follow that Link...very good paper

http://www.ncbi.nlm.nih.gov/pubmed/18253747

Dear Hisham. Perhaps could be useful for what your are looking to have access to the following document: A Model Code of Practice for Tissue Banks; IJOE (2012) ISSN: 1535-4776; Volume 8, Number ½; Nova Science Publishers, Inc.; 2012.

In this document the following text has been included regarding freezing of solid tissues to give ypu an idea of the content of the Code:

Freezing of musculoskeletal and soft human tissue

If human tissue is to be frozen to be preserved, then it shall be frozen at a specific rate to a predetermined specific end-point (a temperature of -40°C or colder). If human tissue is to be preserved using other methods, appropriate protocols shall be determined and described in writing procedures.

Freezing of human skin shall be done in a manner that ensures a slow cooling rate to maintain the structural integrity of the skin. Variable-rate cooling using insulated heat sink boxes or programmed control-rate freezing techniques are acceptable methods of human skin cryopreservation. If a programmed control-rate freezing technique is employed, a record of the freezing profile shall be evaluated and approved and become a permanent part of the processing record.

Frozen human skin that has been thawed shall not be returned to the skin bank inventory. Frozen human skin shall not be assigned for use to another patient, if the package has been opened.

Procedures for freezing musculoskeletal and soft human tissues shall be established and documented. Freezer chamber temperature shall be monitored during each freezing cycle. The thermal profile for each vial or batch shall be logged with the specimen records.

Other paragraphs on the same topic is included in the mentioned document.