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

Drug Nanocrystals in Oral Absorption: Factors That Influence Pharmacokinetics

Despite the safety and convenience of oral administration, poorly water-soluble drugs compromise absorption and bioavailability. These drugs can exhibit low dissolution rates, variability between fed and fasted states, difficulty permeating the mucus layer, and P-glycoprotein efflux. Drug nanocrystals offer a promising strategy to address these challenges. This review focuses on the opportunities to develop orally administered nanocrystals based on pharmacokinetic outcomes. The impacts of the drug particle size, morphology, dissolution rate, crystalline state on oral bioavailability are discussed. The potential of the improved dissolution rate to eliminate food effects during absorption is also addressed. This review also explores whether permeation or dissolution drives nanocrystal absorption. Additionally, it addresses the functional roles of stabilizers. Drug nanocrystals may result in prolonged concentrations in the bloodstream in some cases. Therefore, nanocrystals represent a promising strategy to overcome the challenges of poorly water-soluble drugs, thus encouraging further investigation into unclear mechanisms during oral administration.

Shielding against breast tumor relapse with an autologous chemo-photo-immune active Nano-Micro-Sera based fibrin implant

Local recurrence post-surgery in early-stage triple-negative breast cancer is a major challenge. To control the regrowth of a residual tumor, we have developed an autologous therapeutic hybrid fibrin glue for intra-operative implantation. Using autologous serum proteins as stabilizers, we have optimized high drug-loaded lapatinib-NanoSera (Lap-NS; ∼66% L.C.) and imiquimod-MicroSera (IMQ-MS; ∼92% L.C). Additionally, plasmonic nanosera (PNS) with an ∼67% photothermal conversion efficiency under 980 nm laser irradiation was also developed. While localized monotherapy with either Lap-NS or PNS reduced the tumor regrowth rate, their combination with IMQ-MS amplified the effect of immunogenic cell death with a high level of tumor infiltration by immune cells at the surgical site. The localized combination immunotherapy with a Nano-MicroSera based hybrid fibrin implant showed superior tumor inhibition and survival with significant promise for clinical translation.

Julolidinyl aza-BODIPYs as NIR-II fluorophores for the bioimaging of nanocarriers

The aggregation-caused quenching (ACQ) rationale has been employed to improve the fluorescence imaging accuracy of nanocarriers by precluding free probe-derived interferences. However, its usefulness is undermined by limited penetration and low spatiotemporal resolution of NIR-I (700-900 nm) bioimaging owing to absorption and diffraction by biological tissues and tissue-derived autofluorescence. This study aimed to develop ACQ-based NIR-II (1000-1700 nm) probes to further improve the imaging resolution and accuracy. The strategy employed is to install highly planar and electron-rich julolidine into the 3,5-position of aza-BODIPY based on the larger substituent effects. The newly developed probes displayed remarkable photophysical properties, with intense absorption centered at approximately 850 nm and bright emission in the 950-1300 nm region. Compared with the NIR-I counterpart P2, the NIR-II probes demonstrated superior water sensitivity and quenching stability. ACQ1 and ACQ6 exhibited more promising ACQ effects with absolute fluorescence quenching at water fractions above 40% and higher quenching stability with less than 2.0% fluorescence reillumination in plasma after 24 h of incubation. Theoretical calculations verified that molecular planarity is more important than hydrophobicity for ACQ properties. Additionally, in vivo and ex vivo reillumination studies revealed less than 2.5% signal interference from prequenched ACQ1, in contrast to 15% for P2.

Recent developments in the use of nanocrystals to improve bioavailability of APIs

Nanocrystals refer to materials with at least one dimension smaller than 100 nm, composing of atoms arranged in single crystals or polycrystals. Nanocrystals have significant research value as they offer unique advantages over conventional pharmaceutical formulations, such as high bioavailability, enhanced targeting selectivity and controlled release ability and are therefore suitable for the delivery of a wide range of drugs such as insoluble drugs, antitumor drugs and genetic drugs with broad application prospects. In recent years, research on nanocrystals has been progressively refined and new products have been launched or entered the clinical phase of studies. However, issues such as safety and stability still stand that need to be addressed for further development of nanocrystal formulations, and significant gaps do exist in research in various fields in this pharmaceutical arena. This paper presents a systematic overview of the advanced development of nanocrystals, ranging from the preparation approaches of nanocrystals with which the bioavailability of poorly water-soluble drugs is improved, critical properties of nanocrystals and associated characterization techniques, the recent development of nanocrystals with different administration routes, the advantages and associated limitations of nanocrystal formulations, the mechanisms of physical instability, and the enhanced dissolution performance, to the future perspectives, with a final view to shed more light on the future development of nanocrystals as a means of optimizing the bioavailability of drug candidates. This article is categorized under: Therapeutic Approaches and Drug Discovery > Emerging Technologies Nanotechnology Approaches to Biology > Nanoscale Systems in Biology.

