Phospholipid

They are phospholipid bilayered vesicles with a hydrophilic core with an overall positive charge with the capability of encapsulating cargo inside the aqueous core as well as the lipid membrane.

From: Fundamentals of Bionanomaterials , 2022

Bio-based chemicals from biorefining: lipid and wax conversion and utilization

Y. Yang , B. Hu , in Advances in Biorefineries, 2014

21.2.two Phospholipids

Phospholipids are mostly made from glycerides by substituting one of the three fatty acids by a phosphate group with some other molecule attached to its end. The other form of phospholipids is sphingomyelin, which is derived from sphingosine instead of glycerol. Phospholipids are soluble in both water and oil (amphiphilic) because the hydrocarbon tails of two fatty acids are still hydrophobic, simply the phosphate group end is hydrophilic. Phospholipids are the major component of cell membrane to form lipid bilayers. Figure 21.ane shows the representative structure of common lipids (Gunstone et al., 2007).

21.one. The representative construction of common lipids (Gunstone et al., 2007): (a) Monoglycerides (b) diglycerides, (c) triglycerides, (d) phospholipids derived from glycerol, (eastward) example of phospholipids derived from sphingosine (Sphingomyelin).

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Adsorption and its Applications in Industry and Environmental Protection

S.-W. Tam-Chang , I. Iverson , in Studies in Surface Science and Catalysis, 1999

iii.4 Bilayers and vesicle immobilization

Phospholipid vesicles and bilayers have also been immobilized on gold. One approach to vesicle adsorption uses mixed SAMs with brusk chain ethyleneoxythiols and cholesterol derivatized alkanethiols interim as anchoring units which become integrated into the lower leaflet of the phospholipid bilayer [ 91]. Some other method of anchoring a phospholipid bilayer to a monolayer is elementary fusion. Pierrat and coworkers [90] allowed very long chain alkanethiolates (octadecylmercaptan) to be ordered into a SAM, after which by immersing the surface in a vesicle solution phospholipids were fused into the SAM. A biomimetic associates is and so formed as pyruvate oxidase of East. coli is then incorporated into the phosphonate head of the SAM supported (half) bilayer. Upon incorporation of the enzyme, its activity remains intact.

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Algal spent biomass—A pool of applications

A. Catarina Guedes , ... F. Xavier Malcata , in Biofuels from Algae (Second Edition), 2019

2.3.1 Phospholipids

PLs consist of fat acids, and a phosphate-containing moiety attached to either glycerol or (the amino booze) sphingosine—thus resulting in compounds with fat-soluble and water-soluble regions that are ubiquitous in cell membranes. Glycerol-containing PLs include phosphatidic acid, phosphatidylcholine (PC), phophatidylethanolamine, phosphatidylinositol, and phosphatidylserine. Sphingomyelin (SPH)—a major PL, consisting of sphingosine and PC. PLs and choline have several benefits for human health, every bit depicted in Table 4. The level of PLs in various red macroalgae varies from x% to 21% of full lipids; these are largely PC (62%–78%) and PG (10%–23%) [81].

Dietary PLs act as natural emulsifiers, and as such they facilitate digestion and assimilation of fat acids, cholesterol and other lipophilic nutrients. Algal phopholipids appear to carry a number of advantages relative to fish oils, because they are more resistant to oxidation (rancidity), take college contents of EPA and DHA, with superior bioavailability, and provide a wider spectrum of wellness benefits for humans and animals [sixteen].

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Some approaches to large-scale manufacturing of liposomes

Abdelbary Elhissi , ... Waqar Ahmed , in Emerging Nanotechnologies for Manufacturing (Second Edition), 2015

fifteen.2 Structure and Self-Assembly of Phospholipids

Phospholipids are amphiphilic (amphipathic) molecules having polar (hydrophilic) headgroups and nonpolar (hydrophobic) hydrocarbon chains. Phospholipids are diverse molecules with different headgroups, and different lengths and degrees of saturation of hydrocarbon chains. Phospholipids can be classified every bit constructed, such as dimyristoylphosphatidylcholine and dipalmitoylphosphatidylcholine (DPPC) ( Figure 15.2), and natural, such every bit egg (EPC) or soya (SPC) phosphatidylcholine. Natural phospholipids comprise a mixture of phosphatidylcholines having chains of different lengths and degrees of unsaturation [6].

