Article

Porous Bioceramics use Albumin as a Pore-Forming Material

Ahmad Fadli¹*, Komalasari¹, Irdoni¹, Wan Elsa Novtari Adiani¹

¹Department of Chemical Engineering, Faculty of Engineering, Universitas Riau, Pekanbaru 28293, Riau,

Indonesia

Abstract

Porous bioceramics have been used in biomedical field, especially for bone implant. To generate pores

in bioceramics, pore creating substances are added into the process of making ceramic bodies. The

purpose of this study is to make porous bioceramics with tri calcium phosphate (TCP) raw material using

albumin with variation in the amount of albumin in the raw material and drying temperature on the

physical and chemical properties of TCP. Raw material slurry was made by mixing 7 g of TCP, 2 g of starch

and 1.5 g of Darvan 821A with 5 g, 7 g and 9 g of albumin in a beaker glass while stirring at a rate of 150

rpm for 3 hours. The slurry was poured into a mold and heated in an oven at 180°C, 200°C and 220°C for

1 hour. Subsequently the sample was burned at 600˚C for 1 hour, following with sintering at 1.100°C for

2 hours. Bioceramic porosity is greater by increasing the amount of albumin and drying temperature,

while the compressive strength decreases. Obtained TCP porosity is in the ranges of 68% -78% and

compressive strength 0.14-1.4 MPa.

Keywords: compressive strength, albumin, porosity, tricalcium phosphate

Graphical Abstract

*

Corresponding author

Email addresses: fadliunri@yahoo.com

DOI: 10.22437/chp.v7i1.8131

Received 28 November 2019; Accepted 26 June 2022; Available online 30 July 2023

(https://creativecommons.org/licenses/by/4.0 )

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Chempublish Journal, 7(1) 2023, 8-17

Several pore-forming materials have also been

Introduction

used in the manufacture of porous ceramics, for

example, egg yolk

[8]

and starch ^[9]. Albumin can

The number of patients with bone damage

continues to increase due to several factors such

as traffic accidents, work accidents and

osteoporosis. Bone substitute materials used

conventionally are derived from healthy bones of

other body parts belonging to the patient

concerned or other people. Both ways of bone

replacement are very prone to causing damage

to the part of the bone that is removed ^[1]. In

addition, bone implants can also come from

animals or plants. This method has an impact on

the possibility of disease transmission carried by

animal species and the possibility of being

rejected by the human body because of

be used as a pore-forming agent because it can

expand when heated. This article reports the

production of porous ceramics using TCP raw

materials using albumin as a pore former.

Albumin has a greater ability to expand than egg

yolk ^[10]. Effect of variations in the ratio of albumin

in the slurry and drying temperature on the

physical and chemical properties of the resulting

porous ceramics.

Experimental Section

Materials

differences.

To

overcome

this

problem,

The materials used in the study were tricalcium

phosphate (Sigma Aldrich, Germany), albumin

from chicken eggs available at the local market in

Pekanbaru, sago flour (UD. Puri Pangan

Sejahtera, Indonesia) and Darvan 821 A (R.T.

Vanderbilt, USA).

biomaterials that can be used as bone implants

are needed.

Tricalcium phosphate (TCP) is

a

synthetic

biomaterial that can interact with human body

tissues because it has good biocompatibility and

can play a role in bone growth and regeneration

^[2]. Pore characteristics are very important in

making bone implants because they affect the

rate of bone growth, especially porosity, pore size

Instrumentation

The tools used in this study included a furnace

(Nabertherm,

Germany),

oven

(Cosmos,

Indonesia), magnetic stirrer (Dragonlab, China),

stainless steel mold, beaker, calipers and ruler.

distribution,

morphology,

and

level

.

of

interconnectivity in the implant tissue ^[3]

