption of Cyclosporin A Nanosuspensions

Background

Cyclosporin A (CsA) is a hydrophobic drug widely used as an immunosuppressant and anti-rejection drug in solid organ transplantation. On the market, there are two oral CsA formulations available containing polyoxyethylene castor oil, which can cause serious allergic reactions and nephrotoxicity. In order to eliminate polyoxyethylene castor oil, CsA was formulated into a nanosuspension. This study aimed to design an oral cyclosporin A nanosuspensions (CsA-NSs) and investigate the effect of particle size on absorption of CsA-NSs.

Methods

CsA-NSs were prepared using a wet bead milling method. Particle size, morphology and crystallinity state of CsA-NSs were characterized. The in vitro dissolution, the intestinal absorption properties and pharmacokinetic study of CsA-NSs were investigated.

Results

CsA-NSs with sizes of 280 nm, 522 nm and 2967 nm were prepared. The shape of CsA-NSs with smaller size was similar to that of spheres. The crystallinity of CsA in nanocrystals was reduced. The dissolution rate of CsA-NSs (280 nm) was greater than that of CsA-NSs (522 nm) and CsA-NSs (2967 nm). CsA-NSs (280 nm) showed higher absorption rate constants (K_α) and effective permeability coefficients (P_eff) of different intestinal segments compared with that of CsA-NSs (522 nm) and CsA-NSs (2967 nm). AUC_0-48h of 280 nm CsA-NSs was about 1.12-fold of that of 522 nm CsA-NSs, and about 1.51-fold of that of 2967 nm CsA-NSs. In particular, the particle size of CsA-NSs was nanoscale, and their bioavailability was bioequivalent with marked self-microemulsion (Sandimmun Neoral^®).

Conclusion

It is feasible to prepare CsA-NSs. The dissolution rate, gastrointestinal transport properties and the oral absorption of CsA-NSs were promoted by reducing size. Considering the cost, efficiency and energy consumption, there should be an optimal particle size range in industrial production.

The Evaluation of Meloxicam Nanocrystals by Oral Administration with Different Particle Sizes

Meloxicam (MLX) is a non-steroidal anti-inflammatory drug used to treat rheumatoid arthritis and osteoarthritis. However, its poor water solubility limits the dissolution process and influences absorption. In order to solve this problem and improve its bioavailability, we prepared it in nanocrystals with three different particle sizes to improve solubility and compare the differences between various particle sizes. The nanocrystal particle sizes were studied through dynamic light scattering (DLS) and laser scattering (LS). Transmission electron microscopy (TEM) was used to characterize the morphology of nanocrystals. The sizes of meloxicam-nanocrystals-A (MLX-NCs-A), meloxicam-nanocrystals-B (MLX-NCs-B), and meloxicam-nanocrystals-C (MLX-NCs-C) were 3.262 ± 0.016 μm, 460.2 ± 9.5 nm, and 204.9 ± 2.8 nm, respectively. Molecular simulation was used to explore the distribution and interaction energy of MLX molecules and stabilizer molecules in water. The results of differential scanning calorimetry (DSC) and powder X-ray diffraction (PXRD) proved that the crystalline state did not change in the preparation process. Transport studies of the Caco-2 cell model indicated that the cumulative degree of transport would increase as the particle size decreased. Additionally, plasma concentration-time curves showed that the AUC0-∞ of MLX-NCs-C were 3.58- and 2.92-fold greater than those of MLX-NCs-A and MLX-NCs-B, respectively. These results indicate that preparing MLX in nanocrystals can effectively improve the bioavailability, and the particle size of nanocrystals is an important factor in transmission and absorption.

Resveratrol and its nanocrystals: A promising approach for cancer therapy?

