When Do You Know if an Enyme Degrades

Enzymatic Deposition

Enzymatic degradation of glucose and oxygen in the torso has stimulated the study on the development of an implantable EBC in the human trunk.

From: Handbook of Biofuels , 2022

Responsive polyelectrolyte multilayer nanofilms for drug delivery applications

Anandhakumar Sundaramurthy , in Stimuli Responsive Polymeric Nanocarriers for Drug Commitment Applications, Volume 1, 2018

9.5.3 Biological stimuli

Enzymatic degradation has been shown to be an bonny method for delivering the drugs. Deposition of polymeric films with enzymes resulted in release of film- embedded molecules [78]. Previous reports show that pepsin and DNase I have been used to degrade ALG/CHI and DNA/poly(diallyldimethylammonium chloride) (PDAD) films, respectively [79,80]. Various capsule systems designed with enzymatically or hydrolytically degradable polycations (e.1000., DS/pARG HA/PLL and PSS/pHPMA-DMAE) have been demonstrated using Pronase, a mixture of proteases that degrades polycations in a nonspecific manner [81,82]. Capsules made of HA/PLL undergo degradation later their internalization into the cell that shows their potential in intercellular drug commitment [81].

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Complexes of Starch with Organic Guests*

Piotr Tomasik , Christopher H. Schilling , in Advances in Carbohydrate Chemistry and Biochemistry, 1998

vi Digestibility of Starch-Lipid Complexes

Enzymatic deposition of amylose is inhibited by complexation with lipids. ^848–894 Decreased digestibility of complexes in vitro and in vivo have been observed, and such results suggest the feasibility of enzyme-assaydeterminations of starch. ⁸⁹⁵ These observations also have potential dietetic implications. The combination of starch and lipid components decreases the nutritive value of a meal, and conversely, separation of these components increases the nutritive value. Fatty metabolites (such equally fat acids and mono-glycerides) are adsorbed in a micellar course in the upper part of the intestine. Within this organ, these metabolites can come into contact with nondigested amylose, particularly if its form in food provides for deadening amylolytic degradation (as in breadstuff and cereals). Since approximately ane wt% of lipids in cereal starch can complex about v wt% of amylose, ⁸⁶¹ the formation of dietary fibers in the intestine is quite likely. ⁸⁹⁶ This possibility can positively induce peristaltic action of the human intestine and should exist avoided in animal feedstuffs. Experiments ⁸⁹⁶ in vitro betoken that there is a rather small difference in the charge per unit of degradation past pancreatic alpha to amylase of gelatinized starch and its circuitous with the monoglyceride of oleic acrid. The deviation in this rate (given equally dextrose equivalent) reaches 20%.

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Polymers in Biology and Medicine

S. Taguchi , ... Y. Doi , in Polymer Science: A Comprehensive Reference, 2012

9.09.4.3 Enzymatic Degradation of P(3HB)

The enzymatic deposition of water-insoluble P(3HB) material by water-soluble PHA depolymerase is a heterogeneous reaction, involving two steps, namely, adsorption and hydrolysis; the kickoff stride is adsorption of the enzyme on the surface of P(3HB) material by the binding domain of the enzyme, and the second step is hydrolysis of polymer chains past the active site of the enzyme.

The enzymatic degradation rate of a solid P(3HB) can exist adamant by monitoring the changes in the turbidity of a suspension of polymer granules, in the weight of films, and in the amounts of liberated water-soluble monomers and oligomers, as a part of reaction fourth dimension. Past using each detection system, it has been found that the enzymatic degradation rate of P(3HB) is strongly dependent on enzyme concentration. The degradation rate increases to a maximum value with the concentration of PHA depolymerase, followed by a gradual decrease. ^192–195 Such enzyme concentration dependence has been explained by the rest between the amounts of adsorbed enzymes and free accessible polymer chains on the surface. Based on the kinetic analyses of enzyme adsorption on the surface of P(3HB), the ratio of surface occupation of enzyme molecules is given by the Langmuir adsorption. ¹⁹⁶ Adsorption of each molecule of PHA depolymerase has been plant to be irreversible, while it is easily substituted by the attack of the enzyme molecules in the solution. ¹⁹⁷ Therefore, the apparent adsorption isotherms of PHA depolymerase seem to obey the Langmuir isotherm. Under such kinetic control for enzyme adsorption, information technology has been concluded that the majority of catalytic domains of adsorbed enzyme are able to hydrolyze P(3HB) bondage on the surface at low concentrations of PHA depolymerase, while at loftier concentrations of the enzyme, the majority of catalytic domains are not attainable to P(3HB) chains on the surface due to dumbo coverage of the substrate-binding domains on the surface of P(3HB).

