Minimally invasive and targeted therapeutic cell delivery to the skin using microneedle devices.

BACKGROUND: Translation of cell therapies to the clinic is accompanied by numerous challenges, including controlled and targeted delivery of the cells to their site of action, without compromising cell viability and functionality. OBJECTIVES: To explore the use of hollow microneedle devices (to date only used for the delivery of drugs and vaccines into the skin and for the extraction of biological fluids) to deliver cells into skin in a minimally invasive, user-friendly and targeted fashion. METHODS: Melanocyte, keratinocyte and mixed epidermal cell suspensions were passed through various types of microneedles and subsequently delivered into the skin. RESULTS: Cell viability and functionality are maintained after injection through hollow microneedles with a bore size ≥ 75 µm. Healthy cells are delivered into the skin at clinically relevant depths. CONCLUSIONS: Hollow microneedles provide an innovative and minimally invasive method for delivering functional cells into the skin. Microneedle cell delivery represents a potential new treatment option for cell therapy approaches including skin repigmentation, wound repair, scar and burn remodelling, immune therapies and cancer vaccines.

Evaluating mechanical adhesion of sol-gel titanium dioxide coatings containing calcium phosphate for metal implant application.

The adhesion of thin (< 10 microm) sol-gel calcium phosphate-titanium dioxide films bonded to a titanium substrate was studied using two different tests: a rotating-bending test and a tensile bond test. The former evaluates the impact of both the coating procedure and the surface pre-treatment on the resistance to fatigue of the substrate as well as the adhesion of the coating; the latter measures the tensile adhesion strength of the coating. Both tests gave similar results. A reduction of the thickness of the coating or an increase of the roughness of the substrate improves the quality of the interface. A comparison of the adhesion of the calcium phosphate-titanium dioxide film with that of a pure calcium phosphate coating obtained by a similar route suggests the involvement of a chemical component in the binding.

Thin films of calcium phosphate and titanium dioxide by a sol-gel route: a new method for coating medical implants.

Titanium is a commonly used biomaterial for dental and orthopaedic applications. To increase its ability to bond with bone, some attempts were made to coat its surface with calcium phosphate (CaP). This paper describes a new type of coating. Instead of a pure CaP layer, a mixing of titanium dioxide (TIO2) and CaP is fabricated and deposited as a coating. These layers are deposited by a sol-gel route on pure titanium substrates using various pre-treatments. The method consists of mixing a solution of tetrabutyl ortho-titanate or a sol of titanium dioxide with a solution of calcium nitrate and phosphorous esters. This composite is deposited on to commercially pure titanium plates, mechanically polished or blasted with pure crystalline aluminum oxide, using the spin-coating technique. These coatings are then fired at 650 or 850 degrees C for various times. The samples are characterized by X-ray diffraction for their crystallinity, X-ray photoelectron spectroscopy for their surface chemical composition and scanning electron microscopy for their topography. Samples treated at 850 degrees C present a well-pronounced crystallinity, and a high chemical purity at the surface. The topography is strongly related to the viscosity of the precursor and the substrate pre-treatment. Possibilities to structure the outermost layer are presented.