Characterization of solidified reverse micellar solutions (SRMS) and production development of SRMS-based nanosuspensions

Polysaccharide mediated nanodrug delivery: A review

Polysaccharides have drawn a lot of attention due to their potential as carriers for drugs and other bioactive chemicals. In drug delivery systems, natural macromolecules such as polysaccharides are widely utilized as polymers. This utilization extends to various polysaccharides employed in the development of nanoparticles for medicinal administration, with the goal of enhancing therapeutic efficacy while minimizing side effects. This study not only offers an overview of the existing challenges faced by these materials but also provides detailed information on key polysaccharides expertly engineered into nanoparticles. Noteworthy examples include Bael Fruit Gum, Guar Gum, Pectin, Agar, Cellulose, Alginate, Chitin, and Gum Acacia, each selected for their distinctive properties and strategically integrated into nanoparticles. The exploration of these natural macromolecules illuminates their diverse applications and underscores their potential as effective carriers in drug delivery systems. By delving into the unique attributes of each polysaccharide, this review aims to contribute valuable insights to the ongoing advancements in nanomedicine and pharmaceutical technologies. The overarching objective of this review research is to assess the utilization and comprehension of polysaccharides in nanoapplications, further striving to promote their continued integration in contemporary therapeutics and industrial practices.

Comparative Analysis of PEG-Free and PEG-Based Self-Emulsifying Drug Delivery Systems for Enhanced Oral Bioavailability of Therapeutic (Poly) Peptides

This study aims to compare the potential of Polyethylene glycol (PEG-free and PEG-based self-emulsifying drug delivery systems (SEDDS) for the oral administration of insulin glargine (IG). Hydrophobic ion pairs (HIPs) of IG are formed using various counterions. HIPs are assessed for log P octanol/water and dissociation behavior. They are incorporated into SEDDS based on polyglycerol (PG) and zwitterionic surfactant (ZW) using response surface methodology and compared to conventional PEG-SEDDS in size, stability, and log D SEDDS/release medium . Oral IG bioavailability in PG/ZW-SEDDS and PEG-SEDDS is evaluated in rats. Among the various counterions studied, IG-BIS (bis(isotridecyl)sulfosuccinate) HIPs demonstrated the highest log P and an improved dissociation profile. PG/ZW-SEDDS and PEG-SEDDS have similar ≈40 nm sizes and are stable over 24 h. Both formulations have log D > 4 in water and >2 in 50 mM phosphate buffer pH 6.8. PG/ZW-SEDDS yielded an oral bioavailability of 2.13 ± 0.66% for IG, while the employment of PEG-SEDDS resulted in an oral bioavailability of 1.15 ± 0.35%. This study highlights the prospective utilization of PEG-free SEDDS involving the concurrent application of PG and ZW surfactants, an alternative to conventional PEG surfactants, for improved oral therapeutic (poly) peptide delivery.

Mechanistic insight into the bioactivity of prodigiosin-entrapped lipid nanoparticles against triple-negative breast, lung and colon cancer cell lines

This research investigates the potentials of prodigiosin(PG) derived from bacteria and its formulations against triple-negative breast (TNB), lung, and colon cancer cells. The PG was extracted from S. marcescens using continuous batch culture, characterized, and formulated into lyophilized parenteral nanoparticles (PNPs). The formulations were characterized with respect to entrapment efficiency (EE), DSC, FT-IR, TEM, and proton nuclear magnetic resonance (1H NMR) spectroscopy. In vitro drug release was evaluated in phosphate buffer (pH 7.4) while acute toxicity, hematological and histopathological studies were performed on rats. The in vitro cytotoxicity was evaluated against TNB (MCF-7), lung (A-549), and colon (HT-29) cancer cell lines. High EE (92.3 ± 12%) and drug release of up to 89.4% within 8 h were obtained. DSC thermograms of PG and PG-PNPs showed endothermic peaks indicating amorphous nature. The FT-IR spectrum of PG-PNPs revealed remarkable peaks of pure PG, indicating no strong chemical interaction between the drug and excipients. The TEM micrograph of the PG-PNPs showed nano-sized formulations (20-30 nm) whose particles were mostly lamellar and hexagonal structures. The 1H NMR result revealed the chemical structure of PG showing all assigned proton chemical shifts. Toxicity results of the PG and its formulation up to a concentration of 5000 mg/kg showed insignificant vacuolar changes of hepatocytes in the liver, with normal renal medulla and cortex in the kidney. The PG and PG-PNPs inhibited the growth of breast, lung, and colon cell lines. The nano-sized lipid formulation (PG-PNPs) showed potential in PG delivery and cancer treatments.

