title: Potential of microneedle-assisted micro-particle delivery by gene guns: a review.
abstract: BACKGROUND
  Gene guns have been used to deliver deoxyribonucleic acid (DNA) loaded micro-particle and breach the muscle tissue to target cells of interest to achieve gene transfection.
  
  
  OBJECTIVE
  This article aims to discuss the potential of microneedle (MN) assisted micro-particle delivery from gene guns, with a view to reducing tissue damage.
  
  
  METHODS
  Using a range of sources, the main gene guns for micro-particle delivery are reviewed along with the primary features of their technology, e.g. their design configurations, the material selection of the micro-particle, the driving gas type and pressure. Depending on the gene gun system, the achieved penetration depths in the skin are discussed as a function of the gas pressure, the type of the gene gun system and particle size, velocity and density. The concept of MN-assisted micro-particles delivery which consists of three stages (namely, acceleration, separation and decoration stage) is discussed. In this method, solid MNs are inserted into the skin to penetrate the epidermis/dermis layer and create holes for particle injection. Several designs of MN array are discussed and the insertion mechanism is explored, as it determines the feasibility of the MN-based system for particle transfer.
  
  
  RESULTS
  This review suggests that one of the problems of gene guns is that they need high operating pressures, which may result in direct or indirect tissue/cells damage. MNs seem to be a promising method which if combined with the gene guns may reduce the operating pressures for these devices and reduce tissue/cell damages.
  
  
  CONCLUSIONS
  There is sufficient potential for MN-assisted particle delivery systems.
authors: Department of Chemical Engineering, Loughborough University , Loughborough, Leicestershire , UK.
authors: Dongwei
authors: D
authors: Zhang
authors: Diganta B
authors: DB
authors: Das
authors: Chris D
authors: CD
authors: Rielly
mesh_terms: D000818:Animals; D016503:Drug Delivery Systems; D018014:Gene Transfer Techniques / Q000295:instrumentation*; D006801:Humans; D055616:Microtechnology; D053758:Nanoparticles / Q000008:administration & dosage; D009339:Needles; D012867:Skin
keywords: Gene gun; micro-particle; microneedle; penetration depth; skin