Spray technology for tissues delivers various substances, such as cells, drugs, or biomaterials, directly onto or into biological tissues for medical or scientific objectives. This method precisely applies therapeutic or diagnostic agents to targeted areas. It represents a significant advancement in localized treatment and regenerative approaches, offering new possibilities for a range of medical conditions. The fundamental concept centers on creating a fine mist or stream that can conform to complex biological surfaces.
The Science Behind Spraying Tissues
The effectiveness of spray technology relies on precise control over droplet formation and interaction with biological surfaces. Atomization, the process of breaking a liquid into fine droplets, is central. Different atomization methods produce droplets with varying sizes, influencing how they interact with tissue. For biological applications, maintaining cell viability during and after spraying is a primary concern, as mechanical forces can damage cells.
When a spray interacts with tissue, adhesion and penetration depend on droplet characteristics and tissue properties. Droplet size control is achieved by adjusting parameters like flow rate, pressure, and liquid properties, including viscosity and surface tension. Smaller droplets generally provide more uniform coverage, while larger droplets may improve cell survival, especially when spraying living cells. Optimizing atomization ensures delivered substances are distributed effectively without compromising their integrity or cell viability.
Diverse Medical Applications
Spray technology offers numerous applications in medicine, addressing various conditions through localized delivery.
Wound Healing
In wound healing, this technology facilitates the direct application of therapeutic agents to damaged areas. Skin cell suspensions, including keratinocytes, fibroblasts, and melanocytes, can be sprayed directly onto burns or chronic wounds. This promotes accelerated healing, reduces the need for traditional skin grafts, and allows broad, even distribution of live cells across large wound surfaces from small donor samples.
Tissue Engineering and Regeneration
The field of tissue engineering and regeneration also benefits from spray technology. It enables precise delivery of scaffold materials or cell suspensions for repairing damaged cartilage or facilitating bone regeneration. For example, airbrush-assisted cell spraying can deliver chondrocytes and mesenchymal stromal cells to cartilage defects, offering a minimally invasive option. This method can also create three-dimensional tissue scaffolds by continuously spraying cell suspensions onto electrospun polymer fibers, improving cell distribution within the construct.
Localized Drug Delivery
Spray technology is also employed for localized drug delivery, providing targeted treatment to specific tissue sites. This includes applying antibiotics, anesthetics, or anti-inflammatory drugs directly where needed, enhancing their therapeutic effect while minimizing systemic side effects. Film-forming sprays can create a thin, uniform film on the skin, allowing for sustained drug release and accelerated wound healing through moisture control. These systems can adjust drug dosages based on the volume sprayed, enabling controlled local or systemic effects.
Surgical Adhesives and Sealants
Biocompatible surgical adhesives and sealants can be applied using spray technology during surgical procedures. These sprayable glues seal wounds, stop air and liquid leakages, and adhere strongly to soft tissues. Materials like viscoelastic poly(lactide-co-caprolactone) (PLCL) blends can be spray-deposited as adhesion barriers, preventing fibrotic scar tissue formation while promoting wound healing. These adhesives offer a flexible and elastic solution that rapidly cures on site, providing an immediate bond in less than 60 seconds.
Key Technologies and Materials
Technologies
Various technologies generate fine sprays for tissue applications, each suited for different biological materials.
Air-assisted sprayers use compressed air to atomize liquids, creating fine droplets.
Ultrasonic nebulizers use high-frequency vibrations to produce a mist.
Electrostatic spraying applies an electrical charge to droplets, helping achieve uniform deposition and reduce overspray.
Pressure-assisted nozzles force liquid through a small opening under high pressure, breaking it into a spray.
These methods are selected based on the specific material being delivered and the desired droplet size and distribution.
Materials
The range of substances delivered through spray technology is extensive, including:
Living cells: Fibroblasts, keratinocytes, and mesenchymal stem cells are frequently sprayed for regenerative therapies.
Growth factors and proteins: These can be delivered to stimulate tissue repair and regeneration.
Hydrogels: Water-swollen polymer networks commonly sprayed as scaffolds for cell encapsulation and tissue adhesion.
Biodegradable polymers: Used to create temporary structures that support tissue growth before naturally dissolving.
Why Spraying is a Preferred Approach
Spray technology offers distinct advantages for delivering substances to tissues compared to traditional methods:
Non-invasive or minimally invasive: Reduces trauma and discomfort for the patient compared to injections or surgical implantation.
Uniform and conformal coverage: Ensures irregular tissue surfaces are evenly coated with the therapeutic agent.
Precise targeting: Allows for localized treatment and minimizes exposure to healthy tissues.
Speed and ease of application: Leads to faster procedure times in clinical settings, making it practical for treating larger surface areas, such as extensive burns.
Versatility: Adapts to various tissue types and a wide range of substances, from delicate living cells to complex biomaterials.
Reduced contamination risk: Many spray systems are designed as closed systems, promoting a safer environment for both the patient and the medical professional.