In modern society, much importance has been placed on physical appearance. The relative condition of a person's skin often implies health, youth, and beauty. Dermatological conditions such as acne scarring, stretch marks, surgical scars, melasma, and other conditions detract from the appearance of the skin. There has been much attention and research devoted to beautifying the skin.
The skin comprises the largest organ in the body and as a semi-permeable membrane, provides protection from most elements of the outside environment while also allowing the exchange of oxygen, water, and smaller molecules. The three layers of the skin from superficial to deep are the epidermis, the dermis, and the subcutaneous layer.
The epidermis is comprised of several layers of cells called keratinocytes. The deepest layer of the epidermis is called the basal layer and is comprised of living keratinocytes that both proliferate and differentiate into more specialized keratinocytes called corneocytes. These processes of keratinocytes replicating and turning into dead corneocytes allows the skin to continuously shed its outer layer and replenish the integrity of the skin. The most superficial layer of the skin which contains the corneocytes is the stratum corneum.
The stratum corneum is an effective barrier to many substances. At the molecular level, the stratum corneum's multiple layers of corneocytes prevent larger molecules from crossing it. With respect to beautification treatments, many of the compounds described through marketing as being beneficial to some structure(s) residing below the dead stratum corneum do not actually make it past the stratum corneum and thus cannot act on deeper structures.
Significant research has been performed to determine what characteristics allow a particular molecule to pass through the stratum corneum. Many researchers cite that among all molecular characteristics, the size of the molecule (measured in Daltons) is the single most important factor in determining whether or not a molecule may pass through the epidermis. Several researchers have shown that the stratum corneum has the ability to prevent the transmission of any molecule over 500 daltons without the aid of some enhancement or stratum corneum bypass technology. Vitamin C, for example, has a mass/size of 176 daltons and readily crosses the stratum corneum.
There are thousands of treatment protocols aimed at beautifying the skin and mitigating the appearance of dermatological conditions. Manufacturers of cosmetics market topical creams, liquids, and lotions that are purported to beautify the skin. Many of these are described as having the ability to penetrate deeply into the skin and perform functions such as aid in reversing the aging process or fight free radicals, and many other dubious claims. However, as described above, unless the molecule is under 500 daltons or is aided by a stratum corneum bypass technique, many of these “miracle creams” simply do not pass the stratum corneum. It is important to recognize that the stratum corneum itself, can and does benefit from certain topicals. However, because the stratum corneum is not a living layer of tissue, any claim involving biologically active cells or functions cannot be true.
Skin professionals ranging from doctors to estheticians have developed techniques designed to penetrate, remove, or bypass the stratum corneum and/or deeper layers of the epidermis. Some of these treatment protocols were designed specifically to allow molecules, which normally could not cross the stratum corneum, to penetrate into the dermis. One set of techniques involve the use of penetrating the skin with tiny, solid, sterile, microneedles. These techniques create microchannels that, for a short period of time, allow molecules larger than 500 daltons to cross the stratum corneum. Depending on the relative depth of the microneedles, some practitioners intentionally microneedle the skin for the additional reason of inflicting tiny microinjuries into the dermis that stimulate the body's cutaneous wound response to remodel the dermal tissues in an effort to beautify the skin. Microneedling to a depth that reaches the dermis allows the microneedles to come into contact with blood and bodily fluids. In both cases, many of these treatment protocols involve the use of liquid or cream topicals being applied before, during, and after the microneedling of the skin. Some practitioners employ a more complex protocol which involves removing a volume of blood from the patient via a hypodermic syringe, separating the blood products by means of a centrifuge, adding a chemical agent to the isolated platelet volume extracted, and then applying the activated platelet isolate to the skin before and/or during the microneedling of the skin.
There have been several devices invented all of which rely on the use of tiny microneedles which penetrate the skin. Some of these devices are designed to allow an electric motor housed inside a handheld stylus to attach to a disposable plastic cartridge that has an array of tiny microneedles affixed to the non-attached end. Many of these motorized devices allow the practitioner to adjust both the depth of penetration into the skin as well as the speed in which the motor reciprocally propels and withdraws the microneedle array.
There are various microneedle cartridge designs. Virtually all microneedle cartridges rely on a plastic outer cartridge cylinder to attach to the motorized device, house the internal components, provide the support and structure to direct the path and motion of the microneedles, and provide some measure of protection from accidentally coming into contact with the sharp microneedle array. Virtually all microneedle cartridges rely on a single plastic or metal central rod which attaches or otherwise engages the reciprocal piston rod of the electric motor on one end and has a microneedle array comprised of a differing number and arrangement of microneedles on the other end. Most microneedle designs incorporate a spring mechanism that surrounds the central rod and assists with the withdrawal stroke of the microneedles from the skin. The spring mechanisms currently employed are either a metal coil design or an accordion corrugated silicon/plastic design.