Kasuya et al. ¹⁹³ investigated the kinetics and mechanism of surface hydrolysis of P(3HB) with PHA depolymerase from Ralstonia pickettii T1 at different reaction temperature and pH. The rate abiding of enzymatic hydrolysis increased with a rise in temperature, while the adsorption equilibrium constant decreased. The activation energy of hydrolysis by the catalytic domain calculated from the results obtained was found to exist 82   kJ   mol⁻¹.

The rates of enzymatic degradation of P(3HB) by PHA depolymerase are strongly dependent on not only the backdrop of PHA depolymerase (due east.thou., temperature, pH, and concentration), simply besides the properties of P(3HB) materials (e.g., crystallinity, crystal size, and lamellar thickness). P(3HB) is a semicrystalline thermoplastic, and can be processed by conventional extrusion and molding equipment. Crystallinity, size of spherulites, size of crystals, and lamellar thickness of P(3HB) can vary with the crystallization conditions. The rate of enzymatic hydrolysis of melt-crystallized P(3HB) picture by PHA depolymerase from R. pickettii T1 decreased with an increment in the crystallinity of P(3HB) movie, while the size of spherulites hardly affected the rate of hydrolysis. ¹⁹⁸ Information technology is suggested that the PHA depolymerase predominantly hydrolyzes polymer chains in the amorphous phase and subsequently erodes the crystalline phase. Tomasi et al. ¹⁹⁹ prepared cook-crystallized P(3HB) films of different crystal size and examined the charge per unit of enzymatic hydrolysis by PHA depolymerase from Pseudomonas lemoignei. They reported that the rate of enzymatic erosion of melt-crystallized P(3HB) films by PHA depolymerase decreased with an increase in the average size of P(3HB) crystals. Koyama and Doi ²⁰⁰ and Abe et al. ²⁰¹ investigated the enzymatic degradation rates of melt-crystallized films of P(3HB) and its copolymers with both different crystallinity and dissimilar lamellar thickness. They confirmed that the overall erosion rate of melt-crystallized films significantly decreased every bit the degree of crystallinity was increased ( Effigy 16 (a)). In addition, it was revealed that the enzymatic erosion rate of the crystalline stage determined from overall erosion rate and crystallinity of the films decreased with an increment in the lamellar thickness (see Effigy 16 (b)).

Figure 16. Relation between the charge per unit of enzymatic erosion and the degree of crystallinity (a) and the lamellar thickness (b) for melt-crystallized PHA films.

Reproduced with permission from Abe, H.; Doi, Y.; Aoki, H.; Akehata, T. Macromolecules 1998, 31, 1791. ²⁰¹ Copyright 1990 American Chemic Order.

Thus, the crystalline region plays a decisive role in the degradation process of P(3HB) materials. To elucidate the mechanism of enzymatic degradation of the crystalline region of P(3HB) past PHA depolymerase, the enzymatic degradation of unmarried crystals of P(3HB) by PHA depolymerases from bacteria and fungi has been studied. ^202–206 Marchessault and co-workers first performed the enzymatic deposition of P(3HB) single crystals by PHA depolymerases. They evaluated the deposition beliefs by turbidimetric and titrimetric assays as well as by monitoring the changes in the molecular weight of the polymer. No decrease in molecular weight was observed in the partly degraded polymer, suggesting preferential degradation from the crystal edges rather than the chain folds of the lamellar surface and supporting the hypothesis of a combined endo- and exo-deposition machinery by the fungus Aspergillus fumigatus and the bacterium P. lemoignei. Nobes et al. used TEM to evidence the conversion of PHA single crystals into fibril-like morphologies after enzymatic degradation. Iwata et al. ^{204,205,207–209} investigated the enzymatic degradation of single crystals of P(3HB) and its copolymer single crystals by PHA depolymerases from Pseudomonas stutzeri and R. pickettii T1 by TEM and atomic strength microscopy (AFM). All these researchers reported that the unmarried crystals were enzymatically hydrolyzed preferentially at the crystal edges (ac airplane) and ends (bc plane) rather than at the chain-folding surfaces (ab plane) (see Figure 17 ). In add-on, many narrow cracks and minor crystal fragments along the crystallographic a-axis were produced from P(3HB) single crystals by the enzymatic reaction, independent of both surface morphology of the single crystals and the types of PHA depolymerases. This is considering loose-concatenation packing regions existing along the a-axis with higher molecular mobility are preferentially degraded rather than the tight-chain packing regions by PHA depolymerases.

