Van der Waals Interactions

Weak van der Waals interactions or hydrophobic forces aggregate the organic matter with phosphorus compounds (Piccolo, 2002) that may pb to organic affair fraction insoluble in water and poor food extractability.

From: Microbes in Land Utilise Change Management , 2021

Bulk Level Backdrop and its Role in Formulation Evolution and Processing

Shruti Moondra , ... Rakesh G. Tekadle , in Dosage Form Design Parameters, 2018

6.3.ii Van der Waals Force

van der Waals interaction is primarily responsible for these intermolecular forces, the ii molecules of the aforementioned textile (though electrically neutral) are brought together, the nonbonding electrons of both overlap each other and result in the repulsive forcefulness due to the presence of the surface electron. This molecule acts as a permanent dipole and the charge distribution results in formation of partially charged dipoles. Due to the presence of electrostatic allure, the opposite charged dipoles point at each other, and this allure is known every bit dipole–dipole interaction, also known as Keesom force. This interaction is a weak attraction observed in a large molecule with a force of 1–seven   kcal/mol and is inversely proportional to the distance betwixt molecules (Aulton, 2013).

These are weaker forces than covalent bonds, and the solids which are held together past van der Waals forces possess low melting point and are softer in nature every bit compared to other solids. They are independent of direction and are never diminished or saturated. The strength of this forcefulness is less, so this strength is non ordinarily seen in large molecules of size more than than 10   μm as information technology is linear to item bore. They do not agglomerate with each other; they only course a cluster. If van der Waals forces were not express to their force, the powder would cake instead of forming manageable particles. van der Waals forces are omnidirectional and then to manage this force relative to particle properties like size, the surface morphology of the substances should be managed (Aulton, 2013).

Moreover, the permanent dipoles cause baloney of the electric charge and shift the electrostatic charge to the neighboring polar and nonpolar molecules and induce polarizability. These attractive forces betwixt the permanent dipole and ion are known every bit a dipole-induced dipole, or Debye strength and the free energy required for this interaction is one–3   kcal/mol. Sarkar et al. demonstrated that the force of the allure is dependent on the dipole moment size and polarizability of the electron present. For example, phenylalanine is more polarizable than isoleucine (both are amino acids having a office in major biological functions in the human being body) due to the presence of π electron (Sarkar et al. 2017).

In add-on to the dipolar interaction known as van der Waals forces, there exists the attractive force betwixt polar and nonpolar molecules, which are held between cation and anion and this interaction is known as induced dipole-induced dipole interaction or London forces. The electron density in the molecules vibrates leading to fluctuating or varying dipoles, which are non oriented only held together by dispersive force, and inducing polarity in one some other. This attractive force helps in increasing the solubility of ionic crystals, the strength of the attraction is dependent on the number of electrons nowadays. The energy required for this force is 0.5   kcal/mol and vary inversely with the altitude betwixt the molecule (one/r7) (Sarkar et al., 2017).

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Antibody – Antigen Complexes, Three-Dimensional Structures

Steven Sheriff , in Encyclopedia of Immunology (Second Edition), 1998

Chemic nature of the interactions between antibody and antigen

The interactions of antibiotic with antigen are mostly van der Waals interactions involving surface residues, which despite being solvent exposed are relatively hydrophobic in nature. Even so, nigh antibody–antigen interactions contain at least i hydrogen bond or table salt link and typically contain many. For example, protein antigens form on the lodge of fifteen–twenty hydrogen bonds and/or salt links with antibody. However, it is impossible to extrapolate from the number of hydrogen bonds and salt links to the strength of the interaction between antibody and antigen. For case, the 26-10–digoxin complex has no hydrogen bonds and no salt links, but its association constant (∼1 × x 10m −1) is as strong every bit any whose three-dimensional construction is known. In the antibiotic–protein complexes, some water molecules accept been establish to be part of the interface between antibiotic and antigen.

In the antigen-bounden site, tyrosines and tryptophans occur more frequently than in the residue of the antibiotic. These ii residues are both capable of forming hydrogen bonds to solvent or antigen, but take big hydrophobic surfaces. Moreover, these large hydrophobic surfaces can exist immobilized with limited entropy loss due to restricted rotation of bonds in the circuitous. Thus the preference for tyrosines and tryptophans is most likely due to the unique nature of the antigen-binding site, which spends part of its time accessible to solvent and part of its time cached in a complex.