There has been a significant research interest in nanocrystals as a promising technology for improving the therapeutic efficacy of poorly water-soluble drugs, such as resveratrol. Little is known about the interaction of nanocrystals with biological tissue. The aim of this study was to investigate the potential use of resveratrol (RSV) and its nanocrystals (NANO-RSV) as antitumor agents in Ehrlich ascites tumour (EAT)-bearing mice and the interaction of nanocrystals with biological tissue through biochemical and histological changes of kidney, liver and EAT cells. After intraperitoneal injection of 2.5 × 10⁶ cells into the abdominal cavity of mice, treatment of animals was started next day by injecting RSV or NANO-RSV at a dose of either 25 or 50 mg/kg every other day for 14 days. The results show that the administration of resveratrol and its nanocrystals lead to significant reductions in the proliferation of tumour cells in the abdominal cavity, and a reduction of the number of blood vessels in the peritoneum, with low systemic toxicity. In histopathological examinations, greater hepatocellular necrosis and apoptosis, hepatic fibrosis around the central vein and degeneration with minor fatty change were observed with RSV than with NANO-RSV. Inflammation with proximal tubular necrosis and renal glomerulus swelling were also observed, together with slight elevation of several biochemical parameters in both the RSV and NANO-RSV groups. In order to increase the beneficial effects and reduce risks associated with resveratrol nanocrystals, additional factors such as dose, genetic factors, health status, and the nature of the target cells should also be considered.

Nanocrystal-Loaded Micelles for the Enhanced In Vivo Circulation of Docetaxel

Prolonging in vivo circulation has proved to be an efficient route for enhancing the therapeutic effect of rapidly metabolized drugs. In this study, we aimed to construct a nanocrystal-loaded micelles delivery system to enhance the blood circulation of docetaxel (DOC). We employed high-pressure homogenization to prepare docetaxel nanocrystals (DOC(Nc)), and then produced docetaxel nanocrystal-loaded micelles (DOC(Nc)@mPEG-PLA) by a thin-film hydration method. The particle sizes of optimized DOC(Nc), docetaxel micelles (DOC@mPEG-PLA), and DOC(Nc)@mPEG-PLA were 168.4, 36.3, and 72.5 nm, respectively. The crystallinity of docetaxel was decreased after transforming it into nanocrystals, and the crystalline state of docetaxel in micelles was amorphous. The constructed DOC(Nc)@mPEG-PLA showed good stability as its particle size showed no significant change in 7 days. Despite their rapid dissolution, docetaxel nanocrystals exhibited higher bioavailability. The micelles prolonged the retention time of docetaxel in the circulation system of rats, and DOC(Nc)@mPEG-PLA exhibited the highest retention time and bioavailability. These results reveal that constructing nanocrystal-loaded micelles may be a promising way to enhance the in vivo circulation and bioavailability of rapidly metabolized drugs such as docetaxel.

Pharmaceutical nanocrystals: A promising approach for improved topical drug delivery

The barrier function of skin and non-optimal physicochemical properties of drug present a challenge to skin penetration of many drugs, thus motivating the development of novel drug delivery systems. Recently, nanocrystal-based formulations have been investigated for topical drug delivery and demonstrated improved skin penetration. This review highlights barriers in skin penetration, current techniques to improve topical delivery and application of nanocrystals in conquering obstacles for topical delivery. Nanocrystals can improve delivery through the skin by mechanisms like higher concentration gradient across skin resulting in increased passive diffusion, hair follicle targeting, diffusional corona and adhesion to skin. This would be of interest for formulation scientists for product development of molecules that are 'difficult-to-deliver' topically.

Intracellular uptake of nanocrystals: Probing with aggregation-induced emission of fluorescence and kinetic modeling

Nanocrystal formulations have been explored to deliver poorly water-soluble drug molecules. Despite various studies of nanocrystal formulation and delivery, much more understanding needs to be gained into absorption mechanisms and kinetics of drug nanocrystals at various levels, ranging from cells to tissues and to the whole body. In this study, nanocrystals of tetrakis (4-hydroxyphenyl) ethylene (THPE) with an aggregation-induced emission (AIE) property was used as a model to explore intracellular absorption mechanism and dissolution kinetics of nanocrystals. Cellular uptake studies were conducted with KB cells and characterized by confocal microscopy, flow cytometry, and quantitative analyses. The results suggested that THPE nanocrystals could be taken up by KB cells directly, as well as in the form of dissolved molecules. The cellular uptake was found to be concentration- and time-dependent. In addition, the intracellular THPE also could be exocytosed from cells in forms of dissolved molecules and nanocrystals. Kinetic modeling was conducted to further understand the cellular mechanism of THPE nanocrystals based on first-order ordinary differential equations (ODEs). By fitting the kinetic model against experimental measurements, it was found that the initial nanocrystal concentration had a great influence on the dynamic process of dissolution, cellular uptake, and exocytosis of THPE nanocrystals. As the nanocrystal concentration increased in the culture media, dissolution of endocytosed nanocrystals became enhanced, subsequently driving the efflux of THPE molecules from cells.