Currently, microneedle cartridges attach to a fixed, non-removable nose cone apparatus by various threaded or slotted adaptations on both the microneedle cartridge and the nose cone apparatus. The microneedle cartridges are designed to be opened from sterile packaging, affixed to the nose cone, used on the patient, removed from the nose cone, and then disposed of in a safe container.
Currently, the design of microneedling cartridges utilizing a metal coil spring mechanism allow topical and bodily fluids to enter into the cartridge via the gap between the outer cartridge wall and the inner microneedle array block. These fluids then travel towards and enter into the motorized microneedling device via the gap between the outer cartridge connection to the motorized device and the central rod affixing the microneedling array. Based on current designs, both of these gaps were necessary to allow the internal central rod with the microneedle array to freely reciprocate inside the outer plastic housing cylinder. Fluid movement through the cartridge is facilitated by the suction pressure created by the reciprocal action of the microneedle array which is, in effect, sealed to the skin via the outer plastic cylinder housing being pressed against moist skin during the treatment. Additionally, capillary action facilitates movement of fluid through the microneedle cartridge.
Currently, all motorized microneedling devices are not able to be dry or steam autoclave sterilized as the electrical components cannot be removed and would be destroyed in the autoclave. This poses a cross contamination problem to both patient and practitioner as all current motorized microneedle devices only allow the practitioner to attempt to remove the topical and bodily fluids that have entered the motorized device nose cone by the use of liquid disinfectants such as isopropyl alcohol. Indeed, many manufacturers specifically direct practitioners to either dip the nose cone into alcohol or use an alcohol soaked cotton swab to clean the nose cone of the motorized microneedling device.
The Center for Disease Control and many other entities such as the American Medical Association cite that the only methods to effectively sterilize a surgical instrument that comes into contact with bodily fluids are properly performed dry heat sterilization, steam sterilization or chemical gas sterilization. The use of disinfectants, even high level disinfectants, cannot adequately kill pathogens derived from bodily fluids.
Even though the current microneedle cartridges are single use and disposable, the bodily fluids that leak into the nose cone apparatus of the motorized microneedling device cannot be effectively removed and decontaminated from pathogens because the devices, as they are designed now, cannot be sterilized. These pathogens remain inside the nose cone section of the microneedling pen and, in some cases for certain motorized microneedling device designs, inside the motor chamber. Once inside, these pathogens can potentially multiply. When the next microneedle cartridge is inserted and the device is used on the next patient, the bodily fluids from the new patient may come in contact with the bodily fluid residue trapped inside the motorized microneedling device potentially allowing transmission of pathogens to the new patient.
Microneedle cartridge manufacturers have attempted to mitigate the cross contamination issue by replacing the metal spring with an accordion corrugated silicon spring that provides some assistance with removing the microneedles from the skin during the withdrawal stroke while also acting as a gasket to attempt to seal the gap between the outer cartridge connection to the motorized device and the central rod affixing the microneedling array. However, these silicon based springs are not as effective in assisting the withdrawal stroke as are metal springs. As a result of the device being inefficient in removing the needles on the withdrawal stroke, especially at greater depths of penetration, more power is required of the motor. Once the motor has reached its maximum power output, the inefficiency of the silicon spring against the increased friction of the skin against the microneedle array at greater depths of penetration causes the microneedle array to drag in the skin, tearing it. Additionally, the life of the motor is significantly shortened.
Other approaches to mitigate cross contamination include the addition of a small hole in the outer cartridge cylinder wall to minimize suction. One manufacturer has developed a plastic perforated outer plastic guide that contacts the skin guiding the needles to go through narrow, aligned channels which reduces the amount of fluids that can reach the gap between the outer cartridge wall and the inner microneedle array. However, this device utilizes a metal spring with the gap between the outer cartridge connection to the motorized device and the central rod affixing the microneedling array. Both of these designs have been shown to reduce, but not completely eliminate, the chances of bodily fluids entering the motorized microneedling device.
In summary, as they are designed now, motorized microneedling devices as well as the microneedling cartridges attached to them allow bodily fluids (including blood) to enter the motorized microneedling nose cone. Once inside, the device cannot be sterilized increasing the risk of transmitting blood borne pathogens from patient to patient.