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Enzymatic Biocatalysis in Chemic Transformations

Jenny M. Blamey , ... Manfred Zinn , in Biotechnology of Microbial Enzymes, 2017

fourteen.3.two.2 Immobilization of Enzymes on Surfaces

The main interactions of biocatalysts with a support material ranges from uncomplicated van der Waals interaction to irreversible covalent bonding (Brady and Jordaan, 2009). The support itself may have diverse morphologies and one differentiates between surface zipper and lattice entrapment (Dark-brown et al., 1968).

In the case of surface zipper, a polymer particle or an inorganic particle serves as back up and anchor material. As polymeric materials polysaccharides, proteins and carbon materials are frequently used, only also synthetic polymers, such equally polystyrenes, polyacrylates, polyurethanes, polyamides, polypeptides, maleic acrid anhydride polymers and polyamides, are employed. Beside organic polymers, besides inorganic materials are used. Some are of natural origin, such as kieselgur, bentonite, attapulgite clays, and pumic rock. Also synthetic materials, such every bit porous and nonporous glasses, metal oxides, and silicates, have been studied and are practical today. Permeabilized or nonviable cells, multienzyme complexes, enzyme-cofactor pairs or simply purified enzymes are either covalently or noncovalently leap to the support fabric. For covalent binding the Schiff's base of operations formation, alkylation and arylation, amide and peptide formation, diazotization equally well as amidination have been described as suitable methods. The noncovalent binding can be established by a specific interaction among binding partners (hydrophobic interaction, antibody-antigen, lectin-carbohydrate, polyphenol-protein, biotin-streptavidin) or rather unspecific by free-free energy reduction, induced dipole interaction or ionic interaction.

With the onset of the era of nanotechnology, as well new technologies in biotechnology have evolved, coining the term nanobiotechnology. A new manufacture has emerged over the by fifteen years and many large companies have entered into this field but also new, innovative companies have been founded. Inofea, a Swiss company founded in 2011, has successfully entered into the field of biocatalysis focused on the production of novel biocatalysts for nutrient and drinkable, pharma and biotech, as well as for the cleantech market. Their choice of using magnetic carrier materials enables the client to completely recover the valuable catalysts from the reaction broth. With the application of an boosted matrix blanket on the surface (see likewise side by side department), the nano-sized catalysts became significantly more robust with respect to temperature, pH, and harsh treatments (ultrasound, urea, SDS, freeze-thawing, and protease). Thus, novel fluidized bed reactors tin can exist established where the biocatalyst is fully retained. With respect to immobilization, information technology was found that the blanket on the nano-magnets plays a significant role for the product efficiency of covalently bound enzymes (Zlateski et al., 2014).

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Molecular Cell Biology

East. London , in Encyclopedia of Jail cell Biology, 2016

What Agree Rafts Together?

The tight packing of lipid molecules in an ordered state bilayer arises from both van der Waals interactions between acyl bondage and polar headgroup interactions. Acyl chains with kinks due to cis double bonds, peculiarly in the eye of the chain, tend to resist tight packing, while long saturated acyl bondage favor tight packing. Nevertheless, a lipid having long saturated acyl chains does not guarantee that it has a stiff trend to form a tightly packed state with neighboring lipids because very large polar headgroups can inhibit tight acyl chain packing due to steric clashes with neighboring lipid headgroups. H-bonding between lipids may also contribute significantly to ordered domain germination (Li et al., 2001; Ramstedt and Slotte, 1999). In this regard, it should be noted that H-bonding groups in the polar headgroup and upper acyl chain region (due east.g., alpha OH groups on fatty acids) are in an environment significantly less polar than aqueous solution, and thus may H-bail to each other more strongly than they would in a fully aqueous environment.

