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A biomimetic approach of composition and natural function of natural moisturizing factor (NMF) with the amino acid content of silk fibroin was advantageously used to reconstruct the skin moisturizing system. The isolation of silk hydrolysate with water and sodium chloride treatment was complete in one hour. Lithium ion from LiBr effectively penetrated crystal domains of fibroin and gave desired solubility. Silk fibroin from Bombyx mori cocoons was non-allergic and biocompatible in skin and rabbit eye tests. The concentration dependent moisturizing efficacy of fibroin (1-5% w/v) in solution and cream form has been demonstrated by TEWL in vitro and in volunteers. As compared to dry and normal skin the fibroin containing cream revealed increased substantivity. The increased hydroxproline content was responsible for retaining higher moisture in the skin. This in turn maintained the skin in soft and supple state. The significant drop in impedance was observed within 1 hr of the application of fibroin and the effect was sustained for more than 6 hrs. Thus, increased hydration level in stratum corneum was achieved by fibroin treatment. The SEM of fibroin treated skin replicas showed a desired attribute of soft, smooth skin texture and improved flexibility. The increased state of hydration caused interdigitating of cell edges as evident in microphotographs. The rapid and sustained moisturizing efficiency observed with silk fibroin was well substantiated by the results of skin substantivity and impedance tests.
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Indian Journal of Biotechnology
Vol 4, January 2005, pp 115-121
Moisturizing efficiency of silk protein hydrolysate: Silk fibroin
A V Daithankar, M N Padamwar, S S Pisal*, A R Paradkar and K R Mahadik
Department of Pharmaceutics, Poona College of Pharmacy and Research Centre, Bharati Vidyapeeth Deemed University
Pune 411 038, India
Received 19 September 2003; revised 11 February 2004; accepted 25 February 2004
A biomimetic approach of composition and natural function of natural moisturizing factor (NMF) with the amino acid
content of silk fibroin was advantageously used to reconstruct the skin moisturizing system. The isolation of silk hydrolysate
with water and sodium chloride treatment was complete in one hour. Lithium ion from LiBr effectively penetrated crystal
domains of fibroin and gave desired solubility. Silk fibroin from Bombyx mori cocoons was non-allergic and biocompatible
in skin and rabbit eye tests. The concentration dependent moisturizing efficacy of fibroin (1-5% w/v) in solution and cream
form has been demonstrated by TEWL in vitro and in volunteers. As compared to dry and normal skin the fibroin containing
cream revealed increased substantivity. The increased hydroxproline content was responsible for retaining higher moisture
in the skin. This in turn maintained the skin in soft and supple state. The significant drop in impedance was observed within
1 hr of the application of fibroin and the effect was sustained for more than 6 hrs. Thus, increased hydration level in stratum
corneum was achieved by fibroin treatment. The SEM of fibroin treated skin replicas showed a desired attribute of soft,
smooth skin texture and improved flexibility. The increased state of hydration caused interdigitating of cell edges as evident
in microphotographs. The rapid and sustained moisturizing efficiency observed with silk fibroin was well substantiated by
the results of skin substantivity and impedance tests.
Keywords: silk fibroin, natural moisturizer, in vivo, TEWL, SEM, impedance
IPC Code: Int. Cl.7 A 61 K 7/40, 7/48
Dry skin conditions are the most frequent derma-
tological disorders of the skin. The lack of adequate
flexibility and extensibility due to environmental
changes results in cracking and flaking of the stratum
corneum. Water is the only plasticizer of the skin.
Environmental factors and use of detergents is the
prime factor responsible for excess water loss and dry
skin condition1. The hydrophilic substances lost from
the stratum corneum (natural moisturizing factor,
NMF) reduce the ability of the skin to hold the water
and thereby maintain the extensibility2. The NMF is
made up of amino acids (free, 40%), pyrrolidone car-
boxylic acid (12%), urea derivatives (8.5%), inorganic
salts (17%), lactate (12%) and unidentified peptides
(9.5%). The epidermis contains most of the twenty-
two amino acids normally occurring in living tissue.
NMF is amino-lipoidal in nature. The free amino ac-
ids content of NMF predominantly contains glycine
and histidine.
The facile addition of water does not suffice to
plasticize skin. It is bound up in protein-lipid mixture,
most probably within the dead cells of epidermis. The
oil containing preparations form an occlusive layer on
skin, which prevents the moisture loss from the stra-
tum corneum. This allows water to be accumulated in
the horny layer of the skin3. Straianse initiated the
research in the field of regulating moisture in the
skin4. A number of emollients lubricating the skin and
moisturizers enhancing the hydration of the skin have
been reported5. The significance of natural hygro-
scopic components is emphasized by researchers and
the nourishment of the skin with products containing
hydrophilic substances has been advised. Oils and
fatty acids containing preparations give temporary
softness to the skin. However, their prolonged use can
be harmful due to sealing of horney layer resulting in
edema and inflammation.
Several synthetic and semi-synthetic compounds
are used as moisturizers. The most valuable approach
to moisturization of skin is to determine the precise
mechanism of NMF and access the damage due to
deficient material. This approach is used in natural
products from animal milk, palm fruit, gingili seed
*Author for correspondence:
Tel: 91-20-2543 7237; Fax: 91-20-2543 9383
and Aloe vera. Such products enjoy excellent popular-
ity as moisturizers in crude and paste form6. Protein
and protein hydrolysates from natural sources are
common ingredients of skin creams. Literature re-
vealed that protein hydrolysates from natural sources
can stimulate the skin to rebuild tissue and replace
amino acids in the stratum corneum7. India produces
nearly 14,500 million tonnes of silk per annum. The
abundant amount of silk produced is predominantly
used in textile and dyeing industry. Silk is continuous
strand of two filaments of fibroin cemented together
by silk gum (silk sericin). The unique physico-
chemical properties of fibroin have been successfully
evaluated as enzyme inhibitor, immunostimulant, ma-
terial of construction of contact lens and for con-
trolled release of drugs in gel forms8-11. Researchers
have reported that silk fibroin has, improved affinity
of eye shadows, long lasting effect for deodorants,
reduced colour bleeding from lipsticks and as anti-
wrinkle agent by promoting the collagen formation12.
