The impact of digestion is essential to the understanding of milk as a drug delivery system for poorly water soluble drugs

Counter-intuitive discovery in the formulation of poorly water-soluble drugs: Amorphous small-molecule gels

Amorphous strategies have been extensively used in improving the dissolution of insoluble drugs for decades due to their high free energy. However, the formation of amorphous small-molecule gels (ASMGs) presents a counter-intuitive discovery that significantly limits their practical application. Recently, ASMGs have garnered attention because of their noncovalent structures, excellent biodegradability, and significant potential in various drug delivery systems in the pharmaceutical field. Hence, a comprehensive review is necessary to contribute to a better understanding of recent advances in ASMGs. This review aimed to introduce the main formation mechanisms, summarize possible influencing factors, generalize unique properties, outline elimination strategies, and discuss clinical application potential with preclinical cases of ASMGs. Moreover, few ASMGs are advanced to clinical stages. Intensive clinical research is needed for further development. We hope that this review can provide more efficient and rational guidance for exploring further clinical applications of ASMGs.

Infant formula as a solid lipid dose form for enhancement of the oral bioavailability of cannabidiol for paediatric patients

Cannabinoids can save paediatric patients from harmful psychological conditions caused by epilepsy. However, the limited aqueous solubility of the drug presents a limitation to oral absorption and bioavailability. Previous studies have shown the enhancement of oral bioavailability for poorly water-soluble drugs using milk or milk-based products like infant formula as a novel lipid-based formulation, due to digestion of the lipids to enhance drug solubility that is particularly well suited to infants and in low economy settings. Therefore, this study has investigated the in vitro solubilisation enhancement of cannabidiol (CBD) in milk-based products during digestion using synchrotron small angle X-ray scattering, followed by pharmacokinetic studies to determine the relative oral bioavailability. The in vitro results, coupled with in vivo data, demonstrate a two-fold increase in the oral bioavailability of CBD in bovine milk as well as infant formula. The results of this study indicate the potential for infant formula to be considered as a novel formulation approach for CBD. Further study is encouraged for more drugs with infant formula to strengthen the correlation between the solubilisation of drug and their oral bioavailability.

Evaluating human milk as a drug delivery vehicle for clofazimine to premature infants

Human milk is proposed as a drug delivery vehicle suitable for use in neonatal patients. Clofazimine, traditionally used for the treatment of leprosy and tuberculosis, is emerging as a treatment for cryptosporidiosis in infants, however its poor aqueous solubility has led to its commercial formulation as a waxy lipid formulation in a capsule, a format that is not suitable for infants. In this study, the evaluation of pasteurised human milk for the delivery of clofazimine was investigated using an in vitro lipolysis model to simulate gastric and intestinal digestion. The total lipid composition of the human milk was characterised alongside the liberated fatty acid species following digestion for comparison to alternative lipid-based delivery systems. Small-angle X-ray scattering was used to measure the presence of crystalline clofazimine during digestion and hence the extent of drug solubilisation. High-performance liquid chromatography was used to quantify the mass of clofazimine solubilised per gram of human milk fat (drug-to-fat ratio) in digested and undigested human milk. The digestion process was essential for the solubilisation of clofazimine, with digested human milk solubilising a sufficient dose of clofazimine for treatment of a premature infant. Human milk solubilised the clofazimine to a greater extent than bovine milk and infant formula during digestion, most likely as a result of differing lipid composition and increased long-chain fatty acid concentrations. These findings show that human milk enhances the solubility of clofazimine as a model drug and may be a suitable drug delivery vehicle for infant populations requiring therapeutic treatment.

In Situ Monitoring of Drug Precipitation from Digesting Lipid Formulations Using Low-Frequency Raman Scattering Spectroscopy

Low-frequency Raman spectroscopy (LFRS) is a valuable tool to detect the solid state of amorphous and crystalline drugs in solid dosage forms and the transformation of drugs between different polymorphic forms. It has also been applied to track the solubilisation of solid drugs as suspensions in milk and infant formula during in vitro digestion. This study reports the use of LFRS as an approach to probe drug precipitation from a lipid-based drug delivery system (medium-chain self-nanoemulsifying drug delivery system, MC-SNEDDS) during in vitro digestion. Upon lipolysis of the digestible components in MC-SNEDDS containing fenofibrate as a model drug, sharp phonon peaks appeared at the low-frequency Raman spectral region (<200 cm^-1), indicating the precipitation of fenofibrate in a crystalline form from the formulation. Two multivariate data analysis approaches (principal component analysis and partial least squares discriminant analysis) and one univariate analysis approach (band ratios) were explored to track these spectral changes over time. The low-frequency Raman data produces results in good agreement with in situ small angle X-ray scattering (SAXS) measurements with all data analysis approaches used, whereas the mid-frequency Raman requires the use of PLS-DA to gain similar results. This suggests that LFRS can be used as a complementary, and potentially more accessible, technique to SAXS to determine the kinetics of drug precipitation from lipid-based formulations.