High amount of lecithin facilitates oral delivery of a poorly soluble pyrazoloquinolinone ligand formulated in lipid nanoparticles: Physicochemical, structural and pharmacokinetic performances

Preclinical development of deuterated pyrazoloquinolinone ligands, promising drug candidates for various neuropsychiatric disorders, was hindered by unusually low solubility in water and oils. DK-I-60-3 (7-methoxy-d3-2-(4-methoxy-d3-phenyl)-2,5-dihydro-3Hpyrazolo[4,3-c]quinolin-3-one) is one of such pyrazoloquinolinones, and we recently reported about increased oral bioavailability of its nanocrystal formulation (NC). Lipid nanoparticles (LNP) with a high concentration of lecithin, which enhances loading capacity of the lipid matrix, may give rise to further improvement. After preformulation studies by differential scanning calorimetry and polarized light microscopy, LNP were prepared by the hot high pressure homogenization, and characterized in terms of particle size, morphology, and encapsulation efficacy. The layered structure visible on atomic force micrographs was confirmed by nuclear magnetic resonance. Obtained formulations were desirably stable, with small particle size (<100 nm), and high encapsulation efficacy (>99 %). Lecithin was partially fluid and most probably located in the outer shell of the particle, together with DK-I-60-3. While the hydrophobic part of polysorbate 80 was completely immobilized, its hydrophilic part was free in the aqueous phase. In oral neuropharmacokinetic study in rats, an around 1.5-fold increase of area under the curve with LNP compared to NC was noticed both in brain and plasma. In bioavailability study, F value of LNP (34.7 ± 12.4 %) was 1.4-fold higher than of NC (24.5 ± 7.8 %); however, this difference did not reach statistical significance. Therefore, employment of LNP platform in preclinical formulation of DK-I-60-3 imparted an incremental improvement of its physicochemical as well as pharmacokinetic behavior.

Solidified Reverse Micellar Solution- (SRMS-) Based Microparticles for Enhanced Oral Bioavailability and Systemic Antifungal Efficacy of Miconazole Nitrate in Immunocompromised Mice

Purpose. To assess the improvement in oral bioavailability and efficacy in systemic candidiasis treatment of miconazole nitrate (MN) formulations in murine models of candidiasis. Methods. Selected formulations containing 5% of $\text{Softisan}+\text{Phospholipon}$ 90H lipid matrix with 3% of MN ( $A_1$ ), 5% of $\text{stearic}\text{acid}+\text{Phospholipon}$ 90H lipid matrix with 3% of MN ( $B_1$ ), and 5% $\text{Softisan}+\text{stearic}\text{acid}+\text{Phospholipon}$ 90H with 3% of MN ( $C_1$ ) from the in vitro investigation were used for the study. Their acute toxicity was assessed using Lorke’s method (with slight modification) while bioavailability was determined using the bioassay method. The optimized batch ( $A_1$ ) was tested in murine systemic candidiasis induced in cyclophosphamide-immunosuppressed mice. The mice were treated with a single oral dose (100 mg/kg) of the formulations for five days. Serum fungal counts (cfu/mL) were determined on days 1, 3, and 5 of the treatment period. Haematological assessments were done. Results. The lipid formulations were safer than MN powder with LD50 values of 3162.8 and 1118.3 mg/kg. Bioavailability determination revealed a higher area under the curve (AUC) value for formulations $A_1$ (6.11 μg/hr/mL) and $B_1$ (4.91 μg/hr/mL) while formulation $C_1$ (1.80 μg/hr/mL) had a lower AUC than MN (4.46 μg/hr/mL). Fungi were completely cleared from the blood of animals treated with the optimized formulation by day 3 as opposed to the controls (MN and Tween® 20) which still had fungi on day 5. No significant increase ( $p>0.05$ ) in haematological parameters was observed in mice treated with $A_1$ . Conclusion. Formulation $A_1$ successfully cleared Candida albicans from the blood within a shorter period than miconazole powder. This research has shown the potential of orally administered MN-loaded SRMS-based microparticles in combating systemic candidaemia.