Fibroin, a glycoprotein, is composed of two
equimolar protein subunits of 370 and 25 kDa,
respectively. The amino acid composition of silk
fibroin has components resembling to NMF of the
skin13. The crystalline domains of fibroin have high
percentage of glycine (44%) and alanine (30%). Silk
fibroin shows excellent water binding and absorbing
capacity. This property of a non-toxic and
biocompatible natural protein hydrolysate is well
suited for moisturizing effect. The biomimetic
approach based on knowledge of natural function of
NMF can be used to reconstruct a completely new
moisturizing system using silk fibroin. The isolation
of silk fibroin has been optimized and the safety
profile established. The moisturizing efficiency of silk
fibroin in solution and cream form was evaluated
using transepidermal water loss (TEWL) technique as
well as in volunteers. The effect of silk fibroin as
moisturizer was also investgated by hydroxyproline
assay and impedance measurements method to
support the hypothesis. The average changes of
surface of stratum corneum skin replicas were
analyzed using scanning electron microscopy.
Materials and Methods
Silk (Bombyx mori) cocoons were obtained from
Sericulture Institute, Pune. Lithium bromide, L-
hydroxyproline and p-dimethyl amino benzaldehyde
were procured from Loba Chemicals, Mumbai.
Speedex (silicon rubber fluid) was kindly provided by
Medinova Diagnostic Centre, Pune. Freshly shaded
snakeskin was obtained from Rajiv Gandhi Snakes
Park, Pune. Silk-Pro-100 (pure silk fibroin, L10027)
was received as a gift sample from Collaborative
Laboratories, New York. Steric acid, cetyl alcohol
and isopropyl myristate of spectral grade were pur-
chased from Pure Chem Ltd., Mumbai. All other
chemicals of ultra pure grade were used.
Isolation of Silk Fibroin
Silk cocoons (2 g), cut into small pieces (1 cm2)
were boiled in water for 30, 60 and 90 min separately.
The mixture was treated separately with 300 ml of
0.5% w/v aqueous sodium carbonate solution at 90-
100°C for 30, 60 and 90 min. Silk fibres were washed
with hot water till neutral pH, air dried and defatted
with petroleum ether (25 ml). Purified fibres were
dissolved in 5-8 ml of aqueous solution of lithium
bromide (9.3 M) separately. The thick paste of silk
fibres was dialysed with water for 3 days to remove
lithium bromide. The residual lithium bromide con-
tent was analyzed using atomic emission spectros-
Safety Evaluation of Silk Fibroin
The primary skin irritation was measured by open
patch, closed patch and abraded skin tests in albino
rabbits15. Eye irritation test was performed in rabbits.
Ophthalmic and skin irritation tests of 0.1ml of 5%
w/v aqueous solution each of silk fibroin and silk-Pro-
100 were carried out separately using six rabbits (2.5-
3 kg) against water as control. The observations were
scored numerically after 24, 48 and 72 hrs. Intensity
of the skin reaction was graded in accordance to the
data used by National Institute of Occupational
Moisturizing Efficiency of Silk Fibroin
In vitro Evaluation
Shaded snakeskin was washed sufficiently with
distilled water and air-dried. It was rehydrated using
100 ml Tris-HCI buffer (pH 7.4). The TEWL was
estimated using a small diffusion cell, fabricated from
cylindrical aluminum bar, as suggested by Martin and
Deems1. A small piece (1.5 cm diam) of snakeskin
was placed in between two silicon rubber gaskets. The
lower chamber contained 0.4 ml distilled water. The
gasket along with the skin was placed between the
lower chamber and covered with lid. One ml solution
of silk fibroin (1, 3, and 5% w/v) and 5% w/v silk-
Pro-100 was applied on snakeskin. The cell was kept
in constant humidity chamber at 37°C and weighed
every 24 hrs until constant weight. Rate of moisture
loss (mg/cm2/hr) was calculated by using equation 1,
Rate of moisture loss= Moisture loss (mg)/Area (cm2)
of SC exposed × Time in hr … (1)
In vivo Evaluation
A modified miniature desiccator was used to meas-
ure TEWL in human volunteers16. About 600 mg sil-
ica gel (10/20 mesh size) enclosed in small cotton bag
was used as a desiccant. Inner portion of the forearm
(upper and lower) was selected as a test site. Desic-
cant bags were weighed just before the test, and every
two hrs during the test. Normal TEWL of six healthy
volunteers was calculated using equation 2,
DC% = (UL) × 100/l … (2)
where, DC% is percentage difference in moisture loss
of adjacent site of normal, U and L are the weights of
silica bags on the upper and lower sites, respectively.
One ml sample each of fibroin solution (1, 3 and
5% w/v) and silk-Pro-100 (5% w/v) was applied sepa-
rately on the upper portion of the forearm for 15 min.
The lower portion was kept blank. The TEWL (DT%)
was calculated as described above. The actual mois-
ture loss (net effect) was calculated using equation 3.
The in vitro and in vivo moisturizing efficiency of
standard cream, blank base and creams containing 5%
silk fibroin and 5% silk-Pro-100 (separately) was de-
termined similarly.
Net effect = DT% DC% … (3)
Skin Substantivity of Fibroin
The forearms of the subjects were washed with
soap and then towel blotted. The quantity of cream
(5% silk fibroin, 5% silk-Pro-100) equivalent to 1 ml
solution was applied to 3 cm2 skin and allowed to re-
main in place for 3 hrs. Three successive scotch tape
stripping each of 1 cm2 were analyzed for hy-
droxyproline content as described by Sakamuto17.