Implications of the Digestion of Milk-Based Formulations for the Solubilization of Lopinavir/Ritonavir in a Combination Therapy

The development of formulation approaches to coadminister lopinavir and ritonavir antiretroviral drugs to children is necessary to ensure optimal treatment of human immunodeficiency virus (HIV) infection. It was previously shown that milk-based lipid formulations show promise as vehicles to deliver antimalarial drugs by enhancing their solubilization during the digestion of the milk lipids under intestinal conditions. In this study, we investigate the role of digestion of milk and infant formula on the solubilization behavior of lopinavir and ritonavir to understand the fate of drugs in the gastrointestinal (GI) tract after oral administration. Small angle X-ray scattering (SAXS) was used to probe the presence of crystalline drugs in suspension during digestion. In particular, the impact of one drug on the solubilization of the other was elucidated to reveal potential drug-drug interactions in a drug combination therapy. Our results showed that lopinavir and ritonavir affected the solubilization of each other during digestion in lipid-based formulations. While addition of ritonavir to lopinavir improved the overall solubilization of lopinavir, the impact of lopinavir was to reduce ritonavir solubilization as digestion progressed. These findings highlight the importance of assessing the solubilization of individual drugs in a combined matrix in order to dictate the state of drugs available for subsequent absorption and metabolism. Enhancement in the solubilization of lopinavir and ritonavir in a drug combination setting in vitro also supported the potential for food effects on drug exposure.

Small-volume in vitro lipid digestion measurements for assessing drug dissolution in lipid-based formulations using SAXS

Lipid-based formulations improve the absorption capacity of poorly-water-soluble drugs and digestion of the formulation is a critical step in that absorption process. A recent approach to understanding the propensity for drug to dissolve in digesting lipid-based formulations couples an in vitro pH-stat lipolysis model to small-angle X-ray scattering (SAXS) by means of a flow-through capillary. However, the conventional pH-stat apparatus used to measure the extent of lipid digestion during such experiments requires digest volumes of 15–30 mL and drug doses of 50–200 mg, which is problematic for scarce compounds and can require excessive amounts of formulation reagents. This manuscript describes an approach to reduce the amount of material required for in vitro lipolysis experiments coupled to SAXS, for use in instances where the amount of drug or formulation medium is limited. Importantly, this was achieved while maintaining the pH stat conditions, which is critical for maintaining biorelevance and driving digestion to completion. The digestibility of infant formula with the poorly-water-soluble drugs halofantrine and clofazimine dispersed into it was measured as an exemplar paediatric-friendly lipid formulation. Halofantrine was incorporated in its powdered free base form and clofazimine was incorporated both as unformulated drug powder and as drug in nanoparticulate form prepared using Flash NanoPrecipitation. The fraction of triglyceride digested was found to be independent of vessel size and the incorporation of drug. The dissolution of the two forms of clofazimine during the digestion of infant formula were then measured using synchrotron SAXS, which revealed complete and partial solubilisation over 30 min of digestion for the powdered drug and nanoparticle formulations, respectively. The main challenge in reducing the volume of the measurements was in ensuring that thorough mixing was occurring in the smaller digestion vessel to provide uniform sampling of the dispersion medium.

Revisiting the Dissolution of Praziquantel in Biorelevant Media and the Impact of Digestion of Milk on Drug Dissolution

Praziquantel is a poorly water-soluble drug used to treat parasitic infections. Previous studies have suggested that its rate and extent of dissolution in milk and biorelevant media are slow and limited compared to dissolution in the pharmacopoeial-recommended medium, despite being reported as displaying a positive food effect upon administration. This study aimed to revisit the dissolution of praziquantel in biorelevant media and milk to better understand this apparent dichotomy. The context of digestion was introduced to better understand drug solubilisation under more relevant gastrointestinal conditions. The amount of praziquantel solubilised in the various media during digestion was quantified using high performance liquid chromatography (HPLC) and the kinetics of dissolution were confirmed by tracking the disappearance of solid crystalline drug using in situ small angle X-ray scattering (SAXS). For the dissolution media, where sodium lauryl sulfate (SLS) is typically included as a wetting agent, a prominent effect of SLS on drug dissolution was also apparent where >2.5 fold more drug was solubilised in SLS-containing dissolution medium compared to that without (0.1 M HCl only). In milk, significant dissolution of praziquantel was observed only during digestion and not during dispersion, hence suggesting that (1) milk can be potentially administered with praziquantel to improve oral bioavailability and (2) incorporating a digestion step into existing in vitro dissolution testing can better reflect the potential for a positive food effect when lipids are present.

Milk Oral Lyophilizates with Loratadine: Screening for New Excipients for Pediatric Use

The development of suitable formulations for the pediatric population remains a challenging field with great advances reported every year in terms of excipients and technology. When developing pediatric formulations, the acceptability of medicines represents a key element to consider. For this reason, milk can be a widely accepted excipient with taste-masking properties and supplementary advantages for drug solubility. In recent years, the orodispersible dosage forms have come onto the market as child-friendly formulations. The current study aimed to develop freeze-dried orodispersible dosage forms containing bovine milk or infant formulae as the main component. In the first stage, an exploratory study evaluated the mechanical properties of placebo milk formulations and the suitability of milk as a matrix-forming agent. As the appropriate mechanical strength to withstand manipulation was demonstrated, milk oral lyophilizates were loaded with a poorly soluble model API, loratadine. Hence, a D-optimal design was conducted to prepare milk lyophilizates with loratadine and to evaluate the effects of three factors (dose of loratadine, the lyophilizate size, and the type of milk) and their interactions. Finally, three formulations were prepared to confront the predictions of the DoE and further studied to thoroughly understand the observed effects. The experimental results showed the potential of milk in the development of oral lyophilizates loaded with different doses of suspended API.