Assessment of the Anti-Malarial Properties of Dihydroartemisinin- Piperaquine Phosphate Solid Lipid-Based Tablets

BACKGROUND

Artemisininbased combination therapies (ACTs) typified by dihydroartemisinin- piperaquine phosphate are first-line drugs used in the treatment of Plasmodium falciparum malaria. However, the emergence of drug resistance to ACTs shows the necessity to develop novel sustained release treatments in order to ensure maximum bioavailability.

OBJECTIVES

To formulate dihydroartemisinin (DHA)-piperaquine phosphate (PQ) sustained release tablets based on solidified reverse micellar solutions (SRMS).

METHODS

The SRMS was prepared by fusion using varying ratios of Phospholipon® 90H and Softisan® 154 and characterised. The tablets were prepared by using an in-house made and validated mould. The formulations were tested for uniformity of weight, hardness, friability, softening time, erosion time and in vitro-in vivo dissolution rate. Antimalarial properties were studied using modified Peter's 4-days suppressive test in mice. One-way analysis of variance (ANOVA) was used in the analysis of results.

RESULTS

Smooth caplets, with average weight of 1300 ± 0.06 mg to 1312 ± 0.11 mg, drug content of 61 mg for DHA and t 450 mg for PQ. Tablet hardness ranged from 7.1 to 9.0 Kgf and softening time of 29.50 ± 1.90 min. Erosion time of 62.00 ± 2.58 to 152.00 ± 1.89 min were obtained for tablets formulated with Poloxamer 188 (Batches R2, S2 and T2) which significantly reduced the softening and erosion time (p < 0.05). In vitro release showed that the optimized formulations had a maximum release at 12 h. Formulations exhibited significantly higher parasitaemia clearance and in vivo absorption compared to marketed formulations at day 7 (p < 0.05).

CONCLUSION

DHA-PQ tablets based on SRMS were much easier and relatively cheaper to produce than compressed tablets. They also showed exceptionally better treatment of malaria owing to their sustained release properties and improved bioavailability and are recommended to Pharmaceutical companies for further studies.

Intranasal artesunate-loaded nanostructured lipid carriers: A convenient alternative to parenteral formulations for the treatment of severe and cerebral malaria

Early treatment with parenteral antimalarials is key in preventing deaths and complications associated with severe and cerebral malaria. This can be challenging in 'hard-to-reach' areas in Africa where transit time to hospitals with facilities to administer drugs parenterally can be more than 6 h. Consequently, the World Health Organization has recommended the use of artesunate (ATS) suppositories for emergency treatment of patients, however, this treatment is only for children under 6 years. The intranasal route (INR) can provide a safe and effective alternative to parenteral and rectal routes for patients of all ages; thus, reducing delays to the initiation of treatment. Hence, we designed ATS-loaded nanostructured lipid carriers (NLCs) for intranasal administration. ATS-NLCs were formulated using varying concentrations of lipid matrices made up of solidified reverse micellar solutions (SRMS) comprising a 1:2 ratio of Phospholipon ® 90H and lipids (Softisan ® 154 or Compritol ®). ATS-NLCs were spherical, and the small sizes of ATS-NLCs obtained for some formulations (76.56 ± 1.04 nm) is an indication that ATS-NLCs can pass through the nasal mucosa and reach the brain or systemic circulation. Encapsulation efficiency of ATS in NLCs was ≥70% for all formulations. ATS-NLCs achieved up to 40% in vitro drug release in 1 h, while ex vivo permeation studies revealed that formulating ATS as NLCs enhanced permeation through pig nasal mucosa better than drug solution. Most importantly, the activity and reduction in parasitaemia [in mice infected with Plasmodium berghei ANKA in a murine cerebral malaria model] by ATS-NLCs administered through the INR (54.70%, 33.28%) was comparable to intramuscular administration (58.80%, 42.18%), respectively. Therefore, intranasal administration of NLCs of ATS has great potentials to serve as a satisfactory alternative to parenteral administration for the treatment of severe and cerebral malaria in both adults and children in remote areas of sub-Saharan Africa.