Figure 17. A schematic model of enzymatic hydrolysis of P(3HB) unmarried crystals by PHA depolymerase consisting of binding and catalytic domains.

Reproduced with permission from Iwata, T.; Doi, Y.; Kasuya, K.; Inoue, Y. Macromolecules 1997, 30, 833. ²⁰⁵ Copyright 1997 American Chemical Order.

The adsorption of PHA depolymerase to P(3HB) single crystals has been investigated using immunogold labeling techniques. ^204,205 Information technology has been found that PHA depolymerase adsorbed homogeneously on the surfaces of single crystals without site specificity. PHA depolymerases are inactive toward rubbery amorphous polyesters such every bit native amorphous PHA granules and chemosynthetic atactic P(3HB). ²¹⁰ However, when amorphous P(3HB) was composite with crystalline P(3HB) or other crystalline polyesters, the enzymatic erosion was induced. ^210–212 These results suggest that the PHA depolymerase is liable to adsorb to stable crystalline lamellae, only it inappreciably binds to mobile polymer chains in an amorphous state. ²¹⁰

It has been proposed that the substrate-binding domain has another function in addition to its adsorption office. Murase et al. ^213,214 showed that the adsorption of a mutant PHA depolymerase, in which the hydrolysis site of the catalytic domain was inactivated, gave some cracks along the a-centrality of the P(3HB) unmarried crystal. Numata et al. ^215,216 investigated the changes in the surface morphology and property of P(3HB) single crystals by the adsorption of PHA depolymerase using existent-time AFM observations and frictional force microscopic (FFM) assay. PHA depolymerase was detected on P(3HB) crystals before the removal of the enzyme, and afterward a concave feature equally wide as the enzyme molecule (25   nm in width) was generated later the removal of the enzyme. In improver, the values of frictional force on the surface of P(3HB) single crystals after the enzymatic treatment patently decreased in comparison with those before the treatment. These results suggest that the adsorption of PHA depolymerase provides nonhydrolytic disruption of the construction of the polymer on the surface of P(3HB) crystals.

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Formulation design in drug delivery

Ghada Zidan , ... Ali Seyfoddin , in Engineering Drug Delivery Systems, 2020

2.four.2.ii Enzymatic deposition

Polymers that undergo enzymatic degradation can only degrade upon contact with enzymes in the body. Such polymers can be adapted to be organ-specific to only release the loaded drug in a specific tissue site. Adjustments to the degradation profile of the polymer can be achieved past controlling the cantankerous-linking density of the hydrogel. Given the sensitivity and specificity of the enzymatic deposition process, temperature, pH, and ionic strength are key parameters to be considered. Moreover, highly cross-linked networks might crusade steric hindrance to enzyme penetration and thus reduce the degradation rate and release of the drug. Near natural polymers such as proteins (gelatine, collagen, albumin, fibrin) and polysaccharides (sugar and dextran) undergo enzymatic degradation. Enzymatic degradation can besides occur in some synthetic polymers polydiols and PVA [21].

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Disposal

Michael Niaounakis , in Biopolymers Reuse, Recycling, and Disposal, 2013

4.4.2 Enzymatic Hydrolysis

The enzymatic degradation of aliphatic polyesters by hydrolysis is a two-pace process. The beginning step involves adsorption of the enzyme on the surface of the substrate through the surface-binding domain, and the second step involves hydrolysis of the ester bond [14].

