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Nanotechnology and Delivery System for Bioactive Antibiofilm Dental Materials
Published in Mary Anne S. Melo, Designing Bioactive Polymeric Materials for Restorative Dentistry, 2020
Jin Xiao, Yuan Liu, Marlise I. Klein, Anna Nikikova, Yanfang Ren
Recently, some new molecules are designed for efficient intraoral delivery of antimicrobials to prevent and treat the periodontal infection. The salivary statherin fragment, which has a high affinity for the tooth surfaces, was used as a carrier peptide. This was linked through the side chain of the N-terminal residue to the C-terminus of a defensive-like 12-residue peptide to generate two bifunctional hybrid molecules: one with an ester linkage, and the other with an anhydride bond between the carrier and the antimicrobial components. The bifunctional hybrid molecules could adhere to the tooth and pellicle surfaces uniformly and inhibit microbial accumulation. In addition, these bifunctional molecules would decrease the limitations and discomfort associated with the currently available local drug-delivery devices (Raj et al. 2008).
Chemical Structure of Lipid A: Recent Advances in Structural Analysis of Biologically Active Molecules
Published in Helmut Brade, Steven M. Opal, Stefanie N. Vogel, David C. Morrison, Endotoxin in Health and Disease, 2020
Ulrich Zähringer, Buko Lindner, Ernst T. Rietschel
The structure of E. coli lipid A is shown in Figure 1 and consists of a β-(1’→6)-interlinked GlcpN-disaccharide to which two phosphate residues are bound, one in ester linkage at position 4’ of the distal GlcN (II) and the other being α-glycosidically linked to the proximal GlcN (I) residue, forming the lipid A backbone [4’-P-β-d-GlcpN-(1’ →6)-α-d-GlcpN-(1→P]. A characteristic feature of this backbone is that two hydroxyl groups are not substituted, one in position 4 and the other in position 6’, the last serving as the attachment site for the core oligosaccharide. Four (R)-3-hydroxytetradecanoic acids [14:0(3-OH)] are bound by either amide (positions 2’ and 2) or ester linkage (positions 3 and 3) to the lipid A backbone. These acyl groups are termed primary fatty acids (16), distinguishing them from those ester-linked to the (β-hydroxyl groups of 14:0(3-OH), which are termed secondary fatty acids. These latter are exemplified by tetradecanoic (14:0) acid being ester-linked to the 14:0(3-OH) in position 3’ and dodecanoic acid (12:0) being linked to the hydroxyl group of the 14:0(3-OH) in amide linkage to position 2’. Thus, these two pairs of fatty acids form 3-acyloxyacyl acid residues, one being tetradecanoyloxytetradecanoyl [14:0(3-O(14:0))] ester-linked to position 3’, the other being dodecanoyloxytetradecanoyl [14:0(3-O(12:0))] amide-linked to position 2’. E. coli lipid A, therefore, represents a hexaacyl lipid A, having an asymmetric fatty acid distribution (4 + 2).
Fat
Published in Geoffrey P. Webb, Nutrition, 2019
Around 95% of dietary fats and oils and most body storage fat are in the form of triacylglycerol (TAG; the alternative term triglyceride is still widely used). The TAGs are composed of three fatty acids linked to the simple three-carbon molecule glycerol. Glycerol is a carbohydrate moiety which is called a tri-alcohol because it has one hydroxyl (alcohol) group on each of its three carbons. Each of these alcohol groups can form an ester linkage with the carboxyl (acid) group of a fatty acid. The three fatty acids in a TAG can be the same (simple TAG) or different (mixed TSG). A TAG molecule is represented diagrammatically in Figure 12.1a. Note that, the term “fat” is often used to imply a solid substance but oils and solid fats are collectively termed fats in this book.