Chitosan caged liposomes for improving oral bioavailability of rivaroxaban: in vitro and in vivo evaluation

In this study, chitosan (CS) caged classic liposomes (CLs) and flexible liposomes (FLs) were developed to enhance the oral bioavailability of rivaroxaban (RVX) in the fasted condition. The prepared formulations were subjected to physicochemical characterization included: FTIR, DSC, zeta potential, particle size, polydispersity index, entrapment efficiency, in vitro dissolution, and transmission electron microscope imaging. The selected formulation (RVX-TFL2) composed of PL S100/Tween 80 (85/15% w/w) and coated with CS solution in the strength of (0.2% w/v) had a particle size of 105.67 nm, a zeta potential of +5.67 mV and EE of 96.07%. Compared to RXV suspension, the pharmacokinetic parameters (C _max, AUC_0-24, and AUC_0-∞) of RVX-TFL2 showed no statistically significant difference (P > 0.05) in the fasted and fed test animals. Besides, RVX bioavailability with RVX-TFL2 was improved by 59.66% and 26.97% in the fed and fasted states, respectively, compared to RVX suspension in the fed state. The result highlighted the efficacy of the prepared liquid formulation comprising CS coated liposomes in improving the oral bioavailability of RVX regardless of the fed state. Moreover, the studied liquid formulation could be utilized in developing a liquid dosage form that might be useful as a pediatric formulation of RVX.

1-Laurin-3-Palmitin as a Novel Matrix of Solid Lipid Particles: Higher Loading Capacity of Thymol and Better Stability of Dispersions Than Those of Glyceryl Monostearate and Glyceryl Tripalmitate

To develop solid lipid nanoparticles (SLNs) with a new lipid matrix for delivery of hydrophobic bioactive molecules, high purity 1-laurin-3-palmitin (1,3-LP) was synthesized and the prepared 1,3-LP SLNs were compared with those of two common SLN matrices in glyceryl monostearate (GMS) and glyceryl tripalmitate (PPP). Conditions of preparing SLNs were first optimized by evaluating the particle size, polydispersity index (PDI), zeta-potential, and stability. Thereafter, the performance of SLN loading of a model compound in thymol was studied. The loading capacity of thymol in 1,3-LP SLNs was 16% of lipids and higher than 4% and 12% for GMS- and PPP-SLNs, respectively. The 1,3-LP SLNs also had the best efficiency to entrapment thymol during the prolonged storage. X-ray diffraction (XRD) analyses confirmed the excellent crystalline stability of 1,3-LP leading to the stable entrapment efficiency and better stability of thymol-loaded SLNs. Conversely, the polymorphic transformation of GMS and PPP resulted in the declined entrapment efficiency of thymol in the corresponding SLNs. This work indicated the 1,3-diacylglycerol (DAG) SLNs could be used as a promising delivery system for the encapsulation of hydrophobic bioactive molecules with high loading capacity and stability.

Application of SRMS 154 as Sustained Release Matrix for the Delivery of Stavudine: In vitro and in vivo Evaluation and Effect of Poloxamer 188 on the Properties of the Tablets

BACKGROUND

Stavudine is an antiretroviral therapy with so many side effects and has a short half-life of 1.5 h. It degrades to thymine under hydrolytic, oxidative and photolytic conditions hence has major formulation challenges.

OBJECTIVES

To formulate sustained release lipid based stavudine and to study the properties of the formulations by in vitro and in vivo methods.

METHODS

Stavudine tablets were formulated by moulding using validated tablets moulds. The carrier used were solidified reverse micellar solution (SRMS) made up of varying ratios of hydrogenated palm oil and Phospholipid admixtures. Evaluation tests were carried out on the tablets using both Pharmacopoeial and non Pharmacopoeial test. Drug release was studied in both simulated gastric fluid (SGF, pH 1.2) and simulated intestinal fluid (SIF, pH 7.2). In vivo release was studied using Wistar rats.

RESULTS

The results showed that stavudine tablets exhibited weight range of 372 ± 0.14 to 386 ± 0.52 mg, friability ranged from 0.00 to 0.13 % and hardness ranged from 4.27 ± 0.25 to 5.30 ± 0.21 Kgf. Tablets formulated with SRMS 1:2 had erosion time range of 60.80 ± 1.23 to 87.90 ± 2.33 min and was affected significantly by the presence of Poloxamer 188 (p < 0.05). The formulations exhibited T100 % at 10 to13 h in SIF. Stavudine tablets showed the area under the curve (AUC) of 854.0 μg/h/ml, significantly higher than the AUC of the reference (p < 0.05).

CONCLUSION

Stavudine SRMS-based tablets had good stability and sustained release properties. Formulations containing 1 % Poloxamer 188 exhibited enhanced in vivo absorption and hence could be used once daily in order to enhance the bioavailability of this drug.