Analysis

of

the

chemical

structure

and

Porous ceramics can be classified based on their

pore size, namely microporous ceramics, for

pore sizes of less than 2 nm, mesoporous

ceramics, for pore sizes between 2-50 nm,

macroporous ceramics, for pore sizes of more

than 50 nm ^[4]. Researchers have previously

reported methods for making pores in ceramics

such as the starch consolidation method (Ramay

and Zhang, 2003), protein foaming consolidation

^[5], and direct foaming ^[6]. Each of these methods

has drawbacks both in the manufacturing

process and in the results of the products

obtained. For example, the process which is quite

complicated at the drying stage requires a longer

processing time is a drawback of the starch-

consolidation method. While the weaknesses

found in the protein foaming consolidation and

direct foaming methods are weak pore

interconnections and non-uniform pore sizes in

crystallinity in the porous ceramics prepared was

carried out using X-Ray Diffraction (Panalytical,

Xpert Pro, Netherland). The pore and surface

morphology of the sample was analyzed using

Scanning Electron Microscopy (Hitachi, S-3400N,

Japan). To measure the compressive strength,

the Universal Testing Machine (Tokyo Testing

Machine, Japan) was used. The percentage of

shrinkage is done by measuring the sample

volume before and after the sintering process.

Slurry foaming capacity is measured from the

change in slurry volume during the heating

process.

Density is obtained by weighing and calculating

the volume of the sample. The formula for

calculating relative density can be seen in

equation 1, where the theoretical density of

tricalcium phosphate is 3.14 g/cm^{3 [11]}

.

the resulting porous ceramics ^[7]

.

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Chempublish Journal, 7(1) 2023, 8-17

The dried slurry was removed from the mold and

continued with the burning stage in the furnace

at 600°C with a temperature rise rate of

10°C/minute and a residence time of 1 hour.

After that it was continued with the sintering

stage at 1,100°C with a temperature rise rate of

2°C/minute and a residence time of 2 hours.

Sample porosity is calculated using Equation 2.

ρ

s

Relative density, ρ_r=

100% ----------------------(1)

ρ

t

Porosity = 100% − 휌_푟---------------------------------(2)

Where ρs is the sample density, ρr is the relative

density and ρt is the theoretical tricalcium

phosphate density.

Results and Discussions

The resulting porous ceramics

Procedure

A mixed slurry consisting of white TCP, starch,

Darvan, and albumin is poured into a cylindrical

mold. After the drying process at 180°C to 220°C,

the slurry becomes more viscous with a brown

color. The hardened slurry is removed from a

cylindrical mold called a ceramic body. The

brown color on the ceramic body increases to

dark brown when the drying temperature is

increased, as shown in Figure 1a-c.

This research was started by making a slurry by

mixing 7 g of TCP powder and 2 g of starch with

1.5 g of Darvan 821 A and 5, 7 and 9 g of albumin

in a beaker glass. Then the slurry was stirred

using a magnetic stirrer at 150 rpm for 3 hours at

room temperature. The slurry was put into a

mold and heated in an oven with a temperature

variation of 180°C, 200°C and 220°C for 1 hour.

(b)

(c)

(a)

(d)

(f)

(e)

Figure 1. (a) Ceramic body at drying temperature 180°C (b) 200°C (c) 220°C with 5 g of albumin (d) porous

ceramic body at drying temperature 180°C (e) 200°C (f) 220°C with 5 g of albumin.

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Chempublish Journal, 7(1) 2023, 8-17

The color change also occurs on the ceramic

body during the sintering process from brown to

white as shown in Figure 1d-f. This is due to the

burning process occurring at a temperature of

600°C. During the burning process, albumin,

starch and Darvan 821 A are burned in the

ceramic body. The organic materials burn into

carbon dioxide which is released into the air

while the places left by the organic matter will

form pores in the ceramic body. After the

combustion process, it is followed by a sintering

process which aims to strengthen the bond

between the TCP particles on the TCP body wall

thereby increasing the mechanical strength.

The stages of the slurry development process can

be studied by measuring the volume change ratio

of the slurry during the drying process. The

results of measuring the ratio of slurry volume to

the amount of albumin 7 g at 200°C and 220°C

can be seen in Figure 2.

During the drying process there are three stages

of the process, pre-heating, foaming, and

stabilizing. During the pre-heating stage there

was a change in protein structure due to heating

without the volume change that occurred at the

beginning of drying, namely 11 minutes for 200^oC

and 6 minutes for 220^oC. Then the foaming

process occurs with an increase in the slurry

volume until it reaches the maximum volume.

