34
Another pathway via which nanoparticles enter the body is skin absorption. The
exposure to nanomaterials from the dermal route is the common way of exposure
(Mackevica and Foss 2015). Because skin has the largest area, the probability of
exposure is relatively higher and also it is challenging to determine the amount of
nanoparticles that crosses skin for the same reason. Therefore, it performs as a primary defense organ in human body and it faces dangerous agents all the time
(Hagens et al. 2007). Paints and coatings, skin care (lotion), sunscreen (lotion), air
fresheners (spray), and sealants are some of the products to which we expose via
dermal routes (Viswanath and Kim 2016). The exposure level can be higher for
someone who uses commercial skincare products since a number of commercially
available sunscreen products contain titanium dioxide nanoparticles. The presence
of titanium in the epidermis and dermis after the use of sunscreen has been reported
by Tan et al. (1996). Extreme exposure of titanium dioxide can cause reactive oxygen species production such as hydrogen peroxide, singlet oxygen, free hydroxyl
radicals and so may induce oxidative stress, and cause significant damage to DNA
(Gurr et al. 2005a, b). In an animal model, Tinkle et al. showed that fine particles of
beryllium have the ability to penetrate skin while it was not the case for larger particles (Tinkle et al. 2003). There is a consensus that nanoparticles can be assimilated
into the body through skin. A study carried on post-mortem flexed stratum corneum
indicated that dextran beads in the range of 0.5–1.0 μm can pass through it. The
results obtained by Rouse et al. verified Tinkle findings (Rouse et al. 2007). They
demonstrated that buckminsterfullerene amino acid penetrated the skin after
mechanical flexing. Lademann et al. revealed that microparticles of titanium dioxide incorporated in sunscreen penetrate the stratum corneum (Lademann et al.
1999). Not only are the particle dimensions significant but also surface charge can
be a key factor for penetration ability. Kohlia and Alpar demonstrated that positively
charged and neutral latex nanoparticles of 50 and 500 nm could not penetrate the
dermis, while negatively charged particles could (Kohli and Alpar 2004). In addition, size and shape of quantum dots were also shown to be decisive in the penetration process (Ryman-Rasmussen et al. 2006). Nohynek et al. reported a detailed
study related to skin absorption of nanomaterials (Nohynek et al. 2007). According
to the study, there was no significant absorption into the systemic circulation.
There have also arisen questions whether the penetration can be significant for
defected skin in some way, sunburn, abrasion, or other mechanisms. Zang and
Monteiro-Riviere reported that abrasion of rat skin facilitated quantum dots penetration (Monteiro et al. 2005). However, the effect on skin damaged by other mechanisms (e.g. through sunburn), or on infant skin, remains unknown.
Digestive system is another possible portal for entry of nanoparticles. The digestive system includes gastrointestinal tract, liver, pancreas, and gallbladder. Tract of
mouth, esophagus, stomach, small intestine, large intestine, and anus are hollow
parts of the gastrointestinal tract. Because nanoparticle production has increased
steeply and become widespread almost in every aspect of our life and every parts of
environment, the foods we eat and the beverages we drink are extremely likely to
contain engineered nanoparticles. Food industry use nanoparticles for various reasons such as increasing shelf life and achieving delicious tastes or unintentionally
S. Tekmen and S. Öksüz
Another pathway via which nanoparticles enter the body is skin absorption. The
exposure to nanomaterials from the dermal route is the common way of exposure
(Mackevica and Foss 2015). Because skin has the largest area, the probability of
exposure is relatively higher and also it is challenging to determine the amount of
nanoparticles that crosses skin for the same reason. Therefore, it performs as a primary defense organ in human body and it faces dangerous agents all the time
(Hagens et al. 2007). Paints and coatings, skin care (lotion), sunscreen (lotion), air
fresheners (spray), and sealants are some of the products to which we expose via
dermal routes (Viswanath and Kim 2016). The exposure level can be higher for
someone who uses commercial skincare products since a number of commercially
available sunscreen products contain titanium dioxide nanoparticles. The presence
of titanium in the epidermis and dermis after the use of sunscreen has been reported
by Tan et al. (1996). Extreme exposure of titanium dioxide can cause reactive oxygen species production such as hydrogen peroxide, singlet oxygen, free hydroxyl
radicals and so may induce oxidative stress, and cause significant damage to DNA
(Gurr et al. 2005a, b). In an animal model, Tinkle et al. showed that fine particles of
beryllium have the ability to penetrate skin while it was not the case for larger particles (Tinkle et al. 2003). There is a consensus that nanoparticles can be assimilated
into the body through skin. A study carried on post-mortem flexed stratum corneum
indicated that dextran beads in the range of 0.5–1.0 μm can pass through it. The
results obtained by Rouse et al. verified Tinkle findings (Rouse et al. 2007). They
demonstrated that buckminsterfullerene amino acid penetrated the skin after
mechanical flexing. Lademann et al. revealed that microparticles of titanium dioxide incorporated in sunscreen penetrate the stratum corneum (Lademann et al.
1999). Not only are the particle dimensions significant but also surface charge can
be a key factor for penetration ability. Kohlia and Alpar demonstrated that positively
charged and neutral latex nanoparticles of 50 and 500 nm could not penetrate the
dermis, while negatively charged particles could (Kohli and Alpar 2004). In addition, size and shape of quantum dots were also shown to be decisive in the penetration process (Ryman-Rasmussen et al. 2006). Nohynek et al. reported a detailed
study related to skin absorption of nanomaterials (Nohynek et al. 2007). According
to the study, there was no significant absorption into the systemic circulation.
There have also arisen questions whether the penetration can be significant for
defected skin in some way, sunburn, abrasion, or other mechanisms. Zang and
Monteiro-Riviere reported that abrasion of rat skin facilitated quantum dots penetration (Monteiro et al. 2005). However, the effect on skin damaged by other mechanisms (e.g. through sunburn), or on infant skin, remains unknown.
Digestive system is another possible portal for entry of nanoparticles. The digestive system includes gastrointestinal tract, liver, pancreas, and gallbladder. Tract of
mouth, esophagus, stomach, small intestine, large intestine, and anus are hollow
parts of the gastrointestinal tract. Because nanoparticle production has increased
steeply and become widespread almost in every aspect of our life and every parts of
environment, the foods we eat and the beverages we drink are extremely likely to
contain engineered nanoparticles. Food industry use nanoparticles for various reasons such as increasing shelf life and achieving delicious tastes or unintentionally
S. Tekmen and S. Öksüz