Investigation of novel solid lipid microparticles based on homolipids from Bos indicus for the delivery of gentamicin

Background:

The aim of this study was to formulate solidified reverse micellar solution (SRMS)-based solid lipid microparticles (SLMs) using homolipids from tallow fat (Bos indicus) and evaluate its potential for enhanced delivery of gentamicin.

Materials and Methods:

SLMs were formulated by melt-emulsification using SRMS (15% w/w Phospholipon^® 90G in 35% w/w Bos indicus), polyethylene glycol 4000 (PEG) and gentamicin (1.0, 2.0, 3.0% w/w), and characterized with respect to size, morphology, encapsulation efficiency % and pH-dependent stability. The in vitro release of gentamicin from the SLMs was performed in phosphate buffer (pH 7.4) while bioevaluation was carried out using clinical isolates of Staphylococcus aureus and Escherichia coli.

Results:

Results showed that the lipid matrix accommodated gentamicin in a concentration-dependent manner, and that stable and spherical SLMs with size range of 18.62 ± 1.24-20.59 ± 1.36 μm and 21.35 ± 1.57-50.62 ± 2.37 μm respectively for unloaded and drug-loaded formulations were obtained. The in vitro drug release studies revealed that SRMS-based SLMs could better be used to control the release of gentamicin than gentamicin injection. Results of sensitivity test revealed that the SLMs time-dependently and capacity-limitedly produced greater inhibition zone diameters (IZDs) than the standards, an indication of improved bioactivity against the test organisms, with greater IZDs against S. aureus than E. coli. Overall, SLMs containing 2% w/w SRMS, 3% w/w gentamicin and PEG 4000 entrapped the highest amount of drug, achieved complete drug release and gave highest IZD against the organisms within 420 min, while plain gentamicin gave the least.

Conclusion:

This research has shown that SLMs based on Bos indicus and P90G is a potential carrier system for dissolution and bioactivity enhancement of gentamicin.

Enhanced dermal delivery of acyclovir using solid lipid nanoparticles

The present investigation was enthused by the possibility to develop solid lipid nanoparticles (SLNs) of hydrophilic drug acyclovir (ACV) and evaluate their potential as the carrier for dermal delivery. ACV-loaded SLNs (ACV-SLNs) were prepared by the optimized double emulsion process using Compritol 888 ATO as solid lipid. The prepared SLNs were smooth and spherical in shape with average diameter, polydispersity index, and entrapment efficiency of 262 ± 13 nm, 0.280 ± 0.01, and 40.08 ± 4.39% at 10% (w/w) theoretical drug loading with respect to Compritol 888 ATO content. Differential scanning calorimetry and powder X-ray diffraction pattern revealed that ACV was present in the amorphous state inside the SLNs. In vitro skin permeation studies on human cadaver and Sprague-Dawley rat skin revealed 17.65 and 15.17 times higher accumulation of ACV-SLNs in the dermal tissues in comparison to commercially available ACV cream after 24 h. Mechanism of topical permeation and dermal distribution was studied qualitatively using confocal laser scanning microscopy. While free dye (calcein) failed to penetrate skin barrier, the same encapsulated in SLNs penetrated deeply into the dermal tissue suggesting that pilosebaceous route was followed by SLNs for skin penetration. Histological examination and transdermal epidermal water loss measurement suggested that no major morphological changes occurred on rat skin surface due to the application of SLNs. Overall, it was concluded that ACV-loaded SLNs might be beneficial in improving dermal delivery of antiviral agent(s) for the treatment of topical herpes simplex infection.

A brief literature and patent review of nanosuspensions to a final drug product

Particle size reduction can be used for enhancing the dissolution of poorly water-soluble drugs in order to enhance bioavailability. In nanosuspensions, the particle size of the drug is reduced to nanometer size. Nanosuspensions after downstream processing into drug products have successfully shown its impact on formulation design, the augmentation of product life cycle, patent life, and therapeutic efficacy. Formulation considerations for the nanosuspension formulation, its processing into a solid form, and aspects of material characterization are discussed. Technology assessments and feasibility of upstream processes for nanoparticle creation, and subsequently transformation into a drug product via the downstream processes have been reviewed. This paper aims to bridge formulation and process considerations along with patent reviews and may provide further insight into understanding the science and the white space. An analysis of current patent outlook and future trends is described to fully understand the limitations and opportunities in intellectual property generation.