•

Nanocrystals of Tetrakis(4-hydroxyphenyl) ethylene (THPE), an aggregation-induced emission (AIE) probe was used as a model.

•

THPE nanocrystals could be taken up in forms of dissolved molecules and nanocrystals.

•

The dynamic process of dissolution, cellular uptake, and exocytosis of THPE nanocrystals was concentration-dependent.

•

Exocytosis of intracellular THPE-NCs bore different kinetics and/or mechanisms compared with endocytosis.

The contribution of absorption of integral nanocrystals to enhancement of oral bioavailability of quercetin

In this study, self-discriminating hybrid nanocrystals was utilized to explore the biological fate of quercetin hybrid nanocrystals (QT-HNCs) with diameter around 280 nm (QT-HNCs-280) and 550 nm (QT-HNCs-550) following oral and intravenous administration and the contribution of integral nanocrystals to oral bioavailability enhancement of QT was estimated by comparing the absolute exposure of integral QT-HNCs and total QT in the liver. Results showed that QT-HNCs could reside in vivo as intact nanocrystals for as long as 48 h following oral and intravenous administration. A higher accumulation of integral QT-HNCs in liver and lung was observed for both oral and intravenous administration of QT-HNCs. The particle size affects the absorption and biodistribution of integral QT-HNCs and total QT. As compared to QT-HNCs-550, QT-HNCs-280 with smaller particle size is more easily absorbed, but dissolves faster in vivo, leading to higher distribution of QT (146.90 vs. 117.91 h·μg/mL) but lower accumulation of integral nanocrystals (6.8 2e10 vs. 15.27e10 h·[p/s]/[µW/cm²]) in liver following oral administration. Due to its slower dissolution and enhanced recognition by RES, QT-HNCs-550 with larger diameter shows higher liver distribution for both of QT (1015.80 h·μg/mL) and integral nanocrystals (259.63e10 h·[p/s]/[µW/cm²]) than those of QT-HNCs-280 (673.82 & 77.66e10 h·[p/s]/[µW/cm²]) following intravenous administration. The absolute exposure of integral QT-HNCs in liver following oral administration of QT-HNCs are 8.78% for QT-HNCs-280 and 5.88% for QT-HNCs-550, while the absolute exposure of total QT for QT-HNCs-280 and QT-HNCs-550 are 21.80% and 11.61%, respectively. Owing to imprecise quantification method, a surprisingly high contribution of integral QT-HNCs to oral bioavailability enhancement of QT (40.27% for QT-HNCs-280 and 50.65% for QT-HNCs-550) was obtained. These results revealed significant difference in absorption and biodistrbution between integral nanocrystals and overall drugs following oral and intravenous administration of QT-HNCs, and provided a meaningful reference for the contribution of integral nanocrystals to overall bioavailability enhancement.

Folic Acid and Poly(ethylene glycol) Decorated Paclitaxel Nanocrystals Exhibit Enhanced Stability and Breast Cancer-Targeting Capability

