Evolving biomaterials in Faenza, Italy: Institute of ... · Evolving biomaterials in Faenza, Italy: Institute of Science and Technology for Ceramics (ISTEC) Burning Away those Bubbling

page 50 Lab Times 2-2011 Biobusiness

Evolving biomaterials in Faenza, Italy: Institute of Science and Technology for Ceramics (ISTEC)

Burning Away those Bubbling DetergentsIn the fifteenth century, fine tin-glazed pottery from Faenza (“Faience”) became famous for its perfection. More than 600 years later, a group of local scientists is using its unique ceramics know-how for biomedical applications.

For those who love art and pottery, Faenza is well worth a visit. This me-dieval village in the north of Italy, 50

kilometres southeast of Bologna, is known as the “City of Ceramics”, for its long tradi-tion of hand-made pottery. Ceramics, how-ever, are not only suited to high art and til-ing your bathroom floor. They have also become a hightech material that is used in semiconductors and turbine blades as well as in biomedical implants.

Faenza seems the obvious place to work on advanced ceramics. Indeed, it is here that a research group working at the Insti-

tute of Science and Technology for Ceram-ics (ISTEC) has become, in recent years, well experienced in the use of ceramic com-pounds for biomedical applications. This small research group, headed by resident chemist Anna Tampieri, is made up of two physicists, four chemists and one biologist. Your Lab Times reporter met Anna Tamp-ieri in her office at ISTEC, Via Granarolo 64, Faenza.

How can ceramics be applied to bio-re-generative medicine? Ask a chemist. The term “ceramics” doesn’t refer to a specif-ic compound, but to a technological pro-

cess. And this process, Tampieri explains, involves working through the granular phase to obtain a homogeneous material. With such a wide definition, each element in the chemical periodic table can be con-sidered a ceramic. Even the main compo-nent of bone tissue, calcium carbonate, is a ceramic compound, she adds.

Shrinking bonesWhen the mother institute, ISTEC, was

born in 1965, nobody was thinking about bone replacement. The government’s pri-mary intention was to optimise tradition-

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ISTEC’s key staff with researcher Andrea Ruffini (left) and founder Anna Tampieri (right).

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al ceramic manufacture. It was only in the 1980s that a new group undertook the spe-cific goal of working in regenerative medi-cine, focussing on the creation of prosthe-ses for damaged limbs and tissues.

“Prostheses were only made out of me-tallic compounds at that time,” Tampieri explains, “however, things had to improve radically as they very often show unfavour-able behaviour.”

As soon as prostheses are set inside dam-aged tissue, the metal starts to deteriorate and releases molecular debris. Tampieri il-lustrates the consequences, “Tissues suffer from inflammation responses and the bone starts to shrink, leading to a prosthesis desta-bilisation and delocalisation, with the need of follow-up care assistance. This is the rea-son why, still today, metallic prostheses have a life-time not longer than ten years.”

Over time, ISTEC became Italy’s num-ber one ceramics expert, and in the 1980s the group switched to developing ceramic prostheses, which are better tolerated by the human body. And when in late 1996 Tampieri took charge of the group, “we de-cided to focus on the reconstruction of hard connective tissues, as bone, cartilage and sinew”, she continues.

However, there was a problem. “To ful-fill this, we needed a new idea”. They need-ed not just new prostheses but new struc-tures inside their prostheses.

Not simply new prostheses“We decided to create scaffolds that

simulate the natural tissue in its chemical composition and spatial geometry, in or-der to achieve faster tissue regeneration in vivo.” Tampieri calls these scaffolds “bio-mi-metic” structures. But this was not enough. The Italians also wanted their scaffolds to be bio-absorbable, achieving complete re-generation of tissue in the damaged area and thus total patient recovery.

When using a traditional prosthesis, the surgeon puts a foreign object inside the body, where it remains for the rest of the patient’s life. The Faenza method is differ-ent. Their scaffold is a porous frame struc-ture that bone cells, as osteoblasts, can

reach via blood flow. Once they have colo-nised the damaged area, cells enter the scaf-fold pores, adhere and start to grow. After-wards, they start to digest the frame and re-lease new bone tissue.

“With our method, you achieve a com-plete regeneration and repair of the tissue. After some months or years, the scaffold disappears and a new bone-frame replaces it,” Tampieri says. “The main goal is two-fold: To create structures that simulate the natural tissue for its chemical composition and for its spatial geometry in order to have faster tissue regeneration in vivo”.

Research and development is never a one-man-band. “You cannot base your re-search only on literature or theoretical stud-ies. You need feedback from the medical doctors that experience the properties of the scaffolds with their patients”. Tampieri admits that it was only thanks to new col-laborations that her ISTEC team got results, working with the Orthopedic Clinic of the Rizzoli Hospital in Bologna and the Gemel-li Hospital in Rome. Both are experienced in prosthesis implantation and tissue engi-neering and have the clinical infrastructure to test and analyse new materials in vivo.

School work Tampieri’s work is technically compli-

cated and her explanations of it can be diffi-cult to follow. As she seemingly knows this,

she kindly gave your Lab Times reporter a whistle-stop recap of basic chemistry.

Bones are made out of both an organ-ic fraction and the mineral hydroxyapa-tite, she began. Up to fifty percent of bone

is made up of a modi-fied form of this min-eral, with the formu-la Ca5(PO4)3(OH). The chemical nature of hy-droxyapatite lends itself to atom substitutions. In its naturally occurring form, it has often re-placed magnesium and carbonate molecules. Each change also alters the physical-chemical properties of the min-eral and its behaviour in the physiological envi-ronment.