Promising strategies for improving oral bioavailability of poor water-soluble drugs
Published in Expert Opinion on Drug Discovery, 2023
Bruna Rocha, Letícia Aparecida de Morais, Mateus Costa Viana, Guilherme Carneiro
Prodrugs are chemically modified molecules, inactive or partially inactive, that must first be chemically and/or enzymatically biotransformed in vivo, releasing the original active drug at the target site (Table 1). Bioprecursors are prodrugs derived from functional group modifications, which can be reverted by biotransformation in vivo. The more commonly modified functional groups are hydroxyls, carboxyls, carbonyls, amines, phosphates, phosphonates, esters, amidines, and guanines. Modification into esters is a widespread strategy for increasing the membrane partition by converting polar functional groups into nonpolar ones. After absorption, the ester linkage can be easily hydrolyzed by esterases found in the liver, blood, tissues, and other organs [34]. In carrier-linked prodrugs, the active moiety is temporarily linked to a carrier by a covalent bond to be broken by in vivo biotransformation [35]. Prodrugs can be linked to different types of carriers, including transport proteins, enzyme-dependent carriers, and pharmacologically active carriers, generally aiming at specific receptors or enzymes present at the site of drug action [35].
Why mRNA-ionizable LNPs formulations are so short-lived: causes and way-out
Published in Expert Opinion on Drug Delivery, 2023
It is very much proven that the mRNA-ionizable LNPs have gone through physical and chemical instability during storage conditions, which causes a short shelf life for the current commercialized mRNA-ionizable LNPs [22,40,66]. Among the physical instability, the alteration of the particle size is one of the predominant factors observed, which is directly correlated to the chemical instability of the mRNA–ionizable LNPs during the long-term storage condition. One of the causes is anticipated to be the breakdown of phospholipids in ionizable LNPs. The hydroperoxide attacks the unsaturated fatty acid moieties, which breaks down the chain structure of the helper lipids and alters the long-term stability of the mRNA-ionizable LNPs [61,67]. The impurities present in the PEG-group of PEG2000-C-DMG [61] are the source of the toxic substance for DSPC degradation. The carboxylic ester linkage of the DSPC is susceptible to hydrolysis after prolonged storage. The loss of the chain structure of the DSPC breaks down the structural orientation of ionizable LNPs and exposes the mRNA to pH-dependent hydrolysis and degradation. The process is irreversible; once the chain structure of the helper lipid or the PEG-lipid is broken, the specific structural orientation of the lipids inside the mRNA-ionizable LNPs is destroyed, which makes the mRNA vulnerable to rapid degradation like a naked mRNA.
L-Ascorbic acid and phosphatidylcholine complex vesicles: formation and elucidation of their biological activities, and their molecular interactions
Published in Journal of Microencapsulation, 2023
Thapakorn Tree-Udom, Chalermrat Simavong, Prapasiri Phetklung, Kanjanaporn Chompoonuch, Sagaw Prateepchinda, Supatchaya Jaemsai, Andrew William King, Oraphan King
Encapsulation of AA into a liposome vesicles (Gaber et al.2002) or a nanostructured lipid carrier (NLC) (Eh Suk et al.2020) can enhance its stability and protect it from radiation. However, the main drawback of lipid nanocarriers are that the lipid particles agglomerate, have low stability, cannot be stored for prolonged periods, have low loading, and release their loaded ingredients rapidly (Eh Suk et al.2020). Liposomes are constituted of phospholipids and have no reported allergic reactions when administered by parenteral route due to its good biocompatibility to the body (Mathur and Godbole 2018). Phospholipids such as phosphatidylcholine (PC) have an important role in biological membrane as they are soluble in both water and fat (Varde 2012, Kumar et al.2017). The structure of PC comprises of two main functional groups of an ester linkage and a phosphate group, providing hydrogen bonds to biomolecules. PC has been shown to be a viable delivery system for L-carnosine via ocular delivery (Abdelkader et al.2016), curcumin for hepatoprotective effect (Tung et al.2017) and Sinigrin for wound healing action (Mazumder et al.2016).