Figure xv.2. Chemical structure of the synthetic phospholipid DPPC.

Amphiphilic molecules undergo a geometry-dependent rearrangement when aqueous phase is added, in guild to mask the hydrophobic moieties from the polar aqueous surround [ii,7]. If an amphiphilic molecule has a cylindrical geometry (i.east., the cantankerous-sectional expanse of polar and nonpolar moieties are approximately equal), adjacent molecules align parallel to each other to class a monolayer, which in plow arranges symmetrically with some other monolayer to form a bilayer sheet called the lamella or lamellar (cubic) stage.

Lasic [eight] has suggested a mechanism which describes the formation of liposomes from phospholipid molecules. Briefly, when aqueous stage is added to a thin film of phospholipid, the hydration of the outer monolayer predominates compared to the inner layers, resulting in the expansion of the polar headgroups of phospholipid molecules [8] and the germination of "blisters" [9]. Aqueous phase penetration through these "blisters" results in the formation of phospholipid bilayers, which develop into tubular fibrils that in turn increase the area in contact with the aqueous phase. The bilayer sheets will accept hydrophobic moieties of the amphiphile exposed to the aqueous phase. This is thermodynamically unfavorable, which causes the bilayers to round off and form multilamellar liposomes [8]. Even so, it is essential to bear in mind that for liposomes to form, the hydration process must be undertaken at a temperature significantly higher than that of the phase transition (T m) temperature of the phospholipid(s) selected. This is the temperature at which the phospholipid membrane passes from a tightly ordered gel (L ßʹ) stage to the less ordered liquid-crystalline (L α) stage, where the flexibility of phospholipid molecules is higher [vi].

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Lipid Membrane Models for Biomembrane Properties' Investigation

Carine Sebaaly , ... Catherine Charcosset , in Electric current Trends and Future Developments on (Bio-) Membranes, 2019

three.1 Phospholipids

Phospholipids are amphiphilic molecules composed of a glycerol backbone conveying a hydrophilic polar head group and 2 hydrophobic fatty acyl tails ( Van Meer et al., 2008; Vance and Vance, 2002). The major phospholipids in eukaryotes are composed of a glycerol courage conveying a phosphate (phosphatidic acid) esterified to a choline (phosphatidylcholine), ethanolamine (phosphatidylethanolamine), serine (phosphatidylserine), glycerol (phosphatidylglycerol), or inositol (phosphatidylinositol) (Van Meer et al., 2008; Vance and Vance, 2002). Upon hydration in an aqueous medium, the polar region of phospholipids orientates towards the aqueous medium, while the nonpolar sites mutually attract and orientate inward towards each other. Due to their amphipathic structure, phospholipids are able to form lipid bilayers and micelles acting as a diffusing barrier (De Leeuw et al., 2009).

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Electrospun Nanofibers for Food and Food Packaging Technology

Jing Tian , ... Xiangyang Dong , in Electrospinning: Nanofabrication and Applications, 2019

15.2.3.1 Phospholipids

Phospholipids are amphiphilic molecules that contain a polar head grouping and a hydrophobic tail with diverse degrees of instauration ( Kelly et al., 2015). Lecithin contains phospholipids and neutral lipids (Xu and Wu, 2009). Lecithin can course cylindrical and wormlike reverse micelles in nonaqueous solutions (Schurtenberger et al., 1991). The main component of lecithin is phosphatidylcholine, which is one of the main components of biofilm. Lecithin is a nontoxic natural surfactant due to its amphiphilic chemical structure (Ahmadi et al., 1994). Lecithin has been applied in health intendance products in the nutrient industry.