Which experimen-tal approaches led our ISTEC team to a hy-droxyapatite scaffold that resembles the properties of natural bone tissue? Tamp-ieri starts a quick sequence of enthusiastic explanations, “The first we want to achieve when we build up a scaffold is chemical mimicry. Bones are made of hydroxyapatite that had to be reproduced by us. When we started our work, there was already a syn-thetic hydroxyapatite commercially avail-able, but it was unsuitable for scaffold de-sign, being not absorbable by the human organism.”

Chemical mimicry ...The reason for that, as they found out,

was astounding, “It was because that syn-thetic hydroxyapatite didn’t contain any atomic substitutions. However, these substi-tutions change the properties of hydroxyap-atite: For example, silicon atoms are impor-tant for osteoblast adhesion on the scaffold; magnesium influences the geometry of the hydroxyapatite molecule, conferring insta-bility and greater solubility at physiological pH. Greater solubility means that cells have greater likelihood to adhere to and digest the mineral scaffold”.

Faenza’s beautiful main square, Piazza del Popolo, framed by the fountain (in the front) and the Palazzo del Municipio.

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... and geometric mimicryTo get closer to nature, “We started to

study each single atomic substitution pre-sent in natural hydroxyapatite and tried to reproduce a mimetic compound”.

Sounds complicated, doesn’t it?However, there was more hard work

ahead. “The geometric mimicry of the scaf-fold is important as well: to adhere and live, cells need a tridimensional environment closest as possible to the natural bone struc-ture. They have to enter the pores, digest the scaffold and regenerate the damaged tissue.”

How do they create scaffolds that have both of these characteristics in Faenza? They re-create them with sponges and foam, respectively. One of their methods uses cellulosic sponges, another works with the help of foaming agents.

Tampieri explains, “For the first, imag-ine taking a sponge and soaking it with a hydroxyapatite suspension. Then, if you use a thermal cycle that can slowly reach high temperatures, you can make the cellulos-ic sponge burn away. What remains is the ceramic compound with the shape of the sponge it was in. And a sponge’s structure and porosity reproduces very well those of a spongious bone”.

Foaming agents as an alternativeSometimes, however, a scaffold that

has higher porosity to achieve faster regen-eration is needed. In this case, Tampieri’s team uses a different method that involves the use of foaming agents, “We prepare the

same hydroxyapatite suspen-sion but we add chemicals to induce bubble formation.

Then we heat it up in order to burn the de-tergents away and what we obtain is a scaf-fold with higher porosity.” Admittedly, its mechanical properties are poor.

Man isn’t made from bone alone. Often patients undergo tissue damage that also involves connective tissue, called cartilage. For this reason, the group has been devel-oping new scaffolds suitable for both, bone and cartilage reconstruction since 2000, “The osteochondral region of a joint is com-posed of bone and cartilage; the difference is only the percentage in their mineral frac-tion. Moving from the bone to the cartilage you go through a mineral gradient.”

Since it has so far been impossible to reproduce a gradient with ceramics, ISTEC developed a process called bio-mineralisa-tion, “We studied the natural process: in vivo cartilage is assembled with the contem-porary synthesis of collagen fibers and min-eral nuclei. Thus, the spatial organisation of the collagen fibers is coordinated with the synthesis of mineral nuclei that are part of the structure itself and are not simply de-posited on the fibers. This complex struc-ture is intrinsically mineralised and has got specific mechanical features, as elasticity or tolerance, which a synthetic scaffold needs to reproduce.”

Already used in patientsTampieri continues, “We managed to do

so in our laboratories, mimicking the natural process in vitro. We realised a tri-layer scaf-fold, where one layer had the same compo-

sition and structure of the bone, the third was similar to carti-lage and the central layer had a mineral composition in half of the two, as it is in the natu-ral joint. Since the beginning of 2010, we and our collaborators at Rizzoli Hospital were able to repair an osteochondral injury using this scaffold. Actually, it’s certified in the European Union and used in patients”.

Recently, the group has looked for a way to reproduce the exact an-isotropic features of bone tissue, to repro-duce a structure that resembles as much as possible the natural one.

And they landed upon – red oak.Indeed, wood has an internal struc-

ture that is highly suitable for this specif-ic application. “Since 2006, two and a half years have been spent screening hundreds of woods,” Tampieri laughs, “to find out which is the right one for our purposes. Finally, we have chosen the red oak tree” (Quercus rubra).

Thermochemical decompositionAndrea Ruffini, a young researcher

working with Tampieri, leads us in the lab-oratory to show how it is possible to obtain a biomimetic scaffold from a tree.

“First of all we cut out a part that has the exact dimensions of the needed scaf-fold. Then it undergoes a pyrolysis process, that consists of a thermochemical decompo-sition of organic material at elevated tem-peratures in the absence of oxygen. At the end of the process, what is left is a carbon structure. Then, with chemical reactions, we convert carbon into apatite. Thus, the steps are two: wood elimination without changing the intrinsic spatial structure and chemical replacement”.

The suitability of this new kind of scaf-fold is now being examined in animal tests. According to Ruffini, the first trials have been encouraging. Tampieri then shows us additional projects that are looking beyond “wood mimicry”. For example, they are now working on the development of a modified hydroxyapatite with atomic iron substitu-tions to create an electromagnetic sensitive scaffold. The idea is to use electromagnetic fields to direct active molecules, as drugs, into the damaged region, resulting in faster healing of the tissue.

A lot has happened in Faenza since the first tin-glazed Maiolica earthenwares were produced there in the mid-fifteenth cen-tury. Francesca Ceroni

After pyrolysis of ordinary wood from the red oak tree (Quercus rubra, left) and sub-sequent chemical conversion of carbon into apatite, the hy-droxyapatite scaffold shown above is obtained via “wood mimicry”.

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