Similarly, the hydroxyproline content of dry and nor-
mal skin was estimated.
Effect of Fibroin Treatment on Skin Impedance
An electrical equivalent circuit previously reported
by William et al18, was used to study the effect of
creams (5% silk fibroin, 5% silk-Pro-100) on the skin
impedance. Normal impedance values were measured
in five untreated volunteers after every hr. One ml of
the test sample was applied to forearms of the volun-
teers and the impedance was measured every hour for
a period of six hrs.
Scanning Electron Microscopy of Fibroin Treated Skin
The surface topography of normal skin, dry skin
and skin treated with optimized silk fibroin cream and
marketed cream was obtained by SEM19. The quantity
of cream (5% silk fibroin, marketed cream) equivalent
to one-milliliter solution was applied to 3 cm2 skin
and allowed to remain in place for 3 hrs. The skin rep-
licas were taken using silicon rubber fluid, mounted
on stub using double-sided adhesive tape. Skin repli-
cas were gold-coated (20 mm) using sputtering tech-
nique (VG Microtech, UK). The replicas were ob-
served under SEM (Cambridge Instruments, Stereo-
scan 120, UK) and photographed (50 ×).
Results and Discussion
Isolation of Silk Fibroin
Silk mainly contains fibroin (about 80%), gum-
ming agent (sericin) (18%) and fatty substances (2%).
The purification and treatment of silk is essential to be
used in cosmetic products. The time required for
complete solubilization of silk fibres with water
treatment time of 30, 60 and 90 min with the corre-
sponding sodium carbonate (0.5% w/v, 100°C) treat-
ment for 30, 60 and 90 min treatment were found to
be 40, 20 and 15 min, respectively. Insufficient treat-
ment with boiling water results in longer solubiliza-
tion time and poor yield. The precipitates observed in
such case indicate incomplete degumming. A water
boiling and sodium chloride treatment each for one hr
resulted in improved solubility and yield (3.2% w/v).
The purified silk fibroin is insoluble in water but
soluble in 9.3 M LiBr solution. The volume of lithium
bromide solution has significant effect on the product
characteristics. A sediment with large fraction of in-
soluble suspended particles was observed after one
day in 5 and 6 ml LiBr solution batch. However, a
transparent dialyzed solution without visible particles
was obtained with 7 and 8 ml of aqueous LiBr solu-
tion treatment.
Aqueous lithium bromide solution is a good
solvent for the solubilization of silk fibroin. Lithium
ions enter the crystal domains present in the fibroin
fibres by active ionic movement. The peptide chain is
broken by co-ordination between lithium ions and
polar tyrosine and serine. The simultaneous entry of
more water molecules breaks the intermolecular
hydrogen bonds in peptides and gives soluble
fraction20,21. The average final concentration of silk
fibroin was found to be 8.3-8.5% w/v. The residual
lithium content was less than 0.00025 and well below
the safety limit.
Safety Evaluation of Silk Fibroin
Silk fibroin obtained from the silk cocoons is re-
ported to be non-toxic and biocompatible. The results
of safety evaluation of fibroin solution 5% and silk-
Pro-100 (5%) in the rabbit eye test showed no effect
on lacrimation and no signs of irritation to cornea, iris
and conjunctiva. The skin irritation test revealed ab-
sence of any kind of inflammatory response i.e.
edema or erythema (redness) showing the non-allergic
and non-irritant property and safety for human use.
The solution indicated a curing effect on abraded skin
showing tissue-rebuilding nature of proteins. From the
results of both the tests it can be confirmed that the
silk protein is biocompatible natural material22.
In vitro and In vivo Moisturizing Efficiency
The hydration state of stratum corneum can be de-
termined by several methods. The most widely used
and effective method is measurement of TEWL. The
rate of moisture loss from 1, 3 and 5% w/v silk fibroin
solution and 5% w/v silk-Pro-100 is shown in Fig. 1.
The average T/U ratio of 1, 3 and 5% silk fibroin so-
lution and 5% silk-Pro-100 solution was 1.99, 2.20,
2.61 and 2.78, respectively. The net moisture loss in
untreated volunteers and treated with 1, 3 and 5% w/v
silk fibroin and 5% w/v silk-Pro-100 solution for 12
hrs were found to be 1.97±0.434, 11.95±0.923, 14.38
± 0.468, 20.264 ± 1.159 and 21.88 ± 0.633 mg/cm2/2
hrs, respectively.
The 5% silk fibroin and 5% silk-Pro-100 were for-
mulated in o/w cream and evaluated for moisturizing
efficiency along with standard cream (cream base as
blank) by both in vitro and in vivo TEWL techniques.
The o/w creams containing 5% w/v silk fibroin and
5% silk-Pro-100 prepared separately had a viscosity
of 985 ± 15 and 924 ± 21cP respectively. The creams
with a pH of 5.4 ± 0.2 were physically stable on stor-
age at room temperature for three weeks. These
creams did not show interaction with excipients and
hence no gel formation or synerisis. The in vitro rate
of moisture loss from the creams is shown in Fig. 2.
The T/U ratio for cream base, 5% w/v SF cream, 5%
w/v S-P-100 cream and standard cream was found to
be 1.58, 2.88, 2.94 and 2.95, respectively. The rate of
moisture loss of the corresponding creams in volun-
teers was found to be 2.05 (untreated), 3.17 ± 0.98
(cream base), 23.954 ± 2.25 (silk fibroin 5% w/v),
24.07 ± 2.23 (silk-Pro-100 5% w/v) and 26.17 ± 1.21
mg/cm2/2 hrs.
