A novel bottom–up process to produce drug nanocrystals: Controlled crystallization during freeze-drying

Impact of the crystal size of crystalline active pharmaceutical compounds on loading into microneedles

Microneedle (MN) technology offers a promising platform for the delivery of a wide variety of active pharmaceutical compounds into and/or through the skin. Yet, the low loading capacity of MNs limits their clinical translation. The solid state of loaded compounds, crystallinity versus amorphousness and crystal size of the former, could greatly affect their loading. Here, we investigated the effect of the crystal size of crystalline compounds on their loading into dissolving MNs, prepared using the solvent-casting technique. A model crystalline compound was subjected to crystal size reduction via wet bead milling and loaded into dissolving MNs. A range of crystal sizes, from micro to nano, was obtained via different milling periods. The obtained crystals were characterized for their size, morphology, and sedimentation behavior. Besides, their content, solid state inside the MNs, and impact on the MN mechanical strength were assessed. The crystals exhibited size-dependent sedimentation, which dramatically affected their loading inside the MNs. However, crystal size and sedimentation demonstrated a negligible effect on the mechanical strength and sharpness of the needles, hence no anticipated impact on the MNs' drug delivery efficiency. The elucidation of the correlation between the crystal size and MN loading opens new potentials to address a major drawback in MN technology.

Restriction of molecular motion to a higher level: Towards bright AIE dots for biomedical applications

In the late 19th century, scientists began to study the photophysical differences between chromophores in the solution and aggregate states, which breed the recognition of the prototypical processes of aggregation-caused quenching and aggregation-induced emission (AIE). In particular, the conceptual discovery of the AIE phenomenon has spawned the innovation of luminogenic materials with high emission in the aggregate state based on their unique working principle termed the restriction of intramolecular motion. As AIE luminogens have been practically fabricated into AIE dots for bioimaging, further improvement of their brightness is needed although this is technically challenging. In this review, we surveyed the recent advances in strategic molecular engineering of highly emissive AIE dots, including nanoscale crystallization and matrix-assisted rigidification. We hope that this timely summary can deepen the understanding about the root cause of the high emission of AIE dots and provide inspiration to the rational design of functional aggregates.

Antibacterial activity of a berberine nanoformulation

This study describes the preparation of berberine (BBR) in nanoformulation to enhance its solubility and increase its antibacterial effectiveness against hospital-acquired infections. BBR nanoparticles (BBR NPs) were formed by antisolvent precipitation (ASP) using glycerol as a safe organic solvent. UV-vis absorption spectra demonstrated that the solubility of BBR NPs was greatly enhanced compared to that of pure BBR. Glycerol played a role as a stabilizer for BBR NPs through the formation of hydrogen bonds between glycerol and BBR NPs. The prepared BBR NPs have a narrow size distribution with an average diameter of 156 nm at a concentration of 2.0 mg/mL, measured by dynamic light scattering. After nanoformulation, the concentration of BBR NPs could reach up to 5.0 mg/mL, which is much higher than the saturation concentration without treatment. Results show a strongly enhanced antibacterial activity of BBR NPs compared with that of pure BBR at the same concentration. The minimum bactericidal concentration of BBR NPs against methicillin-resistant Staphylococcus aureus and Escherichia coli O157:H7 was found to be 2.0 and 5.0 mg/mL, respectively. Transmission electron microscopy showed that BBR NPs surrounded the bacterial cells and severely damaged the cell walls. Therefore, BBR NPs prepared by ASP appear to be a potential candidate for the treatment of bacterial pathogens.

Hydrogel Microparticle-Templated Anti-Solvent Crystallization of Small-Molecule Drugs

Conventional formulation strategies for hydrophobic small-molecule drug products frequently include mechanical milling to decrease active pharmaceutical ingredient (API) crystal size and subsequent granulation processes to produce an easily handled powder. A hydrogel-templated anti-solvent crystallization method is presented for the facile fabrication of microparticles containing dispersed nanocrystals of poorly soluble API. Direct crystallization within a porous hydrogel particle template yields core-shell structures in which the hydrogel core containing API nanocrystals is encased by a crystalline API shell. The process of controllable loading (up to 64% w/w) is demonstrated, and tailored dissolution profiles are achieved by simply altering the template particle size. API release is well described by a shrinking core model. Overall, the approach is a simple, scalable and potentially generalizable method that enables novel means of independently controlling both API crystallization and excipient characteristics, offering a "designer" drug particle system.

The Promising Role of Chitosan-Poloxamer 188 Nanocrystals in Improving Diosmin Dissolution and Therapeutic Efficacy against Ferrous Sulfate-Induced Hepatic Injury in Rats

Diosmin (DSN) exhibits poor water solubility and low bioavailability. Although nanocrystals (NCs) are successful for improving drug solubility, they may undergo crystal growth. Therefore, DSN NCs were prepared, employing sonoprecipitation utilizing different stabilizers. The optimum stabilizer was combined with chitosan (CS) as an electrostatic stabilizer. NCs based on 0.15% w/v poloxamer 188 (PLX188) as a steric stabilizer and 0.04% w/v CS were selected because they showed the smallest diameter (368.93 ± 0.47 nm) and the highest ζ-potential (+40.43 ± 0.15 mV). Mannitol (1% w/v) hindered NC enlargement on lyophilization. FT-IR negated the chemical interaction of NC components. DSC and XRD were performed to verify the crystalline state. DSN dissolution enhancement was attributed to the nanometric rod-shaped NCs, the high surface area, and the improved wettability. CS insolubility and its diffusion layer may explain controlled DSN release from CS-PLX188 NCs. CS-PLX188 NCs were more stable than PLX188 NCs, suggesting the significance of the combined electrostatic and steric stabilization strategies. The superiority of CS-PLX188 NCs was indicated by the significantly regulated biomarkers, pathological alterations, and inducible nitric oxide synthase (iNOS) expression of the hepatic tissue compared to DSN suspension and PLX188 NCs. Permeation, mucoadhesion, and cellular uptake enhancement by CS may explain this superiority.