Analgesic and Micromeritic evaluations of SRMS-based oral Lipospheres of Diclofenac Potassium

The objective of our work was to study the micromeritic properties of lyophilized diclofenac potassium-loaded lipospheres and to evaluate in vivo, the analgesic properties of diclofenac potassium in the lipospheres in addition to other in vitro properties. Solidified reverse micellar solutions were prepared by fusion using 1:1, 2:1, and 1:2% w/w of Phospholipon(®) 90H and Softisan(®) 154. Diclofenac potassium (1, 3, and 5% w/w) was incorporated into the solidified reverse micellar solutions. Solidified reverse micellar solutions-based lipospheres were formulated by melt homogenization techniques using Ultra-Turrax homogenizer, and thereafter lyophilized to obtain water-free lipospheres. The lipospheres were characterized in terms of particle size and morphology, stability, thermal analysis, drug content, encapsulation efficiency, and loading capacity. The flow properties of the lipospheres were studied using both direct and indirect methods of assessing flow. The analgesic properties of the lipospheres were studied using the hot plate method. Results obtained showed that the yield of diclofenac potassium-loaded lipospheres was high and the particle size ranged from 0.61±0.07 to 2.55±0.04 μm. The lipospheres had high encapsulation efficiency of 95%, which was affected by the amount of drug loaded, while the loading capacity increased with the increase in drug loading. Diclofenac potassium-loaded lipospheres exhibited poor flow. The formulations exhibited good analgesic effect compared with the reference and had 84 to 86% drug release at 13 h. The lipospheres based on solidified reverse micellar solutions could be used for oral delivery of diclofenac potassium.

Formulation and evaluation of novel solid lipid microparticles as a sustained release system for the delivery of metformin hydrochloride

The low encapsulation efficiency of conventional solid lipid microparticles (SLMs) especially for hydrophilic drugs has remained a challenge to drug formulation experts. This work seeks to address the issue of inefficient delivery of metformin hydrochloride (MTH), a potent hydrophilic oral antihyperglycemic agent, using novel SLMs based on solidified reverse micellar solutions (SRMS) prepared by melt-emulsification using a lipid derived from Capra hircus and Phospholipon® 90H. Characterization based on size, morphology, zeta potential, polydispersity index, encapsulation efficiency (EE%), loading capacity (LC) and time-resolved stability were carried out on the SLMs. The in vitro release of MTH from the SLMs was performed in phosphate buffer (pH 7.4) while the in vivo antidiabetic properties were investigated in alloxan-induced diabetic rats. Stable, spherical and smooth SLMs were obtained. Loading of MTH into the SLMs had no effect on the surface charge of the particles. The SLMs with 1.0%w/w PEG 4000 resulted in significantly (p < 0.05) higher EE% while those with 2.0%w/w gave the least. The LC values ranged from 20.3 to 29.1 and 14.6 to 24.1 for SLMs containing 500 mg and 250 mg of MTH, respectively. The in vitro release studies revealed significant release of MTH from the SLMs whereas the in vivo antidiabetic studies indicated that novel SLMs containing 500 mg of MTH gave significantly (p < 0.05) higher glucose reduction than glucophage®. This research has shown that SLMs based on SRMS offer a new and better approach of delivering MTH, thus encouraging further development of this formulation.

Nanocrystals: industrially feasible multifunctional formulation technology for poorly soluble actives

Poor solubility of new drugs and their related low oral bioavailability and general delivery problems are becoming a major challenge. Nanocrystals being a kind of "universal" formulation approach for these molecules are reviewed in this paper regarding the industrial feasibility, i.e. industrially available production processes (bottom-up and top-down technologies), regulatory aspects and nanotoxicology. This article also includes second generation nanocrystals (<<100 nm) as smartCrystals. The status of products on the market and in clinical phases is presented. The different special features of nanocrystals, which are exploited in different products, are described (tablets, capsule, aqueous nanosuspension). The main focus is given for oral and intravenous products. However, the potential and delivery strategies for other administration routes are discussed, i.e. dermal and mucosal, ocular, pulmonary and targeted delivery (e.g. via differential protein adsorption to the brain). In addition, the potential of the nanocrystal technology for delivery of poorly soluble, non-pharmaceutical actives is highlighted, i.e. in cosmetics or nutraceuticals.