The in vitro evaluation revealed that 5% silk fib-
roin solution showed significant increase in the
TEWL values than 1 and 3% w/v silk fibroin concen-
tration. This trend was confirmed in higher T/U ratio
also. The result indicated that increase in concentra-
tion of silk fibroin, increased the water uptake from
the reservoir of the cell into the snakeskin, which then
evaporated into the atmosphere. Thus, the rate of epi-
dermal water turnover was increased. Silk-Pro-100, a
purified silk protein (source and composition not dis-
closed) was found to be equally effective for longer
period of treatment. In vivo evaluation closely ap-
proximates the use and perception of efficiency of the
Fig. 1—In vitro moisture loss through snakeskin (76% RH)
(--Control, -- SF solution 1% w/v, -U- SF solution 3% w/v,
-×-SF solution 5% w/v, -o-SP solution 5% w/v)
Fig. 2—In vitro moisture loss through snakeskin (76% RH)
(-- Control, -- Blank cream -U- SF Cream 5% w/v, -×- SP
Cream 5% w/v, -o- Standard Cream)
material as a moisturizing agent. A trend confirming
the in vitro effect was observed in in vivo moisturiz-
ing efficacy in volunteers. This also confirms the suit-
ability of the in vitro evaluation technique. The in vi-
tro evaluation of creams revealed the supportive role
of the cream base to the moisture control. The rate of
moisture loss from the silk fibroin, silk-Pro-100
creams and standard (marketed) product was higher
than the corresponding solutions. Their in vitro as
well as in vivo evaluation showed insignificant differ-
ence in the moisturizing ability.
The behaviour of the free amino acids in the stra-
tum corneum reflects the physical well being of the
skin. The mechanism of increase in water transport by
silk fibroin lies in the fact that amino acid components
of silk fibroin are similar to natural moisturizing fac-
tor of the stratum corneum. The high molecular
weight (68000 D) of the silk fibroin forms a thin film
over the stratum corneum. This film is porous and is
permeable to water7,23,24. It drags the water from the
reservoir beneath the skin and increases the water cir-
culation across stratum corneum. The desiccant took
up more moisture, thus there was increase in weight
of desiccant showing moisturizing effect of silk pro-
teins. The resulting net effect was the continuous con-
tact of stratum corneum with the water and hence
Skin Substantivity of Fibroin
The water absorption capacity of protein and pep-
tides is measured by the extent of substantivity to stra-
tum corneum. The binding capacity of the silk fibroin
on stratum corneum is estimated by hydroxyproline
assay25. Fig. 3 shows significant increase in the hy-
droxyproline content of the stratum corneum after
application of the 5% w/v silk fibroin and 5% w/v
silk-Pro-100 solution within 3 hrs. The average hy-
droxyproline content for dry and normal skin and skin
treated with fibroin and silk-Pro-100 were 0.0142,
0.627, 1.734 and 1.927 µg/cm2, respectively. In com-
parison with dry and normal skin it revealed increased
substantivity. Skin substantivity measures the amount
of protein, which after extended exposure resist to
extraction by water due to formation of weaker link-
ages with the skin components26. However, the in-
creased protein binding can be analyzed in scotch tape
stripping. The increased hydroxyproline content is
responsible for higher moisture content. This in turn
maintains the skin in soft and supple state. The ob-
served results support skin moisturizing mechanism
of silk fibroin.
Effect of Fibroin Treatment on Skin Impedance
Measurement of skin impedance is sensitive means
to access the hydration state of the skin. Impedance
between two fixed points of the skin depends upon the
hydration state of stratum corneum. Higher moisture
retained in the skin causes drop in the impedance. The
effect of silk fibroin and silk-Pro-100 on skin imped-
ance in volunteers is shown in Fig. 4. The significant
drop in impedance was observed within 1 hr of appli-
cation of fibroin and the effect was sustained for more
than 6 hrs.
Skin moisture is closely related to its normal func-
tioning and its measurement helps in early diagnosis
of non-visible skin conditions. William et al18 have
applied the electrical equivalent principle to evaluate
the performance of drugs and cosmetics by recording
the skin impedance. Low frequency (l mHz) imped-
ance measurement is preferred to higher ones due to
minimum induced changes in skin components and
higher sensitivity. Any substance similar in properties
Fig. 3—Hydroxyproline content after skin treat-
Fig. 4—Effect of skin treatment on skin impedance (-- Normal
skin, -- Silk fibroin cream, -U- SP100 Cream)
to natural moisturizing factors of stratum corneum can
cause drop in impedance e.g. sodium salicylate. How-
ever, highly resistive substances like liquid paraffin
get incorporated in stratum corneum were reported to
increase the impedance. In the present study, increase
in hydration level in stratum corneum was achieved
after treatment with silk fibroin. This change in elec-
trical properties of stratum corneum may be attributed
to more movement of keratin chains due to plasticiz-
ing effect of retained water27. The results are in coor-
dination with the in vitro and in vivo moisturizing ef-
Scanning Electron Microscopy of Fibroin Treated Skin
The visual changes in the surface of the stratum
corneum including uniformity, number and nature of
white ridges, smoothness and scaling can be revealed
by SEM5. The SEM for normal, dry and skin treated
with silk fibroin as well as marketed moisturizing
cream is shown in Fig. 5. Although SEM was ob-
tained at a magnification of 50× and 500×, the magni-
fication at 50× revealed the changes in the skin tex-
ture. Dry skin showed more flakes and cells separated
by more white lines with massive desquamation of
stratum corneum. The normal skin cells are highly
organized with end-to-end arrangement in units of
vertical column. A desired attribute of soft, smooth
skin texture and improved flexibility was evident in
skin treated with silk fibroin (as well as marketed
Epidermal cells construct superficial layer of epi-
dermis, mainly composed of 10-15 cell layers of flat-
tened keratinized dead cells. The horny layer is 10-15
µm thick in dry skin. Average daily loss of 0.5-1 g of
horny layers occurs from the normal skin. The dry
skin condition can be treated by occlusive, humec-
tancy or restoration of deficient material. In the pre-
sent study, cream containing 5% silk fibroin increased
the transepidermal water loss and the process swelled
the dry cells several times its volume. More water was
bound to protein lipid complexes of the dead cells.