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.

Development of Fully Redispersible Dried Nanocrystals by Using Sucrose Laurate as Stabilizer for Increasing Surface Area and Dissolution Rate of Poorly Water-Soluble Drugs

There is much interest in converting poorly water-soluble drugs into nanocrystals as they provide extremely high surface area that increases dissolution rate and oral bioavailability. However, nanocrystals are prepared as aqueous suspensions, and once the suspensions are dried for development of solid dosage forms, the nanocrystals agglomerate as large particles to reduce the excess surface energy. For successful development of drug products, it is essential that any agglomeration is reversible, and the dried nanocrystals regain original particle sizes after redispersion in aqueous media. We have established that sucrose laurate serves as a superb stabilizer to ensure complete redispersion of dried nanocrystals in aqueous media with mild agitation. Nanocrystals (150-300 nm) of three neutral drugs (fenofibrate, danazol and probucol) were produced with sucrose laurate by media milling, and suspensions were dried by tray drying under vacuum, spray drying, and lyophilization. Dried solids and their tablets redispersed into original particle sizes spontaneously. Preliminary studies showed that sucrose laurate can also redisperse acidic and basic drugs, indicating its versatile application. Fatty acid ester of another disaccharide, lactose laurate, also performed like sucrose laurate. Thus, we have developed a method of retaining high dissolution rate and, by implication, high bioavailability of nanocrystals from solid formulations.

Appraisal of Felodipine nanocrystals for solubility enhancement and pharmacodynamic parameters on cadmium chloride induced hypertension in rats

BACKGROUND AND OBJECTIVE

Felodipine (FDP), an antihypertensive drug possesses low water solubility and extensive first-pass metabolism leading to poor bioavailability. This impelled us to improve its solubility, bioavailability, and pharmacodynamic properties through the nanocrystal (NC) approach.

METHODS

FDP-NC were prepared with Poloxamer F125 (PXM) by the antisolvent precipitation method. The experimental setup aimed at fine-tuning polymer concentration, the proportion of antisolvent to solvent, and the duration of ultrasonication for NC formulation.

RESULTS

Optimized formulation was characterized for particle size, solubility, and PDI. Particle reduction of 74.96 times was achieved with a 9X solubility enhancement as equated to pure FDP. The morphology of NC was found to be crystalline through scanning electron microscopy observation. The formation of the crystal lattice in FDP-NC was further substantiated by the XRD and DSC results. Lowering of the heat of fusion of FDP-NC is a clear indication of size reduction. The stability studies showed no substantial change in physical parameters of the FDP-NC as assessed by particle size, zeta potential, and drug content.

CONCLUSION

The crystalline nature and improved solubility of FDP-NC improve the dissolution profile and pharmacodynamic data. The stability study data ensures that FDP-NC can be safely stored at 25℃. It is revealed that FDP-NC had a better release profile and improved pharmacodynamic effects as evident from better control over heart rate than FDP.

Impact of Matrix Surface Area on Griseofulvin Release from Extrudates Prepared via Nanoextrusion

We aimed to examine the impact of milling of extrudates prepared via nanoextrusion and the resulting matrix surface area of the particles on griseofulvin (GF, a model poorly soluble drug) release during in vitro dissolution. Wet-milled GF nanosuspensions containing a polymer (Sol: Soluplus^®, Kol: Kolliphor^® P407, or HPC: Hydroxypropyl cellulose) and sodium dodecyl sulfate were mixed with additional polymer and dried in an extruder. The extrudates with 2% and 10% GF loading were milled–sieved into three size fractions. XRPD–SEM results show that nanoextrusion produced GF nanocomposites with Kol/HPC and an amorphous solid dispersion (ASD) with Sol. For 8.9 mg GF dose (non-supersaturating condition), the dissolution rate parameter was higher for extrudates with higher external specific surface area and those with 10% drug loading. It exhibited a monotonic increase with surface area of the ASD, whereas its increase tended to saturate above ~30 × 10⁻³ m²/cm³ for the nanocomposites. In general, the nanocomposites released GF faster than the ASD due to greater wettability and faster erosion imparted by Kol/HPC than by Sol. For 100 mg GF dose, the ASD outperformed the nanocomposites due to supersaturation and only 10% GF ASD with 190 × 10⁻³ m²/cm³ surface area achieved immediate release (80% release within 30 min). Hence, this study suggests that ASD extrudates entail fine milling yielding > ~200 × 10⁻³ m²/cm³ for rapid drug release, whereas only a coarse milling yielding ~30 × 10⁻³ m²/cm³ may enable nanocomposites to release low-dose drugs rapidly.