Shut packing between sterols and other membrane lipids has been detected via the so-called condensing effect of sterols, in which the lateral surface area taken up by lipids at a given lateral pressure in monolayers is less than additive when sterols are mixed with phospholipid or sphingolipids. Favorable van der Waals interactions are probable to help bulldoze this close packing. In addition, close packing is enhanced by the hydrophobic outcome. The pocket-sized sterol OH group is insufficient to forestall contact of sterol hydrocarbon with water, and close packing allows the sterol to be subconscious from water by the larger polar headgroups of neighboring membrane lipids. This is known as the 'umbrella effect' (Huang and Feigenson, 1999). Gratuitous ceramide besides has a pocket-sized polar group, and its packing with other sphingolipids is also idea to be partly driven by an umbrella effect (Bjorkqvist et al., 2005; Megha and London, 2004; Zitzer et al., 2001). In fact, when ceramide and sterol are both present in a mixture of high-Tm and low-Tm lipids, contest for sites nether polar headgroups of other lipids can pb to displacement of sterols from ordered domains by ceramide (Bjorkqvist et al., 2005; Megha and London, 2004), or a competition that affects binding to proteins (Zitzer et al., 2001). Similar competition reflecting umbrella effects can be observed for several lipid-like molecules with minor polar headgroups (Alanko et al., 2005). Information technology should exist noted that ceramide-rich ordered membrane domains potentially exist in the gel state. Studies in yeast suggest gel-country domains can sometimes exist in cells (Aresta-Branco et al., 2011).

The ground of raft germination in the cytosolic ('inner') lipid leaflet/monolayer of membranes is unclear. Membrane lipid asymmetry is such that there is lilliputian sphingolipid in the cytosolic leaflet of eukaryotic cell membranes. Furthermore, model membrane studies on vesicles roughly mimicking either the exofacial (outer) or cytosolic leaflets of plasma membranes suggest that the lipid composition of the outer leaflet supports spontaneous Lo domain formation while that of the inner leaflet does not (Silvius, 2003; Wang and Silvius, 2001). Withal, numerous lipid-anchored cytosolic peripheral proteins appear to exist raft-associated (Melkonian et al., 1999). How do rafts form in cytosolic leaflets? Our knowledge of lipid disproportion is very incomplete. Mayhap some fraction of inner leaflet lipids are more saturated than mostly idea, and thus tin can aid form rafts. A dissimilar, long-held notion is that at that place is interleaflet coupling of lipid physical backdrop such that lipids organized into Lo domains in the exofacial leaflet might induce Lo state domains in the cytosolic leaflet. Studies using planar lipid bilayers (unsupported or cushioned supported) or lipid vesicles have shown that coupling can be detected in asymmetric model membranes when one leaflet contains SM or a saturated phospholipid and the other does not, and that acyl chain construction can modulate coupling (Chiantia and London, 2012; Collins and Keller, 2008; Wan et al., 2008). However, the details of the relationship between lipid structure and coupling remain largely uncharacterized.

It should as well be noted that membrane proteins could influence raft formation and interleaflet coupling. A poly peptide that has a favorable affinity for rafts by definition contributes to the free free energy of raft formation, and can even trigger raft formation in situations in which rafts formed by lipids alone would have a deadline stability (meet below).

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Nucleic Acids

Antonio Blanco , Gustavo Blanco , in Medical Biochemistry, 2017

Dna Denaturation

The compact construction of the double helix is maintained by the hydrogen bonds between base pairs and the van der Waals interactions betwixt the stacked bases. Diverse agents (estrus, strong alkalis, urea, and formamide) weaken such forces and promote the separation of the strands, in a process called denaturation. The resulting unwound polynucleotide strands adopt a random arrangement.

Deoxyribonucleic acid denaturation can be followed spectrophotometrically by measuring the absorption of UV light at 260 nm. In its native state, Dna absorbs less UV lite than the divide polynucleotide chains, a miracle that is called hypochromicity. If a Dna dispersion is slowly heated and its UV light absorption is followed, the temperature/absorbency relationship is an indicator of DNA denaturation (Fig. vi.fourteen). A sigmoid curve is obtained and every bit the temperature augments, an increment of assimilation (hyperchromic effect) occurs. When a given temperature is reached, the optical density does not further increase, which shows that DNA chains are completely separated and the molecules are maximally denatured.

Figure 6.xiv. Dna denaturation.

The modify in absorbency at 260 nm with increasing temperature (hyperchromic event) is shown. When both Deoxyribonucleic acid helices are completely separated, absorbance does not further increase with temperature. Mt, Melting temperature corresponding to the temperature at which l% of Deoxyribonucleic acid is denatured.