In part because of their high drug loading, nanocrystals (NCs) have seen extensive use in drug delivery, particularly for insoluble or poorly soluble drugs. It remains a challenge, however, to prepare stable nanocrystals with tumor-targeting capability. Here, we designed a novel preparation of stable paclitaxel (PTX) nanocrystals with efficient active tumor-targeting properties. PTX NC was prepared using a bottom-up method and modified with both poly(ethylene glycol) (PEG) and folic acid (FA) derivatives using film hydration. The resulting PTX NC@lipid-PEG-FA had a rodlike shape, with hydrodynamic diameters and drug loading values of 201.90 ± 2.92 nm and 31.07 ± 3.41%, respectively. The size of the PTX NC@lipid-PEG-FA was unchanged after 168 h in the presence of plasma, whereas nonmodified paclitaxel nanocrystals (PTX NC) exceeded 600 nm within 12 h under the same conditions. Cellular uptake and cellular growth inhibition experiments in 4T1 breast cancer cells showed the superiority of PTX NC@lipid-PEG-FA over PTX NC or PEGylated paclitaxel nanocrystals without FA modification (PTX NC@lipid-PEG). A pharmacokinetic evaluation in rats revealed that PTX NC@lipid-PEG-FA significantly prolonged the circulation of PTX in the bloodstream, in comparison with PTX NC or Taxol. Tissue distribution and in vivo antitumor studies in 4T1 orthotopic breast cancer-bearing nude mice showed that PTX NC@lipid-PEG-FA significantly increased the intratumor accumulation of PTX and efficiently inhibited tumor growth, in comparison with PTX NC@lipid-PEG, PTX NC, or Taxol. In summary, PTX NC@lipid-PEG-FA showed good potential for breast cancer-targeted delivery for insoluble therapeutics.

Utility of Pickering emulsions in improved oral drug delivery

Pickering emulsions are surfactant-free emulsions stabilized by solid particles. Their unique structure endows them with good stability, excellent biocompatibility, and environmental friendliness. Pickering emulsions have displayed great potential in oral drug delivery. Several-fold increases in the oral bioavailability or bioaccessibility of poorly soluble drugs, such as curcumin, silybin, puerarin, and rutin, were achieved by using Pickering emulsions, whereas controlled release was found for indomethacin and caffeine. The shell of the interfacial particle stabilizers provides enhanced gastrointestinal stability to the cargos in the oil core. Here, we also discuss general considerations concerning particle stabilizers and design strategies to control lipid digestion.

Deliver Anti-inflammatory Drug Baicalein to Macrophages by Using a Crystallization Strategy

Macrophages are potent to modulate inflammation via phenotypic switch and production of inflammatory factors. Baicalein (BCL) is frequently used to alleviate inflammation; however, its application is always hindered due to low solubility. Herein, BCL nanocrystals (BNRs) were prepared to improve its delivery to macrophages. The prepared BNRs have a diameter of 150 nm with a rod-like structure. The nanocrystals could be well-taken up by macrophages via the caveolar pathway and, therefore, promote the polarization switch from proinflammatory phenotype to anti-inflammatory macrophages and alleviate the inflammation via reducing production cytokine IL-12. In conclusion, the crystallization strategy is promising for the improvement of the solubility of BCL and promotion of its anti-inflammatory activities.

Impacts of particle size on the cytotoxicity, cellular internalization, pharmacokinetics and biodistribution of betulinic acid nanosuspensions in combined chemotherapy

To evaluate the effect of particle size on the cellular internalization, tissue distribution, and bioavailability of betulinic acid nanosuspensions (BA/NSs) and further investigate the combined effect of BA/NSs and Taxol® on breast cancer, BA/NSs with different particle sizes (160 nm, 400 nm, and 700 nm) were prepared by an efficient universal green technology. The use of BA/NS (160 nm) was more likely to increase the BA release rate and enhance bioavailability compared with the use of larger size particles. BA/NSs were internalized by 4T1 cells in different ways, including clathrin-mediated endocytosis, caveolae-mediated endocytosis, and macropinocytosis. For the 4T1 orthotopic tumor model, BA/NS (160 nm) showed a tendency to accumulate at a higher level in tumor tissue. Moreover, combination therapy with BA/NSs and Taxol® showed remarkable potential to enhance antitumor activity in vitro and in vivo. The cytotoxicity and apoptotic ability of the different preparations decreased in the following order: BA/NS (160 nm) + Taxol®, BA/NS (400 nm) + Taxol®, and BA/NS (700 nm) + Taxol®. The tumor inhibition rates of BA/NSs (160 nm, 400 nm, and 700 nm) combined with Taxol® were 2.35-, 1.74- and 1.12-fold higher than that of free BA, respectively. The combined chemotherapy showed good safety, indicating that it had the effect of enhancing treatment and reducing toxicity.