Lecithin solution has been reported to exist electrospun to obtain nanofibers, for which CHCl3 and N,N-dimethylformamide at a ratio of 7/iii (w/w) were used equally the solvent system. Nanofibers of 45   wt% lecithin have an average bore of 3.3   μm. When the phospholipid concentration increases from 47 to 50   wt%, the average diameter of the fibers increases from iv.2 to 5.9   μm (Mckee and Long, 2006). Huang has reported electrospun phospholipid nanofibers from chemically modified phospholipids (Huang et al., 2010b). The homogeneous nanofibers with diameters ranging from 70 to 120   nm are obtained with a polymer concentration of 8   wt%.

Jorgensen et al. (Jørgensen et al., 2015) have reported the fabrication of continuous fibers via electrospinning with a mixture of phospholipid and asolectin (Fig. 15.28C–F). The average diameter of equally-prepared nanofibers is about 3.iii   μm. The impact factors on the morphology and the boilerplate diameter of the electrospun phospholipid nanofibers are investigated. The results indicate that the concentrations of the phospholipid and the solvent have an effective touch on the morphology of fibers.

Figure 15.28. Scanning electron microscopy (SEM) images of nanofibers electrospun from (A) 47% (west/w) and (B) 50% (westward/w) phospholipid solution. (C) SEM prototype of electrospun 45% w/w asolectin solution in CHCl3:dimethylformamide (3:2 five/five). SEM images of nanofibers electrospun from (D) 50% (w/west) asolectin in cyclohexane, (E) 60% (due west/w) asolectin in limonene, and (F) lx% (w/w) asolectin in isooctane.

 (A–F) Adapted from Jørgensen, L., Qvortrup, G., Chronakis, I.S., 2015. Phospholipid electrospun nanofibers: consequence of solvents and co-axial processing on morphology and fiber diameter. RSC Advances 5, 53644–53652. (B) Adapted from Mckee, M.G., Long, T.E., 2006. Phospholipid nonwoven electrospun membranes. Science 311, 353–355.

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Nanolipid Materials for Drug Delivery Systems

Jeetendra Singh Negi , in Label and Biology of Nanomaterials for Drug Delivery, 2019

4 Phospholipids

Phospholipids (PLs) are also amphiphilic molecules similar PEG-fat acid glycerides. The structure of a phospholipid molecule contains 2 hydrophobic tails of fat acids and i hydrophilic head of phosphate moiety, jointed together by an alcohol or glycerol molecule [90]. Due to this structural arrangement, PLs form lipid bilayers and are a key component of all the prison cell membranes. Based on the existence of the type of alcohol present, PLs tin can exist categorized into 2 categories of glycerophospholipids and sphingomyelins. Glycerophospholipids contain a glycerol courage and are the main blazon of PLs in the eukaryotic cells. Generally, naturally occurring glycerophospholipids have alpha construction and L-configuration. Based on the variation in the type of hydrophilic caput group, glycerophospholipids can be further subclassified into subtypes such as phosphatidyl choline (PC), phosphatidyl ethanolamine (PE), phosphatidic acid (PA), phosphatidyl serine, phosphatidyl inositol, and phosphatidyl glycerol [91]. Similarly, other criteria can be used to subclassify the glycerophospholipids such as variation in the polar moiety length, variation in the number, saturation of aliphatic groups, and type of bonding (Tabular array 6.three). Sphingomyelins contain a sphingosine backbone and are the integral part of the lipid bilayer of animal cell membranes. Shapiro and Flowers confirmed that biologic sphingomyelins take a d-erythro configuration [92]. A detail comparing betwixt PC and sphingomyelins is given in Table half dozen.iv.