Hepatic-Accumulated Obeticholic Acid and Atorvastatin Self-Assembled Nanocrystals Potentiate Ameliorative Effects in Treatment of Metabolic-Associated Fatty Liver Disease

Exploration of medicines for efficient and safe management of metabolic-associated fatty liver disease (MAFLD) remains a challenge. Obeticholic acid (OCA), a selective farnesoid X receptor agonist, has been reported to ameliorate injury and inflammation in various liver diseases. However, its clinical application is mainly limited by poor solubility, low bioavailability, and potential side effects. Herein a hepatic-targeted nanodrugs composed of OCA and cholesterol-lowering atorvastatin (AHT) with an ideal active pharmaceutical ingredient (API) content for orally combined treatment of MAFLD is created. Such carrier-free nanocrystals (OCAHTs) are self-assembled, not only improving the stability in gastroenteric environments but also achieving hepatic accumulation through the bile acid transporter-mediated enterohepatic recycling process. Orally administrated OCAHT outperforms the simple combination of OCA and AHT in ameliorating of liver damage and inflammation in both acetaminophen-challenged mice and high-fat diet-induced MAFLD mice with less systematic toxicity. Importantly, OCAHT exerts profoundly reverse effects on MAFLD-associated molecular pathways, including impairing lipid metabolism, reducing inflammation, and enhancing the antioxidation response. This work not only provides a facile bile acid transporter-based strategy for hepatic-targeting drug delivery but also presents an efficient and safe full-API nanocrystal with which to facilitate the practical translation of nanomedicines against MAFLD.

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.

Herbal Medicine Nanocrystals: A Potential Novel Therapeutic Strategy

Herbal medicines have gained recognition among physicians and patients due to their lower adverse effects compared to modern medicines. They are extensively used to treat various diseases, including cancer, cardiovascular issues, chronic inflammation, microbial contamination, diabetes, obesity, and hepatic disorders, among others. Unfortunately, the clinical application of herbal medicines is limited by their low solubility and inadequate bioavailability. Utilizing herbal medicines in the form of nanocrystals (herbal medicine nanocrystals) has shown potential in enhancing solubility and bioavailability by reducing the particle size, increasing the specific surface area, and modifying the absorption mechanisms. Multiple studies have demonstrated that these nanocrystals significantly improve drug efficacy by reducing toxicity and increasing bioavailability. This review comprehensively examines therapeutic approaches based on herbal medicine nanocrystals. It covers the preparation principles, key factors influencing nucleation and polymorphism control, applications, and limitations. The review underscores the importance of optimizing delivery systems for successful herbal medicine nanocrystal therapeutics. Furthermore, it discusses the main challenges and opportunities in developing herbal medicine nanocrystals for the purpose of treating conditions such as cancer, inflammatory diseases, cardiovascular disorders, mental and nervous diseases, and antimicrobial infections. In conclusion, we have deliberated regarding the hurdles and forthcoming outlook in the realm of nanotoxicity, in vivo kinetics, herbal ingredients as stabilizers of nanocrystals, and the potential for surmounting drug resistance through the utilization of nanocrystalline formulations in herbal medicine. We anticipate that this review will offer innovative insights into the development of herbal medicine nanocrystals as a promising and novel therapeutic strategy.

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.

High Drug Loading Nanoparticles Stabilized with Autologous Serum Proteins Passively Inhibits Tumor Growth

We report drug nanocrystals stabilized with host-specific serum proteins with high loading (∼63% w/w). The human serum derived curcumin nanoparticles (Cur-NanoSera) showed superior in vitro anticancer efficiency compared to a free drug with substantial hemocompatibility. The preadsorbed protein coating impeded further protein corona formation, even with repeated serum exposures. Acute and subacute toxicity evaluations post single and dual injections of C57BL/6 mice indicated that Cur-NanoSera showed no prominent inflammatory response or organ damage in the in-bred mice. Passive accumulation of Cur-NanoSera in tumor tissue significantly suppressed its growth in a syngeneic breast tumor model in addition to controlling tumor burden associated splenomegaly.