Enhanced transdermal delivery of curcumin nanosuspensions: A mechanistic study based on co-localization of particle and drug signals

Nanosuspensions have received much attention in enhanced transdermal delivery. However, the corresponding mechanisms have not been clarified. In particular, whether nanosuspensions can directly penetrate across the stratum corneum (SC) and what is the transdermal route for the enhanced penetration. Therefore, curcumin (CUR) was adopted in this study as a model drug, while an aggregation-caused quenching (ACQ) probe was physically embedded in CUR nanosuspensions, i.e., the CUR hybrid nanosuspensions (CUR-HNSs), for bioimaging. The ACQ properties enable identification of intact CUR-HNSs. The co-localization of particle and CUR signals was exploited to outline the translocation profiles of intact nanosuspensions as well as the cargoes. Three sizes of CUR-HNSs are prepared, which are spherical and amorphous. CUR is poor in transdermal transport even in propylene glycol solution, which was enhanced by nanosuspensions. Although 400 nm CUR-HNSs present higher steady state flux than 140 nm and 730 nm ones, the cumulative amount of permeated CUR is yet less than 2% of the applied dose at 12 h. Co-localization of CUR and ACQ probe signals indicates that CUR-HNSs can infiltrate into the SC layer and accumulate in the hair follicles. The intact CUR-HNSs cannot enter into the skin. On the contrary, CUR molecules diffuse into the whole skin tissues following dissolution of CUR-HNSs in the SC and the hair follicles. In conclusion, nanosuspensions are advantageous for transdermal delivery of poorly permeable drugs by filtrate into the SC and accumulate in hair follicles.

Enhancement of oral bioavailability and anti-Parkinsonian efficacy of resveratrol through a nanocrystal formulation

Resveratrol (RES), a non-flavonoid polyphenol extracted from a wide variety of plants, exhibits neuroprotective activities against Parkinson's disease (PD). However, undesirable water solubility of RES reduces its oral bioavailability and demonstrates low efficacy in blood and brain, thus limiting its application. In present study, a nanocrystal formulation of RES (RES-NCs) was developed to enhance its oral bioavailability and delivery into brain for PD treatment. RES-NCs were fabricated with hydroxypropyl methylcellulose (HPMC) stabilizer via antisolvent precipitation approach. The obtained RES-NCs displayed the particle size of 222.54 ± 1.66 nm, the PDI of 0.125 ± 0.035, the zeta potential of -9.41 ± 0.37 mV, and a rapid in vitro dissolution rate. Molecular dynamics simulation of RES and HPMC revealed an interaction energy of -68.09 kJ/mol and a binding energy of -30.98 ± 0.388 kJ/mol, indicating that the spontaneous binding between the two molecules is through van der Waals forces. RES-NCs conferred enhanced cellular uptake as well as improved permeability relative to pure RES. In addition, RES-NCs were able to protect neurons against cytotoxicity induced by MPP+. Meanwhile, RES-NCs exerted no significant toxic effects on zebrafish embryos and larvae, and did not influence their survival and hatching rates. When orally administered to rats, RES-NCs exhibited more favorable pharmacokinetics than pure RES, with higher plasma and brain concentrations. More importantly, MPTP-induced PD mice showed notable improvements in behavior, attenuated dopamine deficiency, and elevated levels of dopamine and its metabolites after the treatment with RES-NCs. Furthermore, immunoblot analysis revealed that the neuroprotective role of RES-NCs may be at least partially mediated by Akt/Gsk3β signaling pathway. Taken altogether, RES-NCs can serve as a potential treatment modality for PD, offering means of improving RES oral bioavailability and brain accumulation.