In vitroassessment of green polyhydroxybutyrate/chitosan blend loaded with kaempferol nanocrystals as a potential dressing for infected wounds

Despite the major medical advancements in recent decades, treating infected wounds successfully remains a challenge. In this research, a functional blend of Polyhydroxybutyrate (PHB) and Chitosan (Cs) was developed for wound infection mitigation with tailored biological and physicochemical properties. Water insoluble kaempferol (KPF) was pre-formulated to water soluble KPF nanocrystals (KPF-NCs) with fine particle size of 145 ± 11 nm, and high colloidal stability (-31 ± 0.4 mV) to improve its drug transdermal delivery. PHB-Cs-KPF-NCs (1:2 ratio) film owned the best physical properties in terms of high breathability, thermal stability and mechanical strength (33 ± 1 MPa). Besides, XRD and FTIR findings indicated the interaction between Cs, PHB and KPF, reducing the film crystallinity. The scanning electron microscopy of the film displayed a highly interconnected porous morphology. KPF-NCs were integrated in PHB-Cs matrix with a marked encapsulation efficiency of 96.6%. The enhanced drug-loading film showed a sustain release pattern of KPF-NCs over 48 h. Interestingly, the developed blend possessed an impressive blood clotting capacity within 20 min. Furthermore, we presented a new naturally-sourced mixture of Cs+KPF-NCs with powerful antibacterial effects against MDRStaphylococcus aureusandAcentibacter baumanniiat very low concentrations. The membrane evidenced a remarkable antibacterial naturein vitrowith almost 100% cell viability reduction against the study strains after 48 h. By virtue of these advantages, this green blend is highly proposed for optimal wound care.

The potential of intranasal delivery of nanocrystals in powder form on the improvement of zaleplon performance: in-vitro, in-vivo assessment

OBJECTIVE

The present work focuses on improving zaleplon (ZAP) performance through nanosizing its insoluble particles which were then delivered intranasally in powder form.

SIGNIFICANCE

Since nanopowders have an exceptional ability to cross cell membrane, their absorption is facilitated in the solid form. Hence, delivering insoluble ZAP nanocrystals (NC) through intranasal route improves its bioavailability due to both nanosization and the escape of hepatic metabolism.

METHODS

Nanocrystals were prepared by anti-solvent precipitation followed by probe sonication in presence of Soluplus^®, Poloxamer-188 (0.25%), sodium lauryl sulfate (0.5%), and mannitol. Physicochemical evaluation of the prepared NC was done by DSC and XRPD. TGA was performed for stability detection. Ex vivo permeation study through isolated cattle nasal mucosal membrane, in addition to an in vivo bioavailability study was performed for assessment of the prepared NC.

RESULTS

Nanosization to 200 nm contributed to the enhancement in dissolution ∼100% within 30 min and reduced half-life to 1.63 min. Confirmation of adsorption of polymers over NC' surface was elucidated. TGA confirmed their thermal stability. Ex vivo permeation study showed a 2.7 enhancement ratio in favor of the prepared NC. Both the extent and rate of NC absorption through nasal mucosa of rabbits were significantly higher (p ˂ .05) than in case of oral tablets. The relative bioavailability of NC was increased 3.14 times as compared to the Sleep aid^® tablets.

CONCLUSION

The intranasal delivery of nanoscale ZAP powder proved to be a successful alternative to oral formulations that suffer poor absorption and limited bioavailability.

Binary Mixtures of Some Active Pharmaceutical Ingredients with Fatty Alcohols-The Criteria of Successful Eutectic Formation and Dissolution Improvement

Pharmaceutical eutectics are solid mixtures, where the crystals of active pharmaceutical ingredients (APIs) are finely divided in the phase-separated microstructures. The size reduction makes the eutectic formation a viable option to improve the dissolution rate of the poorly soluble APIs. In the present study, ibuprofen, naproxen, and sorafenib were investigated in terms of their phase behaviors with fatty alcohols, such as tetradecanol, octadecanol, and docosanol. Among the studied APIs, only ibuprofen was able to form eutectics with the fatty alcohols, and this was in agreement with the feasibility prediction based on the van 't Hoff equation and solubility parameters. In vitro release behavior was significantly improved for the ibuprofen/octadecanol eutectic mixture, although the practical insolubility of octadecanol in water was the opposite of the outstanding hydrophilicity of usual eutectic formers. The feasibility prediction and the choice of eutectic formers in the present study will be useful in advancing the utility of the pharmaceutical eutectics.

Comparison of Downstream Processing of Nanocrystalline Solid Dispersion and Nanosuspension of Diclofenac Acid to Develop Solid Oral Dosage Form

The conventional “top-down”, “bottom-up” and “combination” approaches of generating drug nanocrystals produce a “nanosuspension” (NS). It requires significant downstream processing for drying the liquid by suitable means followed by its granulation to develop an oral solid dosage form (OSD). In this paper, we used a novel, spray drying-based NanoCrySP technology for the generation of drug nanocrystals in the form of nanocrystalline solid dispersion (NCSD). We hypothesized that the NCSD would require minimal downstream processing since the nanocrystals are obtained in powder form during spray drying. We further compared downstream processing of NS and NCSD of diclofenac acid (DCF) prepared by wet media milling and NanoCrySP technology, respectively. The NS and NCSD were characterized for crystallinity, crystal size, assay and dissolution. The NCSD was physically mixed with 0.3% Aerosil^® 200, 1.76% croscarmellose sodium (CCS) and 0.4% sodium stearyl fumarate (SSF) and filled into size 0 hard gelatin capsules. The NS was first wet granulated using Pearlitol^® SD 200 (G1 granules) and Celphere^® 203 (G2 granules) in a fluidized bed processor, and the resulting granules were mixed using the same extra granular excipients as NCSD and filled into capsules. A discriminatory dissolution method was developed to monitor changes in dissolution behavior due to crystal growth during processing. Cost analysis and comparison of process efficiency was performed using an innovation radar tool. The NS and NCSD were successfully fabricated with a crystal size of 363 ± 21.87 and 361.61 ± 11.78, respectively. In comparison to NCSD-based capsules (65.13%), the G1 and G2 granules showed crystal growth and decrease in dissolution to 52.68% and 48.37%, respectively, in 120 min. The overall cost for downstream processing of NCSD was up to 80% lower than that of NS. An innovation radar tool also concluded that the one-step NanoCrySP technology was more efficient and required less downstream processing than the two-step wet media milling approach for conversion of nanocrystals to OSD.

