The effects of Levothyroxine on the structure and dynamics of DPPC liposome: FTIR and DSC studies

Preparation and characterization of niosomes for the delivery of a lipophilic model drug: comparative stability study with liposomes against phospholipase-A2

Vesicular nanocarriers like niosomes and liposomes are widely researched for controlled drug delivery systems, with niosomes emerging as promising alternatives due to their higher stability and ease of manufacturing. This study aimed to develop and characterize a niosomal formulation for the encapsulation and sustained release of temozolomide (TMZ), a model lipophilic drug, and to compare the stability of niosomes and liposomes, with a particular focus on the behavior of their lipid bilayers. Niosomes were prepared using the thin-film hydration method, composed of Span 60 (Sorbitan monostearate), cholesterol, and soy lecithin in varying molar ratios. The study investigated critical properties such as drug loading capacity, release kinetics, and resistance to enzymatic degradation. The optimized formulation was analyzed for drug entrapment efficiency and stability against phospholipase A2 (PLA2) degradation. The optimized niosomal formulation, with a 4:2:1 molar ratio of Span 60: cholesterol, achieved a high TMZ entrapment efficiency of 73.23 ± 1.02% and demonstrated sustained drug release over 24 hours. In comparison, liposomes released their TMZ payload within 4 hours upon exposure to PLA2, while the niosomes maintained their release profile, indicating superior stability. Spectroscopic and thermal analysis confirmed successful drug encapsulation with no component incompatibilities.

Advancing drug safety and mitigating health concerns: High-resolution mass spectrometry in the levothyroxine case study

Levothyroxine is a drug with a narrow therapeutic index. Changing the drug formulation composition or switching between pharmaceutical brands can alter the bioavailability, which can result in major health problems. However, the increased adverse drug reactions have not been fully explained scientifically yet and a thorough investigation of the formulations is needed. In this study, we used a non-targeted analytical approach to examine the various levothyroxine formulations in detail and to reveal possible chemical changes. Ultra-high-performance liquid chromatography coupled with a data-independent acquisition high-resolution mass spectrometry (UHPLC-DIA-HRMS) was employed. UHPLC-DIA-HRMS allowed not only the detection of levothyroxine degradation products, but also the presence of non-expected components in the formulations. Among these, we identified compounds resulting from reactions between mannitol and other excipients, such as citric acid, stearate, and palmitate, or from reactions between an excipient and an active pharmaceutical ingredient, such as levothyroxine-lactose adduct. In addition to these compounds, undeclared phospholipids were also found in three formulations. This non-targeted approach is not common in pharmaceutical quality control analysis. Revealing the presence of unexpected compounds in drug formulations proved that the current control mechanisms do not have to cover the full complexity of pharmaceutical formulations necessarily.

Inhalable drug-loaded silk fibroin carriers for pulmonary drug delivery

The design and development of engineered micro and nano-carriers offering superior therapeutic performance compared to traditional delivery forms, are crucial in pharmaceutical research. Aerosolization and inhalation of carriers with improved solubility/stability of insoluble drugs, has huge potential for targeted drug delivery (DD) in various pulmonary diseases. Indeed, dedicated carriers must meet specific dimensional rules for proper lung delivery. Particles between 2-10 μm in size are normally deposited in the tracheobronchial region, while particles of 0.5-2 μm may be properly deposited in the alveoli. In this work, we report the development of inhalable nanostructured carries made of a 'green' bio-inspired polymer from aqueous solutions, i.e. silk fibroin (SF), efficiently loaded with a hydrophobic drug, i.e. the thyroid hormone levothyroxine (L-T4), a drug for the treatment of idiopathic pulmonary fibrosis. The aim is to optimize a standard method for the synthesis of SF-based nanocarriers with controlled size and shape, where a fine control of their geometrical properties is aimed at efficiently controlling the pulmonary DD. L-T4 loaded SF particles were synthesized through a one-pot co-precipitation method. Optimized systems were determined by varying the chemo-physical parameters during the synthesis. Ethylenediaminetetraacetic acid (EDTA) was used to remove CaCO3 cores. The proposed synthesis routes have led to two SF structures, whose structural heterogeneity and nanostructured morphology have been demonstrated using fluorescence microscopy, DLS, SEM and EDX. Two systems with varying shape and size have been obtained: (i) a flat disk-like SF structure with an irregular surface and an in-plane length of about 1-2 μm; (ii) solid SF nanospheres, obtained using ethylene glycol as additive, showing two size populations (main diameters of 0.5 μm and 1.7 μm). Solid nanospherical systems, in particular, show a tendency to arrange into agglomerates that, when loosely bound into smaller particles, can facilitate the delivery at the alveoli. Both formulations exhibited similar drug loading efficiencies, evaluated by HPLC analysis. However, SF nanospheres showed greater in vitro drug release after 24 hours. The demonstrated control over the characteristics imparted to the proposed DD systems may be critical to select the most suitable size/shape to achieve high rates of delivery to the appropriate lung compartment.

