1. Smart Hydrogels Andrea Cosimi 29, May 2019 Biomaterials and Tissue Engineering Andrea Cosimi | 29.05.2019 | Biomaterials and Tissue Engineering

2. Hydrogels • First studies related to hydrogelsappeared in 1894 • Number of publicationsshowedexponentialgrowth over the last tenyears • Mainapplications: Smart Hydrogels –Introduction • Middle of the 20° century, theyweretermedas water-swollencrosslinkedpolymeric networks Tissue scaffold Super absorbent Cell immobilization Woundhealing Contactlenses Andrea Cosimi | 29.05.2019 | Biomaterials and Tissue Engineering

3. Smart Hydrogels • The word «smart» wasintroduced in 1948 by Kuhn and co-workers • Delivery concept denominatedas «smart» becauseit can detectprevailingstimuli and respondthroughstructural, morphological or functionalchanges • Theiruniqueproperties can be • associated with environmentalfactors • The dynamic nature of supramolecularchemistry makes itapplicable to the development of smart hydrogels • The finalmorphologyexpected for the hydrogelisassociated with a series of variables, whichprimarilyincludes the synthesis or treatment procedures of the originalpolymer, monomercomposition and their ratio Smart Hydrogels – Introduction • First publicationaboutpoly (acrylic acid), PAA, moleculesthatcouldundergostructuraladjustmentsaccording with the media pH Journal of Controlled Release 194 (2014) 1-19 Andrea Cosimi | 29.05.2019 | Biomaterials and Tissue Engineering

4. Smart Hydrogels • A set of criteriahasbeenused to classifythese systems, includingorigin (natural or synthetic), degradability and cross-linking mechanism. • By manipulating the factorsinvolved in these links, we control the structuralproperties of the final system • Expectedresponses can be manifold and include degradation, drug release, swelling, changes in shape or surface, conformationalmodifications or micellization • Responsiveness Smart Hydrogels – Classification Andrea Cosimi | 29.05.2019 | Biomaterials and Tissue Engineering

5. Smart Hydrogels – Thermo-responsive • As medium temperature mayfluctuate in physiological and pathologicalconditions, thermo-responsive hydrogels are one of the moststudied classes of stimuli systems in tissue engineering and drug delivery research • Thermo-responsive hydrogels can be dividedintotwo groups: lowercriticalsolution temperature (LCST) and uppercriticalsolution temperature (UCST) • From 2005 to 2010, only 44 publications per yearwereaddressed to UCST against 330 included LCST • Severalpolymers can be included in both LCST and UCST classes, e.g. PEO, which shows a loop-shapedmiscibility gap with UCST > LCST. PAAsPAMsSulfonate Phasetransitionphenomenon. (a) LCST and (b) UCST phasetransitionbehaviors of thermo-responsive polymers in solution Andrea Cosimi | 29.05.2019 | Biomaterials and Tissue Engineering

6. Smart Hydrogels – Thermo-responsive • For LCST hydrogels, atlower T°, water molecules are arrangedaround the polymer. The increase of environmental T° reduces the energy associated to the water-polymer interaction. Thus, the polymerdehydrates, transformingitselfinto a more hydrophobicstructure and causingphaseseparation Stimuli-responsive behaviour of PNIPAAm. Source: MaterialMatters 2010, 5.3, 56 Andrea Cosimi | 29.05.2019 | Biomaterials and Tissue Engineering

7. Smart Hydrogels – Thermo-responsive PNIPAAm for use as a smart culture surface Source: Material Matters 2010, 5.3, 56 ThermosensitiveinjectablePNIPAAm-hyaluronic acid copolymerhydrogel for adipose tissue engineering Andrea Cosimi | 29.05.2019 | Biomaterials and Tissue Engineering

8. Smart Hydrogels – Light-responsive • Smart Hydrogels – Light-, electric- and magnetic- responsive • Electric, magnetic fields, and light exposure are the mainexternalphysicalstimuliused to tunedrug release kinetics from smart hydrogels. Once thisstimuli can be controlled, theyhave the advantage of modulatingdrug release spatially and temporally. • Photo-sensitive polymers can change their physicochemical properties or degrade in response to light irradiation of appropriate wavelength and intensity. • Two types of UV light response: photopolymerization and photocleavage systems • Photopolymerization: Chemical structure of light-responsive moieties employed in the synthesis of photo-responsive polymers. K. Peng , I. Tomatsu and A. Kros , Chem. Commun., 2010, 46 , 4094 -4096  Andrea Cosimi | 29.05.2019 | Biomaterials and Tissue Engineering