The temperature at which one-half of the DNA is denatured (corresponding to the midpoint or inflection of the curve) is known every bit the Deoxyribonucleic acid melting temperature (Mt). The Mt is characteristic for each Deoxyribonucleic acid nether defined atmospheric condition of pH and salt concentration, information technology ranges from fourscore to 100°C for DNA isolated from different organisms. Determining the value of Mt is useful to approximate the base limerick of DNA. Every bit the GC pair is maintained together by iii hydrogen bonds and the AT pair by two, a higher GC content results in a higher resistance to denaturation and is reflected past a college melting temperature.

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Biofilms and Illness: A Persistent Threat

Cameron Neil Melton , Gregory K. Anderson , in Encyclopedia of Microbiology (4th Edition), 2019

Stage 1: Initial Reversible Attachment

Planktonic or gratuitous-floating bacteria come up into contact with a surface. Lewis acid-base of operations, electrostatic, and van der Waals interactions guide the initial attachment. A variety of factors influences this process including surface hydrophobicity and charge, pH, and hydrodynamic forces in the microenvironment ( Kostakioti et al., 2013). This stride is known as "reversible attachment" because detachment often occurs, and information technology is thought that the microbe is "sampling the surface" (Hoffman et al., 2015). Initial attachment can be mediated by secreted adhesins, flagella, and other surface molecules, depending on the microorganism (Kostakioti et al., 2013). Chemotaxis toward preferred nutrients may also influence the location of initial attachment (Anderson and O'Toole, 2008; Kostakioti et al., 2013).

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Crystalline and Amorphous Solids

Thousand.G.Z. Zhang , D. Zhou , in Developing Solid Oral Dosage Forms (2nd Edition), 2017

2.7.2.1.2 Enthalpy of mixing

Similar to the handling of regular solution theory, molecular interactions can be built into the lattice model. Notwithstanding, the original regular solution theory simply treated van der Waals interactions, which only accounted for positive deviations from Raoult'southward police force. In the lattice model, specific interactions such equally hydrogen bonding were likewise considered, which play an important office in dictating stage miscibility, and possibly physical stability, in baggy solid dispersions. The enthalpy of mixing is often expressed as

(2.39) Δ H mix = R T ( Due north 0 + k N p ) χ Φ 0 Φ p

where χ is called the Flory–Huggins parameter and χkT represents the enthalpy change of introducing one solvent molecule to the polymer. Depending on the nature of polymer-drug interaction, the enthalpy of mixing can be positive (eg, in the instance of merely van der Waals interactions) or negative (eg, in the case of hydrogen bonding). Obviously, positive χ causes an increment in enthalpy and costless energy, which disfavors mixing.

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Biocompatibility, Surface Engineering, and Delivery of Drugs, Genes and Other Molecules

T.F. Moriarty , ... R.G. Richards , in Comprehensive Biomaterials II, 2017

four.8.4.1.two The DLVO theory

The 2d commonly used theory is the DLVO theory. The DLVO theory, much like the thermodynamic theory, assumes that adhesion is the product of interfacial energies. The DLVO theory as well includes Lifshitz–van der Waals interactions, all the same, omits the effects of acid–base interactions. Instead, electrostatic forces are included. The interaction between a particle and a surface equally predicted by the DLVO theory can be simplified as in Eq. (2):

(ii) U DLVO = U LW + U EL

U DLVO is the total interaction free energy, U LW is the Lifshitz–van der Waals interaction energy, and U EL is the electrostatic interaction energy.

The DLVO theory is commonly used to model bacterial adhesion in the literature. 82–86 The DLVO theory is most accurate when electrostatic forces are the predominant interactions and also considers Lifshitz–van der Waals interactions. 63,lxx However, the DLVO theory does non incorporate the Lewis acid–base of operations component, which is the power of a surface to accept or donate electron density to its surroundings. The theory is, therefore, limited in its accurateness because information technology omits an of import aspect of surface chemistry. 63,70,85,86

Summary of the DLVO theory
Considers Lifshitz–van der Waals and electrostatic interactions
Adhesion tin be reversible
Distance dependent: calculated over a range of distances to produce a curve
Does non include the affects of polar interactions

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Book i

Morgan A. Urello , ... Millicent O. Sullivan , in Encyclopedia of Biomedical Applied science, 2019