Development and in vitro antiviral activity of ivermectin liposomes as a potential drug carrier system

This study aimed to assess and compare diverse formulations of ivermectin-loaded liposomes, employing lipid film hydration and ethanol injection methods. Three lipids (DOPC, SPC, and DSPC) were used in predetermined molar ratios. A total of 18 formulations were created, and a factorial design determined the optimal formulation based on particle size, polydispersity index (PDI), zeta potential, and encapsulation efficiency. The average mean particle size, PDI and zeta potential of the selected formulations (F1, F2, F7, F9, and F11) was, respectively, 196.40 ± 44.60 nm, 0.39 ± 0.09, and -40.24 ± 9.17. The encapsulation efficiency exceeded 80%, with a mean loading capacity of 4.00 ± 1.70%. In vitro studies included transmission electron microscopy, Fourier transform infrared spectroscopy, drug release, and antiviral activity assessments against SARS-CoV-2. The liposomal formulations demonstrated superior antiviral activity compared to free ivermectin, as indicated by lower IC50 values. The results of this study emphasize the effectiveness of ivermectin-loaded liposomes in inhibiting viral activity, highlighting their potential as promising candidates for antiviral therapy. The findings suggest that the strategic use of liposomes as drug carriers can significantly modulate and improve the antiviral properties of ivermectin, offering a novel approach to harnessing its full therapeutic potential. Collectively, these results provide a robust foundation for further exploration of ivermectin as a viral protection tool and optimization of its delivery mechanisms.

Study transport of hesperidin based on the DPPC lipid model and the BSA transport model

Hesperidin (HE), a significant flavonoid polyphenolic compound present in citrus plants, exhibits diverse pharmacological effects. Considering the crucial involvement of biological membranes and transporter proteins in the transportation and biological processes of HE, it becomes essential to comprehend the potential mechanisms through which HE interacts with membranes and transporter proteins. In order to simulate the process of active molecule transport, a cell membrane model consisting of 1,2-dipalmitoyl-n-glycero-3-phosphatidylcholine (DPPC) and a transporter protein model of bovine serum albumin (BSA) were employed for investigation. The present study aimed to investigate the mechanism of action of hesperidin (HE) in DPPC and BSA using fluorescence quenching, Fourier transform infrared spectroscopy (FTIR), and differential scanning calorimetry (DSC). The localization and interaction of HE within liposomes were also elucidated. Furthermore, the binding of BSA and HE was analyzed through UV/Vis absorption spectroscopy, fluorescence spectroscopy, infrared spectroscopy, and computational biology techniques. Computational biology analysis revealed that the binding between HE and BSA primarily occurred via hydrogen bonding and hydrophobic interactions. This study aimed to investigate the role and mechanism of HE in the DPPC cell membrane model and the BSA transporter protein model, thereby offering novel insights into the action of HE in DPPC and BSA.

Understanding the Transepithelial Transport and Transbilayer Diffusion of the Antihypertensive Peptide Asn-Cys-Trp: Insights from Caco-2 Cell Monolayers and the DPPC Model Membrane

Understanding the transport mechanism of the peptide Asn-Cys-Trp (NCW) is crucial to improving its intestinal absorption and bioavailability. This study investigated the absorption of NCW through Caco-2 cell monolayers and its interaction with the DPPC bilayers. Results revealed that after a 3 h incubation, the Papp (AP-BL) and Papp (BL-AP) values of NCW at a concentration of 5 mmol/L were (22.24 ± 4.52) × 10-7 and (6.63 ± 2.31) × 10-7 cm/s, respectively, with the transport rates of 1.59 ± 0.32 and 0.62 ± 0.20%, indicating its moderate absorption. NCW was found to be transported via PepT1 and paracellular transport pathways, as evidenced by the significant impact of Gly-Pro and cytochalasin D on the Papp values. Moreover, NCW upregulated ZO-1 mRNA expression. Further investigation of the ZO-1-mediated interaction between NCW and tight junction proteins will contribute to a better understanding of the paracellular transport mechanism of NCW. The interaction between NCW and the DPPC bilayers was predominantly driven by entropy. NCW permeated the bilayers through electrostatic, hydrogen bonding, and hydrophobic interactions, resulting in increased fluidity, flexibility, and disorder as well as phase transition and phase separation of the bilayers.