9. Smart Hydrogels – Light-responsive • Photocleavage: • Disadvantages in using UV light • low penetration • potentiallycarcinogenic • A valid alternative is the use of UCNPs, which are able to convertphoton energy absorbed from NIR light into UV light Photodegradablepolymericmaterialscontaining (a) a photolabilejunction, (b) photo-labile pendant groups, (c) photodegradablebackbone and (d) photo-labile cross-linkers Andrea Cosimi | 29.05.2019 | Biomaterials and Tissue Engineering

10. Smart Hydrogels – Electric-responsive • Smart Hydrogels – Electric- and Magnetic-responsive • Electro-responsive systems are materials that respond to an applied electric field by changing their size or shape. They are termed as electro-conductive hydrogels (ECHs), developed from polyelectrolytes or from ICPs. • The development of magnetic nanomaterials has been the source for the discovery of spectacular new phenomena, with potential applications in numerous fields • HFMFs are less invasive than electric fields or light exposure • Magnetichydrogelsdeveloped by inclusion of MIONs in the polymermatrices. MIONs/polymer ratio determines the saturationmagnetization and consequently the drug release performance Chemical structures of some conductivepolymers. From top leftclockwise: polyacetylene; polyphenylenevinylene ; polypyrrole (X = NH) and polythiophene (X = S); and polypyrrole (X = NH) and polyphenylenesulfide (X = S). Andrea Cosimi | 29.05.2019 | Biomaterials and Tissue Engineering

11. Smart Hydrogels – pH-responsive • The human body exhibits subustantial pH changes in different body parts when functioning normally. Additionally, some diseases can also cause pH changes in the human body • Similar to macromolecules, a polymer network contains ionizable groups that can donate or accept protons in response to pH. In aqueous solutions they are polyelectrolytes • Two classes of pH responsive hydrogels pH values in severalhealthytissues and cellcompartments Andrea Cosimi | 29.05.2019 | Biomaterials and Tissue Engineering

12. Smart Hydrogels – pH-responsive • pH-responsive behavior can also be found among natural polymers such as alginate, albumin, chitosan, pectin and gelatin • Chitosan and alginate are representative natural polyacid and polybasepolysaccharides, that suffer physical cross-linking through hydrophobic or charge interactions Alginate Chitosan Explanation of pH-dependent water permeationthrough (a) a porous membrane and (b) a dense membrane Crystal structure of Chitosan Andrea Cosimi | 29.05.2019 | Biomaterials and Tissue Engineering

13. Smart Hydrogels – Salt- or ionicstrenght-responsive • Important feature of hydrogels, considered that some biological processes such as nerve excitation, muscle contraction and cell locomotion involve ionic strength modification • Generally, the mechanism of the ionic strength-responsive polymers is that the added salt will reduce the electrostatic interactions between copolymers or between polymers and other molecules • Some weak PAAs and MAAs show an increased degree of ionization upon addition of lithium methoxide salt • Hydrogels composed PNIPAM exhibit LCST; its behavior showed also a sharp volume phase transition depending on the NaCl concentration • A PNIPAM hydrogel with specificsensitivitywassynthetized by introducing di-benzo-18-crown-6 comonomersinto the network Andrea Cosimi | 29.05.2019 | Biomaterials and Tissue Engineering

14. Smart Hydrogels – Bio-responsive • Changes might occur in response to increased concentration of specific biomolecule availability • Antibodies, T cells and enzymes are important biomolecules which can be used as important signals for disease diagnosis • Many research groups have focused in the development of smart self-regulated biomaterial systems, useful for drug delivery as well as for diagnosis, cell cultures, biosensors or matrices for tissue engineering and regenerative medicine • Three types of responsiveness • Glucose • Enzyme • Antigen • Glucose-repsonsive are widelyused in diabetes treatment with different strategies for insulin self-regulation • Glucoseoxidase (GOX) • Lecitin (concanvalin A) • Phenylboronic acid Andrea Cosimi | 29.05.2019 | Biomaterials and Tissue Engineering