JP2003221461 A (2003, TOYOTA CENTRAL RES & DEV) discloses a method of efficiently lowering the molecular weight of an aliphatic polyester, especially PLA, and improving its biodegradability. The aliphatic polyester resin is heated and hydrolyzed in the presence of one or more kinds of compounds containing a nucleophilic nitrogen atom in order to lower its molecular weight, thereby preventing the increase of crystallinity that takes place upon lowering the molecular weight past a simple heating hydrolysis. The easily biodegradable aliphatic polyester thus obtained is further subjected to enzymatic monomer decomposition by microorganisms. The monomer decomposition may be an artificial enzymatic or chemical decomposition. The chemical compound containing nitrogen is an ammonium common salt, an amine compound, or urea. The compound containing a nucleophilic nitrogen atom is harmless to organisms, and is used as a establish nutrient. Microorganisms perform enzymatic decomposition in the environment.

JP2010131528 A (2010, TOYO SEIKAN KAISHA LTD) discloses a method of treating an organic waste containing a biodegradable biopolymer by solubilizing the organic waste. Information technology entails adding microorganisms that generate enzymes and/or enzymes that decompose the biopolymer fermenting with solubilized decomposition product, and so collecting the fermented products. The preferred organic solvent is ethanol and the preferred biopolymer is PLA. The enzyme used for solubilization decomposition is protease, lipase, cutinase, cellulase, or esterase.

JP2010116481 A (2010, TOYO SEIKAN KAISHA LTD) discloses a method for the deposition of a resin composition containing two different aliphatic polyesters (A) and (B) by subjecting the resin limerick to a hydrothermal treatment and/or a heat treatment and then to an enzymatic decomposition. Aliphatic polyester (A) has a crystallinity of less than twenty%. Aliphatic polyester (B) has a higher degradation charge per unit than polyester (A) and polyester (B) releases an acid having a pH of 2.0 or less when it is hydrolyzed in water at a concentration of 0.005 g/ml. Polyester (B) hydrolysis releases oxalic acid or maleic acrid. The enzymatic decomposition takes place in an enzyme liquid containing hydrolase. Examples of easily degradable aliphatic polyester (B) include poly(ethylene oxalate), poly(neopentyl oxalate) (PNOx), poly(ethylene maleate), etc.

An exemplary resin limerick is obtained by dispersing polyoxalate (B) in PLA (A). The hydrothermal treatment and heat process are carried out at 250°C or more for less than five min, and 200°C or more for less than five min, respectively. The method is used to break down the compositions institute in items such as containers, cover materials for tray cups, pouches, stickers, and pillow packing bags.

While disposal by hydrolysis is a significant step in minimizing litter and long-term landfill, it has the disadvantage of discarding the valuable polyhydroxycarboxylic acrid.

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Fundamentals of Quorum Sensing, Analytical Methods and Applications in Membrane Bioreactors

Nouha Bakaraki Turan , Güleda Önkal Engin , in Comprehensive Analytical Chemistry, 2018

1.3.2.i AHL Lactonases

Lactonolysis is defined equally the enzymatic degradation of AHL using AHL lactonases enzymes. Members of the genus Bacillus, P. aeruginosa PAIA, Arthrobacter sp., Klebsiella pneumoniae, Agrobacterium tumefaciens, and Rhodococcus sp. are bacteria able to produce an enzyme AiiA, responsible for enzymatic degradation of AHL or lactonolysis (Yeon, 2009). In addition, two different hydrolase from leaf isolates known to support lactonolysis are AiiM and AidH from Microbacterium testaceum StLB037 and Ochrobactrum sp. T63, respectively. AHL lactonase sources are many: (i) some of them derived from soil metagenomes, (ii) others from the marine bacterium such every bit Pseudoalteromonas byunsanensis 1A01261, or (three) from fungi such as Ascomycota and Basidiomycota knowing by their ability to dethrone AHLs, noting that most of AHL lactonase sources are bacterial origin. Metallo-β-lactamase-like lactonases, phosphotriesterase, and paraoxonases are three different enzymes belonging to the lactonases family. Several examples may be listed to highlight the importance of the enzymatic quenching past AHL lactonases as a novel approach able to interfere with the bacterial infection. For instance, aiiA from Bacillus cereus A24 was used to degrade 3OC12-HSL. It prevents the increase in the concentration of C4-HSL, inhibits virulence factors, and swarming motion in P. aeruginosa (Fetzner, 2015).