Biophysical analysis on molecular interactions between chitosan-coated sinapic acid loaded liposomes and mucin

BACKGROUND

The mucus biomembrane is a primary barrier in delivering drugs to the brain via intranasal delivery. The negatively charged nanoformulations suffer from poor mucoadhesive ability and less retention time in the nasal cavity, which limits further therapeutic efficacy. The positively charged chitosan coating on liposomes may overcome the above issues. Hence, understanding the molecular interactions between the chitosan-coated liposomes and mucin is essential for developing an effective drug delivery system.

METHODS

The molecular interactions of mucin with sinapic acid-loaded liposomes (SA-LPs) and mucin with chitosan-coated sinapic acid-loaded liposomes (SA-CH-LPs) were assessed using different biophysical instrumental analyses by interpreting the UV-Vis spectra and observing the particle size, polydispersity index, surface charge, and rheological behavior.

RESULTS

The mucin interaction with SA-CH-LPs showed increased viscosity as compared to SA-LPs with mucin. Moreover, the mucin interaction with SA-CH-LPs showed stronger mucoadhesive properties as compared to SA-LPs with mucin. The electrostatic interaction between positively charged SA-CH-LPs and negatively charged mucin was responsible for the enhanced mucoadhesive property.

CONCLUSION

The positively charged SA-CH-LPs highly interact with mucin as compared to negatively charged SA-LPs. The mucoadhesive property of SA-CH-LPs could improve the retention of SA in the nasal cavity as compared to SA-LPs. These findings emphasize the importance of chitosan in modulating the mucoadhesive behavior of liposomes.

GENERAL SIGNIFICANCE

Overall, this study helps to understand the molecular interactions and mucoadhesive nature of the chitosan-coated liposomes with mucin, which is essential for biological activity in the physiological environment.

ApoE3 Anchored Liposomal Delivery of Rivastigmine for Brain Delivery: Formulation, Characterization, and In Vivo Pharmacokinetic Evaluation

Rivastigmine hydrogen tartrate (RHT) is an acetylcholinesterase (AChE) inhibitor used in the management of Alzheimer's disease (AD). RHT is a BCS class-I drug that undergoes significant first-pass metabolism. Permeating a hydrophilic drug through the brain remains a major challenge in brain delivery. In this study, the RHT was incorporated inside the hydrophilic core of liposomes (LPS) and then coated with the ApoE3. ApoE3-coated RHT-loaded liposomes (ApoE3-RHT-LPS) were fabricated through the thin film hydration method using DSPE-PEG. The coating of LPS with ApoE3 enhances brain uptake and improves Aβ clearance. The results obtained from the physicochemical characterization demonstrated that ApoE3-RHT-LPS shows a particle size of 128.6 ± 2.16 nm and a zeta potential of 16.6 ± 1.19. The % entrapment efficiency and % drug loading were found to be 75% and 17.84%, respectively. The data obtained from TEM and SEM studies revealed that the particle size of the LPS was less than 200 nm. An in vitro AChE assay was performed, and the results demonstrated the AChE inhibitory potential of ApoE3-RHT-LPS. Through the intravenous route, an in vivo pharmacokinetic study of formulation displayed improved brain uptake of RHT by ~ 1.3-fold than pure RHT due to ApoE3 coating. In vivo, biodistribution studies in vital organs suggested that the biodistribution of RHT to the liver was significantly reduced (p < 0.001), signifying an increase in the drug's half-life and blood circulation time. All research findings suggested that ApoE3 coating and LPS strategy are proven effective for improving the brain uptake of RHT designed for the management of AD.

The role of amiodarone in post-operative hypothyroidism patient with factitious thyrotoxicosis and atrial fibrillation: A case report

INTRODUCTION

Factitious thyrotoxicosis includes all causes of thyrotoxicosis from the short or long-term ingestion of thyroid hormone, of which one of the complications is atrial fibrillation.