Table 6.three. Different Classifications for Phospholipids

Criteria Chemic Structure Examples
Head group variation
Phosphatidylcholine (PC)
Phosphatidylethanolamine (PE)
Phosphatidic acid (PA)
Phosphatidylglycerol (PG)
Phosphatidylserine (PS)
Apolar moieties length
Dimyristoyl PC
Dipalmitoyl PC
Distearoyl PC
Aliphatic groups saturation Unsaturated
 Dioleoyl PC
Saturated
 Distearoyl PC
Type of bonding between aliphatic chains and glycerol Ester bail
 Distearoyl PE
Ether bond
 Choline plasmalogen
Ethanolamine plasmalogen
The number of aliphatic chains One acyl groups
 Lysophospholipids
Two acyl groups
 Dioleoyl PE

Table 6.4. Comparison Between Phosphatidylcholine and Sphingomyelin Phospholipids

Criteria Phosphatidylcholines Sphingomyelins
Backbone Glycerol Sphingosine
Double bond in amide-linked acyl bondage i.1–1.5 cis-double bonds 0.ane–0.35 cis-double bonds
Hydrophobic region saturation Lower saturations Higher saturation than PCs
Acyl chain length More than twenty and disproportionate 16–xviii carbon long chain and symmetric
Phase transition temperature (Tc) xxx°C 30–45°C, higher than PCs
Interaction with cholesterol PC-cholesterol bilayer has less compressibility and higher permeability to water SM-cholesterol bilayer has loftier compressibility and lower permeability to water

PLs, i of the main components of prison cell membranes, have an excellent biocompatibility profile. Due to their amphiphilic nature, PLs can form cocky-assembly supermolecular structures in aqueous media under sure conditions [93,94]. Also, like other surfactants, PLs tin be used to stabilize emulsion. PLs can be obtained from both natural and synthetic types of sources. The most widely used sources of natural PLs are vegetable oils such equally soybean and sunflower. PLs can also exist obtained from animate being tissues such as egg yolk [95]. Although both egg yolks and soybeans are the major sources for PLs, there is a difference in content and species of PLs (Tabular array six.5). The PLs such as PC, PE, lyso phosphatidyl choline, and lyso phosphatidyl ethanolamine tin can exist isolated and purified for pharmaceutical use from natural sources. Semisynthetic PLs are prepared by a change in head, tail grouping, or both on natural PLs, for example, the hydrogenation of natural unsaturated PLs into saturated PLs of higher melting point and oxidation stability [91]. Constructed PLs are prepared past attaching both polar and apolar moieties to a glycerol courage via formation of an ester or ether bond linkage. Additionally, the synthesis of sphingomyelins is more than complex than that for the glycerophospholipids. Synthetic PL preparation, isolation, and purification is always a costlier process than that from natural sources. However, the synthetic PLs have a relatively college purity and stability than natural PLs.

Table 6.5. Comparison Between Egg Yolk and Soybean Phospholipids

Criteria Egg Yolk PLs Soybean PLs
Proportion of PCs Higher Lower
Long concatenation poly unsaturated fatty acids Arachidonic acid and docosahexaenoic acid present Absent
Sphingomyelins Nowadays Absent
Saturation level of fat acids Higher Lower
Position of FA
•

sn-i position for saturated fatty acid.

•

sn-2 position for unsaturated fatty acrid.

 Both sn-1 and sn-two positions for unsaturated fatty acrid

PLs can form many types of assemblies in water due to their amphiphilic nature. Mostly, three different types of shapes—micelles, PLs bilayer, and hexagonal (HTwo) stage (Fig. 6.1)—are formed [96,97]. Lysophospholipids can be represented as an inverted cone molecular shape due to a larger caput grouping and a single hydrophobic chain. This inverted cone shape results in the formation of a micellar system. As shown in the figure, the cone-shape arrangement results in HII shape, whereas the cylindrical molecular shape favores the formation of a PLs bilayer. The PLs bilayer or liposome formation can exist affected by various factors that promote conversion of lamellar phase to HII phase:

Effigy 6.ane. Diverse polymorph phases of phospholipids.
•

For smaller PE head group, increase in acyl chain unsaturation, length, and temperature results in HTwo stage formation.

•

With loftier salt concentration, unsaturated PE, PG, CL, and PA can adopt HII phase.

•

At depression pH, protonation of the carboxyl grouping of PS and phosphate group of PA results in transition toward HII stage.