Ricobendazole nanocrystals obtained by media milling and spray drying: Pharmacokinetic comparison with the micronized form of the drug

Helminthic infections are produced by different types of worms and affect millions of people worldwide. Benzimidazole compounds such as ricobendazole (RBZ) are widely used to treat helminthiasis. However, their low aqueous solubility leads to poor gastrointestinal dissolution, absorption and potential lack of efficacy. The formulation of nanocrystals (NCs) have become the strategy of preference for hydrophobic drugs. In this work, we prepared RBZ NCs (RBZ-NCs) by an optimized combination of bead milling and spray-drying. Following the physicochemical characterization, a comparative pharmacokinetic evaluation of RBZ-NCs was performed in dogs using as controls a micronized powdered form of RBZ (mRBZ) and a physical mixture of drug and stabilizer 1:1 (PM). The particle size of the redispersed RBZ-NCs was 181.30 ± 5.93 nm, whereas DSC, PXRD and FTIR analyses demonstrated that the active ingredient RBZ remained physicochemically unchanged after the manufacture process. RBZ-NCs exhibited improved in vitro biopharmaceutical behaviour when compared to mRBZ. Consequently, the pharmacokinetic trial demonstrated a significant increase in the drug oral absorption, with an AUC_0-∞ 1.9-fold higher in comparison to that obtained in animals treated with mRBZ. This novel formulation holds substantial potential for the development of new/alternative treatments for helminth infections both in human and veterinary medicine.

Nano Encapsulated Curcumin: And Its Potential for Biomedical Applications

Curcumin, a yellow-colored polyphenol extracted from the rhizome of turmeric root, is commonly used as a spice and nutritional supplement. It exhibits many pharmacological activities such as anti-inflammatory, anti-bacterial, anti-cancer, anti-Alzheimer, and anti-fungal. However, the therapeutic application of curcumin is limited by its extremely low solubility in aqueous buffer, instability in body fluids, and rapid metabolism. Nano delivery system has shown excellent potential to improve the solubility, biocompatibility and therapeutic effect of curcumin. In this review, we focus on the recent development of nano encapsulated curcumin and its potential for biomedical applications.

Novel Drug Delivery Systems for Loading of Natural Plant Extracts and Their Biomedical Applications

Many types of research have distinctly addressed the efficacy of natural plant metabolites used for human consumption both in cell culture and preclinical animal model systems. However, these in vitro and in vivo effects have not been able to be translated for clinical use because of several factors such as inefficient systemic delivery and bioavailability of promising agents that significantly contribute to this disconnection. Over the past decades, extraordinary advances have been made successfully on the development of novel drug delivery systems for encapsulation of plant active metabolites including organic, inorganic and hybrid nanoparticles. The advanced formulas are confirmed to have extraordinary benefits over conventional and previously used systems in the manner of solubility, bioavailability, toxicity, pharmacological activity, stability, distribution, sustained delivery, and both physical and chemical degradation. The current review highlights the development of novel nanocarrier for plant active compounds, their method of preparation, type of active ingredients, and their biomedical applications.

What is the future for nanocrystal-based drug-delivery systems?

Nanocrystals are used as a drug-delivery platform for poorly water-soluble drugs and have had commercial success in oral drug delivery. We assert that the future of this technique is with cancer treatment and in the development of parenteral preparations. Advances in techniques for uniform and high-quality nanocrystals as well as deciphering the in vivo fate of nanocrystals are critical. The bottom-up technique allows for better control of particle properties, while the hybrid nanocrystal technique provides a novel approach to explore the in vivo fate of nanocrystals. Breakthroughs in these two techniques to further the development of nanocrystals are also discussed.

Fabrication of Fine Puerarin Nanocrystals by Box-Behnken Design to Enhance Intestinal Absorption

Puerarin is widely used as a therapeutic agent to cardiovascular diseases in clinics in China through intravenous administration, which could elicit adverse drug reactions caused by cosolvents, hindering its application in clinics. Therefore, the development of oral dosage is urgently needed. In our previous studies, we proved that the bioavailability of puerarin increased as particle sizes of nanocrystals decreased; however, we have not optimized the best process parameters for nanocrystals. In this study, we aim to fabricate fine nanocrystals (with smallest particle size) by Box-Behnken design and study the intestinal permeability of puerarin and its nanocrystals via employing everted gut sac model and in situ perfusion model. The results showed that the Box-Behnken design could be used to optimize the producing parameters of puerarin nanocrystals, and the particle sizes of fine nanocrystals were about 20 nm. Results of everted gut sacs showed that the polyvinylpyrrolidone (PVP) and verapamil had no influence on the absorption of puerarin and nanocrystals, and the nanocrystals could increase the P_app of puerarin for 2.2-, 2.9-, and 2.9-folds, respectively, in duodenum, jejunum, and ileum. Enhanced Ka and Peff were observed on the nanocrystal group, compared with puerarin, and PVP and verapamil had no influence on the absorption of nanocrystals, while the absorption of puerarin was influenced by P-gp efflux. Combining the results mentioned above, we can conclude that the Box-Behnken design benefits the optimization for preparation of nanocrystals, and the nanocrystals could enhance the intestinal absorption of puerarin by enhanced permeability and inhibited P-gp efflux.