Hydrogels

Hydrogels are three-dimensional hydrophilic networks capable of absorbing a large amount of water. These networks are equanimous of polymeric chains that are cross-linked via chemical conjugation or alternatively by physical interactions such as entanglements, crystallites, van der Waals interactions, and/or hydrogen bonding. Because of their fantabulous biocompatibility, biodegradability, nontoxicity, and disquisitional role in the ECM, native macromolecules such as sugars and proteins are widely used every bit the building blocks for hydrogels. Polysaccharides including alginate, chitosan, cellulose, dextran, and hyaluronic acid take been widely studied, every bit have proteins such as collagen and gelatin. However, although natural materials exhibit a diverseness of well-divers hierarchical structures and important biological functions, such as cell recognition and adhesion, their apply in therapeutic applications can exist limited by immune responses and susceptibility to enzymatic degradation. To overcome these limitations, constructed polymers likewise have been used to fabricate hydrogels for drug and factor delivery. Among the diverse types of polymeric hydrogels, hydrogels synthesized from PEG, an FDA-approved polymer, have been extensively studied with promising preclinical and clinical results. Biomimetic peptides also have been widely studied in hydrogen applications, where they serve either every bit biological stimuli or equally cross-linking sites. For example, CMP, synthetic peptides that mimic the triple-helical conformation of native collagens, accept been conjugated to four-arm PEG. When equipped with a CMP domain, the four-arm PEGs form a hydrogel with these peptides serving as physical cantankerous-linkers. Moreover, at temperatures above the melting temperature (T M) of the CMP, the unfolding of the triple helices induces hydrogel disassembly, assuasive a convenient mechanism to thermally trigger the release of encapsulated drugs.

Due to their biocompatibility, high swelling in aqueous media, and responsiveness to pH, temperature, and other stimuli, hydrogels have been extensively investigated as drug-commitment systems for molecules ranging from nonsteroidal anti-inflammatory drugs (NSAIDs) to proteins. Compared with other drug-delivery systems, hydrogels closely resemble living tissues, with high water content, well-designed mechanical properties, and minimal tendency to adsorb proteins from bodily fluids. Additionally, the pore size of hydrogels can be easily manipulated via changing the chemical composition and cross-linking ratio of the polymeric network, which can in plow be utilized as a method to control the loading and releasing of encapsulated drugs.

Due to their loftier water content, drug release from hydrogels is typically relatively fast and occurs over a period of hours to days. For applications in which a slower release rate is desirable, a wide range of strategies have been employed, including physical entrapment and covalent conjugation to the hydrogel network. One of the most widely used methods to reduce the release rate is to innovate electrostatic interactions between ionic polymer networks and oppositely charged drugs. To improve the strength of the pairwise accuse–charge interactions, multivalently charged polymers, such as phosphate-functionalized polymers, are often used to class the hydrogel. For case, functionalizing a PNIPAAm-based hydrogel with polyoxyethyl phosphate-containing comonomer drastically improved the encapsulation of cationic lysozyme into the hydrogel. In another instance, adding positively charged N-(3-aminopropyl)methacrylamide or iv-vinylpyridine monomer into poly(hydroxyethyl methacrylate) networks increased the amount of encapsulated NSAIDs by more than one order of magnitude and extended the period of sustained release upwardly to approximately 1   calendar week. Chemical conjugation is widely used to load drugs into hydrogel matrices, and these methods can enable stimuli-responsive release depending on the nature of the covalent bonds linking the drug to the gel. The details on environmentally triggered release applications are discussed subsequently in the commodity.

Thermoresponsive hydrogels are commonly developed using the principles previously discussed employing a wide range of polymers that exhibit temperature-responsive stage transitions. The about common characteristic of these polymers is the presence of hydrophobic groups, such equally methyl, ethyl, and/or propyl groups. Hydrogels with desired thermoresponsiveness can be injected into the body in a liquid land with encapsulated drug, followed past gelation in the body at physiological temperature to form a cross-linked hydrogel. Additionally, the transition temperature of the hydrogel can be easily tuned past making copolymers of hydrophobic (due east.chiliad., NIPAAm) and hydrophilic (e.g., acrylic acid) monomers and adjusting the ratio of the hydrophilic and hydrophobic segments of the polymer to tailor therapeutic release. By and large, a higher content of hydrophobic polymers in the hydrogels, a lower transition temperature is obtained.