This stage occurs in 12-17 min for a drying

temperature of 200^oC, while for a drying

temperature of 220^oC the foaming stage occurs

in 7-20 minutes. This expansion occurs due to

To determine the effect of the slurry composition

on porous ceramics, variations were made on the

amount of albumin used, 5 g, 7 g, and 9 g at a

sintering temperature of 1,100°C. As the amount

of albumin used increases, the shrinkage

increases. Shrinkage in ceramic volume occurs

due to the loss of mass of organic matter in

ceramic materials such as albumin, flour, and

Darvan. So the more albumin used will increase

shrinkage. In addition, there is a change in shape

when the amount of albumin is enlarged and the

drying temperature is increased. The ceramic

body also experiences increasing shrinkage

when the drying temperature increases.

protein denaturation and encourages the

[12]

formation of foam due to increased heat

.

Increased drying temperature causes faster

foam formation. This is due to the faster

denaturation of proteins. At 18-30 minutes there

was no change in volume for

a

drying

temperature of 200⁰C, whereas for a drying

temperature of 220^oC there was no change in

volume at 21-30 minutes or it had reached the

stabilizing stage.

Figure 2. Slurry volume ratio during the drying process at 200°C and 220°C.

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Chempublish Journal, 7(1) 2023, 8-17

At low drying temperatures, the slurry expansion

capacity is lower. This is caused by the reduced

ability to expand albumin when the temperature

experienced a shrinkage percentage of 37.47% -

38.17%. The sintering temperature has a direct

impact on the final ceramic structure ^[15]

.

is lowered. This will cause the number of pores

[13]

The initially dispersed TCP particles will contact

each other and form clusters during the burning

and sintering processes. Burning albumin will

leave pores on the ceramic wall. The pore will be

the space which moves from the center towards

the outer surface of the body during the sintering

process and at the same time the particles move

to the inner surface of the ceramic body. The

movement of the particles causes shrinkage of

the body ^[16]. So that the more amount of albumin

used, the higher the shrinkage percentage. The

shrinkage of the ceramic body is also affected by

the drying temperature. The higher the drying

formed and porosity to decrease

and the

regular arrangement of atoms ^[14]. This is in

accordance

with

the

results

of

the

microstructural analysis of the samples with

drying temperatures of 200^oC and 220^oC in

Figure 7.

Effect of drying temperature and amount of

albumin on the physical characteristics of

porous ceramics

The physical characteristics of the ceramics

measured in this study were the percentage of

shrinkage, porosity and density. After the

sintering process at a temperature of 1100^oC the

ceramic samples experienced a decrease in body

volume (shrinkage). Figure 3 shows that the

increasing the amount of albumin, the higher the

shrinkage percentage. The volume shrinkage

that occurred for samples with 5 g albumin

composition was 32.11% - 33.77%, for samples

with 7 g albumin composition experienced a

shrinkage percentage of 35.48% - 36.27%, and for

temperature,

the

higher

the

shrinkage

percentage.

In addition, the higher the drying temperature

causes the porosity to increase. At high drying

temperatures, the expansion capacity increases

and the pores formed also increase. Figure 4

shows the porous TCP porosity in the range of

67.7%-72.77% for 5 g of albumin, 70.09%-75.35%

for 7 g of albumin, and 70.36%-78.13% for 9 g of

albumin.

samples with

9

g

albumin

composition

Albumin 5 gram

Albumin 7 gram

Albumin 9 gram

40

38

36

34

32

30

180

200

Temperature (°C)

220

Figure 3. Graph of the relationship between the percentage of shrinkage and drying temperature of

180^oC, 200^oC, 220^oC with albumin composition of 5 g, 7 g and 9 g.

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Chempublish Journal, 7(1) 2023, 8-17

80

Albumin 5

gram

Albumin 7

gram

75

70

65

60

180

200

220

Temperature (°C)

Figure 4. Graph of porosity relationship to drying temperature 180^oC, 200^oC, 220^oC with albumin

composition of 5 g, 7 g and 9 g.