Advances in biomaterials for the treatment of retinoblastoma

Retinoblastoma is the most common primary intraocular malignancy in children. Although traditional chemotherapy has shown some success in retinoblastoma management, there are several shortcomings to this approach, including inadequate pharmacokinetic parameters, multidrug resistance, low therapeutic efficiency, nonspecific targeting, and the need for adjuvant therapy, among others. The revolutionary developments in biomaterials for drug delivery have enabled breakthroughs in cancer management. Today, biomaterials are playing a crucial role in developing more efficacious retinoblastoma treatments. The key goal in the evolution of drug delivery biomaterials for retinoblastoma therapy is to resolve delivery-associated obstacles and lower nonlocal exposure while ameliorating certain adverse effects. In this review, we will first delve into the historical perspective of retinoblastoma with a focus on the classical treatments currently used in clinics to enhance patients' quality of life and survival rate. As we move along, we will discuss biomaterials for drug delivery applications. Various aspects of biomaterials for drug delivery will be dissected, including their features and recent advances. In accordance with the current advances in biomaterials, we will deliver a synopsis on the novel chemotherapeutic drug delivery strategies and evaluate these approaches to gain new insights into retinoblastoma 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.

Fabrication and Characterization of Tedizolid Phosphate Nanocrystals for Topical Ocular Application: Improved Solubilization and In Vitro Drug Release

Positively charged NCs of TZP (0.1%, w/v) for ocular use were prepared by the antisolvent precipitation method. TZP is a novel 5-Hydroxymethyl-Oxazolidinone class of antibiotic and is effective against many drug-resistant bacterial infections. Even the phosphate salt of this drug is poorly soluble, therefore the NCs were prepared for its better solubility and ocular availability. P188 was found better stabilizer than PVA for TZP-NCs. Characterization of the NCs including the particle-size, PDI, and ZP by Zeta-sizer, while morphology by SEM indicated that the preparation technique was successful to get the optimal sized (151.6 nm) TZP-NCs with good crystalline morphology. Mannitol (1%, w/v) prevented the crystal growth and provided good stabilization to NC₁ during freeze-drying. FTIR spectroscopy confirmed the nano-crystallization did not alter the basic molecular structure of TZP. DSC and XRD studies indicated the reduced crystallinity of TZP-NC₁, which potentiated its solubility. An increased solubility of TZP-NC₁ (25.9 µgmL⁻¹) as compared to pure TZP (18.4 µgmL⁻¹) in STF with SLS. Addition of stearylamine (0.2%, w/v) and BKC (0.01%, w/v) have provided cationic (+29.4 mV) TZP-NCs. Redispersion of freeze-dried NCs in dextrose (5%, w/v) resulted in a clear transparent aqueous suspension of NC₁ with osmolarity (298 mOsm·L⁻¹) and viscosity (21.1 cps at 35 °C). Mannitol (cryoprotectant) during freeze-drying could also provide isotonicity to the nano-suspension at redispersion in dextrose solution. In vitro release in STF with SLS has shown relatively higher (78.8%) release of TZP from NC₁ as compared to the conventional TZP-AqS (43.4%) at 12 h. TZP-NC₁ was physically and chemically stable at three temperatures for 180 days. The above findings suggested that TZP-NC₁ would be a promising alternative for ocular delivery of TZP with relatively improved performance.

Ionic Liquids: Promising Approach for Oral Drug Delivery

Oral administration is the most preferred route for drug administration in clinic. However, due to unsatisfactory physicochemical properties of drugs and various physiological barriers, the oral bioavailability of most poorly water-soluble and macromolecules drugs is low and the therapeutic effect is unsatisfactory. Ionic liquids (ILs), molten salts with unique properties, show amazing potential for oral delivery. In addition to being able to form active pharmaceutical ingredients based ILs (API-ILs) to overcome drug solubility and polymorphism issues, ILs have also been used to enhance the solubility of poorly soluble drugs, enhance drug stability in the gastrointestinal environment, improve drug permeability in intestinal mucus, and facilitate drug penetration across the intestinal epithelial barrier. Furthermore, ILs were attempted as formulation components to develop novel oral drug delivery systems. This review focus on the application progress of ILs in oral drug delivery and the mechanisms. The challenges and perspectives of the development of ILs-based oral delivery systems are also discussed. This article reviews the latest advances of ionic liquids for oral drug delivery, focusing on the application and related mechanisms of ionic liquids in improving the drug physicochemical properties and enhancing drug delivery across physiological barriers.