The pH-sensitive hydrogels are another commonly studied class of stimuli-responsive hydrogels. Hydrogels with pH-sensitivity are primarily used in delivering therapeutics to tumor cells due to the existence of an acidic pH within the tumor stroma. The pH-sensitive hydrogels are usually constructed using polymers with acid-sensitive bonds that tin can be hands cleaved in acidic conditions. For example, hydrogels cross-linked via Schiff's base reactions are mostly stable at physiological pH still can exist degraded under mildly acidic atmospheric condition due to the cleavage of the imine bond. The pH responsiveness also can be obtained by using polymers with ionizable chemical groups whose chemical properties such equally swelling ratio and water solubility are altered based upon the charge state of such groups. For instance, Due south. A. Hegazy and coworkers designed pH-responsive hydrogels that were copolymerized from PEG/acrylic acrid. The diffusion coefficient of the encapsulated model drug ketoprofen was highly dependent upon both the pH and the ionic strength of the medium, as the degree of ionization of the acrylic acid increases with increases in pH resulting in greater numbers of fixed charges, chain repulsion, and thus hydrogel swelling, while increases in solution ionic strength result in increases in the number of counterions and thus a subtract in repulsive forces and swelling.

In tissues and cells, enzymes are secreted to change the structure and properties of ECM, facilitating cell proliferation, differentiation, and tissue regeneration. The incorporation of enzyme substrates as a biologically responsive component in hydrogel networks is a useful strategy to mimic the proteolytic sensitivity of ECM and enable the triggered release of encapsulated drugs. For case, by introducing the matrix metalloproteinase (MMP)-responsive peptide thymosin β4 (Tβ4), Langer and coworkers designed a PEG-based hydrogel that was conducive to human umbilical vein endothelial cell (HUVEC) adhesion, survival, migration, and organization. Incorporation of Tβ4 significantly increased the secretion of MMP-2 and MMP-nine from encapsulated HUVECs, which afterward triggered the degradation of the hydrogel itself and the release of Tβ4. The enzymatically controlled release of the peptide induced vascular-like network formation within the PEG hydrogels. These results indicated that the Tβ4-encapsulating, enzymatically degradable hydrogels may be useful every bit scaffolds for in situ regeneration of ischemic tissues.

In addition to temperature-, pH-, and enzyme-responsive hydrogels, smart hydrogels that respond to other stimuli also have shown promise in regenerative medicine. For example, electric current has been applied as an external trigger to induce cargo release. Polyelectrolyte hydrogels are used for this purpose due to their capacity to undergo swelling or shrinkage when an electric field is applied, allowing the delivery of encapsulated therapeutics such as edrophonium chloride and hydrocortisone in an "on–off" fashion when the practical electric field is switched. Light also has been used as a trigger to induce responses within hydrogels. Calorie-free-sensitive hydrogels are advantageous in terms of their control mechanism since low-cal stimuli can be practical instantly with precisely controlled location and intensity. For case, the add-on of bis(4-di-methylamino)phenylmethyl leucocyanide into a PNIPAAm-based hydrogel produced a network that swelled in response to UV irradiation just shrank when the light was close off. This property was conferred by the bis(4-di-methylamino)phenylmethyl leucocyanide, which is ordinarily a neutral molecule but can dissociate into ion pairs nether UV irradiation. Such a property may have potential for light-sensitive drug-commitment applications.

In addition to the widely used environmental triggers discussed earlier, other types of stimuli responses likewise have been introduced into hydrogels for drug delivery purposes, including sensitivity to magnetic fields, pressure, specific ions, thrombin, and diverse antigens. Readers interested in details of these types of hydrogels are redirected to previous published reviews in the suggested reading.

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Hybrid Composite Biomaterials

Nirmalya Tripathy , ... Gilson Khang , in Principles of Regenerative Medicine (Third Edition), 2019

Polymer–Polymer Blends

A polymer–polymer blend defines a mixture of two different polymers addressing each other'southward drawbacks and giving synergetic advantage to the scaffold design. A miscible composite design with desired features can be fabricated by employing polymers with item intermolecular or van der Waals interactions. I of import example is PLGA and polyphosphazene bends [111]. PLGA is a well-known biomaterial in tissue engineering. Attributable to PLGA acidic by-products upon degradation, it has been a critical outcome for its farther use, because its long-term tissue exposure to acidic products may lead to tissue necrosis and implant failure. On the other hand, polyphosphazene releases neutral or bones products upon degradation. Thus, PLGA has been blended with a broad arena of polyphosphazenes to achieve about-neutral degradation products equally an efficient construct for tissue engineering [112–114].

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