Impact of Recombined Milk Systems on Gastrointestinal Fate of Curcumin Nanoemulsion

Milk powder is an important ingredient in various foods and pediatric formulations. The textural and digestion properties of the formulations depend on the preheat treatment of the milk powder during manufacture. Thus, it is interesting to know how these modifications can influence on the release of fortified bioactive compounds during digestion with a milk matrix. In this study, a curcumin nanoemulsion was incorporated into milks reconstituted from low-heat, medium-heat and high-heat skim milk powders (SMPs) and the milks were subjected to semi dynamic in vitro digestion. All the recombined milk systems formed a curd under gastric conditions, which reduced the gastric emptying of protein and curcumin-loaded oil droplets. Because of the formation of heat-induced casein/whey protein complexes, the open fragmented curd formed by the high-heat-treated reconstituted powder resulted in higher protein and oil droplets emptying to the intestine and higher curcumin bioaccessibility. This study provides useful information for how protein ingredients can govern the fate of added health-promoting compounds during digestion.

Opportunities for milk and milk-related systems as 'new' low-cost excipient drug delivery materials

Milk is well recognised as an amazing delivery system for essential lipids, poorly soluble nutrients, sugars, amino acids and delivery of critical biological molecules to sustain the infant and adult alike. It is also a safe and abundant resource with potential to act as a low-cost material for formulation of medicines, especially for paediatric patients and those in low economy settings. However, its use in low cost formulations has never developed beyond preclinical evaluation. Reasons for this are several-fold including variable composition and therefore regulatory challenges, as well as a lack of clear understanding around when milk or milk-related materials like infant formula could best be deployed by linking drug properties with excipient composition attributes, especially when taking digestion into account. This review collects the current understanding around these issues. It is apparent from the evolving understanding that while milk may be a bridge too far for translation as an excipient, infant formula is positioned to play a key role in the future because, as a powder-based excipient, it has the performance benefits of milk powder together with the controlled specifications during manufacture and versatility of application to function as a low cost lipid excipient to enable potential translation for the oral delivery of poorly water soluble drugs for key populations including paediatrics and low economy medicines.

Vehicles for Drug Administration to Children: Results and Learnings from an In-Depth Screening of FDA-Recommended Liquids and Soft Foods for Product Quality Assessment

Purpose

Mixing with liquids or soft foods is a common procedure to improve acceptability of oral medicines in children but may affect drug stability and the in vivo performance of the administered drug product. The aim of the present study was to obtain an overview of the variability of critical attributes of commonly used vehicles and to identify which vehicle characteristics need to be considered when developing in vitro methods for evaluating product quality.

Methods

One product of each vehicle listed in the FDA draft guidance “Use of Liquids and/or Soft Foods as Vehicles for Drug Administration” was analyzed with regard to composition, calorific content and physicochemical properties.

Results

The studied vehicles show wide variability, both in composition and physicochemical properties. No correlation was observed between vehicle composition and physicochemical properties. Comparison of results of the present study with previously published data also provided variability in physicochemical properties within individual vehicle types.

Conclusions

To identify acceptable (qualified) vehicles for global drug product labeling, it is important that the vehicles selected for in vitro compatibility screening reflect the variability in composition and essential physicochemical properties of the vehicles recommended on the product label, rather than relying on results obtained with a single vehicle of each type. Future activities will focus on the development of standardized dosing vehicles that can represent key vehicle characteristics in all their variability to ensure reliable risk assessment.

Impact of pasteurization on the self-assembly of human milk lipids during digestion

Human milk is critical for the survival and development of infants. This source of nutrition contains components that protect against infections while stimulating immune maturation. In cases where the mother's own milk is unavailable, pasteurized donor milk is the preferred option. Although pasteurization has been shown to have minimal impact on the lipid and FA composition before digestion, no correlation has been made between the impact of pasteurization on the FFA composition and the self-assembly of lipids during digestion, which could act as delivery mechanisms for poorly water-soluble components. Pooled nonpasteurized and pasteurized human milk from a single donor was used in this study. The evolving FFA composition during digestion was determined using GC coupled to a flame ionization detector. In vitro digestion coupled to small-angle X-ray scattering was utilized to investigate the influence of different calcium levels, fat content, and the presence of bile salts on the extent of digestion and structural behavior of human milk lipids. Almost complete digestion was achieved when bile salts were added to the systems containing high calcium to milk fat ratio, with similar structural behavior of lipids during digestion of both types of human milk being apparent. In contrast, differences in the colloidal structures were formed during digestion in the absence of bile salt because of a greater amount of FFAs being released from the nonpasteurized than pasteurized milks. This difference in FFAs released from both types of human milk could result in varying nutritional implications for infants.

The effect of emulsifier type on the secondary crystallisation of monoacylglycerol and triacylglycerols in model dairy emulsions

Dairy emulsions contain an intrinsically heterogeneous lipid phase, whose components undergo crystallisation in a manner that is critical to dairy product formulation, storage, and sensory perception. Further complexity is engendered by the diverse array of interfacially-active molecules naturally present within the serum of dairy systems, and those that are added for specific formulation purposes, all of which interact at the lipid-serum interface and modify the impact of lipid crystals on dairy emulsion stability. The work described in this article addresses this complexity, with a specific focus on the impact of temperature cycling and the effect of emulsifier type on the formation and persistence of lipid crystals at lipid-solution interfaces. Profile analysis tensiometry experiments were performed using single droplets of the low melting fraction of dairy lipids, in the presence and absence of emulsifiers (Tween 80 and whey protein isolate, WPI) and during the temperature cycling, to study the formation of monoacylglycerol (MAG) crystals at the lipid-solution interface. Companion experiments on the same lipid systems, and at the same cooling and heating rates, were undertaken with synchrotron small angle X-ray scattering, to specifically analyse the effect of emulsifier type on the formation of triacylglycerol (TAG) crystals at the lipid-solution interface of a model dairy emulsion. These two complementary techniques have revealed that Tween 80 molecules delay MAG and TAG crystal formation by lowering the temperature at which the crystallisation occurs during two cooling cycles. WPI molecules delay the crystallisation of MAGs and TAGs during the first cooling cycle, while MAG crystals form without delay during the second cooling cycle at the same temperature as MAG crystals in an emulsifier free system. The crystallisation of TAGs is inhibited during the second cooling cycle. The observed differences in crystallisation behaviour at the interface upon temperature cycling can provide further insight into the impact of emulsifiers on the long-term stability of emulsion-based dairy systems during storage.