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The Biodegradation of Biodegradable Polymeric Biomaterials

Chien-Chi Lin , Kristi S. Anseth , in Biomaterials Scientific discipline (Third Edition), 2013

Enzymatic Deposition of Constructed Polymers

Several synthetic polymers are susceptible to enzymatic degradation. For example, amorphous poly( l-lactide) can exist degraded past proteinase Grand, while both baggy and crystalline poly(ε-caprolactone) can be degraded by lipases of diverse origins (Liu et al., 2000). Enzymatic degradation of synthetic polymers can exist either surface erosion or bulk degradation, depending on the location and stability of the acting enzyme. All the same, due to the limited water accessibility of most hydrophobic polymers, surface erosion is the dominant degradation mechanism and the kinetics are like to the hydrolytic surface erosion described in an earlier section of this chapter. For hydrophilic polymers permitting the diffusion of the enzyme to the interior of the polymer, the degradation is also mediated by surface erosion mechanism if the rate of enzymatic polymer bond cleavage is faster than the rate of enzyme diffusion.

Bulk deposition of synthetic polymers induced past enzymatic activity may occur under two atmospheric condition: (i) the enzyme is able to infiltrate and distribute uniformly throughout the bulk of the polymer; and (2) the charge per unit of enzymatic bond cleavage is slower than the diffusion of the enzyme. Typically, hydrogels containing enzymatic cleavable units in their polymer backbone fall into this category of degradation. Nether these assumptions, Michaelis–Menten enzymatic kinetics are commonly used to predict the enzymatic degradation rates of synthetic polymers via bulk deposition machinery:

(23) ${\upsilon }_0={\upsilon }_{\mathit{max}}\frac{[S]}{{\mathrm{Yard}}_G+[S]}$

Hither, five₀ and v_max are the initial and maximum reaction rate of degradation, respectively. [Southward] is the degradable polymeric substrate concentration, and K_M is the Michaelis–Menten constant.

In Eq. (23), v_max tin also be expressed as:

(24) ${\upsilon }_{\mathit{max}}={\mathrm{1000}}_{cat}[\mathrm{East}]$

where k_cat is the catalytic constant describing the charge per unit of enzymatic deposition of polymer bonds and [E] is the concentration of enzyme catalytic sites.

Every bit in other enzymatic reactions, both k_cat and K_M are of import parameters in characterizing the enzymatic deposition of polymers. While k_{true cat} represents the sensitivity of an enzyme for a specific polymeric substrate, K_M is the substrate concentration needed to achieve a one-half-maximum enzyme velocity. Factors affecting these parameters will likewise determine the charge per unit of polymer degradation.

While simple Michaelis–Menten kinetics can be used to describe enzymatic polymer bail cleavage, they do not provide information regarding the mass loss behavior of the polymers. Sophisticated mathematical models are often required in order to correlate microscopic enzymatic bond cleavage to macroscopic polymer mass loss. For instance, to describe the mass loss of cantankerous-linked hydrogels containing enzymatic cleavable substrate (e.one thousand., polycaprolactone), a statistical model (similar to the one described before in the hydrolytic deposition of hydrogels) integrating the structural information of the hydrogels was developed (Rice et al., 2006). In this particular example, Eqs. (eleven) to (fourteen) tin be used again except that f _PLA is at present replaced with f _CAP, where CAP represents caprolactone subunits. In addition to the network information, the Michaelis–Menten reaction equations and the outset-guild decay in agile enzyme (e.g., lipase) concentration can be described by the following equations:

(25) $\mathrm{Fifty}ipas\mathrm{due\; east}+CAP\rightleftharpoons E^{\ast }\mathrm{Due\; south}\stackrel{{\mathrm{1000}}_{\mathrm{two}}}{\to }Lipase+D$

(26) $\mathrm{50}ipase+CAP\stackrel{m_d}{\to }InactiveLipa\mathrm{southward}\mathrm{eastward}$

(27) $\frac{[Lipas\mathrm{east}]}{{[\mathrm{Fifty}ipa\mathrm{due\; south}e]}_0}=e^{-k_{d}t}$

Here, Eastward ∗ Southward is the enzyme–substrate complex, D is the deposition product, CAP is the caprolactone block, k_two is CAP degradation late constant and thousand_d is the first order rate abiding for deactivation of the lipase.