Due to their several advantages, PLs have been used every bit an additive in several drug commitment systems. PLs tin can serves several purposes in drug commitment systems:

•

modified drug release

•

bioavailability enhancement

•

lymphatic transport

•

reduced drug-related side effects

•

modified transdermal permeation

•

act as stabilizer (surfactants, solubilizer, permeation enhancer)

PLs have as well been used every bit a valuable additive in development of various nanocarriers. Physiologically, PC acts as nourishment for brain functions and as a substrate of synthesis of the neurotransmitter acetylcholine. Synthetic PLs are better in terms of quality and stability, but cost is higher than natural PLs. Although both egg phosphatidyl choline (EPC) and soybean phosphatidyl choline (SPC) tin be used for developing liposomes, EPC are favored over SPC. EPC liposomes have a college drug loading capacity and lower leakage charge per unit [98]. For example, Doxil contains hydrogenated soybean phosphatidylcholine (HSPC) and i,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[(polyethylene glycol)-2000] (PEG-DSPE) as a phospholipid to form stable liposomes with less phase transition tendency in physiologic conditions [99].

PEs play an of import part in membrane fusion due to less hydration trend. Similarly, PE-based liposomes also have a better interaction with the lipid bilayer. Dioleoyl phosphatidyl ethanolamine (DOPE) is used to develop pH-sensitive liposomes that tin avert the drug deposition by enzymes during endocytosis [100]. But to allow germination of liposomes, a carboxylic acidic grouping containing materials must be added. The anionic acidic groups provide electrostatic stabilization past repulsion at neutral pH, and liposomes remain stable. At acidic pH, carboxylic groups get protonated, which causes conversion of laminar grade into H2 phase. This unstable phase allows aggregation, fusion, and drug release in acidic pH environment. Further, add-on of DSPE-PEG to DOPE promotes the formation of liposomes, as well equally increase the in vivo apportionment time of liposomes [101].

The phase transition temperature (Tc) property of PLs can be utilized for the development of temperature-sensitive liposomes. Liposomes made upward of PLs having Tc higher than the physiologic temperature tin release drugs in cancer tissues associated with hyperthermia. At higher temperature the gel form transits into a liquid crystalline phase to release encapsulated drugs from the liposomes. Dipalmitoyl phosphatidylcholine (DPPC) has a Tc value of 41°C and is used for developing thermosensitive liposomes [102,103]. Further, drug-loading chapters and release charge per unit of DPPC liposomes tin can exist improved by adding other PLs such every bit distearoyl phosphatidylcholine (DSPC) and HSPC. However, for promoting drug release at tumor site the Tc of combinations of PLs should not exceed the range of 39–42°C. The optimum Tc value of 39–40°C was reported for the PEGylated liposomes of DPPC and lysolipid monopalmitoyl phosphocholine (MPPC) [104,105].

In general, the elimination of liposomes containing PLs such as PS, PG, and PA is very rapid due to MPS. This phagocytosis of liposomes depends on the hydrophilicity at the surface [106,107]. The presence of ganglioside and PI results in decreased uptake of liposomes past MPS and prolonged circulation fourth dimension. The apportionment time of liposomes likewise depends on the membrane fluidity. The liposomes with a rigid bilayer have a reduction in clearance by MPS [108,109]. The addition of loftier Tc (east.g., DSPC) and rigid PLs (east.thou., sphingomyelins) results in improvement in circulation time of liposomes. The presence of a more stable amide bond (difficult to break in vivo) and intermolecular hydrogen bonding potential make a solid lipid bilayer of liposome.

Recently, the circulation time of liposomes has been improved by PEGylation at the surface. But PEGylated liposomes are as well associated with accelerated claret clearance phenomenon on repeated injection [110,111]. The formation of anti-PEG IgM promotes rapid detection and clearance of PEGylated liposomes on subsequent exposures [112,113]. This ABC phenomenon of liposomes was found more for unsaturated PLs (e.g., SPC, EPC, and egg sphingomyelins) than that for saturated PLs (e.m., DPPC and HSPC). Additionally, this ABC phenomenon can also be observed for conventional liposomes. Even so, unlike PEGylated liposomes, the conventional liposomes elicit ABC miracle just at loftier dose (five   μmol/kg) and not at lower lipid dose of 0.001   μmol/kg [114].