Bioinspired synthesis of protein/polysaccharide-decorated folate as a nanocarrier of curcumin to potentiate cancer therapy

Curcumin is a promising anticancer agent, but its clinical utilization has been hindered by its low solubility and bioaccessibility. To overcome these obstacles, we developed a natural protein-polysaccharide nanocomplex made from casein nanoparticles coated with a double layer of alginate and chitosan and decorated with folic acid (fCs-Alg@CCasNPs) for use as a nanocarrier for curcumin. The developed nanoformulation showed a drug encapsulation efficiency = 75%. The measured size distribution of fCs-Alg@CCasNPs was 333.8 ± 62.35 nm with a polydispersity index (PDI) value of 0.179. The recorded zeta potential value of fCs-Alg@CCasNPs was 28.5 mV. Morphologically, fCs-Alg@CCasNPs appeared spherical, as shown by transmission electron microscopy (TEM). The successful preparation of fCs-Alg@CCasNPs was confirmed by Fourier transform infrared (FTIR) spectroscopy of all the constituents forming the nanoformulation. Further in vitro investigations indicated the stability of fCs-Alg@CCasNPs as well as their controlled and sustained release of curcumin in the tumor microenvironment. Compared with free curcumin, fCs-Alg@CCasNPs induced a higher cytotoxic effect against a pancreatic cancer cell line. The in vivo pharmacokinetics of fCs-Alg@CCasNPs showed a significant AUC_0-24 = 2307 ng.h/ml compared to 461 ng.h/ml of free curcumin; these results indicated high curcumin bioavailability in plasma. The in vivo results of tumor weight, the amount of DNA damage measured by comet assay and histopathological examination revealed that treating mice with fCs-Alg@CCasNPs (either intratumorally or intraperitonially) prompted higher therapeutic efficacy against Ehrlich carcinoma than treatment with free curcumin. Therefore, the incorporation of curcumin with protein/polysaccharide/folate is an innovative approach that can synergistically enhance curcumin bioavailability and potentiate cancer therapy with considerable biosafety.

Recent Advances in Enhancement of Dissolution and Supersaturation of Poorly Water-Soluble Drug in Amorphous Pharmaceutical Solids: A Review

Amorphization is one of the most effective pharmaceutical approaches to enhance the dissolution and oral bioavailability of poorly water-soluble drugs. In recent years, amorphous formulations have been experiencing rapid development both in theoretical and practical application. Based on using different types of stabilizing agents, amorphous formulations can be mainly classified as polymer-based amorphous solid dispersion, coamorphous formulation, mesoporous silica-based amorphous formulation, etc. This paper summarizes recent advances in the dissolution and supersaturation of these amorphous formulations. Moreover, we also highlight the roles of stabilizing agents such as polymers, low molecular weight co-formers, and mesoporous silica. Maintaining supersaturation in solution is a key factor for the enhancement of dissolution profile and oral bioavailability, and thus, the strategies and challenges for maintaining supersaturation are also discussed. With an in-depth understanding of the inherent mechanisms of dissolution behaviors, the design of amorphous pharmaceutical formulations will become more scientific and reasonable, leading to vigorous development of commercial amorphous drug products.

A 3D-Printed Polymer-Lipid-Hybrid Tablet towards the Development of Bespoke SMEDDS Formulations

3D printing is a rapidly growing area of interest within pharmaceutical science thanks to its versatility in creating different dose form geometries and drug doses to enable the personalisation of medicines. Research in this area has been dominated by polymer-based materials; however, for poorly water-soluble lipophilic drugs, lipid formulations present advantages in improving bioavailability. This study progresses the area of 3D-printed solid lipid formulations by providing a 3D-printed dissolvable polymer scaffold to compartmentalise solid lipid formulations within a single dosage form. This allows the versatility of different drugs in different lipid formulations, loaded into different compartments to generate wide versatility in drug release, and specific control over release geometry to tune release rates. Application to a range of drug molecules was demonstrated by incorporating the model lipophilic drugs; halofantrine, lumefantrine and clofazimine into the multicompartmental scaffolded tablets. Fenofibrate was used as the model drug in the single compartment scaffolded tablets for comparison with previous studies. The formulation-laden scaffolds were characterised using X-ray CT and dispersion of the formulation was studied using nephelometry, while release of a range of poorly water-soluble drugs into different gastrointestinal media was studied using HPLC. The studies show that dispersion and drug release are predictably dependent on the exposed surface area-to-volume ratio (SA:V) and independent of the drug. At the extremes of SA:V studied here, within 20 min of dissolution time, formulations with an SA:V of 0.8 had dispersed to between 90 and 110%, and completely released the drug, where as an SA:V of 0 yielded 0% dispersion and drug release. Therefore, this study presents opportunities to develop new dose forms with advantages in a polypharmacy context.