Freeze-Drying of Pharmaceutical and Nutraceutical Nanoparticles: The Effects of Formulation and Technique Parameters on Nanoparticles Characteristics

Nanoparticles (NPs) are of the most interesting novel vehicles for effective drug delivery to humans. Freeze drying is known as an engaging process to improve the long lasting stability of NPs formulations. This study aims to elucidate the importance of various parameters involving in freeze-drying of the most common pharmaceutical/nutraceutical NPs including nanosuspensions, nanocrystals (NCs), cocrystals/nanococrystals, nanoemulsions (NEs), nanocapsules (NCPs) and nanospheres (NSPs). Regarding this, the therapeutic goals of NPs and specifications of drug must be considered. According to our survey, the most influential factors for achieving optimum results include type and concentration of cryoprotectant/lyoprotectant, stabilizer structure and concentration, the NPs concentration in solution, freezing, annealing, and drying rate, the interaction between protectants and stabilizer, solvent type and antisolvent to solvent ratio. The study shows that for each class of NPs, specific variables are of highest significance and should be optimized. For instance, about NCs, freezing rate and antisolvent/solvent ratio should be particularly considered and for emulsified NPs, the best results have been obtained by 5-20% of saccharides as cryoprotectants. These findings suggest that to obtain a product with the lowest aggregation and particle size (PS), optimization of the effective factors in formulation and lyophilization process are essential.

Formulation aspects of intravenous nanosuspensions

Intravenous (IV) route is preferred for rapid onset of action, avoiding first pass metabolism and achieving site specific delivery. Development of IV formulations for poorly water soluble drugs poses significant challenges. Formulation approaches like salt formation, co-solvents, surfactants and inclusion complexation using cyclodextrins are used for solubilisation. However, these approaches are not applicable universally and have limitations in extent of solubilisation, hypersensitivity, toxicity and application to only specific type of molecules. IV nanosuspension have been attracting attention as a viable strategy for development of IV formulations of poorly water-soluble drugs. Nanosuspension consists of nanocrystals of poorly water soluble drug suspended in aqueous media and stabilized using minimal concentration of stabilizers. Recent years have witnessed their potential in formulations for toxicological studies and clinical trials. However various challenges are associated with the translational development of IV nanosuspensions. Therefore, the objective of the current review is to provide a holistic view of formulation development and desired properties of IV nanosuspensions. It will also focus on advancements in characterization tools, manufacturing techniques and post-production processing. Challenges associated with translational development and regulatory aspects of IV nanosuspension will be addressed. Additionally, their role in preclinical evaluation and special applications like targeting will also be discussed with the help of case studies. The applications of IV nanosuspensions shall expand as their applications move from preclinical phase to commercialization.

In-Vitro and In-Vivo Evaluation of Velpatasvir- Loaded Mesoporous Silica Scaffolds. A Prospective Carrier for Drug Bioavailability Enhancement

The limited aqueous solubility of many active pharmaceutical ingredients (APIs) is responsible for their poor performance and low drug levels in blood and at target sites. Various approaches have been adopted to tackle this issue. Most recently, mesoporous silica nanoparticles (MSN) have gained attention of pharmaceutical scientists for bio-imaging, bio-sensing, gene delivery, drug solubility enhancement, and controlled and targeted drug release. Here, we have successfully incorporated the poorly water soluble antiviral drug velpatasvir (VLP) in MSN. These spherical particles were 186 nm in diameter with polydispersity index of 0.244. Blank MSN have specific surface area and pore diameter of 602.5 ± 0.7 m2/g and 5.9 nm, respectively, which reduced after successful incorporation of drug. Drug was in amorphous form in synthesized VLP-loaded silica particles (VLP-MSN) with no significant interaction with carrier. Pure VLP showed poor dissolution with progressive increment in pH of dissolution media which could limit its availability in systemic circulation after oral administration. After VLP loading in silica carriers, drug released rapidly over a wide range of pH values, i.e., 1.2 to 6.8, thus indicating an improvement in the solubility profile of VLP. These particles were biocompatible, with an LD50 of 448 µg/mL, and in-vivo pharmacokinetic results demonstrated that VLP-MSN significantly enhanced the bioavailability as compared to pure drug. The above results clearly demonstrate satisfactory in-vitro performance, biocompatibility, non-toxicity and in-vivo bioavailability enhancement with VLP-MSN.

Nanocrystals of Fusidic Acid for Dual Enhancement of Dermal Delivery and Antibacterial Activity: In Vitro, Ex Vivo and In Vivo Evaluation

With the alarming rise in incidence of antibiotic-resistant bacteria and the scarcity of newly developed antibiotics, it is imperative that we design more effective formulations for already marketed antimicrobial agents. Fusidic acid (FA), one of the most widely used antibiotics in the topical treatment of several skin and eye infections, suffers from poor water-solubility, sub-optimal therapeutic efficacy, and a significant rise in FA-resistant Staphylococcus aureus (FRSA). In this work, the physico-chemical characteristics of FA were modified by nanocrystallization and lyophilization to improve its therapeutic efficacy through the dermal route. FA-nanocrystals (NC) were prepared using a modified nanoprecipitation technique and the influence of several formulation/process variables on the prepared FA-NC characteristics were optimized using full factorial statistical design. The optimized FA-NC formulation was evaluated before and after lyophilization by several in-vitro, ex-vivo, and microbiological tests. Furthermore, the lyophilized FA-NC formulation was incorporated into a cream product and its topical antibacterial efficacy was assessed in vivo using a rat excision wound infection model. Surface morphology of optimized FA-NC showed spherical particles with a mean particle size of 115 nm, span value of 1.6 and zeta potential of −11.6 mV. Differential scanning calorimetry and powder X-ray diffractometry confirmed the crystallinity of FA following nanocrystallization and lyophilization. In-vitro results showed a 10-fold increase in the saturation solubility of FA-NC while ex-vivo skin permeation studies showed a 2-fold increase in FA dermal deposition from FA-NC compared to coarse FA. Microbiological studies revealed a 4-fofd decrease in the MIC against S. aureus and S. epidermidis from FA-NC cream compared to commercial Fucidin cream. In-vivo results showed that FA-NC cream improved FA distribution and enhanced bacterial exposure in the infected wound, resulting in increased therapeutic efficacy when compared to coarse FA marketed as Fucidin cream.