CASE PRESENTATION

A woman, 71 years old, complained of chest palpitations. She had a medical history of thyroidectomy, hypertension, and dyslipidemia. In addition, she took Levothyroxine, amlodipine and simvastatin regularly. On physical examination, the general status was weak, with vital signs showing blood pressure (BP) of 170/100 mmHg, heart rate (HR) of 130-150 bpm, irregular rhythm, respiratory rate (RR) of 20×/min, axillary temperature of 36.8 °C, and oxygen saturation (SpO2) 98 % with room air. The abnormal laboratory found were significant increase in total T4, total T3, FT4, and low levels of TSH. The first electrocardiogram (ECG) showed AF and Burch Watorfsky's score was 45. The AF was treated with a loading dose of amiodarone 150 mg in 10 min and decreased gradually. She had received a high-calorie, protein and low-salt diet of 2100 kcal/day, termination Levothyroxine usage, propranolol of 10 mg/8 h, amlodipine of 5 mg/day, and lisinopril of 5 mg/day. Treatment for AF was continued with a maintenance dose of amiodarone IV 300 mg in 6 h, then 600 mg in 18 h, warfarin tablet 2 mg/day (according to treatment from a cardiologist), and atorvastatin 20 mg/day at night. After 6 days of treatment, the patient experienced improvement and continued discharge. The patient improved on an outpatient basis and was monitored periodically.

DISCUSSION

Monitored treatment of thyrotoxicosis and AF management with 3 principles can minimize complication severity.

CONCLUSION

Early, effective and monitored treatment of thyrotoxicosis is vital to manage AF in achieving a better outcome.

Liposomal Forms of Fluoroquinolones and Antifibrotics Decorated with Mannosylated Chitosan for Inhalation Drug Delivery

The severe course of COVID-19 leads to the long-terming pulmonary diseases, such as bacterial pneumonia and post-COVID-19 pulmonary fibrosis. Thus, the essential task of biomedicine is a design of new effective drug formulations, including those for inhalation administration. In this work, we propose an approach to the creation of lipid–polymer delivery systems for fluoroquinolones and pirfenidone based on liposomes of various compositions decorated with mucoadhesive mannosylated chitosan. A generalizing study on the physicochemical patterns of the interactions of drugs with bilayers of various compositions was carried out, and the main binding sites were identified. The role of the polymer shell in the stabilization of vesicles and the delayed release of the contents has been demonstrated. For the liquid–polymer formulation of moxifloxacin, a prolonged accumulation of the drug in lung tissues was found after a single endotracheal administration to mice, significantly exceeding the control intravenous and endotracheal administration of the drug.

Ruscogenin interacts with DPPC and DPPG model membranes and increases the membrane fluidity: FTIR and DSC studies

Ruscogenin, a kind of steroid saponin, has been shown to have significant anti-oxidant, anti-inflammatory, and anti-thrombotic characteristics. Furthermore, it has the potential to be employed as a medicinal medication to treat a variety of acute and chronic disorders. The interaction of a drug molecule with cell membranes can help to elucidate its system-wide protective and therapeutic effects, and it's also important for its pharmacological activity. The molecular mechanism by which ruscogenin affects membrane architecture is still a mystery. Ruscogenin's interaction with zwitterionic dipalmitoyl phosphatidylcholine (DPPC) and anionic dipalmitoyl phosphatidylglycerol (DPPG) multilamellar vesicles (MLVs) was studied utilizing two non-invasive approaches, including: Fourier Transform Infrared (FTIR) spectroscopy and Differential Scanning Calorimetry. Ruscogenin caused considerable alterations in the phase transition profile, order, dynamics and hydration state of head groups and glycerol backbone of DPPC and DPPG MLVs at all concentrations. The DSC results indicated that the presence of ruscogenin decreased the main phase transition temperature (T_m) and enthalpy (ΔH) values of both membranes and increased half height width of the main transition (ΔT_1/2). The FTIR results demonstrated that all concentrations (1, 3, 6, 9, 15, 24 and 30 mol percent) of ruscogenin disordered the DPPC MLVs both in the gel and liquid crystalline phases while it increased the order of DPPG MLVs in the liquid crystalline phase. Moreover, ruscogenin caused an increase in the dynamics of DPPC and DPPG MLVs in both phases. Additionally, it enhanced the hydration of the head groups of lipids and the surrounding water molecules implying ruscogenin to interact strongly with both zwitterionic and charged model membranes.