Effects of food matrix and probiotics on the bioavailability of curcumin in different nanoformulations

BACKGROUND

Nanoparticles can improve the bioavailability of bioactive compounds. Concomitant intake of food can affect pharmacokinetic profiles by altering dissolution, absorption, metabolism, and elimination behavior. Studies on the effects of food and its supplements on the bioavailability of bioactives in nanoformulations are few. In this study, the effects of typical food (milk, sugar, high-fat diet, and regular kibble) and a widely consumed probiotic [Bifidobacterium lactis Bb-12® (Bb-12)] on the bioavailability of curcumin in four formulations [simply suspended curcumin (Cur-SS) and curcumin in nanoemulsions (Cur-NEs), in single-walled carbon nanotubes (Cur-SWNTs), and in nanostructured lipid carriers (Cur-NLCs)] were investigated.

RESULTS

Fasting treatment and sugar co-ingestion can significantly enhance the bioavailability of curcumin in Cur-NEs and Cur-SWNTs, respectively. Compared with the fasting treatment, co-ingestion with regular kibble reduced the absorption of curcumin in Cur-NEs and Cur-SWNTs. Ingesting milk along with Cur-NE is also not recommended. The mechanisms behind these phenomena were briefly discussed. This study revealed for the first time that the intestinal colonization of Bb-12 reduces the bioavailability of curcumin and this reduction can be attenuated by nanoformulations SWNTs and NLCs, but not NEs. The reason for this difference was the protective effects of the former two nanoformulations against curcumin degradation by Bb-12 according to in vitro experiments.

CONCLUSION

Dietary status (including supplementary probiotics) can dramatically influence the bioavailability of curcumin in nanoformulations. © 2021 Society of Chemical Industry.

The influence of lipid digestion on the fate of orally administered drug delivery vehicles

This review will focus on orally administered lipid-based drug delivery vehicles and specifically the influence of lipid digestion on the structure of the carrier lipids and their entrained drug cargoes. Digestion of the formulation lipids, which are typically apolar triglycerides, generates amphiphilic monoglycerides and fatty acids that can self-assemble into a diverse array of liquid crystalline structures. Tracking the dynamic changes in self-assembly of the lipid digestion products during digestion has recently been made possible using synchrotron-based small angle X-ray scattering. The influence of lipid chain length and degree of unsaturation on the resulting lipid structuring will be described in the context of the critical packing parameter theory. The chemical and structural transformation of the formulation lipids can also have a dramatic impact on the physical state of drugs co-administered with the formulation. It is often assumed that the best strategy for drug development is to maximise drug solubility in the undigested formulation lipids and to incorporate additives to maintain drug solubility during digestion. However, it is possible to improve drug absorption using lipid digestion in cases where the solubility of the dosed drug or one of its polymorphic forms is greater in the digested lipids. Three different fates for drugs administered with digestible lipid-based formulations will be discussed: (1) where the drug is more soluble in the undigested formulation lipids; (2) where the drug undergoes a polymorphic transformation during lipid digestion; and (3) where the drug is more soluble in the digested formulation lipids.

Formation of Self-Assembled Mesophases During Lipid Digestion

Lipids play an important role in regulating bodily functions and providing a source of energy. Lipids enter the body primarily in the form of triglycerides in our diet. The gastrointestinal digestion of certain types of lipids has been shown to promote the self-assembly of lipid digestion products into highly ordered colloidal structures. The formation of these ordered colloidal structures, which often possess well-recognized liquid crystalline morphologies (or “mesophases”), is currently understood to impact the way nutrients are transported in the gut and absorbed. The formation of these liquid crystalline structures has also been of interest within the field of drug delivery, as it enables the encapsulation or solubilization of poorly water-soluble drugs in the aqueous environment of the gut enabling a means of absorption. This review summarizes the evidence for structure formation during the digestion of different lipid systems associated with foods, the techniques used to characterize them and provides areas of focus for advancing our understanding of this emerging field.

Enzymatic hydrolysis of monoacylglycerols and their cyclopropanated derivatives: Molecular structure and nanostructure determine the rate of digestion

Colloidal lipidic particles with different space groups and geometries (mesosomes) are employed in the development of new nanosystems for the oral delivery of drugs and nutrients. Understanding of the enzymatic digestion rate of these particles is key to the development of novel formulations. In this work, the molecular structure of the lipids has been systematically tuned to examine the effect on their self-assembly and digestion rate. The kinetic and phase changes during the lipase-catalysed hydrolysis of mesosomes formed by four synthetic cyclopropanated lipids and their cis-unsaturated analogues were monitored by dynamic small angle X-ray scattering and acid/base titration. It was established that both the phase behaviour and kinetics of the hydrolysis are greatly affected by small changes in the molecular structure of the lipid as well as by the internal nanostructure of the colloidal particles.

Nano-encapsulated Iron and Folic Acid-Fortified Functional Yogurt Enhance Anemia in Albino Rats

Iron deficiency anemia (IDA) is a major health concern in developing countries, and these see an increased incidence in pregnant women and children in particular. The contribution of dairy products as natural products in drug delivery approaches is inspiring. This study aimed to analyze the application of iron (Fe) and folic acid (FA) bovine serum albumin-nanoparticles (BSA-NPs) as anti-anemic pharmacological agents that fortify stirred functional yogurt (SFY), comparing these with a plain control and SFY fortified with Fe and FA in free forms. The physicochemical, cytotoxicity, microbiological, viscosity, oxidative interactions, microstructural, sensorial analyses, and bioavailability properties of IDA-induced Albino rats were examined. The Transmission Electron Microscope (TEM), Zetasizer, and Scan Electron Microscope (SEM) were applied. Nanocapsule-fortified SFY showed an enhanced apparent viscosity, water-holding capacity, microstructure, least lipid oxidation, and overall sensorial acceptability. Feed that included Fe + FA nanocapsule-fortified SFY (G6) succeeded in restoring hemoglobin (16.53 gdL-1), iron (109.25 μgdL-1), ferritin (33.25 μgdL-1), and total protein (8.6 gdL-1) at the end of the 4-week feeding period, with significant competition revealed in calcium and zinc absorbance. Nanocapsule-fortified SFY showed no adverse effects or architectural alterations in the liver, kidney, or spleen, as indicated by biochemical and histological examinations. Bovine serum albumin-nanoparticles (BSA-NPs) of iron (Fe) and folic acid (FA) can be recommended as anti-anemia supplements in different functional food applications.