An Aseptic One-Shot Bottom-Up Method To Produce Progesterone Nanocrystals: Controlled Size and Improved Bioavailability

Progesterone (PG) is an essential sex hormone with a variety of important biological functions, but its insolubility leads to low bioavailability of most water-based formulations. What is more, the commercial oil-based formulations often cause severe side effects after long-term injection due to poor tissue absorption of oil. Herein, we report an aseptic bottom-up method utilizing emulsion freeze-drying technology that produces size-controllable, highly bioavailable, and water-based PG nanocrystal injection. The key factors that can determine the features of nanocrystals were investigated, including solvents, water-to-oil ratio, drug concentrations, type of surfactants, temperature in freeze-drying process, and lyoprotectants. Mechanisms of crystal growth formation process for PG nanocrystals were also analyzed theoretically. The prepared water-based PG nanocrystal suspension injection (PG/NSI) not only showed quick dissolution behaviors but also had significantly improved bioavailability in vivo. Therefore, this method can effectively control the size of nanocrystals, enhance bioavailability of insoluble drugs, and produce aseptic water-based nanocrystals that can be directly used for injection. Moreover, this method can also be used to prepare nanocrystals with the desired size under aseptic conditions for other poorly water-soluble drugs.

Nanocrystals as Effective Delivery Systems of Poorly Water-soluble Natural Molecules

Natural products are an important source of therapeutically effective compounds throughout the world. Since ancient times, a huge amount of both plant extracts and isolated compounds have been largely employed in treatment and prevention of human disorders and, currently, more than 60% of the world's population trusts on plant medicaments as demonstrated by the increasing quantity of herbal therapeutics in the market. Unfortunately, several promising natural molecules for the treatment of the most diverse ailments are characterized by extremely unfavourable features, such as low water solubility and poor/irregular bioavailability, which hinder their clinical use. To overcome these limitations and to make herbal therapy more effective, different formulative approaches have been employed. Among the different strategies for increasing drug solubility, nanocrystals can be considered one of the most interesting and successful approaches. Drug nanocrystals are nanosized drug particles usually formulated as nanosuspensions, namely submicron dispersions in liquid media where surfactants, polymers, or a mixture of both act as stabilisers. In this review, we described the most significant results and progresses concerning drug nanocrystal formulations for the delivery of natural compounds with a significant pharmacological activity. The text is organized in nine sections, each focusing on a specific poorly water- soluble natural compound (apigenin, quercetin, rutin, curcumin, baicalin and baicalein, hesperetin and hesperidin, resveratrol, lutein, silybin). To foster the clinical translation of these natural nanomedicines, our opinion is that future research should pair the essential pharmacokinetic studies with carefully designed pre-clinical experiments, able to prove the formulation efficacy in relevant animal models in vivo.

Design, development and characterization of ketorolac tromethamine polymeric nanosuspension

Aim: At present, various ophthalmic formulations show low bioavailability. The rationale of present work was to design and develop stable ketorolac tromethamine nanosuspension with sustained effect and greater permeability for ocular drug delivery and increased ocular residence. Materials & methods: Formulations were designed by using central composite design, developed by combined nanoprecipitation and probe sonication method. Results & discussion: Nanosuspensions depicted the size range of the particles in between 199 and 441 nm with slight reduction in crystallinity of drug. In vitro drug release revealed that higher % entrapment efficiency of drug in nanosuspension delays the drug release. Conclusion: Eudragit RL-100-based nanosuspension increases viscosity and avoids problems like drug loss from precorneal surface and rapid drainage through nasolacrimal areas.

Parenteral nanosuspensions: a brief review from solubility enhancement to more novel and specific applications

Advancements in in silico techniques of lead molecule selection have resulted in the failure of around 70% of new chemical entities (NCEs). Some of these molecules are getting rejected at final developmental stage resulting in wastage of money and resources. Unfavourable physicochemical properties affect ADME profile of any efficacious and potent molecule, which may ultimately lead to killing of NCE at final stage. Numerous techniques are being explored including nanocrystals for solubility enhancement purposes. Nanocrystals are the most successful and the ones which had a shorter gap between invention and subsequent commercialization of the first marketed product. Several nanocrystal-based products are commercially available and there is a paradigm shift in using approach from simply being solubility enhancement technique to more novel and specific applications. Some other aspects in relation to parenteral nanosuspensions are concentrations of surfactant to be used, scalability and in vivo fate. At present, there exists a wide gap due to poor understanding of these critical factors, which we have tried to address in this review. This review will focus on parenteral nanosuspensions, covering varied aspects especially stabilizers used, GRAS (Generally Recognized as Safe) status of stabilizers, scalability challenges, issues of physical and chemical stability, solidification techniques to combat stability problems and in vivo fate.

