Nanomaterial Lipid-Based Carrier for Non-Invasive Capsaicin Delivery; Manufacturing Scale-Up and Human Irritation Assessment

Capsaicin is an active compound in chili peppers (Capsicum chinense) that has been approved for chronic pain treatment. The topical application of high-strength capsaicin has been proven to reduce pain; however, skin irritation is a major drawback. The aim of this study was to investigate an appropriate and scalable technique for preparing nanostructured lipid carriers (NLCs) containing 0.25% capsaicin from capsicum oleoresin (NLC_C) and to evaluate the irritation of human skin by chili-extract-loaded NLCs incorporated in a gel formulation (Gel NLC_C). High-shear homogenization with high intensity (10,000 rpm) was selected to create uniform nanoparticles with a size range from 106 to 156 nm. Both the NLC_C and Gel NLC_C formulations expressed greater physical and chemical stabilities than the free chili formulation. Release and porcine biopsy studies revealed the sustained drug release and significant permeation of the NLCs through the outer skin layer, distributing in the dermis better than the free compounds. Finally, the alleviation of irritation and the decrease in uncomfortable feelings following the application of the Gel NLC_C formulation were compared to the effects from a chili gel and a commercial product in thirty healthy volunteers. The chili-extract-loaded NLCs were shown to be applicable for the transdermal delivery of capsaicin whilst minimizing skin irritation, the major noncompliance cause of patients.


HPLC Method Validation
A simple and validated RP-HPLC method for capsaicin according to the ICH and AOAC guidelines demonstrated the good specificity, linearity, accuracy, and precision in the range of 0.25100 µ g/mL. The limit of detection (LOD) and limit of quantitation (LOQ) were 0.1 and 0.25 µ g/ml. The results of accuracy and precision are summarized in Table 1. The method was found to be suitable for the analysis of capsaicin from the entrapment, content, and release studies.

Invitation
You are being invited to take part in this research project. Before you decide to participate in this project, it is important to understand why the research is being done and what it will involve.
Please take time to read the following information carefully and discuss it with others if you wish. Ask us if there is anything that is unclear or if you want more information. Take time to decide whether or not you wish to take part. Thank you for reading this.

What is this trial about?
Chili extract has been incorporated in many topical products applied for various diseases such as musculoskeletal pain, osteoarthritis, rheumatoid arthritis, diabetic neuropathy, and post-herpetic neuralgia. However, the major problem of chili extract after its application can cause on skin irritation. Therefore, the development of chili-extract delivery system has been performed in order to harness the benefits of capsaicin while avoiding its irritation effects.

What is the project's purpose?
1. To study the skin irritation effects from the chili-extract delivery system incorporated in a topical formulation.
2. To evaluate the sensory severity of skin irritation and satisfaction in the chili-extract delivery system incorporated in a topical formulation.

Why have I been chosen?
You have been chosen because you are a healthy volunteer with normal skin, so called a healthy volunteer, who is appropriate to be a volunteer for skin irritation study for the developed topical formulation.

Do I have to take part?
It is up to you to decide whether or not to take part in this study. Your decision to participate is voluntary.
If you do decide to take part, you will be asked to sign a consent form. You will be given a copy of this signed consent form for your record. Additionally, you are still free to withdraw at any time and without giving a reason.

What will happen to me if I take part?
Before you start the trial, the doctor or staff will talk to you about the trial. If you agree to participate in the trial, you will have to sign an informed consent.
Then, your forearms will be screened for the existing open wound and skin disease. At least one week before the study, you need to avoid using topical steroid products or other topical medicines.
During a visit day, the staff will show you how to apply the formulation on your trial area. Your arms will be washed and marked the trial area in six areas (1.5  1.5 cm per area) before you apply the formulations. The formulations will be left in contact with the skin for 15 min, and then they will be removed by wipes. Patch test will be performed on your forearms and the erythema will be evaluated by using Mexameter ® (CK Electronic, Cologne, Germany). The skin irritation will be visual analyzed by capture and followed by skin-color measurement with probe analysis (Mexameter ® ) at various times; before and 60, 120, and 180 min after exposure to the formulations and controls. Self-observations in a questionnaire about your symptoms, and satisfaction on these formulations will be observed at each time; 15, 30, 60, 90, 120, 180 min and 24 h after applied the formulations. It will take approximately 5 minutes to complete the questionnaire.

What are the possible side-effects of taking part?
The unwanted side effect after applying the chili extract formulations is skin irritation including pain, itching, erythema and burning; however, the severe skin irritation is a rare case which upon an individual response. If you suffer these or any other symptoms and become worried, please contact the doctor or the staff.

What will happen if I don't want to carry on with the trial?
If you decide not to take part or withdraw from the trial, this will not affect the standard of care you receive or loss of any benefits you would otherwise receive. If you want to stop your participation in the trial, please tell the doctor or staff.

What are possible benefits of taking part?
We cannot guarantee that you will receive any benefits from this study; however, results may benefit patients who have used the developed topical formulation from chili-extract delivery system for pain relief in the future.

What if something goes wrong?
If you suffer or become severe skin irritation as a result of participating in this trial, necessary medical treatment will be made available at no cost to you to the full extent provided.
Your arms will be washed and marked the trial area in six areas (1.5  1.5 cm per area) before you apply the formulations. Patch test will be performed on the forearms of volunteers and the erythema will be evaluated by using Mexameter ® The 50 mg of each formulations will be left in contact with the skin for 15 min, and then will be removed by wipes.
The skin irritation will be measured before and 60, 120, and 180 min after exposure to the formulations and controls. At each time point, a visual analysis was captured and followed by probe analysis (Mexameter ® ).
You will further fill in some questionnaires about your symptoms and satisfaction of formulation on a scale at each time points; 15, 30, 60, 90, 120, 180 min and 24 h after application.
The doctor or staffs will talk to you about the trial. If you agree to participate in the trial, you will have to sign informed consent.
The six-test areas for samples application