This caused the cells to interdigitate their lateral edges
with adjacent cells to form a cohesive lamina. The
plasticizing effect of increased water in dead cells
enhanced mildness and imparts substantivity28. The
microphotographs reveal that the silk fibroin as mois-
turizer brought out significant improvement in the
texture of dry skin. The qualitative assessment
showed better surface texture as compared to mar-
keted product. Hence, it can be confirmed that the silk
hydrolysate helped to rebuild the skin tissues29.
Occlusive type of moisturizers has limitations of
temporary softness with grease filling. The resem-
blance of amino acid composition of natural moistur-
izing factor and silk fibroin (high molecular weight)
can be advantageously used as skin moisturizer. The
fibroin isolated with lithium bromide revealed the
biocompatible nature of silk hydrolysate. The mois-
turizing efficiency of the silk fibroin and silk-Pro-100
has been demonstrated and correlates well in in vitro
and in vivo techniques. The increased hydroxproline
content, rapid drop in skin impedance and a soft,
Fig. 5—Scanning electron microphotographs of skin replicas
(50×): a. Dry skin, b. Silk fibroin cream, c. Standard cream
smooth skin texture with improved flexibility in scan-
ning electron microscopy substantiate the effect ob-
served in transdermal water loss technique. The study
revealed silk fibroin as a promising new natural mois-
turizing agent.
SSP gratefully acknowledges All India Council for
Technical Education (AICTE), New Delhi, for pro-
viding financial assistance as research fellowship in
the form of ‘Career Award for Young Teachers 2002’.
Authors are thankful to Dr Shivajirao S Kadam, Prin-
cipal, Poona College of Pharmacy, Bharati Vid-
yapeeth Deemed University, Pune for support in the
implementation of the research scheme.
1 Martin M R & Deems D E, Skin moisturizers, J Soc Cosmet
Chem, 25 (1974) 239-242.
2 Blank I H, Factors which influence the water content of stra-
tum corneum, J Invest Dermatol, 46 (1952) 433-437.
3 Blank I H, Dry skin treatment, Drug Cosmet Ind, 76 (1955)
4 Strainase S J, Human skin moisturizing mechanism and natu-
ral moisturizers, Cosmet & Toilet, 93 (1978) 37-42.
5 Isdon B, Skin treatment cosmetics: An overview, Drug Cos-
met Ind, 133 (1987) 40-45.
6 Chvapil M & Eckmayer Z, Role of proteins in cosmetics, Int
J Cosmet Sci, 7 (1985) 41-49.
7 Ute C, Classic additives and actives for skin and hair care,
Cosmet & Toilet, 113 (1998) 69-74.
8 Hanawa T & Watanabe A, New oral dosage form for elderly
patients: Preparation and characterization of silk fibroin gel,
Chem Pharm Bull, 43 (1995) 284-288.
9 Hanawa T & Watanabe A, New oral dosage form for elderly
patients: II Release behavior of benfotamine from silk fibroin
gel, Chem Pharm Bull, 43 (1995) 872-876.
10 Yoshimizu H & Asakura T, The structure of Bombyx mori
silk fibroin membrane swollen by water studied with ESR,
13C-NMR and FT-IR spectroscopies, J Appl Poly Sci, 40
(1990) 1745-1756.
11 Tsukada M & Norihiko M, Oxygen permeable membranes,
JP 02233128 A2 (to Agency of Industrial Science and Tech-
nology, Japan) 14 September 1990; Chem Abstr, 114 (1991)
12 Miyashita T, Sweat and sebum absorbing cosmetics contain-
ing cellulose fibres, JP 11152206 A2 (to Kokai Tokkyo
Koho, Japan) 8 June 1999; Chem Abstr, 131(1999) 23271.
13 Nadiger G S & Bhat N V, Investigation of amino acid com-
position in the crystalline region of silk fibroin, J Appl Poly
Sci, 30 (1985) 221-225.
14 Tsukada M & Freddi G, Preparation and application of po-
rous silk fibroin materials, J Appl Poly Sci, 54, (1994) 507-
15 Romanowski P & Schuller R, Fundamentals of cosmetic
product testing, Cosmet & Toilet, 111 (1996) 79-86.
16 Powers D H & Fox C, A method of evaluation of moisturiz-
ing efficiency for skin, Proc Sci Sect T G A, 24 (1957) 21.
17 Sakamuto K, The development of two new moisturizing in-
gredients, Cosmet & Toilet, 99 (1984) 110-117.
18 William C & Gary L G, Non-invasive method for assessing
moisturizers, Cosmet Sci Tech, 8 (1999) 120-129.
19 Levcque J L & Rigal J, Impedance method for studying skin
moisturizing, J Soc Cosmet Chem, 34 (1983) 419-428.
20 Nakamae K & Nishino T, Elastic modulus of crystalline re-
gions of silk fibroin, Polymer, 30 (1989) 1245-1247.
21 Ayub Z A & Arai M, Quantitative structural analysis and
physical properties of silk fibroin hydrogels, Polymer, 35
(1994) 2199-2200.
22 Raje S S & Rekha V D, Regenerated silk fibroin—A review,
Man Made Text India, (June 1998) 249-254.
23 Tsubouchi K, Wound covering material containing silk fib-
roin and silk sericin as the main components and process for
producing the same, JP1997-177705 (to National institute of
sericulture Japan). June 1997; Chem Abstr, 130(1997) 43418.