Nanomedicine in the diagnosis and therapy of neurodegenerative disorders

Neurodegenerative and infectious disorders including Alzheimer's and Parkinson's diseases, amyotrophic lateral sclerosis, and stroke are rapidly increasing as population's age. Alzheimer's disease alone currently affects 4.5 million Americans, and more than $100 billion is spent per year on medical and institutional care for affected people. Such numbers will double in the ensuing decades. Currently disease diagnosis for all disorders is made, in large measure, on clinical grounds as laboratory and neuroimaging tests confirm what is seen by more routine examination. Achieving early diagnosis would enable improved disease outcomes. Drugs, vaccines or regenerative proteins present "real" possibilities for positively affecting disease outcomes, but are limited in that their entry into the brain is commonly restricted across the blood-brain barrier. This review highlights how these obstacles can be overcome by polymer science and nanotechnology. Such approaches may improve diagnostic and therapeutic outcomes. New developments in polymer science coupled with cell-based delivery strategies support the notion that diseases that now have limited therapeutic options can show improved outcomes by advances in nanomedicine.

Structural investigations on lipid nanoparticles containing high amounts of lecithin

Solid lipid nanoparticles (SLN), an alternative colloidal drug delivery system to polymer nanoparticles, emulsions and liposomes, possess inherent low incorporation rates resulting from the crystalline structure of the solid lipid. To increase the drug loading capacity of SLN, matrix modification by incorporation of the amphiphilic lipid lecithin within the lipid matrices has been proposed as a promising alternative. The objective of this work is to investigate the effects of the lecithin on the microstructure of matrix modified SLN. In addition, these systems were checked for the existence of aggregates like mixed micelles, liposomes, etc., which could possibly be formed by lecithin leakage into the aqueous phase during the preparation process. For this purpose, laser diffraction, photon correlation spectroscopy (PCS), small angle X-ray scattering (SAXS), nuclear magnetic resonance (NMR) and transmission electron microscopy (TEM) were performed to investigate the structure, mobility, and molecular environment of the compounds. Lecithin incorporation within the lipid matrices resulted in a concentration dependent decrease in particle size up to a critical concentration of 30%. Lecithin incorporation up to 50% was investigated but caused no further particle size decrease. TEM revealed anisometrical and crystalline platelets of ellipsoidal to disc-like shape. Furthermore, SAXS and TEM showed no signs of lecithin and nonionic emulsifier derived aggregates in the aqueous phase. This points in agreement with NMR measurements to a strong attachment of both substances to the SLN surfaces. The proposed structure of the particles after melt emulsification consists of two different layers: a crystalline triglyceride-rich core is covered in dependence of the lecithin content either by a monomolecular or multimolecular lecithin/Solutol HS15 (SOL) layer.

Characterisation of surface-modified solid lipid nanoparticles (SLN): influence of lecithin and nonionic emulsifier

Solid lipid nanoparticles (SLN), an alternative colloidal drug delivery system to polymer nanoparticles, emulsions and liposomes, are generally produced by high pressure melt-emulsification. However, the harsh production process is not applicable for formulations containing shear and temperature sensitive compounds. For that reason, subsequent adsorptive SLN loading might be a promising alternative. The aim of the present study was the development and characterisation of surface-modified SLN for adsorptive protein loading by variation of both the lipid matrix and the emulsifier concentration in the continuous phase. Variations in SLN composition resulted in particle sizes between 674 and 61 nm corresponding to specific surfaces of 4.5 m(2)/g and 48.9 m(2)/g and zeta potentials between -23.4 mV and -0.9 mV. In dependence of SLN surface properties, albumin payload ranged from 2.5 to 15%. Thermoanalysis, X-ray diffraction and electron microscopy revealed anisometrical and crystalline particles. In vitro cytotoxicity was low in terms of both haemolysis, which was between 1 and 2%, and neutral red test (NRT) showing a half lethal dose between 1.1 and 4.6%.

Drug release and permeation studies of nanosuspensions based on solidified reverse micellar solutions (SRMS)