Current challenges and future perspectives in oral absorption research: An opinion of the UNGAP network

Although oral drug delivery is the preferred administration route and has been used for centuries, modern drug discovery and development pipelines challenge conventional formulation approaches and highlight the insufficient mechanistic understanding of processes critical to oral drug absorption. This review presents the opinion of UNGAP scientists on four key themes across the oral absorption landscape: (1) specific patient populations, (2) regional differences in the gastrointestinal tract, (3) advanced formulations and (4) food-drug interactions. The differences of oral absorption in pediatric and geriatric populations, the specific issues in colonic absorption, the formulation approaches for poorly water-soluble (small molecules) and poorly permeable (peptides, RNA etc.) drugs, as well as the vast realm of food effects, are some of the topics discussed in detail. The identified controversies and gaps in the current understanding of gastrointestinal absorption-related processes are used to create a roadmap for the future of oral drug absorption research.

Alginate hydrogels: Sustained release system to analyze the effect of traditional excipients on curcumin availability

Curcumin, a molecule of immense pharmacological significance is also known to exhibit poor aqueous solubility and low bioavailability. Different strategies have been adopted to enhance the aqueous solubility of curcumin, but report on the effect of traditional excipients on curcumin solubility still stand in need of. Here, we presented the significance of different traditional excipients used in anti-inflammatory formulations on curcumin solubility. The endeavor has been undertaken with the hypothesis that "traditional formulation used since ages have a scientific basis". To meet the quest we encapsulated 28 different formulations containing varying concentrations of milk, sugar, cow milk fat, and black pepper in alginate hydrogels. After the characterization of formulations through FT-IR, solubility studies were conducted. Milk was found to be an essential component for improved curcumin availability. Individually, cow milk fat and piperine exhibited lesser effect but their synergistic effect was observed in the presence of milk. Dual behavior of sugar has been observed. Traditionally used excipients greatly enhanced the solubility of curcumin. The results have also been validated through anti-oxidant activities of different formulations. Intermolecular interactions have been explained using Molecular modeling studies.

Sustained absorption of delamanid from lipid-based formulations as a path to reduced frequency of administration

Delamanid is a poorly water-soluble drug currently being used for the treatment of tuberculosis. The high frequency of dosing leads to poor adherence for patients who live in lower economic and nomadic populations. Non-digestible self-assembling lipids as a formulation approach for poorly water-soluble drugs have previously been shown to extend the window of absorption through gastric retention. We hypothesise that this approach could lead to the reduction of dosing frequency for delamanid and thereby has potential to improve adherence. Formulations of delamanid were prepared in selachyl alcohol and phytantriol as non-digestible self-assembling lipid vehicles, and their behaviour was compared with reconstituted milk powder, as a digestible lipid-based formulation, and an aqueous suspension. The self-assembly of selachyl alcohol and phytantriol in aqueous media in the presence of delamanid was studied using small angle X-ray scattering and produced the inverse hexagonal (H₂) and inverse bicontinuous cubic (V₂) liquid crystal structures, respectively. The times at which maximum delamanid levels in plasma were observed (T_max) after oral administration of the phytantriol, selachyl alcohol and reconstituted milk powder formulations of delamanid to rats were 27 ± 3, 20 ± 4 and 6.5 ± 1.0 h, respectively, compared with the aqueous suspension formulation with a T_max of 3.4 ± 1 h, which confirms the hypothesis of an extended duration of absorption after administration in non-digestible self-assembling lipids. The digestion products of the triglycerides in the milk formulation increased the solubilisation of delamanid in the gastrointestinal tract, leading to an increase in exposure compared with the aqueous suspension formulation but did not significantly extend T_max. Overall, the non-digestible nanostructured lipid formulations extended the duration of absorption of delamanid well beyond that from milk or suspension formulations.

Lipid Compositions in Infant Formulas Affect the Solubilization of Antimalarial Drugs Artefenomel (OZ439) and Ferroquine during Digestion

Recent studies have shown that the solubilization of two antimalarial drug candidates, artefenomel (OZ439) and ferroquine (FQ), designed to provide a single-dose combination therapy for uncomplicated malaria can be enhanced using milk as a lipid-based formulation. However, milk as an excipient faces significant quality and regulatory hurdles. We therefore have investigated infant formula as a potential alternative formulation approach. The significance of the lipid species present in a formula with different lipid compositions upon the solubilization of OZ439 and FQ during digestion has been investigated. Synchrotron small-angle X-ray scattering was used to measure the diffraction from a dispersed drug during digestion and thereby determine the extent of drug solubilization. High-performance liquid chromatography was used to quantify the amount of drug partitioned into the digested lipid phases. Our results show that both the lipid species and the amount of lipids administered were key determinants for the solubilization of OZ439, while the solubilization of FQ was independent of the lipid composition. Infant formulas could therefore be designed and used as milk substitutes to tailor the desired level of drug solubilization while circumventing the variability of components in naturally derived milk. The enhanced solubilization of OZ439 was achieved during the digestion of medium-chain triacylglycerols (MCT), indicating the potential applicability of MCT-fortified infant formula powder as a lipid-based formulation for the oral delivery of OZ439 and FQ.