In vivo self-assembled drug nanocrystals for metastatic breast cancer all-stage targeted therapy

Chemotherapy is still the mainstay treatment for metastatic triple-negative breast cancers (TNBC) currently in clinical practice. The unmet needs of chemotherapy for metastatic TNBC are mainly from the insufficient drug delivery and unavailable targeting strategy that thwart the whole progression of metastatic TNBC. The in vivo ligands-mediated active targeting efficiency is usually affected by protein corona. While, the protein corona-bridged natural targeting, in turn, provides a new way for specific drug delivery. Herein, we develop a novel metastatic progression-oriented in vivo self-assembled Cabazitaxel nanocrystals (CNC) delivery system (PC/CNC) through the CNC automatically absorbing functional plasma proteins (transferrin, apolipoprotein A-IV and apolipoprotein E) in vivo, aiming to achieve the simultaneously targeted delivery to primary tumors, circulating tumor cells and metastatic lesions. With the unique advantages of superhigh drug-loading and protein corona empowered active targeting properties to tumor cells, HUVECs, active-platelets and blood-brain barrier/blood-tumor barrier, the PC/CNC exhibits a significantly improved therapeutic effect in metastatic TNBC therapy compared with free drug and CNC-loaded liposomes.

Eplerenone nanocrystals engineered by controlled crystallization for enhanced oral bioavailability

Poor aqueous solubility of eplerenone (EPL) is a major obstacle to achieve sufficient bioavailability after oral administration. In this study, we aimed to develop and evaluate eplerenone nanocrystals (EPL-NCs) for solubility and dissolution enhancement. D-optimal combined mixture process using Design-Expert software was employed to generate different combinations for optimization. EPL-NCs were prepared by a bottom-up, controlled crystallization technique during freeze-drying. The optimized EPL-NCs were evaluated for their size, morphology, thermal behavior, crystalline structure, saturation solubility, dissolution profile, in vivo pharmacokinetics, and acute toxicity. The optimized EPL-NCs showed mean particle size of 46.8 nm. Scanning electron microscopy revealed the formation of elongated parallelepiped shaped NCs. DSC and PXRD analysis confirmed the crystalline structure and the absence of any polymorphic transition in EPL-NCs. Furthermore, EPL-NCs demonstrated a 17-fold prompt increase in the saturation solubility of EPL (8.96 vs. 155.85 µg/mL). The dissolution rate was also significantly higher as indicated by ∼95% dissolution from EPL-NCs in 10 min compared to only 29% from EPL powder. EPL-NCs improved the oral bioavailability as indicated by higher AUC, C_max, and lower T_max than EPL powder. Acute oral toxicity study showed that EPL-NCs do not pose any toxicity concern to the blood and vital organs. Consequently, NCs prepared by controlled crystallization technique present a promising strategy to improve solubility profile, dissolution velocity and bioavailability of poorly water-soluble drugs.

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.

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

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

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

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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.

Theoretical analysis of the structural and electronic properties of the interaction of boron nitride diamantane nanocrystal with the drug hydroxyurea as an anticancer drug

The density functional theory calculations with hybrid B3LYP/6-31G(d,p) basis sets have been used to examine the structural and electronic properties of boron nitride (BN) diamantane interacted with the drug hydroxyurea (HU) as an anticancer drug. The findings have been shown that there is a decrease in the total energy after combining the drug with diamantane. The energy levels of HOMO and LUMO analyses indicate that the value of HOMO energy increased slightly, while the value of LUMO energy decreased significantly in these systems in the HU/BN diamantane. In addition, the decreasing of the energy gap between HOMO and LUMO confirms a strong bond between the drug hydroxyurea and BN diamantane. Finally, the drug's stability and reactivity with BN diamantane were investigated by measuring chemical reaction characteristics such as chemical potential, electron affinity, global hardness, and electrophilicity index. As a result, the nanocrystal of BN diamantane can be considered a vector for the delivery of anticancer drugs within biological systems.

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.