Fabrication and characterization of dexibuprofen nanocrystals using microchannel fluidic rector

Purpose

Dexibuprofen is an enantiomer of ibuprofen with low bioavailability which results from its hydrophobic nature. Nanosuspensions have developed a podium to solve the in vitro dissolution problem that frequently occurs in current research.

Materials and methods

The drug and polymer solutions were mixed in a microchannel fluid reactor and the successive embryonic nanosuspension was decanted into a vial having the polymer solution. The impact of different process and formulation parameters including inlet angle, antisolvent and solvent flow rate(s), mixing time, drug concentration, polymer type and concentration was evaluated.

Results and discussion

Stable dexibuprofen nanocrystals with a particle size of 45±3.0 nm and polydispersity index of 0.19±0.06 were obtained. Differential scanning calorimetry and powder X-ray diffraction confirmed the crystallinity. The key parameters observed were inlet angle 10°, antisolvent to solvent volume of 2.0/0.5 mL/min, 60 minutes mixing with 5 minutes sonication, Poloxamer-407 with a concentration of 0.5% w/v and drug concentration (5 mg/mm). The 60-day stability studies revealed that the nanocrystals were stable at 4°C and 25°C. The scanning electron microscopy and transmission electron microscopy images showed crystalline morphology with a homogeneous distribution.

Conclusion

Stable dexibuprofen nanocrystals with retentive distinctive characteristics and having marked dissolution rate compared to raw and marketed formulations were efficiently fabricated. In future perspectives, these nanocrystals could be converted to solid dosage form and the process can be industrialized by chemical engineering approach.

General and Scalable Approach to Bright, Stable, and Functional AIE Fluorogen Colloidal Nanocrystals for in Vivo Imaging

Fluorescent nanoparticles built from aggregation-induced emission-active organic molecules (AIE-FONs) have emerged as powerful tools in life science research for in vivo bioimaging of organs, biosensing, and therapy. However, the practical use of such biotracers has been hindered owing to the difficulty of designing bright nanoparticles with controlled dimensions (typically below 200 nm), narrow size dispersity and long shelf stability. In this article, we present a very simple yet effective approach to produce monodisperse sub-200 nm AIE fluorescent organic solid dispersions with excellent redispersibility and colloidal stability in aqueous medium by combination of nanoprecipitation and freeze-drying procedures. By selecting polymer additives that simultaneously act as stabilizers, promoters of amorphous-crystalline transition, and functionalization/cross-linking platforms, we demonstrate a straightforward access to stable nanocrystalline FONs that exhibit significantly higher brightness than their amorphous precursors and constitute efficient probes for in vivo imaging of the normal and tumor vasculature. FONs design principles reported here are universal, applicable to a range of fluorophores with different chemical structures and crystallization abilities, and are suitable for high-throughput production and manufacturing of functional imaging probes.

Bioavailability Enhancement of Poorly Water-Soluble Drugs via Nanocomposites: Formulation⁻Processing Aspects and Challenges

Drug nanoparticles embedded in a dispersant matrix as a secondary phase, i.e., drug-laden nanocomposites, offer a versatile delivery platform for enhancing the dissolution rate and bioavailability of poorly water-soluble drugs. Drug nanoparticles are prepared by top-down, bottom-up, or combinative approaches in the form of nanosuspensions, which are subsequently dried to prepare drug-laden nanocomposites. In this comprehensive review paper, the term “nanocomposites” is used in a broad context to cover drug nanoparticle-laden intermediate products in the form of powders, cakes, and extrudates, which can be incorporated into final oral solid dosages via standard pharmaceutical unit operations, as well as drug nanoparticle-laden strip films. The objective of this paper is to review studies from 2012⁻2017 in the field of drug-laden nanocomposites. After a brief overview of the various approaches used for preparing drug nanoparticles, the review covers drying processes and dispersant formulations used for the production of drug-laden nanocomposites, as well as various characterization methods including quiescent and agitated redispersion tests. Traditional dispersants such as soluble polymers, surfactants, other water-soluble dispersants, and water-insoluble dispersants, as well as novel dispersants such as wet-milled superdisintegrants, are covered. They exhibit various functionalities such as drug nanoparticle stabilization, mitigation of aggregation, formation of nanocomposite matrix⁻film, wettability enhancement, and matrix erosion/disintegration. Major challenges such as nanoparticle aggregation and poor redispersibility that cause inferior dissolution performance of the drug-laden nanocomposites are highlighted. Literature data are analyzed in terms of usage frequency of various drying processes and dispersant classes. We provide some engineering considerations in comparing drying processes, which could account for some of the diverging trends in academia vs. industrial practice. Overall, this review provides rationale and guidance for drying process selection and robust nanocomposite formulation development, with insights into the roles of various classes of dispersants.

Production of pure drug nanocrystals and nano co-crystals by confinement methods

The use of drug nanocrystals in the drug formulation is increasing due to the large number of poorly water-soluble drug compounds synthetized and due to the advantages brought by the nanonization process. The downsizing processes are done using a top-down approach (milling and homogenization currently employed at the industrial level), while the crystallization process is performed by bottom-up techniques (e.g., antisolvent precipitation, use of supercritical fluids or spray and freeze drying). In addition, the production of nanocrystals in confined environment can be achieved within microfluidics channels. This review analyzes the processes for the preparation of nanocrystals and co-crystals, divided by top-down and bottom-up approaches, together with their combinations. The combination of both strategies merges the favorable features of each process and avoids the disadvantages of single processes. Overall, the applicability of drug nanocrystals is highlighted by the widespread research on the production processes at the engineering, pharmaceutical, and nanotechnology level.