24 Anthony S N & Neghme B M, Protein hydrolysates and con-
densates in creams and lotions, Cosmet & Toilet, 95 (1980)
25 Highely D R, Measurement of moisturizing efficacy, Cosmet
Toilet, 93 (1978) 35-41.
26 Daithankar A V, Evaluation of moisturizing efficiency of silk
fibroin in cosmetic cream, M Pharm Thesis, Bharati Vid-
yapeeth Deemed University, Pune, 2001.
27 Martinsen O, Skin impedance and moisturization, J Soc
Cosmet Chem, 52 (1999) 338-344.
28 Marino C, Safety and health assessment and research for
prevention program, Report no. 56 (2), (State Department of
Washington) August 2001.
29 Wu C & Tian B, Wound protection film and its preparation
method, CN 95-111703 (to Silk Engineering College, Peo-
ples Republic of China), July 1995; Chem Abstr, 130 (1995)
... Images of SEM demonstrated that the cracking and flaking of skin decreased as well [106]. ...
Silk is a globally renowned abundant biopolymer obtained from various sources of the Lepidoptera family, among which the most commonly used and researched are spider silk and silk worm silk. All varieties of silk have beneficial characteristics such as high tensile strength, biocompatibility, producing a reduced immune response in a biological system, biodegradability, and the ability to withstand environmental stresses as well. These features make silk suitable for a number of applications as a biomaterial. The vast potential of silk and its proteins in cosmetics, oncology, tissue engineering, TOC screenings, for preserving food, cosmetic product as a silk gel and bioremediation makes it a well-sought biopolymer among researchers. Experiments over the years have revealed that biomaterials constituting silk are very potent but are yet to be scaled up for commercial uses, but the various advantageous properties of silk biomaterial far overshadows the impeding problems of production.
... To separate the raw fibroin from the sericin, the milled cocoons were subjected to an alkaline digestion by immersing them in a Na 2 CO 3 solution, with magnetic stirring at 600 rpm at a constant boiling temperature. This alkaline digestion step was carried out with different Na 2 CO 3 concentrations (0:5 M and 1 M) and agitation times (30 min and 90 min), as shown in Table 1 (Daithankar et al., 2005;Lozano et al., 2017). ...
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Silk fibroin (SF) is a biomacromolecule composed of proteins with properties, such as biocompatibility, biodegradability, and low immunogenicity. Thus, Silk fibroin nanoparticles (FNps) overcome the disadvantages of non-degradable synthetic nanoparticles. We studied the structural and thermal properties of SF and FNps from Bombyx mori L. cross-breed Pilamo I cocoons. Raw fibroin (RF) was obtained using a sodium Na2CO3 solution as part of an experimental design to improve extraction, and FNps were obtained by denaturing RF with a ternary solution of CaCl2:H2O:CH3CH2OH, followed by precipitation using an anti-solvent method with propanol. Pilamo I cocoon, RF, and FNps were characterized using Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy(SEM), and elemental chemical analysis of energy dispersive X-rays (EDS). The Light Scattering (DLS) and the thermal properties of RF and FNps were studied by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The FTIR results showed that sericin-free raw fibroin was obtained, and the SEM results showed that the nanometer-sized particles had a globular structure and apparent porosity. The differences in the enthalpy of the crystallization peaks in the DSC and TGA curves showed that the FNps had higher thermal stability than RF fibers. This result furthers the development of alternative materials as vehicles of active compounds from natural extracts.
... Applying moisturizing cosmetics can not only protect healthy and normal skin, but also repair damaged skin [8]. Silk fibroin, obtained from silk, has a close affinity to human skin and can moisturize skin, because it is rich in various amino acids and trace elements [9]. Also, silk fibroin can increase the moisture content of the cuticle, promote the synthesis of collagen and repair the barrier dysfunction of the skin epidermis, which results in relieving dry and itchy skin [10]. ...
... Sericin, which is composed of 18 different amino acids (Cao and Zhang 2016) and is highly hydrophilic, has strongly polar amino, hydroxyl, and carboxyl side groups (Padamwar and Pawar 2004;Kundu et al. 2008). Sericin has found places in areas, such as cell culture additives ( Minoura et al. 1995;Takahashi et al. 2003), cosmetic ( Daithankar et al. 2005;Padamwar et al. 2005), dietary food ( Sasaki et al. 2000a, b;Zhaorıgetu et al. 2001;Yang et al. 2009), biomedical (Soong and Kenyon 1984;Dewair et al. 1985;Panilaitis et al. 2003), and anticoagulants ( Tamada et al. 2004) due to its properties like biocompatibility, biodegradability, UV resistance, resistance to oxidation, moisture absorption and abilities to scavenge radicals and attack microbes Kundu et al. 2008;Joseph and Raj 2012;Shahid et al. 2013). Moreover, sericin has become an essential biopolymer in the textile industry. ...
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A large amount of salt has been used in reactive dyeing of cotton. In this study, the reduction in the amount of salt used in reactive dyeing of cotton fabric after the sericin application by different methods was investigated in detailed. The effects of different cross-links (citric acid and butane tetracarboxylic acid) for the bonding of the sericin to the cotton fabric were also investigated. The results were evaluated in terms of color coordinates and color strength, washing and rubbing fastness, and crease recovery angle. Presence of the sericin onto cotton fabric after the application was evidenced with FT-IR spectra. The application of sericin and subsequent dyeing resulted in similar color depths to the conventional dyeing even with half the salt used in conventional reactive dyeing. The presence of cross-links in the pre-treatment baths did not reveal significant differences in color strengths compared to used only sericin. The fastness values of reactive dyed fabrics after sericin application had similar fastness values with traditional dyed ones. Crease recovery angles showed an increase after sericin pre-treatment. Sericin application before reactive dyeing could be one of the best alternative ways to reduce salt usage in reactive dyeing. Graphical abstract Open image in new window
The paper presents an effective antistatic composition for forming the web from silk waste on a carding machine. As a result, the needle punched nonwoven material modified with silver and copper nanoparticles was obtained from Bombyx mori natural silk. The specific surface area of the material is 0.223 m²/g, the average size of macropores is 85 μm; the minimum is 30 μm and the maximum is 370 μm. The holding capacity in case of dolomite dust is 99.4%. The presence of silver and copper nanoparticles gives the material antifungal properties that remain stable after no less than 4 washings.