Correlating Digestion-Driven Self-Assembly in Milk and Infant Formulas with Changes in Lipid Composition

Lipids in mammalian milks such as bovine milk and human breast milk have been shown to self-assemble into various liquid crystalline materials during digestion. In this study, the direct correlation between the composition of the lipids from three types of mammalian milk, three brands of infant formulas (IFs), and soy milk and the liquid crystalline structures that form during their digestion was investigated to link the material properties to the composition. The self-assembly behavior was assessed using in vitro digestion coupled with in situ small-angle X-ray scattering (SAXS). Lipid composition was determined during in vitro digestion using ex situ liquid chromatography–mass spectrometry. All tested milks self-assembled into ordered structures during digestion, with the majority of milks displaying nonlamellar phases. Milks that released mostly long-chain fatty acids (>95 mol % of the top 10 fatty acids released) with more than 47 mol % unsaturation predominantly formed a micellar cubic phase during digestion. Other milks released relatively more medium-chain fatty acids and medium-chain monoglycerides and produced a range of ordered liquid crystalline structures including the micellar cubic phase, the hexagonal phase, and the bicontinuous cubic phase. One infant formula did not form liquid crystalline structures at all as a consequence of differences in fatty acid distributions. The self-assembly phenomenon provides a powerful discriminator between different classes of nutrition and a roadmap for the design of human milklike systems and is anticipated to have important implications for nutrient transport and the delivery of bioactives.

Low-Frequency Raman Scattering Spectroscopy as an Accessible Approach to Understand Drug Solubilization in Milk-Based Formulations during Digestion

Techniques enabling in situ monitoring of drug solubilization and changes in the solid-state of the drug during the digestion of milk and milk-based formulations are valuable for predicting the effectiveness of such formulations in improving the oral bioavailability of poorly water-soluble drugs. We have recently reported the use of low-frequency Raman scattering spectroscopy (region of analysis <200 cm^-1) as an analytical approach to probe solubilization of drugs during digestion in milk using ferroquine (SSR97193) as the model compound. This study investigates the wider utilization of this technique to probe the solubilization behavior of other poorly water-soluble drugs (halofantrine, lumefantrine, and clofazimine) in not only milk but also infant formula in the absence or presence of bile salts during in vitro digestion. Multivariate analysis was used to interpret changes to the spectra related to the drug as a function of digestion time, through tracking changes in the principal component (PC) values characteristic to the drug signals. Characteristic low-frequency Raman bands for all of the drugs were evident after dispersing the solid drugs in suspension form in milk and infant formula. The drugs were generally solubilized during the digestion of the formulations as observed previously for ferroquine and correlated with behavior determined using small-angle X-ray scattering (SAXS). A greater extent of drug solubilization was also generally observed in the infant formula compared to milk. However, in the case of the drug clofazimine, the correlation between low-frequency Raman scattering and SAXS was not clear, which may arise due to background interference from clofazimine being an intense red dye, which highlights a potential limitation of this new approach. Overall, the in situ monitoring of drug solubilization in milk and milk-based formulations during digestion can be achieved using low-frequency Raman scattering spectroscopy, and the information obtained from studying this spectral region can provide better insights into drug solubilization compared to the mid-frequency Raman region.

The Biopharmaceutics Classification System (BCS) and the Biopharmaceutics Drug Disposition Classification System (BDDCS): Beyond guidelines

The recent impact of the Biopharmaceutics Classification System (BCS) and the Biopharmaceutics Drug Disposition Classification System (BDDCS) on relevant scientific advancements is discussed. The major advances associated with the BCS concern the extensive work on dissolution of poorly absorbed BCS class II drugs in nutritional liquids (e.g. milk, peanut oil) and biorelevant media for the accurate prediction of the rate and the extent of oral absorption. The use of physiologically based pharmacokinetic (PBPK) modeling as predictive tool for bioavailability is also presented. Since recent dissolution studies demonstrate that the two mechanisms (diffusion- and reaction-limited dissolution) take place simultaneously, the neglected reaction-limited dissolution models are discussed, regarding the biopharmaceutical classification of drugs. Solubility- and dissolution-enhancing formulation strategies based on the supersaturation principle to enhance the extent of drug absorption, along with the applications of the BDDCS to the understanding of disposition phenomena are reviewed. Finally, recent classification systems relevant either to the BCS or the BDDCS are presented. These include: i) a model independent approach based on %metabolism and the fulfilment (or not) of the current regulatory dissolution criteria, ii) the so called ΑΒΓ system, a continuous version of the BCS, and iii) the so-called Extended Clearance Classification System (ECCS). ECCS uses clearance concepts (physicochemical properties and membrane permeability) to classify compounds and differentiates from BDDCS by bypassing the measure of solubility (based on the assumption that since it inter-correlates with lipophilicity, it is not directly relevant to clearance mechanisms or elimination).