Time-derivatives of lipase and CAP concentrations tin can be expressed every bit (Rice et al., 2006):

(28) $\begin{array}{c}\frac{d[\mathrm{Fifty}ipase]}{dt}=-k_1[CAP][Lipase]+k_{-1}[E\ast \mathrm{Due\; south}]\\ \text{undefined}\text{undefined}\text{undefined}\text{undefined}\text{undefined}\text{undefined}\text{undefined}\text{undefined}\text{undefined}\text{undefined}\text{undefined}\text{undefined}\text{undefined}\text{undefined}\text{undefined}\text{undefined}\text{undefined}\text{undefined}\text{undefined}\text{undefined}\text{undefined}+{\mathrm{1000}}_{\mathrm{ii}}[E\ast S]-{\mathrm{thou}}_d[Lipa\mathrm{southward}\mathrm{due\; east}]\end{array}$

(29) $\frac{d[CAP]}{dt}=-{\mathrm{1000}}_{\mathrm{ane}}[CAP][Lipase]+{\mathrm{1000}}_{-\mathrm{i}}[\mathrm{Due\; east}\ast S]$

where thou₁ and k₋₁ are the forward and backward enzymatic reaction charge per unit constants for lipase and CAP units, respectively. Solving equations (27) to (29) yields an equation related to the fraction of CAP unit degradation (Rice et al., 2006):

(30) $\frac{N_{CAP}}{{\mathrm{Due\; north}}_{CA{P}_0}}=\mathit{exp}\left[\frac{\mathrm{thousand}\ast {[\mathrm{Fifty}ipase]}_0}{{\mathrm{thousand}}_d}(e^{-{\mathrm{thousand}}_{d}t}-1)\right]$

Effigy Ii.iv.3.6 illustrates the mass loss profiles as a office of fourth dimension by solving Eq. (30). It can be seen that the rates of PEG-PCL hydrogel mass loss are functions of several factors, including kinetic parameters (k∗) and the one-half-lives of the acting enzyme. One must notation that the assumption of bulk deposition will not hold at high enzyme concentrations (i.e., loftier reaction rates) or in thick gels where the diffusion timescale is big. Nether these conditions significant surface erosion will occur, which complicates the interpretation of modeling results.

Figure Two.iv.3.six. Calculated mass loss profiles for varying values of thousand∗ or lipase concentration. Baseline values are shown in solid blackness line, with k∗ = 31.iv Fifty⋅mol⁻ⁱ⋅min⁻¹, lipase concentration = 0.2 mg/mL, and active lipase half-life = twenty.4 h (corresponding to k _d = 5.66 × 10⁻⁴ min⁻¹). Baseline values for each variable were multiplied past 0.5 (solid grey line), i.5 (dashed black line), and two.0 (dashed gray line).due north₀ = twoscore in all calculated profiles. Enzyme was refreshed at 116 hr and 216 hr.

(From Rice et al. (2006). Biomacromolecules.)

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Inclusion (Clathrate) Compounds

Jerry L. Atwood , in Encyclopedia of Physical Science and Technology (Tertiary Edition), 2003

III.B Cyclodextrins

Cyclodextrins are cyclic oligosaccharides formed by the enzymatic degradation of starch. In the process, one portion of the starch helix is hydrolyzed off, and the ends are joined together. The nigh mutual results are molecules made up of six, vii, or 8 glucose units; α-, β-, or γ-cyclodextrins, respectively. A schematic view of these structures is shown in Fig. eighteen.

Figure 18. Representations of the structures of α-, β-, and γ-cyclodextrins. (The α-cyclodextrin is the smallest.)