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Biological polymers are versatile class of chemicals that are either synthesized from biological resource or fabricated by biological systems. Novel biopolymers are classified based on their origin, which includes natural and synthetic biopolymers. Currently, biocompatible and non-toxic biopolymers have been used to develop efficient systems for the applications in different fields. Especially, in recent times, such materials have gained more attention in biomedical field (tissue engineering, wound healing, burn dressing, and fungal infection). These biopolymer composites are efficient in protecting and discharging bioactive drugs including nutraceuticals, pharmaceuticals, enzymes, and probiotics. Hence, this chapter provides an overview of the importance of bio-based polymers, fabricated or degraded naturally, classification, applications and biological activities.
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Bio-based polymers are engineered for automotive applications due to their multifunctional characteristic properties, such as biocompatibility, biodegradability, and lower disposal as well as mechanical properties in some cases. Automotive Industry can shift to use renewable materials that exhibit equal or outstanding performance compared to the other conventional counterparts. Good life span and lightweight polymeric automotive parts as a way to reduce fuel consumption and therefore limit the outflow of ozone-depleting substances will continue to prompt comprehensive research into the applicability and employment of polymers and their obtained composites in the automotive industry. In this chapter, Biocomposite’s Characteristic Properties containing biomaterials as Polymeric Matrix, i.e., Natural rubber, polylactic acid or Filler, Glass, Cellulose, Wood, Flax,…, in plastic and elastic parts, tires, and foams have been reviewed. Using biopolymers improves Tensile Strength and tear strength, Young’s Modulus, higher Stiffness, lightweight, reduction in fuel consumption, lower Mooney viscosity, and better rolling resistance compared to conventional polymers.KeywordsBiopolymerNaturalAutomotiveBio-based compositesPlasticElastomer
Biopolymers have been extensively explored as a potential class of material for wide range of applications owing to its excellent biomimicking characteristics. The biopolymers are found in natural environments with ideal physicochemical properties such as stretchability, plasticizing ability, pseudoelasticity, and unique bioactive properties like biocompatibility, biodegradability, non-carcinogenicity, non-immunogenicity, and antimicrobial nature that makes them ideal biomaterials. However, these properties greatly vary based on the source, method of isolation, structure, molecular weight, etc., that significantly influence the activity of the biopolymer. Various advanced technologies are being adopted for extracting and processing biopolymers for enhancing their activity and developing them into smart materials for immediate biomedical applications. The bioactive properties aid their applicability as scaffolds, implants, sustained drug release carriers, bioimaging, while for cosmetic applications owe to their biocompatibility and enhanced bioactivity as they can be readily modified as moisturizers, creams, serums, and dermal patches. This chapter discusses the different properties of biopolymers from animal, plant, and microbial origin to develop them as novel molecules for cosmetics, pharmaceutical, and biomedical applications.KeywordsBiopolymers and their originPhysicochemical propertiesBioactivitiesPotential applications
Cosmetics procedures and products combined with environmental insults and daily routines induce irreversible changes in hair. As result of damage, the hair loses some of its properties like strength, elasticity, and smoothness. Recent studies revealed the positive effects of protein-based cosmetics in providing protection to hair. Additionally, these cosmetic products have also shown a great ability to modify hair fibers. We review the effect of protein-based cosmetic formulations on hair properties like color, scent, strength, shape, and volume, highlighting the potential of keratin-based particles and keratin-fusion proteins. In the future, incorporating multifunctional proteins and peptides in the development of alternative hair formulations will result in advanced, sustainable, ecofriendly cosmetic products with a great impact on the cosmetic industry.
Background Skin aging is an inevitable process with one of the key features of aging being dryness or flakiness of the skin. Previous in vivo and in vitro testing has highlighted that a silk‐based product may be effective in improving moisture retention in skin. Methods We evaluated the safety and efficacy of our silk‐based product through a combination of objective‐ including scanning electron microscopy (SEM) and EpiDerm Skin Irritation tests ‐ and subjective tests – including direct evaluation of patient’s own perception of their skin. Results In alignment with previous studies, patients reported significant concerns about aging, wrinkling, or saggy skin. We found that our silk‐based product was safe and effective in improving hydration and resilience of facial skin and a majority of participants stated they would continue to use this product, when commercially available. Conclusion Our novel silk‐based product, NanoSilk Cosmo, is safe for use on human facial skin and it improves skin resiliency and hydration.
This review covers literature dealing with the regeneration of silk polymer from silk fibre. The silk fibre used is that could not be used in the production of continuous thread, and waste collected during processing. The subjects covered include the classification of waste silk, separation of the polymer from the waste, properties of silk fibroil powder, the formation and properties of thin films and applications in fibres, films and membranes.
The effect of dehydration on the molecular structures and physical properties of fibroin gels was investigated. The physical properties that are discussed include strength, water content and thermal stability. It was found that the molecular structure of fibroin was not changed by the change in water content of the gel, while the physical properties of the gel, however, were changed significantly. A quantitative analysis of the molecular structures was carried out by separating the components of the i.r. spectra. The spectral parameters of the amide I, II, and III absorption bands, corresponding to the silk I, β, and random coil conformations, respectively, have been derived. In addition, the fibroin gels were characterized by their water contents, strength and thermal stability.