15. Smart Hydrogels – Glucose-responsive • Changes might occur in response to increased concentration of specific biomolecule availability • Antibodies, T cells and enzymes are important biomolecules which can be used as important signals for disease diagnosis • Many research groups have focused in the development of smart self-regulated biomaterial systems, useful for drug delivery as well as for diagnosis, cell cultures, biosensors or matrices for tissue engineering and regenerative medicine • Three types of responsiveness • Glucose • Enzyme • Antigen • Glucose-repsonsive are widelyused in diabet treatment with different strategies for insulin self-regulation • Glucoseoxidase (GOX) • Lecitin (concanvalin A) • Phenylboronic acid Andrea Cosimi | 29.05.2019 | Biomaterials and Tissue Engineering

16. Smart Hydrogels – Glucose-responsive • Changes might occur in response to increased concentration of specific biomolecule availability • Antibodies, T cells and enzymes are important biomolecules which can be used as important signals for disease diagnosis • Many research groups have focused in the development of smart self-regulated biomaterial systems, useful for drug delivery as well as for diagnosis, cell cultures, biosensors or matrices for tissue engineering and regenerative medicine • Three types of responsiveness • Glucose • Enzyme • Antigen • Glucose-repsonsive are widelyused in diabet treatment with different strategies for insulin self-regulation • Glucoseoxidase (GOX) • Lecitin (concanvalin A) • Phenylboronic acid Andrea Cosimi | 29.05.2019 | Biomaterials and Tissue Engineering

17. Smart Hydrogels – Glucose-responsive • Changes might occur in response to increased concentration of specific biomolecule availability • Antibodies, T cells and enzymes are important biomolecules which can be used as important signals for disease diagnosis • Many research groups have focused in the development of smart self-regulated biomaterial systems, useful for drug delivery as well as for diagnosis, cell cultures, biosensors or matrices for tissue engineering and regenerative medicine • Three types of responsiveness • Glucose • Enzyme • Antigen • Glucose-repsonsive are widelyused in diabet treatment with different strategies for insulin self-regulation • Glucoseoxidase (GOX) • Lecitin (concanvalin A) • Phenylboronic acid (PBA) Andrea Cosimi | 29.05.2019 | Biomaterials and Tissue Engineering

18. Smart Hydrogels – Glucose-responsive • Changes might occur in response to increased concentration of specific biomolecule availability • Antibodies, T cells and enzymes are important biomolecules which can be used as important signals for disease diagnosis • Many research groups have focused in the development of smart self-regulated biomaterial systems, useful for drug delivery as well as for diagnosis, cell cultures, biosensors or matrices for tissue engineering and regenerative medicine • Three types of responsiveness • Glucose • Enzyme • Antigen • Glucose-repsonsive are widelyused in diabet treatment with different strategies for insulin self-regulation • Novelglucose-responsive system based on covalentdynamic bonds Andrea Cosimi | 29.05.2019 | Biomaterials and Tissue Engineering

19. Smart Hydrogels – Enzyme-responsive • In cellular environment, most stimuli-responsive mechanisms are under control of enzymes • Since enzymes are highly selective in their reactivity, responsiveness is specific • First application related to tissue engineering for cartilage repair and chondrocyte culture • Enzyme-repsonsive are alsowidelyexploited to release drugsspecifically in the colon • Biodegradablepolymers include naturallyderivedpolymerssuchaspectin, amylose, gelangum, chitosan, alginate and dextran • Artificial non-biodegradablepolymers include PEG, PEO, pHEMA, PNIPA • Antigen-responsive hydrogels are able to undergo volume or structuralchanges in the presence of antibodies Andrea Cosimi | 29.05.2019 | Biomaterials and Tissue Engineering

20. Smart Hydrogels – Functional delivery systems • The application of these bioactuating systems requires a sophisticated molecular design, which increases their potential application • Some disease are known for significant changes on the homeostasis state • Pathological aspects that can be explored toward this objective • Inflammatory processes • Cancer therapy • Diabetes mellitus • Which applications of smart polymers will likely succeed in clinic and why? • Tissue Engineering • Harder to simulate bodily environment for tests • Also, difficult to assess performance of grafts/ scaffolds/other devices in vivo • May be developed for longer-term applications, so in turn it will take longer to test the materials • Depends on whether you want to implant polymer scaffold with cells or wait for scaffold to degrade before implantation • Drug delivery • Short-term operation, so it may take less time to complete testing • Simple methods available to study release in vitro and able to test drug concentration for in vivo tests • Smart diagnosticapplications • Testing material, ifnot in body the regulations are mucheasier to meet/test Andrea Cosimi | 29.05.2019 | Biomaterials and Tissue Engineering

21. Andrea Cosimi | 29.05.2019 | Biomaterials and Tissue Engineering