Since the glucose unit of measurement is a rigid one, the cyclodextrins possess cavities even every bit isolated molecules in the absence of guests. All cyclodextrins have a height of about 8.0   Å and an outer diameter of xv–xviii   Å. The diameter of the cavity is iv.seven–5.2   Å for α-, 6.0–6.4   Å for β-, and 7.5–8.3   Å for γ-cyclodextrin. These values are comparable to molecular dimensions for many simple organic molecules. Figure nineteen shows a model view of the complex of p-iodoaniline with α-cyclodextrin.

Effigy xix. Structure of the circuitous of α-cyclodextrin and p-iodoaniline. Space-filling models have been used.

Information technology is significant to annotation that the cyclodextrins have good water solubilities. They are finding extensive use in the pharmaceutical industries of some countries as vehicles either to solubilize drugs or to protect them as they pass through the digestive organisation. Other applications in such diverse areas as that of food additives and in pesticide formulations have been realized.

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Sustainable cyclodextrin in fabric applications

Nagender Singh , Omprakash Sahu , in The Impact and Prospects of Greenish Chemical science for Textile Engineering, 2019

4.2.ane Chemistry of cyclodextrins

The cyclodextrins (CDs) are produced by enzymatic deposition of saccharide and starch. These are cyclic oligosaccharides comprised of glucose units linked by α-1,four-glycosidic bonds. Cyclodextrins are bachelor in three forms such as α-cyclodextrin, β-cyclodextrin, and γ-cyclodextrin, which comprised of six, 7, and eight α-1,4-glycosidic bonds (equally shown in Figs. 4.1 and iv.two). These are lipophilic from inside which tin host the guest molecules such as oils, waxes, and fats. The ability to form host-guest complexes is vital for stabilizing and solubilizing hydrophobic compounds in solvents (Singh et al., 2002).

Fig. iv.ane. Schematic representations of cyclodextrins.

Modified from Harada, A., Takashima, Y., 2013. Macromolecular recognition and macroscopic interactions by cyclodextrins. Chem. Rec. xiii(5), 420–431.

Fig. four.two. Chemic structures of cyclodextrins.

Modified from Myrick, J.Thousand., Vendra, V.M., Krishnan, South., 2014. Self-assembled polysaccharide nanostructures for controlled-release applications. Nanotechnol. Rev. 3(4), 319–346.

The β-cyclodextrin and its derivatives are about consumed and attractive cyclodextrin as compared to other cyclodextrins, considering of its uncomplicated production, lower cost, no skin sensibilization and irritation, and no mutagenic upshot. The structural framework β-CD is quite attractive with molecular weight 1135   1000/mol, height 750–800   pm, external diameter 1530   pm, and internal diameter 600–680   pm (as shown in Fig. 4.iii). The crenel volume is 260–265   Å^three and the water dissolution is 1.85   thou/100   mL. β-CD is sensitive to acid and stable in brine solutions due to the hydrophobic cavity and hydrophilic nature of the outer department (Seel and Vögtle, 1992; Loftsson et al., 2005).

Fig. 4.3. Structural framework of cyclodextrins.

Modified from Tonelli, A.E., 2003. The potential for improving medical textiles with cyclodextrin inclusion compounds. J. Text. App. Technol. Manag. 3(2), 1233.

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Tissue-engineered heart valves

Petra Mela , ... Anthal I.P.M. Smits , in Principles of Heart Valve Technology, 2019

6.5.one.ane Natural polymer–based hydrogels

Natural polymers offering the advantage of inherent bioactivity and enzymatic degradation when compared with their synthetic counterparts. Withal, they suffer from batch-to-batch reproducibility and are, to some extent, more limited in the manufacturability, every bit the apply of harsh solvents and large temperature ranges normally practical to constructed polymers may not be uniform with maintaining their bioactivity and functionality. Natural polymers have been extensively applied for the fabrication of TEHVs. Mainly, purified collagen and fibrinogen have been used, with only few examples involving GAGs, alginate, and gelatin being reported.