Gibson

&

Asby (1988) stated

that

the

Effect of drying temperature and amount of

albumin on compressive strength

compressive strength of porous ceramics will

decrease with increasing porosity ^[17]. And the

higher the drying temperature, the more

compressive strength will decrease. The resulting

compressive strength of porous TCP is in the

range of 1.03-1.4 MPa for 5 g of albumin, 0.45-

1.26 MPa for 7 g of albumin, and 0.14-0.81 MPa

for 9 g of albumin. There are slices of several

compressive strength values caused by different

drying temperatures and struts thickness.

Compressive strength is a very important factor

in determining the feasibility of porous ceramics

as bone implants. From Figure 5 it shows that the

more the amount of albumin used, the

compressive strength will decrease. This is due to

an increase in foaming capacity when the

amount of albumin increases in the slurry. High

foaming capacity will result in large pore sizes

and increased porosity.

Figure 5. Graph of the relationship of compressive strength to drying temperature 180⁰C, 200⁰C, 220⁰C

with albumin composition of 5 g, 7 g and 9 g.

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Chempublish Journal, 7(1) 2023, 8-17

The microstructure of porous ceramics will also

change due to an increase in drying temperature.

In Figure 7b it can be seen that the pore

distribution is more even and the pore size is

larger when compared to 7a. At higher drying

temperatures, the pores spread to the pore walls

which are less dense and thinner ^[18]. The smaller

the pore size causes the ceramic to become

denser, so that the compressive strength of the

ceramic will increase as shown in Figure 7.

Effect of drying temperature and ratio of

albumin

composition

on

macro

and

microstructure

The difference in drying temperature affects the

structure of the porous ceramics ^[12]stated that

as the drying temperature increases, the pore

size also increases. This is because drying at low

temperatures will reduce the foaming capacity. In

Figure 6a it has a pore size of 50-150 µm smaller

than in Figure 6b it has a pore size of 200-350 µm.

(a)

(b)

Figure 6. Sample macrostructure with drying temperature (a) 200°C (b) 220°C with 9 g of albumin.

(b)

(a)

Figure 7. Sample Microstructure with Drying Temperature (a) 200°C (b) 220°C with Total Albumin 9 g.

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Chempublish Journal, 7(1) 2023, 8-17

(a)

TCP

(b)

2 Theta (⁰)

Figure 8. Graph of Effect of Albumin Addition on Chemical Structure (a) TCP Powder, (b) 5 g of Albumin

Addition.

The XRD analysis aims to determine the effect of

adding albumin on the material content of

ceramics which have become porous ceramics

with raw ceramic powder. Figure 8 shows a

comparison of the content between TCP used as

a raw material and TCP that has been made into

porous ceramics.

Conclusions

Porous TCP has been successfully prepared by

the

protein

foaming-starch

consolidation

method using albumin as a pore former. The

albumin composition and drying temperature

affected the physical properties and did not

affect the chemical properties of the porous TCP.

The greater the amount of albumin and the

higher the drying temperature, the greater the

percentage of shrinkage, the greater the

porosity, the smaller the density, and the smaller

the compressive strength. The obtained TCP has

a porosity of 67.7–70.36% for 5 g of albumin,

71.8-75% for 7 g of albumin, and 72.8-78.1% for 9

g of albumin. The resulting compressive strength

is 1.03–1.40 MPa for 5 g of albumin, 0.45–1.26

MPa for 7 g of albumin, and 0.15-0.81 MPa for 9

g of albumin.

The crystal analysis pattern of the porous

ceramic is the same as the crystal pattern of the

raw material ceramic powder or in other words

the addition of albumin and the sintering process

at 1,100°C does not affect the chemical

composition of the ceramic material. In other

words, the sintering process is only to remove

organic compounds without changing the crystal

content in the ceramic. Sintering generally plays

a role in stabilizing the metal and detoxifying the

metal, and without melting the material and

changing the metal components ^[19]

.

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Chempublish Journal, 7(1) 2023, 8-17

8. Fadli, A., Rasyid, A., & Firmansyah, R. (2014). Effect

of Sintering Temperature Rate on Physical

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Acknowledgements

The author would like to thank the Ministry of

Research, Technology and Higher Education,

Indonesia for funding this research through an

insinas grant.

9. Yatim, N. H., & Rahman, H. A. (2020). Influences of

Starch on Ceramic-Foam Fabrication: A Short

Review. IOP Conference Series: Materials Science and

Engineering,

824(1),

012001.

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