Advanced modification of drug nanocrystals by using novel fabrication and downstream approaches for tailor-made drug delivery

Drug nanosuspensions/nanocrystals have been recognized as one useful and successful approach for drug delivery. Drug nanocrystals could be further decorated to possess extended functions (such as controlled release) and designed for special in vivo applications (such as drug tracking), which make best use of the advantages of drug nanocrystals. A lot of novel and advanced size reduction methods have been invented recently for special drug deliveries. In addition, some novel downstream processes have been combined with nanosuspensions, which have highly broadened its application areas (such as targeting) besides traditional routes. A large number of recent research publication regarding as nanocrystals focuses on above mentioned aspects, which have widely attracted attention. This review will focus on the recent development of nanocrystals and give an overview of regarding modification of nanocrystal by some new approaches for tailor-made drug delivery.

Nanotechnology for Medical and Surgical Glaucoma Therapy-A Review

Glaucoma is the second leading cause of blindness worldwide. Even though significant advances have been made in its management, currently available antiglaucoma therapies suffer from considerable drawbacks. Typically, the success and efficacy of glaucoma medications are undermined by their limited bioavailability to target tissues and the inadequate adherence demonstrated by patients with glaucoma. The latter is due to a gradual decrease in tolerability of lifelong topical therapies and the significant burden to patients of prescribed stepwise antiglaucoma regimens with frequent dosing which impact quality of life. On the other hand, glaucoma surgery is restricted by the inability of antifibrotic agents to efficiently control the wound healing process without causing severe collateral damage and long-term complications. Evolution of the treatment paradigm for patients with glaucoma will ideally include prevention of retinal ganglion cell degeneration by the successful delivery of neurotrophic factors, anti-inflammatory drugs, and gene therapies. Nanotechnology-based treatments may surpass the limitations of currently available glaucoma therapies through optimized targeted drug delivery, increased bioavailability, and controlled release. This review addresses the recent advances in glaucoma treatment strategies employing nanotechnology, including medical and surgical management, neuroregeneration, and neuroprotection.

Species differences in ocular pharmacokinetics and pharmacological activities of regorafenib and pazopanib eye-drops among rats, rabbits and monkeys

Age-related macular degeneration (AMD) is the leading cause of severe vision impairment in patients over the age of 60 years. Choroidal neovascularization (CNV) is the hallmark of neovascular AMD and vascular endothelial growth factor (VEGF) plays a causal role in the formation of CNV. Although regorafenib and pazopanib, small molecule VEGF receptor (VEGFR) inhibitors, were developed as eye-drops, their efficacies were insufficient in clinical. In this study, we evaluated ocular pharmacokinetics and pharmacological activities of regorafenib and pazopanib after ocular instillation in multiple animal species. In rats, both regorafenib and pazopanib showed high enough concentrations in the posterior eye tissues to inhibit VEGFR. In laser-induced rat CNV model, regorafenib showed clear reduction in CNV area. On the other hand, the concentrations of regorafenib and pazopanib in the posterior eye tissues were much lower after ocular instillation in rabbits and monkeys compared to those in rats. Pazopanib did not show any improvement in monkey model. Regorafenib was nano-crystalized to improve its drug delivery to the posterior eye tissues. The nano-crystalized formulation of regorafenib showed higher concentrations in the posterior segments in rabbits compared to its microcrystal suspension. From these studies, large interspecies differences were found in ocular delivery to the posterior segments after ocular instillation. Such large interspecies difference could be the reason for the insufficient efficacies of regorafenib and pazopanib in clinical studies. Nano-crystallization was suggested to be one of the effective ways to overcome this issue.