The cationic lipid dimethyl dioctadecyl ammonium (DDA) has also been used to course cationic liposomes. Cationic liposomes have a do good of meliorate cell uptake, but at the same time, cationic nature also limits their apply due to undesirable toxicity. Yusuf et al. developed a novel lyophilized liposome by combining both cationic lipid DDA and TPGS [115]. The cell uptake of these liposomes was improved due to the glace activity of nanoparticles through mucus due the presence of TPGS and electrostatic allure between the cationic lipid and negatively charged nasal mucosa. Cationic liposomes also bind with anionic Dna and class a neutral system known as "Lipoplex" for cistron commitment.

Cholesterol is also added to liposome formulation with PLs every bit a membrane-stabilizing condiment. The presence of cholesterol in the lipid bilayer improves the stability of liposomes and also reduces the bilayer's permeability. This permeability alteration of the bilayer results in a reduction in encapsulated drug leakage during circulation.

Hu et al. prepared the hybrid nanoparticles by combining 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP) liposomes and PLGA with unlike concentrations of cholesterol [116]. The presence of cholesterol promoted fusion between nanoparticles, and at very high concentration, it can likewise slowed the release of antigen. Farther, fusion of nanoparticles during storage was prevented past PEGylation with DSPE-PEG. Liposomes can likewise exist modified into various types by adding a detail additive such as ethosomes, cubosomes, etc. PLs can too be used as an emulsifier in nanoemulsion formulations. Intralipid was the first safe nutritional intravenous fatty emulsion that contains egg phospholipids as an emulsifier. Apart from EP, egg lecithin is besides used equally an emulsifier for nanoemulsions. Yet, natural lecithin can too go converted to lysophospholipids, which may cause hemolysis after Four injection. Lenzo et al. reported the emulsification behavior of various PLs such as EPC, dioleoyl phosphatidylcholine (DOPC), dimyristoyl phosphatidylcholine (DMPC), 1-palmitoyl-2-oleoyl phosphatidylcholine (POPC), and DPPC [117]. They found a different blazon pathway of metabolism for different PLs. The elimination rate of DPPC-containing emulsions was slowest due to absence of both lipoprotein lipase–mediated hydrolysis and high-density lipoprotein association. Farther, presence of sphingomyelins in nanoemulsion tin can likewise increase apportionment fourth dimension and reduction in uptake by liver. Sphingomyelins is also an important function of lipoprotein surface and prevents binding of apolipoprotein Due east binding with emulsion and too reduces lipoprotein lipase-mediated hydrolysis [118]. Additionally, the combination of egg PLs and synthetic surfactants such as pluronic F68 has too been preferred. Tran et al. besides studied the effect of SPC inclusion in SEDDS. They observed the increase in droplet size in the presence of SPC, but in significant variation observed in bioavailability [119].

Due to their amphiphilic nature, PLs can also form micelles at or above a certain CMC value. The combination of PC and bile salt can form a mixed micelle organisation that acts equally delivery system by encapsulating poorly soluble drugs [120,121]. Although PC is generally water insoluble, the mixed micelles with bile salts forms a articulate solution and promotes the adsorption of lipophilic drugs. Similarly, SPC and glycocholic acrid–based mixed micelles also exhibit better stability and compatibility and are available commercially as Valium and Konakion [94]. PE and PEG mixtures can as well course sterically stabilized micelles instead of liposomes if their content exceeds certain limits. The PEG residual on the surface can forestall the MPS uptake, and the PL core can provide stability to SMM. Besides the circulation half-life of SMM tin can be reduced past replacing DSPE every bit the lipid component with DOPE [122]. Merely the solubilization capacity of SMM is limited for poorly h2o soluble drugs. The add-on of optimum proportion of EPC into PE-PEG SMM tin increase the solubilization potential.

Few drugs similar flavonoids accept a special affinity for phospholipids, and they tin can form complexes also known as phytosomes [123,124]. These PL and drug complexes have a better assimilation through the GI membrane, thus improving bioavailability of the parent drug. The stability of drugs is as well improved in complexed form with prolongation of drug action.