Solidified reverse micellar solutions (SRMS), i.e. mixtures of lecithin and triglycerides, offer high solubilisation capacities for different types of drugs in contrast to simple triglyceride systems [Friedrich, I., Müller-Goymann, C.C., 2003. Characterisation of SRMS and production development of SRMS-based nanosuspensions. Eur. J. Pharm. Biopharm. 56, 111-119]. Nanosuspensions based on SRMS were prepared by homogenisation close to the melting point of the SRMS matrix. In a first step the SRMS matrices of 1:1 (w/w) ratios of lecithin and triglycerides were loaded with 17beta-estradiol-hemihydrate (EST), hydrocortisone (HC) or pilocarpine base (PB), respectively, and subsequently ground in liquid nitrogen to minimise drug diffusion later on. The powder was then dispersed in a polysorbate 80 solution using high pressure homogenisation. The drug loading capacities of the nanosuspensions were very high in the case of poorly water-soluble EST (99% of total 0.1%, w/w, EST) and HC (97% of total 0.5%, w/w, HC) but not sufficient with the more hydrophilic PB (37-40% of total 1.0%, w/w, PB). These findings suggest SRMS-based nanosuspensions to be promising aqueous drug carrier systems for poorly soluble drugs like EST and HC. Furthermore, in vitro drug permeation from the different drug-loaded nanosuspensions was performed across human cornea construct (HCC) as an organotypical cell culture model. PB permeation did not differ from the nanosuspension and an aqueous solution whereas the permeation coefficients of HC-loaded nanosuspensions were reduced in comparison to aqueous and oily solutions of HC. However, the permeated amount was higher from the nanosuspensions due to a much lower HC concentration in the solution than that in the nanosuspension (solution 0.02%, w/w, versus nanosuspension 0.5%, w/w). The high drug load of the nanoparticles provides prolonged HC release. Permeated amounts of EST were reduced in comparison to HC and only detectable with an ELISA technique. The EST release from nanosuspensions and different EST-loaded systems revealed a prolonged EST release from the nanoparticulate systems in contrast to a faster release of an oily solution of an equal EST concentration. With regard to an aqueous EST suspension of similar concentration which represents a depot system the release rate from the nanosuspensions revealed the same order of magnitude which points again to a prolonged release potential of the nanosuspensions.

Saturated phospholipids promote crystallization but slow down polymorphic transitions in triglyceride nanoparticles

Some matrix materials proposed for the preparation of solid lipid nanoparticles (e.g. trilaurin) are difficult to crystallize after processing by melt-homogenization. In an attempt to overcome this difficulty, the effect of saturated long-chain phospholipids on the crystallization of nanoparticles based on trilaurin, trimyristin, tripalmitin and tristearin was studied. The phospholipids were used as emulsifiers in combination with sodium glycocholate. Saturated phospholipids increased the crystallization temperature of the triglyceride by several degrees compared to soybean phospholipids. The crystallization pattern was more complex in such systems due to solidification of the phospholipid chains prior to triglyceride crystallization. For most triglycerides, egg lecithin also induced crystallization at higher temperatures than natural soybean lecithin. With trilaurin dispersions, the effect of phospholipids can be utilized to induce crystallization at temperatures relevant for larger scale preparation. The polymorphic transitions of the triglycerides were slower in the presence of egg and saturated lecithin leading to a higher stability of the metastable alpha-form. These effects were particularly pronounced in tristearin systems where a predominant fraction of alpha-phase particles could be observed even after long-term cold storage in dispersions containing hydrogenated soybean lecithin or DPPC. The possibility to prepare triglyceride nanoparticles stable in specific modifications offers new opportunities to study effects of polymorphic form on colloidal stability, drug loading and release properties of such dispersions.

Thermal analysis of the crystallization and melting behavior of lipid matrices and lipid nanoparticles containing high amounts of lecithin

Lipid nanoparticles (LNP) based on triglycerides containing high amounts of the amphiphilic lipid lecithin have been proposed as a promising alternative drug delivery system with regard to drug loading capacity. Aim of the present study is to evaluate the influence of lecithin within the lipid matrix (LM) on the crystallization behavior by thermoanalysis and wide angle X-ray diffraction (WAXD). The crystallinity of LM and LNP is mainly determined by the triglyceride content. However, lecithin influences the crystallization behavior significantly. WAXD shows an accelerated polymorphic transition of the LM to the beta-modification upon storage with increasing lecithin content. Both, the melting point and the crystallization temperature are not affected by the lecithin concentration and are comparable to recrystallized triglyceride bulk. However, the crystallinity indices (CI) of LM show a general decrease by 10% suggesting an incomplete crystallization. For the formation of LNP at least 10% lecithin is necessary and all systems are present in the stable beta-modification. In comparison to the undispersed LM, the crystallization temperature of LNP is significantly decreased by about 20 degrees C whereas the melting point is reduced by about 5 degrees C only. Melting enthalpy is comparable to the untreated triglyceride bulk and elevated in comparison to the undispersed LM. Isothermal heat-conduction microcalorimetry (IMC) enables the determination of crystallization kinetics after fitting of the heat flow volume according to the Avrami equation.