Interaction mechanism of three egg protein derived ACE inhibitory tri-peptides and DPPC membrane using FS, FTIR, and DSC studies

Understanding the interaction of food derived angiotensin converting enzyme (ACE) inhibitory peptides and intestinal epithelial cell membrane may help to improve their absorption. This research aimed to study the molecular interaction of ACE inhibitory tri-peptides ADF, FGR, and MIR with DPPC membrane during absorption process. The DPPC liposome was prepared and characterized, then used as a model membrane. The permeability of tri-peptides across the membrane was investigated using Fluorescence spectroscopy. The effect of tri-peptides on the structure and dynamics of DPPC bilayers was determined using Fourier transform infrared spectroscopy. The effect of tri-peptides on the phase transition temperature in the DPPC membrane was also analyzed using Differential scanning calorimetry. The results showed that ACE inhibitory tri-peptides ADF, FGR, and MIR can penetrate into both the membrane-water interface and hydrophobic region of DPPC bilayer, and the tri-peptide FGR have higher permeability across the membrane.

Microfluidic-mediated self-assembly of phospholipids for the delivery of biologic molecules

The encapsulation of biologic molecules using a microfluidic platform is a procedure that has been understudied but shows great promise from initial reported studies. The study focusses upon the encapsulation of bovine serum albumin (BSA) under various parameters and using multiple phospholipids to identify optimal conditions for the manufacturing of protein loaded lipid nanoparticles. Additionally, encapsulation of the enzyme trypsin (TRP) has been investigated to show the eligibility of the system to other biological medications. All liposomes were subject to rigorous physicochemical characterisation, including differential scanning calorimetry (DSC) and Fourier-transform infrared spectroscopy (FTIR), to document the successful synthesis of the liposomes. Drug-loaded liposome stability was investigated over a 28-day period at 5 °C and 37 °C, which showed encouraging results for 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) at all concentrations of BSA used. The sample containing 1 mg/ml BSA grew by only 10% over the study, which considering liposomes should be affected highly by biologic adsorption, shows great promise for the formulations. Encapsulation and in vitro release studies showed improved loading capacity for BSA compared to conventional methods, whilst maintaining a concise controlled release of the active pharmaceutical ingredient (API).

Interaction of DPPC liposomes with cholesterol and food protein during in vitro digestion using Dynamic Light Scattering and FTIR spectroscopy analysis

The influence of cholesterol (CHO), bovine serum albumin (BSA) and lactoferrin (LF), on the phase transition temperature (T_m) and structure of DPPC liposomes during in vitro digestion was investigated using Dynamic Laser Scattering (DLS) and Fourier Transform Infrared Spectroscopy technologies (FTIR). CHO enhanced bilayers thickness and acyl chain order, especially in DPPC:CHO of 6:1, with the average size increase to 1.77 ± 0.20 μm and broaden of phase transition (T_m 45.8 °C). Protein critically impacted on the liposomal structure through formation of hydrogen bonds between in DPPC and protein. Liposomal size and T_m were significantly changed after simulated gastric digestion, whereas the pancreatic incubation can broaden transition phase and weaken functional groups of liposomes. Our data provided a better understanding on structure changes of CHO-containing membrane and protein addition by revealing T_m and chemical bonds details, and added to current knowledge for evaluating the different component on liposomal digestibility in food area.

Design and development of topical liposomal formulations in a regulatory perspective

The skin is the absorption site for drug substances intended to treat loco-regional diseases, although its barrier properties limit the permeation of drug molecules. The growing knowledge of the skin structure and its physiology have supported the design of innovative nanosystems (e.g. liposomal systems) to improve the absorption of poorly skin-permeable drugs. However, despite the dozens of clinical trials started, few topically applied liposomal systems have been authorized both in the EU and the USA. Indeed, the intrinsic complexity of the topically applied liposomal systems, the higher production costs, the lack of standardized methods and the more stringent guidelines for assessing their benefit/risk balance can be seen as causes of such inefficient translation. The present work aimed to provide an overview of the physicochemical and biopharmaceutical characterization methods that can be applied to topical liposomal systems intended to be marketed as medicinal products, and the current regulatory provisions. The discussion highlights how such methodologies can be relevant for defining the critical quality attributes of the final product, and they can be usefully applied based on the phase of the life cycle of a liposomal product: to guide the formulation studies in the early stages of development, to rationally design preclinical and clinical trials, to support the pharmaceutical quality control system and to sustain post-marketing variations. The provided information can help define harmonized quality standards able to overcome the case-by-case approach currently applied by regulatory agencies in assessing the benefit/risk of the topically applied liposomal systems.