Turk et al. developed HLPNs for delivery of a hydrophobic drug using DSPE-PEG and PLGA. PLGA formed a hydrophobic core, where the hydrophobic drug becomes entrapped, and DSPE forms a shell around the core [125–128]. Similarly, SPC is also used to class a nanoshell around a PLGA core for delivery of methotrexate. The presence of PLs at the surface of HLPNs can mimic the biologic membrane and assist in ameliorate penetration through it [129]. Another type of HLPN involving PLs is PL-capped mesoporous silica nanoparticles [130]. Zhang et al. [132] developed such nanoparticles having a core of mesoporous silica for encapsulation of drugs surrounded past cationic PL, which allows prolonged release of drug [132]. At the outermost surface, they also attached another layer of negatively charged carboxy methyl chitosan, which governs pH-dependent release of the drug. Zhang et al. also developed HLPNs having a mesoporous silica cadre loaded with doxorubicin and covered it with a thermo-responsive PL layer containing DPPC/DSPC/cholesterol/DSPE-PEG [131]. This HLPN system prevents premature release of drug from mesoporous silica and releases drug at a faster rate only at pH   5, in comparison with pH   7.iv.

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Lubricants

Johannes Fink , in Petroleum Engineer's Guide to Oil Field Chemicals and Fluids (3rd Edition), 2021

iv.2.viii Phospholipids

In aqueous drilling fluids, phospholipids are constructive lubricating agents [ 35]. Phospholipids are naturally occurring compounds, for case, lecithin belongs to the class of phospholipids. An introduction to phospholipid chemistry has given by Hanahan [36]. Phospholipids find also use as polymers [37]. The structural units of a phospholipid are shown in Figure 4.i.

Figure 4.1

Figure 4.i. Structural units of a phospholipid (up) and the phospholipid formed from them (bottom).

Because of their ionic nature, some phospholipids are soluble in water. A preferred compound as lubrication condiment for aqueous drilling fluids is cocoamido propyl propylene glycol diammonium chloride phosphate [35]. Phosphatides or phospholipids are environmentally condom lubricating additives [19].

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Advanced biomaterials for biosensor and theranostics

Haoran Liu , ... Lei Yang , in Biomaterials in Translational Medicine, 2019

10.three.2.3 Lipid-based carriers

Phospholipids, the major component of prison cell membrane, take recently attracted extensive attending in drug commitment applications due to their excellent biocompatibility and amphiphilic characteristic for transporting both hydrophilic and hydrophobic agents. Liposomes are composed of natural or constructed phospholipids and their amphiphilicity helps them demark different polar molecules at the aforementioned time. In the work reported past Weng et al., QD-conjugated immunoliposome-based nanoparticles (QD-ILs), in which the luminescent quantum dots (QDs) were incorporated into immunoliposomes, were adult for cancer diagnosis and handling [160]. This liposomes-based carrier could significantly prolong circulation of QDs with a plasma concluding half-life of ~two.9   hours and therefore show highly efficient anticancer capability.

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Proceedings of the International Briefing on Colloid and Surface Scientific discipline

East. Okamura , ... Thou. Nakahara , in Studies in Surface Science and Catalysis, 2001

two SPECIATION OF BILAYER INTERFACES AS DD SITES

Phospholipid bilayer membranes can encompass a wide range of polarity in a limited colloidal or mesoscopic space [3]. In view of amphiphilic features of phospholipids, we can dissever membranes into the three zones; the polar headgroup (zone I), the amphiphilic interface between the headgroup and alkyl chains (zone II), and the hydrophobic bondage (zone III). In the polar zone I, the dielectric constant ε and the h2o density ρ(H2O) are very close to the majority aqueous phase. No substantial hydration tin can be recognized in the hydrophobic zone III. The amphiphilic zone II consisting of glycerol and ester carbonyl groups is characterized by a marked subtract in ε and ρ(HiiO) with an extreme gradient.

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