Collagen is a chief component of the ECM of native cardiovascular structures responsible for their mechanical strength. Purified collagen hydrogels have been applied to engineer matrices and consummate valvular conduits, alone or in combination with other valvular ECM components [69–74]. Neidert and colleagues made a bileaflet heart valve by molding bovine collagen entrapping dermal neonatal homo dermal fibroblasts. The authors exploited the cell-induced gel compaction to obtain biomimetic commissure-to-commissure fibril alignment in the leaflets and circumferential alignment in the root. Still, the synthesized ECM was mechanically weaker than the native one and was well-nigh entirely composed of collagen, defective other components of fundamental importance for the valve functionality [73]. With the rationale of improving the bioactivity, Brougham et al. reported the fabrication of a semilunar heart valve by freeze-drying a collagen–GAG copolymer suspension in a custom-designed mold. They were able to obtain the complex 3D geometry with homogeneous, interconnected porosity, showing the potential of the established method for complex 3D constructs [74]. Chen and colleagues introduced another fundamental protein for middle valves and fabricated a bilayered collagen–elastin scaffold with well-connected interface and anisotropic bending moduli depending on the loading directions, which recapitulated the behavior of the native heart valves. Furthermore, asymmetric distribution of cardiosphere-derived cells within the scaffold was shown [69].

Fibrin has also demonstrated first-class properties as heart valve matrix material. Information technology offers many advantages, such every bit its autologous origin [75], the rapid polymerization, the tuneable degradation via protease inhibitors [76], the autologous release of growth factors [77], and the manufacturability into complex 3D geometries with homogeneous prison cell seeding [78]. Fibrin is known to facilitate ECM synthesis by seeded cells in higher amounts than in collagen gels and, importantly for cardiovascular tissue applied science, elastin production in fibrin gels is too clearly enhanced [79]. Fibrin has been employed as a cell carrier in combination with some other scaffold material [23,lxxx] or every bit main scaffold material [26,78,81–84] to engineer heart valves with good functionality. Like to what has been accomplished with a collagen-based valve, the compaction of the fibrils that occurs in the poly peptide-based gels nether the contraction forces of the polish muscle cells could exist beneficially exploited to create ECM alignment in the constructs [83]. However, cell-mediated tissue compaction has been proven as one of the major drawbacks of middle valves, including those employing fibrin, resulting in valvular insufficiency in vitro and in vivo [11,18,23,26–30]. A farther disadvantage is the weak mechanical properties that have fabricated the implantation of such valves in the systemic circulation rather challenging. Different strategies take been adopted by the various groups to overcome these limitations, including the removal of the cells through decellularization processes (treated afterward on in this section) to avoid tissue shrinkage, the adoption of a tubular leaflet design, and the reinforcement of the scaffolds with macroporous textiles to contrast tissue shrinkage and increment the mechanical backdrop. Fiber reinforcement of fibrin-based constructs resulted in mitral valves, aortic valve conduits, and aortic valves with tubular design leaflets able to withstand the systemic circulation in vitro, to be implanted either surgically or by minimally invasive delivery (Fig. 6.4B) [25,67,85,86]. Although the fabric reinforcement has the potential of preventing tissue contraction, further noesis volition be gained past the in vivo evaluation of these valves.

A multistep molding technique [81] and 3D bioprinting (eastward.g., Fig. 6.4F) [68] of hydrogel-based heart valves have also proven adequate for the realization of complete valved conduits with spatially controlled material and/or cells distribution contrary to most studies relying on just one material and one ECM synthesizing cell type. Duan and colleagues fabricated living alginate/gelatin hydrogel valve conduits with anatomical compages and direct encapsulation of polish muscle cells in the valve root and VIC in the leaflets [68].

Elastin-similar recombinamers were added to fibrin-based construct with the rational of providing a functional elastic network to overcome the claiming of generating mature elastin in vitro in cardiovascular constructs [81,87]. Elastin is a central component of center valves as information technology provides elasticity and resilience, besides modulating important cellular processes [88–90]. The mechanisms leading to a lack of elastogenesis in vitro is all the same not understood, and groups that were able to induce elastin germination in jail cell-laden gels in vitro were, however, not able to transfer the results to TEHVs fabricated with the aforementioned materials [79,91,92].

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