Pickles, Samantha Fay
(2018)
The bio-footprint of a wound debridement device containing Lucilia sericata larvae.
PhD thesis, University of Nottingham.
Abstract
The BB-50 is a wound debridement product which contains live larvae of the common greenbottle blow-fly, Lucilia sericata (Diptera: Calliphoridae). It forms part of the ‘BioBag’® range of Class I sterile medical devices developed by BioMonde©, a multinational wound care company, specialising in the manufacture and distribution of larval products. In the United Kingdom, the devices are approved for use by the Medicines and Healthcare Products Regulatory Agency, under the ‘Specials’ License (reference number MS 25595) to meet the clinical needs of a patient, when a suitable licensed medicine is not available. Despite having been offered by the National Health Service for almost two decades, and supported by clinically-proven efficacy, it is estimated that ‘maggot therapy’ is administered to only 1% of the 200,000 patients currently suffering with senescent chronic wounds. In order to improve acceptability, sterile maggots have been incorporated within fully-sealed yet porous pouches, to provide ease of application, and to create a physical barrier between the patient and the insects. Globally, larval-assisted debridement is considered as a successful treatment, but one of last resort, after conventional therapies have failed. Furthermore, there are numerous anecdotal reports detailing the disinfecting and healing properties of substances produced by the maggots as they feed upon the necrotic material of the chronic wound, but clinical evidence is lacking.
The original contribution to knowledge provided by this thesis, is the concept of the ‘bio-footprint’ of the BB-50, which is created upon the initial introduction of the BioBag into the wound environment. The aim of this study was to visualise the impact of this device over 24 hours and to harvest the alimentary products which give rise to the bio-footprint, and ultimately the therapeutic effects of the treatment. From here, the first standard operating procedure for the collection of larval substances was developed, leading to the creation of a Quality Control assay for the assessment of the devices. The project then addressed the possibility that the manufacturing processes were contributing to the activity of the bio-footprint. Once confidence in the quality of the larval substances was achieved, it was possible to undertake the first systematic exploration of a standardised, regulated product, which is in current clinical use.
High and low molecular weight investigations were employed to characterise the content of the alimentary products, with a view to identifying compounds which could be linked to therapeutic effects. It is acknowledged that the mechanisms behind maggot therapy are unclear, but that a range of substances are likely to be responsible for the beneficial outcomes observed. However, only two compounds have been fully characterised from larval material. The enzyme chymotrypsin and the antimicrobial peptide lucifensin, are linked to therapeutic effects and have been detected in the environment of the chronic wound following larval treatment. Contemporary studies have yet to characterise a substance which is associated with the promotion of healing.
This study further contributes to the discipline following the detection of 132 putatively identified compounds, which may be produced by the larvae within the first 24 hours of treatment. Additionally, many of these possess multifactorial actions, which have the potential to positively alter the chronic wound and bring about the onset of healing.
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