Factors Influencing the Retention of Organic Solvents in Products Freeze-Dried From Co-Solvent Systems

Controlling residual solvent levels is a major concern in pharmaceutical freeze-drying from co-solvent systems. This review provides an overview of the factors influencing this process and estimates their potential to reduce residual solvents in freeze-dried products. Decreased solvent contents are potentially correlated with the lower solid content, complete excipient crystallization, higher water solubility, and smaller molecular sizes of the solvent. Although no general rule can be derived for the selection of appropriate freezing conditions, the freezing stage appears to play a major role in subsequent volatile retention. In contrast, diverse secondary drying conditions do not appear to impact the amount of solvent retained in lyophilisates, and modification of this stage is thus not assumed to be expedient. Co-solvents are strongly entrapped in an amorphous product matrix as soon as the local moisture content decreases below a certain level. Thus, the moisture content in the dried product layer adjacent to the sublimation interface might be a key factor. Therefore, extension of the high moisture content period during the primary drying phase as well as a postlyophilization humidification of the dried products are presumably promising approaches to promote solvent release.

Enhanced oral bioavailability of glycyrrhetinic acid via nanocrystal formulation

The purpose of this study was to prepare solid nanocrystals of glycyrrhetinic acid (GA) for improved oral bioavailability. The anti-solvent precipitation-ultrasonication method followed by freeze-drying was adopted for the preparation of GA nanocrystals. The physicochemical properties, drug dissolution and pharmacokinetic of the obtained nanocrystals were investigated. GA nanocrystals showed a mean particle size of 220 nm and shaped like short rods. The analysis results from differential scanning calorimetry and X-ray powder diffraction indicated that GA remained in crystalline state despite a huge size reduction. The equilibrium solubility and dissolution rate of GA nanocrystal were significantly improved in comparison with those of the coarse GA or the physical mixture. The bioavailability of GA nanocrystals in rats was 4.3-fold higher than that of the coarse GA after oral administration. With its rapid dissolution and absorption performance, the solid nanocrystal might be a more preferable formulation for oral administration of poorly soluble GA.

Enhancing the Solubility of Fenofibrate by Nanocrystal Formation and Encapsulation

Development of techniques to enhance bioavailability of drugs having poor water solubility is a big challenge for pharmaceutical industry. Solubility can be enhanced by particle size reduction and encapsulation using hydrophilic polymers. Fenofibrate (FF) is a drug for regulating lipids. Multi-fold enhancement in solubility of FF has been achieved by nanocrystal formation in the present study. Nanoparticles were prepared by an evaporation-assisted solvent-antisolvent interaction (EASAI) approach. Water-soluble polymers, viz. polyvinylpyrrolidone (PVP), polyvinyl alcohol (PVA), and hydroxypropyl methylcellulose (HPMC), were used to encapsulate and thus control the particle size of FF nanocrystals. Spherical particles having average particle size well below 30 nm could be prepared under optimum conditions. Almost complete release of the drug molecules from the polymer-stabilized nanocrystals within 2 h was clearly evident from the in vitro drug release studies. Infrared (FTIR) spectroscopy indicated the absence of solvent impurities and any strong interaction between the drug and stabilizers. The polymorphic form of raw-FF was retained in the nanoparticles as per the X-ray diffraction (XRD) patterns. Lower crystallinity of the nanoformulated samples compared to raw-FF was confirmed by differential scanning calorimetric (DSC) studies.

NanoCrySP technology for generation of drug nanocrystals: translational aspects and business potential

Drug nanocrystals have rapidly evolved into a mature drug delivery strategy in the last decade, with almost 16 products currently on the market. Several "top-down" technologies are available in the market for generation of nanocrystals. Despite several advantages, very few bottom-up technologies have been explored for commercial purpose. This short communication highlights a novel, bottom-up, spray drying based technology-NanoCrySP-to generate drug nanocrystals. Nanocrystals are generated in the presence of non-polymeric excipients that act as crystallization inducer for the drug. Excipients encourage crystallization of drug by plasticization, primary heterogeneous nucleation, and imparting physical barrier to crystal growth. Nanocrystals have shown significant improvement in dissolution and thereby oral bioavailability. NanoCrySP technology is protected through patents in India, the USA, and the European Union. NanoCrySP can be utilized for (i) pharmaceutical development of new chemical entities, (ii) differentiated products of existing molecules, and (iii) generic drug products. The aggregation of drug nanocrystals generated using NanoCrySP poses significant challenges in the nanocrystal-based product development. Addition of stabilizers either during spray drying or during dissolution has shown beneficial effects.

Drug nanocrystals for cancer therapy

Drug nanocrystals (NCs) with fascinating physicochemical properties have attracted great attention in drug delivery. High drug-loading efficiency, great structural stability, steady dissolution, and long circulation time are a few examples of these properties, which makes drug NCs an excellent formulation for efficient cancer therapy. In the last two decades, there are a lot of hydrophobic or lipophilic drugs, such as paclitaxel (PTX), camptothecin (CPT), thymectacin, busulfan, cyclosporin A, 2-devinyl-2-(1-hexyloxyethyl) pyropheophorbide (HPPH), and so on, which have been formulated into drug NCs for cancer therapy. In this review, we summarized the recent advances in drug NCs-based cancer treatment. So far, there are main three methods to synthesize drug NCs, including top-down, bottom-up, and combination methods. The characterization methods of drug NCs were also elaborated. Furthermore, the applications and mechanisms of drug NCs were introduced by their administration routes. At the end, we gave a brief conclusion and discussed the future perspectives of drug NCs in cancer therapy. This article is categorized under: Implantable Materials and Surgical Technologies > Nanomaterials and Implants Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease Nanotechnology Approaches to Biology > Nanoscale Systems in Biology.