Mechanistic Understanding from Molecular Dynamics in Pharmaceutical Research 2: Lipid Membrane in Drug Design

We review the use of molecular dynamics (MD) simulation as a drug design tool in the context of the role that the lipid membrane can play in drug action, i.e., the interaction between candidate drug molecules and lipid membranes. In the standard "lock and key" paradigm, only the interaction between the drug and a specific active site of a specific protein is considered; the environment in which the drug acts is, from a biophysical perspective, far more complex than this. The possible mechanisms though which a drug can be designed to tinker with physiological processes are significantly broader than merely fitting to a single active site of a single protein. In this paper, we focus on the role of the lipid membrane, arguably the most important element outside the proteins themselves, as a case study. We discuss work that has been carried out, using MD simulation, concerning the transfection of drugs through membranes that act as biological barriers in the path of the drugs, the behavior of drug molecules within membranes, how their collective behavior can affect the structure and properties of the membrane and, finally, the role lipid membranes, to which the vast majority of drug target proteins are associated, can play in mediating the interaction between drug and target protein. This review paper is the second in a two-part series covering MD simulation as a tool in pharmaceutical research; both are designed as pedagogical review papers aimed at both pharmaceutical scientists interested in exploring how the tool of MD simulation can be applied to their research and computational scientists interested in exploring the possibility of a pharmaceutical context for their research.

The distinct effects of two imidazolium-based ionic liquids, [C4mim][OAc] and [C6mim][OAc], on the phase behaviours of DPPC

Ionic liquids (ILs) are potential green solvents with very broad application prospects. Their toxicity and other biological effects are largely related to their hydrophobic properties. In this work, the effects of two imidazolium-based ILs with either a butyl or a hexyl chain, [C₄mim][OAc] or [C₆mim][OAc], on the phase behaviours of a representative phospholipid, dipalmitoylphosphatidylcholine (DPPC), were examined using synchrotron small- and wide-angle X-ray scattering and differential scanning calorimetry techniques. A series of samples with a lipid : IL molar ratio ranging from 1 : 0 to 1 : 4/1 : 5 were prepared as aqueous dispersions in the form of multi-lamellar vesicles. The two ILs were found to have distinct effects on the phase behaviours of DPPC. For [C₄mim][OAc], its effect is very limited. In contrast, for [C₆mim][OAc], it could eliminate the pre-transition of DPPC, markedly affect the main phase transition of the lipid, and insert into the DPPC bilayer at gel state to form an interdigitated gel phase. The findings increased our understanding on the biological effects of imidazolium-based ILs and might shed light on the design of novel IL-based antimicrobials.

Structure of DPPC Monolayers at the Air/Buffer Interface: A Neutron Reflectometry and Ellipsometry Study

Langmuir monolayers of 1,2-dipalmitoyl-sn-glycerol-3-phosphocholine, known as DPPC, at the air/water interface are extensively used as model systems of biomembranes and pulmonary surfactant. The properties of these monolayers have been mainly investigated by surface pressure–area isotherms coupled with different complementary techniques such as Brewster angle microscopy, for example. Several attempts using neutron reflectometry (NR) or ellipsometry have also appeared in the literature. Here, we report structural information obtained by using NR and ellipsometry on DPPC monolayers in the liquid condensed phase. On one side, NR can resolve the thickness of the aliphatic tails and the degree of hydration of the polar headgroups. On the other side, ellipsometry gives information on the refractive index and, therefore, on the physical state of the monolayer. The thickness and surface excess obtained by multiple-angle-of-incidence ellipsometry (MAIE) is compared with the results from NR measurements yielding a good agreement. Besides, a novel approach is reported to calculate the optical anisotropy of the DPPC monolayer that depends on the orientation of the aliphatic chains. The results from both NR and ellipsometry are also discussed in the context of the existing results for DPPC monolayers at the air/water interface. The differences observed are rationalized by the presence of buffer molecules interacting with phospholipids.