Application of Low-Frequency Raman Scattering Spectroscopy to Probe in Situ Drug Solubilization in Milk during Digestion

We have recently shown that real-time monitoring of drug solubilization and changes to solid state of the drug during digestion of milk can be achieved using synchrotron small-angle X-ray scattering. A complementary laboratory-based method to explore such changes is low-frequency Raman spectroscopy, which has been increasingly used to characterize crystalline drugs and their polymorphs in powders and suspensions. This study investigates the use of this technique to monitor in situ drug solubilization in milk during the process of digestion, using a lipolysis model/flow-through configuration identical to that used previously for in situ synchrotron small-angle X-ray scattering studies. An antimalarial drug, ferroquine (SSR97193), was used as the model drug for this study. The Raman spectra were processed using multivariate analysis to extract the drug signals from the milk digestion background. The results showed disappearance of the ferroquine peaks in the low-frequency Raman region (<200 cm^-1) after approximately 15-20 min of digestion when milk fat was present in the system, which indicated drug solubilization and was in good agreement with the in situ small-angle X-ray scattering measurements. This proof-of-concept study therefore suggests that low-frequency Raman spectroscopy can be used to monitor drug solubilization in a complex digesting milk medium because of the unique vibrational modes of the drug crystal lattices.

Solid-State Behavior and Solubilization of Flash Nanoprecipitated Clofazimine Particles during the Dispersion and Digestion of Milk-Based Formulations

Clofazimine, a drug previously used to treat leprosy, has recently been identified as a potential new drug for the treatment for cryptosporidiosis: a diarrheal disease that contributes to 500 000 infant deaths a year in developing countries. Rapid dissolution and local availability of the drug in the small intestine is considered key to the treatment of the infection. However, the commercially available clofazimine formulation (Lamprene) is not well-suited to pediatric use, and therefore reformulation of clofazimine is desirable. Development of clofazimine nanoparticles through the process of flash nanoprecipitation (FNP) has been previously shown to provide fast and improved drug dissolution rates compared to clofazimine crystals and Lamprene. In this study, we investigate the effects of milk-based formulations (as possible pediatric-friendly vehicles) on the in vitro solubilization of clofazimine formulated as either lecithin- or zein/casein-stabilized nanoparticles. Milk and infant formula were used as the lipid vehicles, and time-resolved synchrotron X-ray scattering was used to monitor the presence of crystalline clofazimine in suspension during in vitro lipolysis under intestinal conditions. The study confirmed faster dissolution of clofazimine from all the FNP formulations after the digestion of infant formula was initiated, and a reduced quantity of fat was required to achieve similar levels of drug solubilization compared to the reference drug material and the commercial formulation. These attributes highlight not only the potential benefits of the FNP approach to prepare drug particles but also the fact that enhanced dissolution rates can be complemented by considering the amount of co-administered fat in lipid-based formulations to drive the solubilization of poorly soluble drugs.

Impact of Ferroquine on the Solubilization of Artefenomel (OZ439) during in Vitro Lipolysis in Milk and Implications for Oral Combination Therapy for Malaria

Milk is an attractive lipid-based formulation for the delivery of poorly water-soluble drugs to pediatric populations. We recently observed that solubilization of artefenomel (OZ439) during in vitro intestinal lipolysis was driven by digestion of triglycerides in full-cream bovine milk, reflecting the ability of milk to act as an enabling formulation in the clinic. However, when OZ439 was co-administered with a second antimalarial drug, ferroquine (FQ) the exposure of OZ439 was reduced. The current study therefore aimed to understand the impact of the presence of FQ on the solubilization of OZ439 in milk during in vitro intestinal digestion. Synchrotron small-angle X-ray scattering was used for in situ monitoring of drug solubilization (inferred via decreases in the intensity of drug diffraction peaks) and polymorphic transformations that occurred during the course of digestion. Quantification of the amount of each drug solubilized over time and analysis of their distributions across the separated phases of digested milk were determined using high-performance liquid chromatography. The results show that FQ reduced the solubilization of OZ439 during milk digestion, which may be due to competitive binding of FQ to the digested milk products. Interactions between the protonated FQ-H⁺ and ionized liberated free fatty acids resulted in the formation of amorphous salts, which removes the low-energy crystalline state as a barrier to dissolution of FQ, while inhibiting the solubilization of OZ439. We conclude that although milk could enhance the solubilization of poorly water-soluble OZ439 during in vitro digestion principally due to the formation of fatty acids, the solubilization efficiency was reduced by the presence of FQ by competition for the available fatty acids. Assessment of the solubilization of both drugs during digestion of fixed-dose combination lipid formulations (such as milk) is important and may rationalize changes in bioavailability when compared to that of the individual drugs in the same formulation.

Variations in gastrointestinal lipases, pH and bile acid levels with food intake, age and diseases: Possible impact on oral lipid-based drug delivery systems

The lipids and some surfactants present in oral lipid-based drug delivery systems are potential substrates for the various lipases involved in gastrointestinal (GI) lipolysis. The levels of these enzymes, together with pH and biliairy secretion, are important parameters that condition the fate of lipid-based formulations (LBF) and the dispersion, solubilization and absorption of lipophilic drugs in the GI tract. Since in vitro methods of digestion are now combined with dissolution assays for a better assessment of LBF performance, it is essential to have a basic knowledge on lipase, pH and bile acid (BA) levels in vivo to develop relevant in vitro models. While these parameters and their variations in healthy subjects are today well documented, in vivo data on specific populations (age groups, patients with various diseases, patients with treatment affecting GI tract parameters, …) are scarce and obtaining them from clinical studies is sometimes difficult due to ethical limitations. Here we collected some in vivo data already available on the levels of digestive lipases, gastric and intestinal pH, and BAs at various ages and in patients with exocrine pancreatic insufficiency, a pathological situation that leads to drastic changes in GI tract parameters and impacts pharmacological treatments.