Downstream drug product processing of itraconazole nanosuspension: Factors influencing tablet material properties and dissolution of compacted nanosuspension-layered sugar beads

There has been limited research done on the downstream processing of nanosuspensions into solid oral dosage forms. This paper demonstrates the bead layering process with a layering level at 150% and 240%, as well as the selection and justification of the outer phase excipients for tabletability and disintegrating properties. In a previous study, an itraconazole nanosuspension stabilised by SDS and HPMC E5 was layered onto sugar beads with coating polymer HPMC VLV. In the current study, compression studies with these layered beads utilising the small bead size at 150% or 240% layering levels with outer phase cushioning excipients MCC, copovidone or isomalt were performed. Other excipients such as co-compressed crospovidone-PEG 4000; DCP functioning as a disintegrant; and HPC as a binder was also added. Target output variables were achieved with a balance between an adequate tensile strength and fast dissolution rate with a release of 99.0% (±1.0% SD) within 10min, which is in accordance with the FDA guidance for dissolution testing. The results show that the compaction of nanosuspension-layered beads is a suitable process for processing an itraconazole nanosuspension into a solid dosage form such as a compacted tablet without compromising on drug release.

Anhydrous reverse micelle nanoparticles: new strategy to overcome sedimentation instability of peptide-containing pressurized metered-dose inhalers

The objective of this study was to develop a novel anhydrous reverse micelle nanoparticles (ARM-NPs) system to overcome the sedimentation instability of peptide-containing pressurized metered-dose inhalers (pMDIs). A bottom-up method was utilized to fabricate ARM-NPs. Tertiary butyl alcohol (TBA)/water system, freeze-drying and lipid inversion method were successively used to produce the ARM-NPs for pMDI. Various characteristics of ARM-NPs were investigated including particle size, morphology, secondary structure of the peptide drug, aerosolization properties and storage stability. As revealed by the results, ARM-NPs with spherical shape possessed 147.7 ± 2.0 nm of particle size with 0.152 ± 0.021 PdI. The ARM-NPs for pMDI had satisfactory fine particle fraction (FPF) value of 46.99 ± 1.33%, while the secondary structure of the peptide drug was unchanged. Stability tests showed no pronounced sedimentation instability for over 12 weeks at 4–6 °C. Furthermore, a hypothesis was raised to explain the formation mechanism of ARM-NPs, which was verified by the differential scanning calorimetry analysis. The lecithin employed in the reverse micelle vesicles could serve as a steric barrier between peptide drugs and bulk propellant, which prevented the instability of peptide drugs in hydrophobic environment. Homogenous particle size could avoid Ostwald ripening phenomenon of particles in pMDIs. It was concluded that the ARM-NPs for pMDI could successfully overcome sedimentation instability by the steric barrier effect and homogeneous particle size.

Aminoclay-lipid hybrid composite as a novel drug carrier of fenofibrate for the enhancement of drug release and oral absorption

This study aimed to prepare the aminoclay-lipid hybrid composite to enhance the drug release and improve the oral bioavailability of poorly water-soluble fenofibrate. Antisolvent precipitation coupled with an immediate freeze-drying method was adopted to incorporate fenofibrate into aminoclay-lipid hybrid composite (ALC). The optimal composition of the ALC formulation was determined as the ratios of aminoclay to krill oil of 3:1 (w/w), krill oil to fenofibrate of 2:1 (w/w), and antisolvent to solvent of 6:4 (v/v). The morphological characteristics of ALC formulation were determined using scanning electron microscopy, differential scanning calorimetry, and X-ray powder diffraction, which indicated microcrystalline state of fenofibrate in ALC formulation. The ALC formulation achieved almost complete dissolution within 30 minutes, whereas the untreated powder and physical mixture exhibited less than 15% drug release. Furthermore, ALC formulation effectively increased the peak plasma concentration (C max) and area under the curve (AUC) of fenofibric acid (an active metabolite) in rats by approximately 13- and seven-fold, respectively. Furthermore, ALC formulation exhibited much lower moisture sorption behavior than the lyophilized formulation using sucrose as a cryoprotectant. Taken together, the present findings suggest that ALC formulation is promising for improving the oral absorption of poorly soluble fenofibrate.

Injected nanocrystals for targeted drug delivery

Nanocrystals are pure drug crystals with sizes in the nanometer range. Due to the advantages of high drug loading, platform stability, and ease of scaling-up, nanocrystals have been widely used to deliver poorly water-soluble drugs. Nanocrystals in the blood stream can be recognized and sequestered as exogenous materials by mononuclear phagocytic system (MPS) cells, leading to passive accumulation in MPS-rich organs, such as liver, spleen and lung. Particle size, morphology and surface modification affect the biodistribution of nanocrystals. Ligand conjugation and stimuli-responsive polymers can also be used to target nanocrystals to specific pathogenic sites. In this review, the progress on injected nanocrystals for targeted drug delivery is discussed following a brief introduction to nanocrystal preparation methods, i.e., top-down and bottom-up technologies.

Recent advances in the engineering of nanosized active pharmaceutical ingredients: Promises and challenges

The advances in the field of nanotechnology have revolutionized the field of delivery of poorly soluble active pharmaceutical ingredients (APIs). Nanosized formulations have been extensively investigated to achieve a rapid dissolution and therefore pharmacokinetic properties similar to those observed in solutions. The present review outlines the recent advances, promises and challenges of the engineering nanosized APIs. The principles, merits, demerits and applications of the current 'bottom-up' and 'top-down' technologies by which the state of the art nanosized APIs can be produced were described. Although the number of research reports on the nanoparticle engineering topic has been growing in the last decade, the challenge is to take numerous research outcomes and convert them into strategies for the development of marketable products.