The elastic modulus E1 of crystalline regions of silk fibroin of Bombyx mori (silk II) parallel to the chain axis was determined by X-ray difraction. The E1 values for both the (002) and (006) plane (c axis; chain direction) of silk II coincided with each other and were obtained as 23 GPa. This small E1 value was due to the skeletal conformation of silk II being contracted 5.6% compared with the fully extended planar zig-zag conformation, and the deformation of the chain was mainly performed through the change of internal rotation angle with a small force constant. The specimen modulus was 10 GPa. This value was 43.5% of the E1 value and the elasticity of elongation work was almost unity after undergoing the recycle test five times. This means the macroscopic deformation of the specimen was largely influenced by the crystal elasticity.
Synopsis-Four parameters for assessing the interaction between human STRATUM COR- NEUM and WATER are described. Two methodologies, ELASTIC MODULUS and STRESS RELAXATION, for determining the MECHANICAL PROPERTIES of stratum corneum have been utilized. It is shown that both of these parameters depend on the moisture content of the stratum corneum, i.e., the ambient relative humidity. The rate of WATER VAPOR ABSORPTION by human stratum corncure, the third parameter exam- ined, is a function of the ambient relative htmidity. Surprisingly, the equilibrium moisture content of stratum corneum at humidities below approximately 80% appears to be essen- tially the same for unextracted stratum corncure and for stratum corncure extracted with lipid solvents. The fourth parameter, the rate of WATER VAPOR TRANSMISSION through stratum corncure in vitro, is a linear ftmction of the ambient relative humidity and has been shown to be markedly affected by changes in temperature.
Structure of Bombyx mori silk fibroin membrane insolubilized with methanol, especially in the swollen state, is studied by means of spin-label ESR, 13C-NMR, and FT-IR (ATR method) spectroscopies. FT-IR data indicate that the conformational transition from random coil to antiparallel β-sheet occurs at the surface of the membrane upon immersion into 80% aqueous methanol. High resolution 13C-NMR observation of the membrane swollen in water shows that, the random coil portion whose segmental motion is very fast remains in the inner part of the swollen membrane. The fraction of this portion decreases with increasing methanol treatment time in the sample preparation. The heterogeneous structure of the swollen membrane was clarified from the complicated ESR spectra of the spin-labeled silk fibroin membranes. The ESR spectra were analyzed quantitatively and the fractions of the fast, slow, and very slow motions of the spin-label site (tyrosine side chain) were determined. A model is proposed for the heterogeneous structure of the swollen silk fibroin membrane.
Accurate estimation of amino acids composition has been carried out for hydrolysates of four varieties of Indian silks, viz., Mulberry, Tasar, Eri, and Muga. These studies have revealed that the hydrolysate (hydrofibroin or crystalline region) in the case of Mulberry consists of glycine, alanine, and serine, whereas in the case of Tasar, Eri, and Muga, it is found to be mainly alanine. Other amino acids were also found to be present in the hydrolysate of these silks. But, the quantities present in each case were found to be negligible when compared to those amino acids cited above. Furthermore, these results are in conformity with the structure elucidation made by infrared spectral studies and x-ray diffraction.
The review critically evaluates the safety and effectiveness of proteins or peptides in cosmetic formulations designed for skin and hair care. Special attention is paid to soluble collagen and the use of this fibrillar protein in combination with detergents. The authors indicate various misconceptions on the mechanism of the effect of collagen and possible risks if the formulations containing collagen are not used on intact skin. Besides the moisturizing effect of collagen on the stratum corneum, the formation of a protective layer on the surface of the skin or hair, and the formation of complexes with detergents and the mechanisms of the effectiveness of this protein are considered. Le role des proteines dans les cosmetiques L'article évalue de façon critique l'innocuité et l'efficacité des proteines ou des peptides dans les formulations cosmétiques pour le soin de la peau et du cheveu. Une attention particulière est apportèe au collagène soluble et à l'emploi de cette proteine fibreuse en combination avec des détergents. Les auteurs mentionnent plusieurs conceptions erronées sur le mécanisme de l'action du collagène et les risques possibles si les formulations qui en contiennent ne sont pas utilisées sur des peaux saines. Sont notamment développés, la fonction hydratante du collagène sur le stratum corneum; la formation d'une couche protectrice superficielle sur la peau et le cheveu; la formation de complexes en présence de détergents; et les mécanismes de l'efficacité de cette proteine.
Silk fibroin gel (SFG) containing benfotiamine (BTMP) was prepared. The release behavior of BTMP from SFG was studied as a function of silk fibroin (SF) content and glycerol content, and the influence of the existence of beta-cyclodextrin (beta-CD) on the physicochemical properties of SFG were investigated. The release rate of BTMP from SFG was retarded by an increase in SF concentration. The addition of beta-CD affected both the release properties and rheological properties of the SFG. It was found from the results of the "paddle-bead method" that the release profiles of BTMP from SFG were inversely proportional to the SFG firmness.
The pharmaceutical utility of silk fibroin as a possible material for an oral dosage form for elderly patients was investigated. Silk fibroin gel (SFG) was prepared from its aqueous solution. The gel formation was studied as a function of adjusted pH and concentration of silk fibroin (SF). On the basis of Fourier transform infrared spectroscopy of SFG, the transition from the random coil to the beta-structure was observed. The rate of gelation was sufficiently accelerated by the addition of glycerol to the SF aqueous solution. The glycerol content also affected the rate of gelation of the SF solution. Rheological properties of SFG were evaluated using a creep meter. The SF content and/or glycerol content affected the breaking stress of SFG. Moisture desorption from SFG was retarded with an increase in glycerol content. It was found that SFG was able to be prepared at room temperature (20 +/- 5 degrees C), and the SF content and glycerol content affected the formation and physicochemical properties of SFG.